OLGA Manual 6.2.3.pdf

Table of Contents OLGA

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1

Welcome to OLGA 6 ......................................................................................................................................................................... 1 Release Information .......................................................................................................................................................................... 2 Introduction ............................................................................................................................................................................................ 3 Introduction ..................................................................................................................................................................................... 3 Background ..................................................................................................................................................................................... 4 OLGA as a Strategic Tool ........................................................................................................................................................... 5 OLGA Model Basics ..................................................................................................................................................................... 6 How to use in general .................................................................................................................................................................. 7 Threaded Execution ................................................................................................................................................................... 11 Applications ................................................................................................................................................................................. 12 Input files ...................................................................................................................................................................................... 16 Simulation model ....................................................................................................................................................................... 22

24 Introduction .................................................................................................................................................................................. 24 New Project ................................................................................................................................................................................. 25 New case ...................................................................................................................................................................................... 26 Open existing case .................................................................................................................................................................... 27 Start page .................................................................................................................................................................................... 28 Model view ................................................................................................................................................................................... 29 File view ........................................................................................................................................................................................ 31 Component view ......................................................................................................................................................................... 32 Property editor ............................................................................................................................................................................ 33 Network view ............................................................................................................................................................................... 35 Flowpath view ............................................................................................................................................................................. 47 Connection view ......................................................................................................................................................................... 49 Output window ............................................................................................................................................................................ 50 Time series editor ...................................................................................................................................................................... 52 Plotting .......................................................................................................................................................................................... 54 Active case trend plot ............................................................................................................................................................. 55 Active case profile plot ........................................................................................................................................................... 56 Fluid properties ...................................................................................................................................................................... 58 Multi-case plotting .................................................................................................................................................................. 59 Some general features of the plotting tool .............................................................................................................................. 60 Export/import data to/from MS Excel ...................................................................................................................................... 61 Parametric Studies .................................................................................................................................................................... 63 Geometry editor .......................................................................................................................................................................... 66 Activating ................................................................................................................................................................................ 67 Enter a new profile ................................................................................................................................................................. 69 Edit geometries ...................................................................................................................................................................... 71 Edit the table ................................................................................................................................................................... 72 Edit the graph .................................................................................................................................................................. 73 Check angle distribution ................................................................................................................................................... 74 Filter the data .................................................................................................................................................................. 75 Complete the data ............................................................................................................................................................ 76 Define sectioning ............................................................................................................................................................. 77 Use the new geometry ...................................................................................................................................................... 79 Menus .................................................................................................................................................................................... 80

Graphical User Interface ..............................................................................................................................................................

81 Moving windows ......................................................................................................................................................................... 82 Hot keys ........................................................................................................................................................................................ 83 Moving view in 3D ...................................................................................................................................................................... 84 Graphic Configuration ............................................................................................................................................................... 85 Menus ........................................................................................................................................................................................... 86 Toolbars ........................................................................................................................................................................................ 88 Properties and settings ............................................................................................................................................................. 90 Simulation with bundles ........................................................................................................................................................... 92 Simulation with controllers ...................................................................................................................................................... 94 Simulation with separators ...................................................................................................................................................... 97 Model descriptions .......................................................................................................................................................................... 99 2nd Order Scheme .................................................................................................................................................................... 99 Purpose .................................................................................................................................................................................. 99 When to use ........................................................................................................................................................................ 100 Methods and assumptions .................................................................................................................................................. 101 Limitations ........................................................................................................................................................................... 104 How to use .......................................................................................................................................................................... 105 Blackoil ...................................................................................................................................................................................... 106 Purpose ............................................................................................................................................................................... 106 When to use ........................................................................................................................................................................ 107 Methods and assumptions .................................................................................................................................................. 108 Limitations ........................................................................................................................................................................... 116 How to use ........................................................................................................................................................................... 117 Complex Fluid .......................................................................................................................................................................... 118 Purpose ............................................................................................................................................................................... 118 When to use ........................................................................................................................................................................ 119 Methods and assumptions .................................................................................................................................................. 120 How to use .......................................................................................................................................................................... 121 Compositional Tracking ......................................................................................................................................................... 122 Purpose ............................................................................................................................................................................... 122 When to use ........................................................................................................................................................................ 123 Methods and assumptions .................................................................................................................................................. 124 Limitations ........................................................................................................................................................................... 125 How to use .......................................................................................................................................................................... 126 Controller .................................................................................................................................................................................. 131 Controller introduction ......................................................................................................................................................... 131 Analog Vs Digital Controllers .............................................................................................................................................. 132 Controller mode ................................................................................................................................................................... 133 Controller activation deactivation ......................................................................................................................................... 135 Constraining the controller output ....................................................................................................................................... 136 Controller details ................................................................................................................................................................. 137 Controller terminals ............................................................................................................................................................. 139 Actuator time of controlled device ....................................................................................................................................... 140 Connecting the controllers .................................................................................................................................................. 141 Controller Setpoint ............................................................................................................................................................... 142 Controller measured variable ............................................................................................................................................... 143 Algebraic controller ............................................................................................................................................................. 144 Purpose ....................................................................................................................................................................... 144 When to use ................................................................................................................................................................. 145 Methods and assumptions ............................................................................................................................................. 146 How to use ................................................................................................................................................................... 147 Limitations ..............................................................................................................................................................................

ASC controller ..................................................................................................................................................................... 148

148 149 Methods and assumptions ............................................................................................................................................. 150 How to use ................................................................................................................................................................... 151 Cascade controller .............................................................................................................................................................. 152 Purpose ....................................................................................................................................................................... 152 When to use ................................................................................................................................................................. 153 Methods and assumptions ............................................................................................................................................. 154 Limitations ................................................................................................................................................................... 156 How to use ................................................................................................................................................................... 157 ESD controller ..................................................................................................................................................................... 158 Purpose ....................................................................................................................................................................... 158 When to use ................................................................................................................................................................. 159 Methods and assumptions ............................................................................................................................................. 160 How to use ................................................................................................................................................................... 161 Manual controller ................................................................................................................................................................. 162 Purpose ....................................................................................................................................................................... 162 When to use ................................................................................................................................................................. 163 Methods and assumptions ............................................................................................................................................. 164 How to use ................................................................................................................................................................... 165 Override controller ............................................................................................................................................................... 166 Purpose ....................................................................................................................................................................... 166 When to use ................................................................................................................................................................. 167 Methods and assumptions ............................................................................................................................................. 168 How to use ................................................................................................................................................................... 170 PID controller ...................................................................................................................................................................... 171 Purpose ....................................................................................................................................................................... 171 When to use ................................................................................................................................................................. 172 Methods and assumptions ............................................................................................................................................. 173 How to use ................................................................................................................................................................... 175 PSV controller ..................................................................................................................................................................... 179 Purpose ....................................................................................................................................................................... 179 When to use ................................................................................................................................................................. 180 Methods and assumptions ............................................................................................................................................. 181 How to use ................................................................................................................................................................... 182 Scaler controller .................................................................................................................................................................. 183 Purpose ....................................................................................................................................................................... 183 When to use ................................................................................................................................................................. 184 Methods and assumptions ............................................................................................................................................. 185 How to use ................................................................................................................................................................... 186 Selector controller ............................................................................................................................................................... 187 Purpose ....................................................................................................................................................................... 187 When to use ................................................................................................................................................................. 188 Methods and assumptions ............................................................................................................................................. 189 How to use ................................................................................................................................................................... 191 STD Controller .................................................................................................................................................................... 192 Purpose ....................................................................................................................................................................... 192 When_to_use ............................................................................................................................................................... 193 Methods_and_assumptions ........................................................................................................................................... 194 Limitations ................................................................................................................................................................... 195 How_to_use ................................................................................................................................................................. 196 Purpose .......................................................................................................................................................................

When to use .................................................................................................................................................................

Switch controller .................................................................................................................................................................. 197

197 198 Methods and assumptions ............................................................................................................................................. 199 How to use ................................................................................................................................................................... 200 Table controller .................................................................................................................................................................... 201 Purpose ....................................................................................................................................................................... 201 When to use ................................................................................................................................................................. 202 Methods and assumptions ............................................................................................................................................. 203 Limitations ................................................................................................................................................................... 204 How to use ................................................................................................................................................................... 205 Transmitter .......................................................................................................................................................................... 206 Purpose ....................................................................................................................................................................... 206 When to use ................................................................................................................................................................. 207 Methods and assumptions ............................................................................................................................................. 208 Limitations ................................................................................................................................................................... 209 How to use ................................................................................................................................................................... 210 Corrosion ................................................................................................................................................................................... 211 Purpose ............................................................................................................................................................................... 211 When to use ........................................................................................................................................................................ 212 Methods and assumptions .................................................................................................................................................. 213 How to use .......................................................................................................................................................................... 215 Limitations ........................................................................................................................................................................... 218 Drilling Fluid ............................................................................................................................................................................. 219 Purpose ............................................................................................................................................................................... 219 When to use ........................................................................................................................................................................ 220 Methods and assumptions .................................................................................................................................................. 221 How to use .......................................................................................................................................................................... 222 Hydrate Check ......................................................................................................................................................................... 223 HydrateCheck - Purpose ..................................................................................................................................................... 223 HydrateCheck - When to use .............................................................................................................................................. 224 HydrateCheck - Methods and assumptions ........................................................................................................................ 225 HydrateCheck - Limitations ................................................................................................................................................. 227 HydrateCheck - How to use ................................................................................................................................................ 228 Hydrate Kinetics ...................................................................................................................................................................... 229 Purpose ............................................................................................................................................................................... 229 When to use ........................................................................................................................................................................ 230 Methods and assumptions .................................................................................................................................................. 231 Limitations ........................................................................................................................................................................... 233 How to use .......................................................................................................................................................................... 234 Inhibitor Tracking .................................................................................................................................................................... 235 Purpose ............................................................................................................................................................................... 235 When to use ........................................................................................................................................................................ 236 Methods and assumptions .................................................................................................................................................. 237 Limitations ........................................................................................................................................................................... 239 How to use .......................................................................................................................................................................... 240 Leak ............................................................................................................................................................................................ 241 Purpose ............................................................................................................................................................................... 241 When to use ........................................................................................................................................................................ 242 Methods and assumptions .................................................................................................................................................. 243 Limitations ........................................................................................................................................................................... 244 How to use .......................................................................................................................................................................... 245 Purpose .......................................................................................................................................................................

When to use .................................................................................................................................................................

Near-Wellbore .......................................................................................................................................................................... 246 Purpose ............................................................................................................................................................................... 246 When to use ........................................................................................................................................................................ 247

248 250 How to use .......................................................................................................................................................................... 251 Phase Split Node .................................................................................................................................................................... 252 Purpose ............................................................................................................................................................................... 252 When_to_use ...................................................................................................................................................................... 253 Methods_and_assumptions ................................................................................................................................................ 254 Limitations ........................................................................................................................................................................... 255 How_to_use ........................................................................................................................................................................ 256 Pig ............................................................................................................................................................................................... 257 Purpose ............................................................................................................................................................................... 257 When to use ........................................................................................................................................................................ 258 Methods and assumptions .................................................................................................................................................. 259 Limitations ........................................................................................................................................................................... 261 How to use .......................................................................................................................................................................... 262 Process Equipment ................................................................................................................................................................ 263 Check Valve ........................................................................................................................................................................ 263 Purpose ....................................................................................................................................................................... 263 When to use ................................................................................................................................................................. 264 Methods and assumptions ............................................................................................................................................. 265 Limitations ................................................................................................................................................................... 266 How to use ................................................................................................................................................................... 267 Compressor ........................................................................................................................................................................ 268 Purpose ....................................................................................................................................................................... 268 Methods and assumptions ............................................................................................................................................. 269 Limitations ................................................................................................................................................................... 274 How to use ................................................................................................................................................................... 275 Gas Lift Valve ...................................................................................................................................................................... 276 Purpose ....................................................................................................................................................................... 276 When to use ................................................................................................................................................................. 277 Methods and assumptions ............................................................................................................................................. 278 Limitations ................................................................................................................................................................... 281 How to use ................................................................................................................................................................... 282 Heat Exchanger .................................................................................................................................................................. 283 Purpose ....................................................................................................................................................................... 283 When to use ................................................................................................................................................................. 284 Methods and assumptions ............................................................................................................................................. 285 Limitations ................................................................................................................................................................... 286 How to use ................................................................................................................................................................... 287 Pump .................................................................................................................................................................................. 288 Purpose ....................................................................................................................................................................... 288 When to use ................................................................................................................................................................. 289 Methods and assumptions ............................................................................................................................................. 290 Limitations ................................................................................................................................................................... 299 How to use ................................................................................................................................................................... 300 Separator ............................................................................................................................................................................ 304 Purpose ....................................................................................................................................................................... 304 When to use ................................................................................................................................................................. 305 Methods and assumptions ............................................................................................................................................. 306 Methods and assumptions ..................................................................................................................................................

Limitations ...........................................................................................................................................................................

309 How to use ................................................................................................................................................................... 310 Valve ................................................................................................................................................................................... 312 Purpose ....................................................................................................................................................................... 312 When to use ................................................................................................................................................................. 313 Choke - Methods and assumptions ................................................................................................................................. 314 Valve - Methods and assumptions ................................................................................................................................... 317 Valve - Cv To Area ......................................................................................................................................................... 319 Limitations ................................................................................................................................................................... 320 How to use ................................................................................................................................................................... 321 Single Component .................................................................................................................................................................. 322 Purpose ............................................................................................................................................................................... 322 When to use ........................................................................................................................................................................ 323 Methods and assumptions .................................................................................................................................................. 324 How to use .......................................................................................................................................................................... 329 Slug Tracking ........................................................................................................................................................................... 330 Purpose ............................................................................................................................................................................... 330 When to use ........................................................................................................................................................................ 331 Methods and assumptions .................................................................................................................................................. 332 Limitations ........................................................................................................................................................................... 334 How to use .......................................................................................................................................................................... 335 Slug Tuning .............................................................................................................................................................................. 338 Purpose ............................................................................................................................................................................... 338 When to use ........................................................................................................................................................................ 339 Methods and assumptions .................................................................................................................................................. 340 Limitations ........................................................................................................................................................................... 341 How to use .......................................................................................................................................................................... 342 Source ........................................................................................................................................................................................ 343 Purpose ............................................................................................................................................................................... 343 When to use ........................................................................................................................................................................ 344 Methods and assumptions .................................................................................................................................................. 345 How to use .......................................................................................................................................................................... 349 Steady State Processor ......................................................................................................................................................... 350 Purpose ............................................................................................................................................................................... 350 When to use ........................................................................................................................................................................ 351 Methods and assumptions .................................................................................................................................................. 352 Limitations ........................................................................................................................................................................... 353 How to use .......................................................................................................................................................................... 354 Steam\Water-HC ..................................................................................................................................................................... 355 Purpose ............................................................................................................................................................................... 355 When to use ........................................................................................................................................................................ 356 Methods and assumptions .................................................................................................................................................. 357 How to use .......................................................................................................................................................................... 361 Thermal Components ............................................................................................................................................................ 362 Annulus ............................................................................................................................................................................... 363 Purpose ....................................................................................................................................................................... 363 When to use ................................................................................................................................................................. 364 Methods and assumptions ............................................................................................................................................. 365 Limitations ................................................................................................................................................................... 366 How to use ................................................................................................................................................................... 367 FEMTherm .......................................................................................................................................................................... 368 Purpose ....................................................................................................................................................................... 368 Limitations ...................................................................................................................................................................

369 Methods and assumptions ............................................................................................................................................. 370 Limitations ................................................................................................................................................................... 375 How to use ................................................................................................................................................................... 376 Bundle ................................................................................................................................................................................. 377 Purpose ....................................................................................................................................................................... 377 When to use ................................................................................................................................................................. 378 Methods and assumptions ............................................................................................................................................. 379 Limitations ................................................................................................................................................................... 380 How to use ................................................................................................................................................................... 381 LINE .................................................................................................................................................................................... 382 Purpose ....................................................................................................................................................................... 382 When to use ................................................................................................................................................................. 383 Limitations ................................................................................................................................................................... 384 How to use ................................................................................................................................................................... 385 Thermal Computations .......................................................................................................................................................... 386 Purpose ............................................................................................................................................................................... 386 Methods and assumptions .................................................................................................................................................. 387 Limitations ........................................................................................................................................................................... 389 How to use .......................................................................................................................................................................... 390 Tracer Tracking ........................................................................................................................................................................ 391 Purpose ............................................................................................................................................................................... 391 When_to_use ...................................................................................................................................................................... 392 Methods_and_Assumptions ................................................................................................................................................ 393 Limitations ........................................................................................................................................................................... 394 How_to_use ........................................................................................................................................................................ 395 Transmitter ............................................................................................................................................................................... 206 Purpose ............................................................................................................................................................................... 206 When to use ........................................................................................................................................................................ 207 Methods and assumptions .................................................................................................................................................. 208 Limitations ........................................................................................................................................................................... 209 How to use .......................................................................................................................................................................... 210 Tuning ........................................................................................................................................................................................ 396 Tuning - Purpose ................................................................................................................................................................ 396 Tuning - When to use ......................................................................................................................................................... 397 Tuning - Methods and assumptions .................................................................................................................................... 398 Tuning - How to use ............................................................................................................................................................ 399 Water ......................................................................................................................................................................................... 400 Purpose ............................................................................................................................................................................... 400 When to use ........................................................................................................................................................................ 401 Methods and assumptions .................................................................................................................................................. 402 Limitations ........................................................................................................................................................................... 405 How to use .......................................................................................................................................................................... 406 Wax ............................................................................................................................................................................................ 408 Purpose ............................................................................................................................................................................... 408 When to use ........................................................................................................................................................................ 409 Methods and assumptions .................................................................................................................................................. 410 Limitations ........................................................................................................................................................................... 414 How to use .......................................................................................................................................................................... 415 Well ............................................................................................................................................................................................ 416 Purpose ............................................................................................................................................................................... 416 When to use ........................................................................................................................................................................ 417 When to use .................................................................................................................................................................

418 Limitations ........................................................................................................................................................................... 425 How to use .......................................................................................................................................................................... 426 REFERENCES ........................................................................................................................................................................ 428 Keywords .......................................................................................................................................................................................... 432 CaseDefinition ......................................................................................................................................................................... 435 CASE .................................................................................................................................................................................. 435 DTCONTROL ..................................................................................................................................................................... 436 FILES .................................................................................................................................................................................. 437 INTEGRATION ................................................................................................................................................................... 438 OPTIONS ........................................................................................................................................................................... 439 RESTART ........................................................................................................................................................................... 441 Compositional .......................................................................................................................................................................... 442 BLACKOILCOMPONENT .................................................................................................................................................. 442 BLACKOILFEED ................................................................................................................................................................ 443 BLACKOILOPTIONS ......................................................................................................................................................... 444 COMPOPTIONS ................................................................................................................................................................ 445 FEED .................................................................................................................................................................................. 447 Controller .................................................................................................................................................................................. 448 Algebraic Controller ............................................................................................................................................................. 448 ASC Controller .................................................................................................................................................................... 451 Cascade Controller ............................................................................................................................................................. 454 ESD Controller .................................................................................................................................................................... 457 Manual controller ................................................................................................................................................................. 459 Override Controller .............................................................................................................................................................. 461 PID Controller ..................................................................................................................................................................... 463 PSV Controller .................................................................................................................................................................... 466 Scaler Controller ................................................................................................................................................................. 468 Selector Controller ............................................................................................................................................................... 469 STD Controller .................................................................................................................................................................... 472 Switch Controller ................................................................................................................................................................. 474 Table Controller ................................................................................................................................................................... 476 Output ................................................................................................................................................................................. 477 OUTPUTDATA ............................................................................................................................................................. 477 TRENDDATA ................................................................................................................................................................ 478 FA-models ................................................................................................................................................................................. 479 FLUID ................................................................................................................................................................................. 479 SINGLEOPTIONS .............................................................................................................................................................. 481 SLUGTRACKING ............................................................................................................................................................... 483 SLUGTUNING .................................................................................................................................................................... 485 WATEROPTIONS .............................................................................................................................................................. 486 FlowComponent ...................................................................................................................................................................... 488 NODE ................................................................................................................................................................................. 488 NODE .......................................................................................................................................................................... 488 Output ......................................................................................................................................................................... 492 NODE_OUTPUTDATA .............................................................................................................................................. 492 NODE_TRENDDATA ................................................................................................................................................ 493 FLOWPATH ........................................................................................................................................................................ 494 FLOWPATH ................................................................................................................................................................. 494 Piping .......................................................................................................................................................................... 495 BRANCH .............................................................................................................................................................. 495 GEOMETRY .......................................................................................................................................................... 496 Methods and assumptions ..................................................................................................................................................

PIPE

.................................................................................................................................................................... 497

POSITION

............................................................................................................................................................. 498

499 CHECKVALVE ....................................................................................................................................................... 499 COMPRESSOR ...................................................................................................................................................... 500 HEATEXCHANGER ................................................................................................................................................. 502 LEAK ................................................................................................................................................................... 503 LOSS .................................................................................................................................................................. 505 PUMP .................................................................................................................................................................. 507 TRANSMITTER ....................................................................................................................................................... 511 VALVE ................................................................................................................................................................. 512 Boundary&InitialConditions ............................................................................................................................................ 514 HEATTRANSFER .................................................................................................................................................... 514 INITIALCONDITIONS ................................................................................................................................................ 517 NEARWELLSOURCE .............................................................................................................................................. 520 SOURCE .............................................................................................................................................................. 522 WELL .................................................................................................................................................................. 531 Output ......................................................................................................................................................................... 544 PROFILEDATA ....................................................................................................................................................... 544 OUTPUTDATA ........................................................................................................................................................ 545 TRENDDATA .......................................................................................................................................................... 546 FA-models ................................................................................................................................................................... 548 CORROSION ......................................................................................................................................................... 548 DTCONTROL ......................................................................................................................................................... 550 HYDRATECHECK ................................................................................................................................................... 551 HYDRATEKINETICS ................................................................................................................................................ 552 PIG ..................................................................................................................................................................... 554 SLUGILLEGAL ....................................................................................................................................................... 557 SLUGTRACKING .................................................................................................................................................... 558 TUNING ................................................................................................................................................................ 560 WAXDEPOSITION ................................................................................................................................................... 562 Library ........................................................................................................................................................................................ 566 DRILLINGFLUID ................................................................................................................................................................ 566 HYDRATECURVE .............................................................................................................................................................. 568 MATERIAL .......................................................................................................................................................................... 569 SHAPE ............................................................................................................................................................................... 571 TABLE ................................................................................................................................................................................ 572 TIMESERIES ...................................................................................................................................................................... 573 TRACERFEED ................................................................................................................................................................... 575 WALL .................................................................................................................................................................................. 576 Output ........................................................................................................................................................................................ 577 OUTPUT ............................................................................................................................................................................. 578 OUTPUTDATA ................................................................................................................................................................... 579 PLOT .................................................................................................................................................................................. 580 PROFILE ............................................................................................................................................................................ 581 PROFILEDATA ................................................................................................................................................................... 582 TREND ............................................................................................................................................................................... 583 TRENDDATA ...................................................................................................................................................................... 584 ProcessEquipment ................................................................................................................................................................. 585 PHASESPLITNODE ........................................................................................................................................................... 585 SEPARATOR ...................................................................................................................................................................... 587 Output ................................................................................................................................................................................. 590 ProcessEquipment ........................................................................................................................................................

590 TRENDDATA ................................................................................................................................................................ 591 ThermalComponent ............................................................................................................................................................... 592 ANNULUS .......................................................................................................................................................................... 592 ANNULUS .................................................................................................................................................................... 592 AnnulusComponents ..................................................................................................................................................... 593 COMPONENT ........................................................................................................................................................ 593 FLUIDBUNDLE .................................................................................................................................................................. 594 FLUIDBUNDLE ............................................................................................................................................................. 594 BundleComponents ....................................................................................................................................................... 595 COMPONENT ........................................................................................................................................................ 595 FEMTherm/Solidbundle ...................................................................................................................................................... 596 SOLIDBUNDLE ............................................................................................................................................................ 596 BundleComponents ....................................................................................................................................................... 598 COMPONENT ........................................................................................................................................................ 598 Drilling ........................................................................................................................................................................................ 600 TOOLJOINT ....................................................................................................................................................................... 600 How to use ....................................................................................................................................................................................... 105 2nd Order Scheme ................................................................................................................................................................. 105 Annulus ...................................................................................................................................................................................... 367 Blackoil ....................................................................................................................................................................................... 117 Check valve .............................................................................................................................................................................. 267 Complex Fluid .......................................................................................................................................................................... 121 Compositional Tracking ......................................................................................................................................................... 126 Compressor .............................................................................................................................................................................. 275 Controller .................................................................................................................................................................................. 147 Algebraic controller ............................................................................................................................................................. 147 ASC controller ..................................................................................................................................................................... 151 Cascade controller .............................................................................................................................................................. 157 ESD controller ..................................................................................................................................................................... 161 Manual controller ................................................................................................................................................................ 165 Override controller ............................................................................................................................................................... 170 PID controller ...................................................................................................................................................................... 175 PSV controller ..................................................................................................................................................................... 182 Scaler controller .................................................................................................................................................................. 186 Selector controller ............................................................................................................................................................... 191 Switch controller .................................................................................................................................................................. 200 Table controller .................................................................................................................................................................... 205 Transmitter .......................................................................................................................................................................... 210 Corrosion .................................................................................................................................................................................. 215 Drilling Fluid ............................................................................................................................................................................. 222 FEM Therm ............................................................................................................................................................................... 376 Fluid Bundle ............................................................................................................................................................................. 381 Gas Lift Valve ........................................................................................................................................................................... 282 Heat Exchanger ....................................................................................................................................................................... 287 HydrateCheck .......................................................................................................................................................................... 228 Inhibitor Tracking .................................................................................................................................................................... 240 Leak ............................................................................................................................................................................................ 245 LINE ........................................................................................................................................................................................... 385 Near-Wellbore .......................................................................................................................................................................... 251 Pig ............................................................................................................................................................................................... 262 Pump ........................................................................................................................................................................................ 300 OUTPUTDATA .............................................................................................................................................................

Separator ................................................................................................................................................................................. 310 SingleComponent ................................................................................................................................................................... 329 Slug Tracking .......................................................................................................................................................................... 335 SlugTuning ................................................................................................................................................................................ 342 Source ........................................................................................................................................................................................ 349 Steady state processor .......................................................................................................................................................... 354 SteamWater-HC ...................................................................................................................................................................... 361 Thermal computations ........................................................................................................................................................... 390 Transmitter ............................................................................................................................................................................... 210 Tuning ........................................................................................................................................................................................ 399 Valve ........................................................................................................................................................................................... 321 Water Module ........................................................................................................................................................................... 406 Wax ........................................................................................................................................................................................... 415 Well ............................................................................................................................................................................................ 426

577 Boundary Output Variables .................................................................................................................................................. 601 Branch Output Variables ....................................................................................................................................................... 605 Bundle Output Variables ....................................................................................................................................................... 608 Check valve Output Variables .............................................................................................................................................. 609 Compositional Output Variables ......................................................................................................................................... 610 Compositional slugtracking Output Variables ................................................................................................................. 614 Compressor Output Variables ............................................................................................................................................. 616 Controller Output Variables .................................................................................................................................................. 617 Conversion Factors ................................................................................................................................................................ 618 Corrosion Output Variables .................................................................................................................................................. 626 Drilling Output Variables ....................................................................................................................................................... 627 Global Output Variables ........................................................................................................................................................ 629 Heat exchanger Output Variables ....................................................................................................................................... 630 Hydrate kinetics Output Variables ...................................................................................................................................... 631 Inhibitor Output Variables ..................................................................................................................................................... 633 Leak Output Variables ........................................................................................................................................................... 634 Node Output Variables .......................................................................................................................................................... 636 Pig Output Variables .............................................................................................................................................................. 637 Pump Output Variables ......................................................................................................................................................... 639 Separator Output Variables .................................................................................................................................................. 640 Slugtracking Output Variables ............................................................................................................................................. 643 Source Output Variables ....................................................................................................................................................... 648 SteamAndSingle Output Variables ..................................................................................................................................... 650 TracerTracking Output Variables ........................................................................................................................................ 651 Valve Output Variables .......................................................................................................................................................... 653 Volume Output Variables ...................................................................................................................................................... 654 Waxdeposition Output Variables ......................................................................................................................................... 657 Well Output Variables ............................................................................................................................................................ 659 Data Files ......................................................................................................................................................................................... 660 Compressor data file .............................................................................................................................................................. 661 Wax table file ........................................................................................................................................................................... 663 Hydrate curve definition file .................................................................................................................................................. 665 OLGA Rocx ............................................................................................................................................................................... 666 Fluid Properties File ............................................................................................................................................................... 667 Feed file for compositional tracking ..................................................................................................................................... 668 PVT properties for non-existing phase ................................................................................................................................ 669 Keyword based .................................................................................................................................................................... 670 Output Variables ...........................................................................................................................................................................

671 Table Structure ............................................................................................................................................................. 672 Keyword PVTTABLE ..................................................................................................................................................... 673 Examples ..................................................................................................................................................................... 678 Standard conditions ...................................................................................................................................................... 684 Standard format .................................................................................................................................................................. 685 Complex fluid module .................................................................................................................................................... 692 Pump Data Files ..................................................................................................................................................................... 694 Pump Data Table for Centrifugal Pumps ............................................................................................................................. 695 Pump Data Table for Displacement Pumps ........................................................................................................................ 698 Restrictions and Limitations ..................................................................................................................................................... 700 Restrictions and Limitations ................................................................................................................................................. 700 Memory consumption ............................................................................................................................................................ 701 Fluid properties ........................................................................................................................................................................ 702 Input/Output Limitations ........................................................................................................................................................ 703 Standard Conditions in OLGA ............................................................................................................................................. 704 Flow Model Limitations .......................................................................................................................................................... 705 Important Numerical Recommendations .......................................................................................................................... 706 Sample cases ................................................................................................................................................................................. 708 Sample cases .......................................................................................................................................................................... 708 2nd-order scheme ................................................................................................................................................................... 709 Advanced Well ......................................................................................................................................................................... 711 Blackoil ...................................................................................................................................................................................... 712 Centrifugal Pump .................................................................................................................................................................... 714 CO2 - Single Component ...................................................................................................................................................... 716 Compositional Tracking ......................................................................................................................................................... 717 Corrosion .................................................................................................................................................................................. 719 Displacement Pump ............................................................................................................................................................... 721 Drilling Fluid ............................................................................................................................................................................. 723 Fluid bundle .............................................................................................................................................................................. 725 H2O - Single Component ...................................................................................................................................................... 727 H2O - Steam/Water-HC ........................................................................................................................................................ 728 Hydrate Kinetics ...................................................................................................................................................................... 729 Hydrodynamic slugging ......................................................................................................................................................... 731 MEG Tracking .......................................................................................................................................................................... 733 Network ..................................................................................................................................................................................... 734 PID Controller .......................................................................................................................................................................... 736 Pigging ....................................................................................................................................................................................... 738 Process Equipment ................................................................................................................................................................ 740 Pump Battery ........................................................................................................................................................................... 742 Separator .................................................................................................................................................................................. 744 Simplified Pump ...................................................................................................................................................................... 745 Solid bundle .............................................................................................................................................................................. 747 Source, Leak and Choke ....................................................................................................................................................... 749 Start-up slug ............................................................................................................................................................................. 751 Tracer Tracking ........................................................................................................................................................................ 753 Wateroptions ............................................................................................................................................................................ 755 Waxdeposition ......................................................................................................................................................................... 756 Troubleshooting ............................................................................................................................................................................. 758 Geometry Editor problems ................................................................................................................................................... 759 GUI uses a lot of Memory ..................................................................................................................................................... 760 Inp files assosciated with GUI ............................................................................................................................................. 761 The syntax of the keyword ..............................................................................................................................................

License issues ......................................................................................................................................................................... 762 Mouse pointer changed to an unrecognize symbol ........................................................................................................ 763 Plots-no units ........................................................................................................................................................................... 764 Problems showing the graphics .......................................................................................................................................... 765 Restore layout .......................................................................................................................................................................... 766 Simualtion state runnable ..................................................................................................................................................... 767 Simulation not runnable ........................................................................................................................................................ 768 Update Graphical driver ........................................................................................................................................................ 769

OLGA 7

Welcome to OLGA 6 User Manual This is the OLGA 6 User Manual. The User Manual includes both information about the OLGA 6 engine and the graphical user interface (GUI). The complete program documentation includes - Release Document for OLGA 6.2 - OLGA 6 User Manual (this document) - OLGA 6 GUI User Manual - OLGA 6 Conversion Guide - Well GUI User Manual - Tutorial - Installation Guide All documents listed above are available from the Start Menu (Start - All Programs - SPT Group - OLGA 6.2 - Documentation). The OLGA 6 User Manual, OLGA 6 GUI User Manual, OLGA 6 Conversion Guide, Wells GUI User Manual and the Tutorial are also available from the Help menu in the GUI). User Manuals for other tools included with the OLGA 6 installation are available from the Help menus in the tools.

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OLGA 7

Release Information Please refer to the Release Document for detailed release information for OLGA 6.2. The Release Document describes changes in OLGA 6.2 relative to OLGA 5 and OLGA 6.1, and should be read by all users of the program. The complete program documentation consists of the OLGA User Manual, OLGA 6 GUI User Manual, OLGA 6 Conversion Guide, Wells GUI User Manual, Tutorial, Installation Guide, and the Release Document. The program is available on PC’s with Microsoft Windows operating systems (Windows XP, Windows Vista and Windows 7). Several versions of OLGA may be installed in parallel. Note that you may also run several versions of the engine from one version of the GUI - please refer to the Installation Guide to learn how to configure the GUI for several engines. The support center provides useful information about frequently asked questions and known issues. The support center is available from the SPT Group Support Center Please contact SPT Group if problems or missing functionality are encountered when using OLGA or any of the related tools included in the OLGA software package. E-mail: olgasupport@sptgroup.com Telephone: +47 6484 4550 Fax: +47 6484 4500 Address: SPT Group AS, P.O. Box 113, N-2027 Kjeller

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OLGA 7

Introduction OLGA is the industry standard tool for transient simulation of multiphase petroleum production. The purpose of this manual is to assist the user in the preparation of the input data for an OLGA simulation. In this manual you can find a general introduction to OLGA an overview of the required and the optional input to OLGA. It also describes in some detail different simulation options such as wax deposition, corrosion etc. a detailed description of all input data and the required fluid property tables a description of the output The sample cases presented with the installation of OLGA are intended to illustrate important program options and typical simulation output. A description of the sample cases are also included in this manual. OLGA comes in a basic version with a number of optional modules;FEMTherm, Multiphase Pumps, Corrosion, Wells, Slug Tracking, Wax Deposition, Inhibitor Tracking, Compositional Tracking, Single Component Tuning, Hydrate Kinetics and Complex Fluid. In addition there is a number of additional programs like the OLGA GUI and the FEMThermViewer for preparation of input data and visualisation of results. These optional modules and additional programs are available to the user according to the user's licensing agreement with SPT Group. See also: Background OLGA as a strategic tool OLGA Model Basics How to use in general Graphical User Interface Simulation model Input files Applications Threaded Execution

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Background OLGA 6 is the latest version in a continuous development which was started by the Institute for Energy Research (IFE) in 1980. The oil industry started using OLGA in 1984 when Statoil had supported its development for 3 years. Data from the large scale flow loop at SINTEF, and later from the medium scale loop at IFE, were essential for the development of the multiphase flow correlations and also for the validation of OLGA. Oil companies have since then supported the development and provided field data to help manage uncertainty, predominantly within the OLGA Verification and Improvement Project (OVIP). OLGA has been commercially available since the SPT Group started marketing it in 1990. OLGA is used for networks of wells, flowlines and pipelines and process equipment, covering the production system from bottom hole into the production system. OLGA comes with a steady state preprocessor included which is intended for calculating initial values to the transient simulations, but which also is useful for traditional steady state parameter variations. However, the transient capabilities of OLGA dramatically increase the range of applicability compared with steady state simulators.

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OLGA as a strategic tool

OLGA is applied for engineering throughout field life from conceptual studies to support of operations. However the application has been extended to be an integral part of operator training simulators, used for making operating procedures, training of operators and check out of control systems. Further, OLGA is frequently embedded in on-line systems for monitoring of pipeline conditions and forecasting and planning of operations. OLGA can dynamically interface with all major dynamic process simulators, such as Hysys, DynSim, UniSim, D-SPICE, INDISS and ASSETT. This allows for making integrated engineering simulators and operator training simulators studying the process from bottom hole all the way through the process facility in a single high fidelity model. Note that the OLGA flow correlation has been implemented in all major steady state simulators providing consistent results moving between different simulators.

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OLGA Model Basics OLGA 6 is a three-fluid model, i.e. separate continuity equations are applied for the gas, for the oil (or condensate) and water liquids and also for oil (or condensate) and water droplets. These may be coupled through interfacial mass transfer. Three momentum equations are used; one for each of the continuous liquid phases (oil/condensate and water) and one for the combination of gas with liquid droplets. The velocity of any liquid droplets entrained in the gas phase is given by a slip relation. One mixture energy equation is applied; assuming that all phases are at the same temperature. This yields seven conservation equations to be solved: three for mass, three for momentum, and one for energy. Two basic flow regime classes are recognised ; distributed and separated flow. The former comprises bubble and slug flow [1], the latter stratified and annular mist flow.

Figure A Flow patterns in horizontal flow Transition between the regime classes is determined by the program on the basis of a minimum slip concept combined with additional criteria. To close the system of equations, fluid properties, boundary and initial conditions are required. The equations are linearised and a sequential solution scheme is applied. The pressure and temperature calculations are de-coupled i.e. current pressure is based on previous temperature. The semi-implicit time integration implemented allows for relatively long time steps, orders of magnitudes longer than those of an explicit method (which would be limited by the Courant Friedrich Levy criterion based on the speed of sound). The numerical error is corrected for over a period of time. The error manifests as an error in local fluid volume (as compared to the relevant pipe volume). [1] In standard OLGA a slug unit model is applied which calculates average liquid hold-up and pressure, but which does not give any details about individual slugs. To follow individual slugs through the system the slug tracking module must be applied.

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How to use in general Numerics OLGA applies one global time-step for the time integration and there is an automatic time-step control based on the limitation that a fluid particle should not spend less than one time-step on passing through any numerical section length of a pipe (the Courant Friedrich Levy (CFL) criterion based on the fluid velocity). The user controls the time integration by specifying simulation period in time, time-step parameters such as initial time-step and maximum and minimum time-step values. The latter overrules the automatic control. There is also an option for using the second-derivative of pressure as a time step controlling criterion. Some functions in OLGA, e.g. slug-tracking, take control of the time-stepping in order to ensure a successful simulation. The spatial integration is performed on a user-defined grid. There are tools available to facilitate the gridding. There are no formal limitations on the numerical section lengths, but it is considered good practice to keep all neighbour section length ratios between 0.5 and 2: 0.5 ≤ Dxi/Dxi+1 ≤ 2 for all i Additionally it is recommended that each pipe should have at least two sections. Due to the numerical solution scheme, OLGA is particularly well suited for simulating rather slow mass flow transients. This is important for the simulation of long transport lines and thermal calculations, where typical simulation times in the range of hours to several days, and sometimes years, will require long time steps, to obtain efficient use of the computer. OLGA is also being used successfully for fast transients such as water hammer and pressure surges in general. Certain precautions w.r.t. spatial grid and time-stepping may be needed in order to keep the numerical error within acceptable limits. Since OLGA not accounts for pipe elasticity the calculated pressure peaks should be conservative. The de-coupling of temperature from pressure would normally give a pressure wave propagation velocity in gas which would be about 15% too low. However, in OLGA 6 a quasi implicit correction of temperature reduces this error considerably. Critical flow calculations are performed in the OLGA valve model, only. A valve with cross section equal to the pipe should then be positioned on e.g. a pipe outlet if choked flow is expected.

Temperature OLGA is particularly well suited for sophisticated thermal simulations. Since OLGA is one-dimensional (calculates along the pipe axis) any 2 and 3-dimensional effects must be modelled explicitly. The basic OLGA thermal model calculates the inner wall heat transfer coefficient. The built-in correlations are valid for natural- and forced convection and also for the transition between them. Flow pattern is accounted for. The user may specify pipe walls with material properties, including emissivity to account for radiation, and must give the ambient properties, i.e. temperature and heat transfer coefficient. Based on this the fluid temperature is calculated. Special features like Annulus, Solid- and Fluid bundles make it possible to simulate very complex structures of pipe-in-pipe and parallel pipes within structures of various solid materials. Taking into account that temperature is calculated along the pipes one obtains a combination of two-dimensional convective heat transfer within 3-dimensional heat conducting structures. Solid bundle cross section of 4 vertical tubes within rock – neighbour tubes are 2.5 m apart. The black "line" is a 7 / 769

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neighbour tubes are 2.5 m apart. The black "line" is a temperature iso-line. One clearly sees how the area between the tubes is subject to inter-tube heating.

Initial Conditions The requirement for initial conditions is a fundamental difference between a transient and a steady state model, e.g. the results of a steady state calculation may serve as the initial condition (at t=0 ) for a transient simulation. With OLGA the user decides, and later specifies in the input, whether the simulation is to start from a user defined condition (for instance a specific shut-in condition), or from a steady state multiphase flowing situation calculated by the program. The steady state pre-processor in OLGA can be used to provide good initial values for most production situation. In addition, the user may specify the initial condition in detail, for example for a shut-in system, by defining the initial values for pressures, temperatures, mass flow and gas fractions. Tools for interpolation are available, for filling in the initial values in all numerical sections of the system. Finally, the restart capability may be used to start a simulation from conditions saved during a previous simulation.

Boundary Conditions The boundary conditions define the interface between the simulated system and its surroundings and they are crucial to the relevance to any type of simulations. For a network of pipelines and wells there are several options available, but basically flow rate or pressure, in addition to temperature and gasliquid ratio must be specified at each flow path inlet and outlet boundary (at least one pressure must be given). The boundary conditions, e.g. a pressure, can be given as time series to model a certain transient situation.

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Moreover, the ambient temperature along the flow paths and ambient heat transfer coefficient (film heat transfer resistance) must be specified and OLGA provides a number of options for this, including water and air velocity profiles and seasonal variations of temperature. Inflow from reservoirs to well-bores define the most important boundary in a petroleum production network. In addition to various well-inflow correlations and options OLGA comes with an implicit coupling facility to the OLGA Rocx module which is a complete 3-D, 3-phase reservoir simulator. Separators, pumps, compressors and valves, all with controllers, can be modelled to improve the relevance of the outlet boundaries.

Fluid properties The necessary fluid properties (gas/liquid mass fraction, densities, viscosities, enthalpies etc.) are normally assumed to be functions of temperature and pressure only, and have to be supplied by the user as tables in a special input file. Thus, the total composition of the multiphase mixture is assumed to be constant both in time and space for a given part of the network. The user may specify different fluid property tables for each flow path, but has to ensure that a realistic fluid composition has been used to make a table for a flow path with a fluid mixture coming from two or more pipeline branches merging upstream.

It is also possible to perform simulations using Compositional Tracking, where the basic information on the chemical components is provided in a separate text file and then OLGA calculates the fluid properties internally with PVT routines provided by Calsep A/S. This means that the total composition may vary both in time and space, and that no special considerations are needed for the downstream system. Special models are also available for tracking hydrate inhibitors like MEG and methanol. The numerical solution of the OLGA model is generally able to handle multi component fluid systems but will normally have problems with single component systems or systems with a very narrow phase envelope.

Rheology The standard OLGA flow models assume a Newtonian rheology (viscosities are well defined fluid characteristics). Dispersions and non-Newtonian behavior are quite common in petroleum production and OLGA provides several semi-empirical models to account for more complex rheologies. In some cases the model takes care of the rheology with a minimum of user interference (e.g. for oil-water dispersions and also for waxy oils). For other systems the user needs to specify the various parameters for such fluids to describe e.g. Bingham or power law non-Newtonian behavior.

Network In OLGA the network comprises flow paths coupled with nodes which have a volume. General networks with closed loops can then be modelled, see below. The flow paths have a user defined direction but the flow is invariant to direction as such and any fluid phase may flow co-currently or counter-currently with respect to the pre-defined direction at any time and position. 9 / 769

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Pipe-bends are not accounted for as such (except for differences in static head). The user may apply pressure loss coefficients at boundaries between numerical sections. Equipment is positioned on the flow path – usually on a pipe-boundary. However, the separator in OLGA is a network component similar to a node. Controllers are specified as integral parts of the simulation model and they have their own network formalism.

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Threaded Execution Pipe sections belonging to the same branch may be updated in parallel. Suppose a branch has 100 sections, and that two threads are available to the OLGA engine: Section 1 and section 51 will be updated simultaneously, then section 2 and section 52 are updated, and so on. Depending on the computer hardware, this method can drastically reduce the time OLGA takes to advance one time-step. Normally, you do not need to change the default settings of neither OLGA nor your operating system. Parallel updating of segments is usually activated in the OLGA engine if your PC supports it.

Controlling the degree of parallelism The Windows operating system decides how many threads will be used. If your PC is equipped with a quad-core CPU, typically four threads will be simultaneously running to update four sections in parallel. Is your CPU a single-core Intel Xeon processor with "hyper-threading" (HT), probably two engine threads will be used. It is possible to overrule the choice of the operating system by setting the environment variable OMP_NUM_THREADS; use Windows' Control Panel to do this. However, the preferred way to change the degree of parallelisation is do so from the OLGA menu system. Setting the value here takes precedence over the OMP_NUM_THREADS environment variable. A situation where you might want to reduce the number of threads, arise if you execute parametric studies. Given that your license permits, it would be preferable to spend the CPU's cores on simultaneous simulations, rather than on speeding up each simulation in the study. Another situation could be when you don't want OLGA to consume all your computing power, e.g., if you want to write a report while OLGA is working. Most large cases will benefit from the parallelisation. Still, please note that some of your PC's cache memory will be used for forking and joining the threads, and doing the necessary book-keeping. As a consequence, special cases will run faster with a single engine thread.

Parallel speed-up The parallelisation encompasses heat calculations in section walls, updating fluid properties and flashing, and, most importantly, calls to the flow model which decides friction factors, liquid holdup and the flow regime. If the flow model calculations dominate the overall simulation, the utilization of the CPUs is most efficient.

Monitoring the OLGA process The Task Manager can be used to check how OLGA loads your CPU. When the number of engine threads equals the number of cores (or equals two on a single core HT-CPU) you should see the CPU usage being clearly over fifty percent when OLGA is simulating. In the Task Manager's list of processes it is possible to view the number of threads for each process. With 1 engine thread, it uses a total of 5 threads in batch mode, and 8 threads while running under control of the GUI. With 2 engine threads allowed, the task manager would display 6 threads for a batch run and 9 threads for a GUI run; with 4 engine threads the total number of threads would be 8 and 11, respectively.

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Applications When the resources become more scarce and complicated to get to careful design and optimisation of the entire production system is vital for investments and revenues. The dimensions and layout of wells and pipelines must be optimised for variable operational windows defined by changing reservoir properties and limitations given by environment and processing facilities. OLGA is being used for design and engineering, mapping of operational limits and to establish operational procedures. OLGA is also used for safety analysis to assess the consequences of equipment malfunctions and operational failures. REFERENCES contains a list of papers describing the OLGA model and its applications.

Design and Engineering OLGA is a powerful instrument for the design engineer when considering different concepts for hydrocarbon production and transport - whether it is new developments or modifications of existing installations. OLGA should be used in the various design phases i.e. Conceptual, FEED [2] and detailed design and the following issues should be addressed: • Design Sizes of tubing and pipes Insulation and coverage Inhibitors for hydrate / wax Liquid inventory management / pigging Slug mitigation Processing capacity (Integrated simulation) • Focus on maximizing the production window during field life Initial Mid-life Tail • Accuracy / Uncertainty management Input accuracy Parameter sensitivity • Risk and Safety Normally the engineering challenge becomes more severe when accounting for tail-end production with reduced pressure, increasing water-cut and gas-oil ratio. This increase the slugging potential while fluid temperature reduces which in turn increase the need for inhibitors and the operational window is generally reduced.

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Operation OLGA should be used to establish Operational procedures and limitations Emergency procedures Contingency plans OLGA is also a very useful tool for operator training Training in flow assurance in general Practicing operational procedures Initial start up preparations When systems become more complex and critical e.g. with long and deep Flow lines/risers, start-up situations need to be forecasted on a short-term basis and OLGA is regularly being used for assistance at start-up. Some typical operational events suitable for OLGA simulations are discussed below.

Pipeline shut-down If the flow in a pipeline for some reason has to be shut down, different procedures may be investigated. The dynamics during the shut-down can be studied as well as the final conditions in the pipe. The liquid content is of interest as well as the temperature evolution in the fluid at rest since the walls may cool the fluid below a critical temperature where hydrates may start to form. Pipeline blow-down One of the primary strategies for hydrate prevention in case of a pipeline shut-down is to blow down. The primary aim to reduce the pipeline pressure below the pressure where hydrates can form. Main effect that can be studied are the liquid and gas rates during the blow-down, the time required and the final pressure. Pipeline start-up The initial conditions of a pipeline to be started is either specified by the user or defined by a restart from a shut-down case. The start-up simulation can determine the evolution of any accumulated liquid slugs in the system. A start-up procedure is often sought whereby any terrain slugging is minimised or altogether avoided. The slug tracking module is very useful in this regard. In a network case a strategy for the start-up procedure of several merging flow lines could be particularly important.

Change in production Sometimes the production level or type of fluid will change during the lifetime of a reservoir. The modification of the liquid properties due to the presence of water, is one of the important effects accounted for in OLGA. A controlled change in the production rate or an injection of another fluid are important cases to be simulated. Of particular interest is the dynamics of network interactions e.g. how the transport line operation is affected by flow rate changes in one of several merging flow lines.

Process equipment Process equipment can be used to regulate or control the varying flow conditions in a multi-phase flow line. This is of special interest in cases where slugging is to be avoided. The process equipment simulated in OLGA includes critical- and sub-critical chokes with fixed or controlled openings, check-valves, compressors with speed and anti- surge controllers, separators, heat 13 / 769

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exchangers, pumps and mass sources and sinks.

Pipeline pigging OLGA can simulate the pigging of a pipeline. A user specified pig may be inserted in the pipeline in OLGA at any time and place. Any liquid slugs that are created by the pig along the pipeline can be followed in time. Of special interest is the determination of the size and velocity of a liquid slug leaving the system ahead of a pig that has been inserted into a shut-down flow line. Hydrate control Hydrate prevention and control are important for flow assurance. Passive and active control strategies can be investigated: Passive control is mainly achieved by proper insulation while there are several options for active control which can be simulated with OLGA: Bundles, electrical heating, inhibition by additives like MEG. Wax deposition In many production systems wax would tend to deposit on the pipe wall during production. The wax deposition depends on the fluid composition and temperature. OLGA can model wax deposition as function of time and location along the pipeline. Tuning Even if the OLGA models are sophisticated models made for conceptual studies and engineering will be based on input and assumptions which are not 100% relevant for operations. Therefore OLGA is equipped with a tuning module which can be used on-line and off-line to modify input parameters and also critical model parameters to match field data. Wells - Flow stability e.g. permanent or temporary slugging, rate changes - Artificial lift for production optimization - Shut-in/start-up - water cut limit for natural flow - Cross flow between layers under static conditions - WAG injection - Horizontal wells / Smart wells - Well Clean-up and Kick-off - Well Testing - Well control and Work-over Solutions

Safety Analysis Safety analysis is an important field of application of OLGA. OLGA is capable of describing propagation of pressure fronts. For such cases the time step can be limited by the velocity of sound across the shortest pipe section. OLGA may be useful for safety analysis in the design phase of a pipeline project, such as the positioning of valves, regulation equipment, measuring devices, etc. Critical ranges in pipe monitoring equipment may be estimated and emergency procedures investigated. Consequence analysis of possible accidents is another interesting application. The state of the pipeline after a specified pipe rupture or after a failure in any process equipment can be determined using OLGA. Simulations with OLGA can also be of help when defining strategies for accident management, e.g. well killing by fluid injection. Finally it should be mentioned that the OLGA model is well suited for use with simulators designed for particular pipelines and process systems. Apart from safety analysis and monitoring, such simulators are powerful instruments in the training of operators. 14 / 769

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powerful instruments in the training of operators. [2] Front End Engineering and Design

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Input files The OLGA simulator uses text files for describing the simulation model:

.opi; generated and used by the OLGA GUI .inp; input format used by OLGA 5 and earlier versions .key; input format used by OLGA The .key format has been introduced as the new input file format for the OLGA engine. The OLGA GUI will automatically generate files in this format (with the extension .genkey). The .key format reflects the network model described in the simulation model and should be the preferred format. In addition to the simulation file, OLGA handles input in several other formats as described in Data files.

Simulation description The input keywords are organised in Logical sections, with Case level at the top, followed by the various network components and then the connections at the end.

Case level Case level is defined as the global keywords specified outside of the network components and connections. Case level keywords can be found in the CaseDefinition, Library, FA-models and Output sections. The following keywords must or can be defined at Case level: CaseDefinition; CASE, FILES, INTEGRATION, OPTIONS, DTCONTROL, RESTART Library; MATERIAL, WALL, SHAPE, TABLE, DRILLINGFLUID, HYDRATECURVE Compositional; COMPOPTIONS, FEED, BLACKOILOPTIONS, BLACKOILCOMPONENT, BLACKOILFEED, SINGLEOPTIONS FA-models; CORROSION, FLUID, WATEROPTIONS, SLUGTRACKING, TUNING, SLUGTUNING Output; OUTPUT, TREND, PROFILE, PLOT, OUTPUTDATA, TRENDDATA, PROFILEDATA Drilling; TOOLJOINT CASE PROJECT="OLGA Manual", TITLE="Example case", AUTHOR="SPT Group AS" INTEGRATION STARTTIME=0, ENDTIME=7200, DTSTART=0.1, MINDT=0.1, MAXDT=5 FILES PVTFILE=fluid.tab MATERIAL LABEL=MAT-1, DENSITY=0.785E+04, CAPACITY=0.5E+03, CONDUCTIVITY=0.5E+02 WALL LABEL=WALL-1, THICKNESS=(0.9000E-02, 0.2E-01), MATERIAL=(MAT-1, MAT-1)

Network components The network components are the major building blocks in the simulation network. Each network component is enclosed within start (NETWORKCOMPONENT) and end (ENDNETWORKCOMPONENT) tags as shown below. Each data group belonging to this network component will be written within these tags. NETWORKCOMPONENT TYPE=FlowPath, TAG=FP_BRAN ... ENDNETWORKCOMPONENT

The following network component keywords can be specified (see links for further details on each component):

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component): FlowComponent;FLOWPATH, NODE ProcessEquipment;PHASESPLITNODE, SEPARATOR Controller;CONTROLLER ThermalComponent;ANNULUS, FLUIDBUNDLE, SOLIDBUNDLE FLOWPATH Piping The flowpath can be divided into several pipes, which can have an inclination varying from the other pipes in the flowpath. Each pipe can again be divided into sections as described above. All sections defined within the same pipe must have the same diameter and inclination. Each pipe in the system can also have a pipe wall consisting of layers of different materials. The following keywords are used for Piping: BRANCH; Defines geometry and fluid labels. GEOMETRY; Defines starting point for flowpath. PIPE; Specifies end point or length and elevation of a pipe. Further discretization, diameter, inner surface roughness, and wall name are specified. POSITION; Defines a named position for reference in other keywords. BRANCH LABEL=BRAN-1, GEOMETRY=GEOM-1, FLUID=1 GEOMETRY LABEL=GEOM-1 PIPE LABEL=PIPE-1, DIAMETER=0.12, ROUGHNESS=0.28E-04, NSEGMENT=4, LENGTH=0.4E+03, ELEVATION=0, WALL=WALL-1

Boundary&Initialconditions For the solution of the flow equations, all relevant boundary conditions must be specified for all points in the system where mass flow into or out of the system. Initial conditions at start up and parameters used for calculating heat transfer must also be specified. The following keywords are used for Boundary & Initial conditions: HEATTRANSFER; Definition of the heat transfer parameters. INITIALCONDITION; Defines initial values for flow, pressure, temperature and holdup. INITIALCONDITIONS is not required when a steady state calculation is performed. NEARWELLSOURCE; Defines a near-wellbore source used together with OLGA Rocx. SOURCE; Defines a mass source with name, position, and data necessary for calculating the mass flow into or out of the system. The source flow can be given by a time series or determined by a controller. WELL; Defines a well with name, position and flow characteristics. HEATTRANSFER PIPE=ALL, HAMBIENT=6.5, TAMBIENT=6, HMININNERWALL=0.5E+03 SOURCE LABEL=SOUR-1-1, PIPE=1, SECTION=1, TIME=0, TEMPERATURE=62, GASFRACTION=-1, TOTALWATERFRACTION=-1, PRESSURE=70 bara, DIAMETER=0.12, SOURCETYPE=PRESSUREDRIVEN

Process Equipment In order to obtain a realistic simulation of a pipeline system, it is normally required to include some process equipment in the simulation. OLGA supports a broad range of different types of process equipment, as shown below. It should be noted that the steady state preprocessor ignores the process equipment marked with (*) in the list below. 17 / 769

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the list below. The following keywords are used for Process equipment: CHECKVALVE (*); Defines name, position and allowed flow direction for a check valve. COMPRESSOR (*); Defines name, position and operating characteristics of a compressor. HEATEXCHANGER; Defines name, position and characteristic data for a heat exchanger. LOSS; Defines name, position and values for local pressure loss coefficients. LEAK; Defines the position of a leak in the system with leak area and back pressure. The leak can also be connected to another flowpath to simulate gas lift etc. PUMP (*); Defines name, type and characteristic data for a pump. TRANSMITTER (*); Defines a transmitter position. VALVE; Defines name, position and characteristic data for a choke or a valve. VALVE LABEL=CHOKE-1-1, PIPE=PIPE-1, SECTIONBOUNDARY=4, DIAMETER=0.12, CD=0.7, TIME=0, OPENING=1.0

Output OLGA provides several output methods for plotting simulation results. The following keywords are used for Output: OUTPUT(DATA); Defines variable names, position and time for printed output. PLOT; Defines variable names and time intervals for writing of data to the OLGA viewer file. PROFILE(DATA); Defines variable names and time intervals for writing of data to the profile plot file. TREND(DATA); Defines variable names and time intervals for writing of data to the trend plot file. TRENDDATA PIPE=1, SECTION=1, VARIABLE=(PT bara, TM, HOLHL, HOLWT) PROFILEDATA VARIABLE=(GT, GG, GL)

NODE Boundary&Initialconditions PARAMETERS; A collection keyword for all node keys. This keyword is hidden in the GUI. Output OLGA provides several output methods for plotting simulation results. The following keywords are used for Output: OUTPUTDATA; Defines variable names, position and time for printed output. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. NETWORKCOMPONENT TYPE=Node, TAG=NODE_INLET PARAMETERS LABEL=INLET, TYPE=CLOSED ENDNETWORKCOMPONENT NETWORKCOMPONENT TYPE=Node, TAG=NODE_OUTLET PARAMETERS LABEL=OUTLET, GASFRACTION=-1, PRESSURE=50 bara, TEMPERATURE=32, TIME=0, TOTALWATERFRACTION=-1, TYPE=PRESSURE, FLUID=1 ENDNETWORKCOMPONENT

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Boundary&Initialconditions PARAMETERS; A collection keyword for all phase split node keys. This keyword is hidden in the GUI. Output OLGA provides several output methods for plotting simulation results. The following keywords are used for Output: OUTPUTDATA; Defines variable names, position and time for printed output. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. SEPARATOR Boundary&Initialconditions PARAMETERS; A collection keyword for all separator keys. This keyword is hidden in the GUI. Output OLGA provides several output methods for plotting simulation results. The following keywords are used for Output: OUTPUTDATA; Defines variable names, position and time for printed output. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. CONTROLLER Boundary&Initialconditions PARAMETERS; A collection keyword for all controller keys. This keyword is hidden in the GUI. Output OLGA provides several output methods for plotting simulation results. The following keywords are used for Output: OUTPUTDATA; Defines variable names, position and time for printed output. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. NETWORKCOMPONENT TYPE=ManualController, TAG=SetPoint-1 PARAMETERS SETPOINT=(2:0.1,2:0.2,0.3), TIME=(0,2000,2010,4000,4010) s, STROKETIME=0.0, MAXCHANGE=1.0 ENDNETWORKCOMPONENT

ANNULUS Initialconditions PARAMETERS; A collection keyword for all annulus keys. This keyword is hidden in the GUI. AmbientConditions AMBIENTDATA; A collection keyword for specifying the Annulus ambient conditions. AnnulusComponents COMPONENT; A component to place within the annulus definition. 19 / 769

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Output PROFILEDATA; Defines variable names and time intervals for writing of data to the profile plot file. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. FLUIDBUNDLE Initialconditions PARAMETERS; A collection keyword for all fluid bundle keys. This keyword is hidden in the GUI. AmbientConditions AMBIENTDATA; A collection keyword for specifying the fluid bundle ambient conditions. BundleComponents COMPONENT; A component to place within the fluid bundle definition. Output PROFILEDATA; Defines variable names and time intervals for writing of data to the profile plot file. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file. SOLIDBUNDLE Initialconditions PARAMETERS; A collection keyword for all solid bundle keys. This keyword is hidden in the GUI. AmbientConditions AMBIENTDATA; A collection keyword for specifying the solid bundle ambient conditions. BundleComponents COMPONENT; A component to place within the solid bundle definition. Output PROFILEDATA; Defines variable names and time intervals for writing of data to the profile plot file. TRENDDATA; Defines variable names and time intervals for writing of data to the trend plot file.

Connections The CONNECTION keyword is used to couple network components, such as a node and a flowpath. Each flowpath has an inlet and an outlet terminal that can be connected to a node terminal. Boundary nodes (i.e. CLOSED, MASSFLOW, PRESSURE) has one terminal, while internal nodes has an arbitrary number of terminals where flowpaths can be connected to. CONNECTION TERMINALS = (FP_BRAN INLET, NODE_INLET FLOWTERM_1) CONNECTION TERMINALS = (FP_BRAN OUTLET, NODE_OUTLET FLOWTERM_1)

Separator and PhaseSplitNode has special handling of terminals. The CONNECTION keyword is also used for coupling signal components. CONNECTION TERMINALS = (FP_BRAN SOUR-1-1@INPSIG, SETPOINT-1 OUTSIG_1)

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Example file The keyword examples shown above can be combined to an OLGA .key file. CASE PROJECT="OLGA Manual", TITLE="Example case", AUTHOR="SPT Group AS" INTEGRATION STARTTIME=0, ENDTIME=7200, DTSTART=0.1, MINDT=0.1, MAXDT=5 FILES PVTFILE=fluid.tab MATERIAL LABEL=MAT-1, DENSITY=0.785E+04, CAPACITY=0.5E+03, CONDUCTIVITY=0.5E+02 WALL LABEL=WALL-1, THICKNESS=(0.9000E-02, 0.2E-01), MATERIAL=(MAT-1, MAT-1) NETWORKCOMPONENT TYPE=FlowPath, TAG=FP_BRAN BRANCH LABEL=BRAN-1, GEOMETRY=GEOM-1, FLUID=1 GEOMETRY LABEL=GEOM-1 PIPE LABEL=PIPE-1, DIAMETER=0.12, ROUGHNESS=0.28E-04, NSEGMENT=4, LENGTH=0.4E+03, ELEVATION=0, WALL=WALL-1 HEATTRANSFER PIPE=ALL, HAMBIENT=6.5, TAMBIENT=6, HMININNERWALL=0.5E+03 SOURCE LABEL=SOUR-1-1, PIPE=1, SECTION=1, TIME=0, TEMPERATURE=62, GASFRACTION=-1, TOTALWATERFRACTION=-1, PRESSURE=70 bara, DIAMETER=0.12, SOURCETYPE=PRESSUREDRIVEN VALVE LABEL=CHOKE-1-1, PIPE=PIPE-1, SECTIONBOUNDARY=4, DIAMETER=0.12, CD=0.7, TIME=0, OPENING=1.0 TRENDDATA PIPE=1, SECTION=1, VARIABLE=(PT bara, TM, HOLHL, HOLWT) PROFILEDATA VARIABLE=(GT, GG, GL) ENDNETWORKCOMPONENT NETWORKCOMPONENT TYPE=Node, TAG=NODE_INLET PARAMETERS LABEL=INLET, TYPE=CLOSED ENDNETWORKCOMPONENT NETWORKCOMPONENT TYPE=Node, TAG=NODE_OUTLET PARAMETERS LABEL=OUTLET, GASFRACTION=-1, PRESSURE=50 bara, TEMPERATURE=32, TIME=0, TOTALWATERFRACTION=-1, TYPE=PRESSURE, FLUID=1 ENDNETWORKCOMPONENT NETWORKCOMPONENT TYPE=ManualController, TAG=SetPoint-1 PARAMETERS SETPOINT=(2:0.1,2:0.2,0.3), TIME=(0,2000,2010,4000,4010) s, STROKETIME=0.0, MAXCHANGE=1.0 ENDNETWORKCOMPONENT CONNECTION TERMINALS = (FP_BRAN INLET, NODE_INLET FLOWTERM_1) CONNECTION TERMINALS = (FP_BRAN OUTLET, NODE_OUTLET FLOWTERM_1) CONNECTION TERMINALS = (FP_BRAN SOUR-1-1@INPSIG, SETPOINT-1 OUTSIG_1) ENDCASE

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Simulation model An OLGA simulation is controlled by defining a set of data groups consisting of a keyword followed by a list of keys with appropriate values. Each data group can be seen as either a simulation object, information object, or administration object.

Logical sections The different keywords are divided into logical sections: · CaseDefinition; administration objects for simulation control · Library; information objects referenced in one or more simulation objects · Controller; controller simulation objects · FlowComponent; network simulation objects · Boundary&InitialConditions; simulation objects for flow in and out of flowpath · ProcessEquipment; simulation objects for flow manipulation · ThermalComponent; thermal simulation objects · FA-models; administration objects for flow assurance models · Compositional; administration and information objects for component tracking · Output; administration objects for output generation · Drilling; drilling simulation object · OLGA Well; OLGA Well simulation object

Network model A simulation model is then created by combining several simulation objects to form a simulation network, where information objects can be used within the simulation objects and the administration objects control various parts of the simulation. The simulation objects can again reference both information and administration objects. The network objects can be of the following types: · Flowpath; the pipeline which the fluid mix flows through · Node; a boundary condition or connection point for 2 or more flowpaths · Separator; a special node model that can separate the fluid into single phases · Controller; objects that perform supervision and automatic adjustments of other parts of the simulation network · Thermal; objects for ambient heat conditions The simulation model can handle a network of diverging and converging flowpaths. Each flow path consists of a sequence of pipes and each pipe is divided into sections (i.e. control volumes). These sections correspond to the spatial mesh discretization in the numerical model. The staggered spatial mesh applies flow variables (e.g. velocity, mass flow, flux) at section boundaries and volume variables (e.g. pressure, temperature, mass, volume fractions) as average values in the middle of the section. The figure below shows a flow path divided into 5 sections.

Each flowpath must start and end at a node, and there are currently three different kinds of nodes available: · Terminal; boundary node for specifying boundary conditions · Internal; for coupling flowpaths (e.g. split or merge) · Crossover; hybrid node for creating a closed-loop network

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OLGA 7 The figure below shows a simple simulation network consisting of three flowpaths and four nodes.

The flowpath is the main component in the simulation network, and can also contain other simulation objects (e.g. process equipment, not shown in the figure above). It is also possible to describe the simulation model with a text file. See Input files for further descriptions.

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Introduction With OLGA 5 a new graphical user interface (GUI) was introduced that replaced the OLGA 2000 GUI. OLGA 6 uses the same GUI as OLGA 5 with some additional features. The main new features in the OLGA 6 GUI are: Plot configurations (variables, colours, etc) may be saved as templates for easy recreation of plots Graphical configuration of signal network (controllers) New graphical configuration of Bundles New utility for running cases in batch (without having to start the GUI) The main new features of the OLGA 5 GUI compared with the OLGA 2000 GUI are: Graphical configuration and visualization of complex networks with Drag and drop Graphical copy paste Automatic detection and classification of internal nodes Positive flow direction can be indicated on flow path Pressure boundary nodes are distinguished Network coupling table with configuration capability Design time verification of model and listing missing items Errors are detected while the model is created Action buttons for missing items GEOMETRY Editor with spreadsheet type input Copy directly from Exce l Both XY and Length-Elevation input are displayed. Automatic Sectioning without simplification Direct access to simplification procedure with new angle distribution details Automatic inversion of pipe profiles which facilitates e.g. annular models New Plotting Functions Select variables from a complete list with descriptions Make your own standard sets of variables with units Within a graph - copy directly to and from Excel Spreadsheet type input and visualization of input series New Parametric study function New RESTART function Context sensitive help

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New Project A new project is defined by:

· Select File/New/Project · Ctrl+Shift+N · Click the New Case icon

or New Project at the base of the Start Page.

When starting a new project a new folder can optionally be created by checking the ”Create folder” box.

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New case A new case is defined in one of the following ways:

· Select File/New/Case (you will be taken into a dialog to create a new project if not already done) · Ctrl+N · Click the New Case icon Then, the window below appears:

Enter a case name (or use default), fill in location (or use default) and select template.

· OLGA Case File. This generates an empty case. · OLGA Basic Case. This generates a complete basic case. Ready for simulation. · OLGA Network case. This generates a complete basic case with an internal merge node.

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Open existing case You may open an existing Project, an existing OLGA case or an existing OLGA 2000 case (*.inp). If you open an existing case after you have opened or created a project the case will be added to the project. However, if you open an existing case without having a project, a project with the case name is created. You should save this project immediately. Open project Select either of these: · Select File/Open/Project · Ctrl+Shift+o and open a file with extension .opp. Open case Select either of these: · Select File/Open/Case · Ctrl+o · Click the Open Case icon and open a file with extension .opi, .key or .inp.

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Start page When opening the OLGA graphical user interface the Start page will appear. The central window contains a list of recent projects and the date when they were last modified. A project can be opened by double clicking on the case name. A new project can be started from the New Project button at the bottom of the screen.

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Model view

The Model View is used for navigation between the objects of the system. The objects are ordered hierarchically with a Project on top comprising one or more cases. A case contains Case Definitions, Libraries, Output, Network Connections and Network Components.

· Case Definitions describe information common to the whole system simulated. · Network Components describe the properties of the flow network (currently either a node or a flow path). · Libraries contain keywords that can be accessed globally (for instance Material and Wall). · Output contains global output definitions, such as plotting intervals for trend, profile and output. · FA-models contains input to flow assurance models. · Compositional has input to the compositional model. · Advanced thermal contains input to the FEMTherm and bundle models and input to annulus calculations. When selecting an object in the project explorer, the object is made active and its properties may be edited in the ”Properties” view. The model view contains input for all cases in the project. Switching between the different cases is done by clicking on the file name in model view. See also 29 / 769

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Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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File view The ”File View” shows the input files of the project. By right clicking on a file the file can be removed or opened. If the file is a .opi-file (case-file) you get the option to open it as a text file. The text file is the OLGA 6 .key-format which resembles the OLGA 2000 inp-format. You may edit the key-file, save it and then reopen the case from the edited key fileby selecting 'reload from text file'

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Component view

Simulation objects may be fetched from the ”Components” window by Drag&Drop onto the Graphical Editor. Only objects available at the network level presented are available. This means that e.g. process equipment can be introduced this way only when the Flowpath is open. See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Property editor The ”Properties” window is a common interface to all simulation objects (keywords). Here the objects are defined setting values on the different keys. The left column gives the property name (currently the key name), the right its value. Units may be altered as shown in the figure. By default the value will update when the unit is changed. To keep the value: Press the Shift key while changing the unit. When a property is selected, a description is shown in the field at the bottom. Values may be inserted by typing or by selecting one or several values presented by the interface. The colours of the keys are the following meaning: Black : Key can be given but not required. Red : Key required. Grey : Key can not be given. Note that the colours will change as input is given. As an example: Two keys are mutually exclusive and one of them must be given. Both will then initially be red (required). When a value is given for one of the keys its colour will change to black (key is given and no more input required for that key) while the other key will turn grey (can not be given).

Some keywords have a special property page to make the process of entering data easier. These property pages can be accessed through the property editor button at the top bar of the property editor window.

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See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Network view Below you see a snapshot from the GUI with the template case Case0 loaded. All the windows are described in the following sections. The windows may be moved around (outside or inside the frame) and may be docked as described in Moving windows .

Click left button on canvas and use mouse wheel to zoom in/out

The central view in the figure above shows the Network view with its Graphical editor functions. Zooming in and out is done by the mouse wheel. Moving the mouse while the left mouse button is held down will move the layout within the window. Pressing Q adjusts the graphical view to the frames. Holding Shift and pressing Q zooms out in steps. Focus is shifted away from selected objects by pointing to the background while holding down the Shift key. Nodes and flow lines are drawn schematically. Network components (Nodes and Flowpaths) can be dragged into this view from the ”Components” window. Sources, Pressure boundaries and Process equipment are visible and their properties may be entered or modified by selecting the object (left-click) and filling in their "Properties”. In the figure the properties of the NODE OUTLET are shown to the right.

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The window above is the 2-dimensional Flowpath view which shows one Flowpath at the time. The functions for "moving" the graph are the same as for the Network view, see flowpath view for more details. You can drag equipment to the canvas from the Process Equipment Components on the left. When e.g. a valve is dropped on the canvas it "attach" to the middle of the Flowpath as illustrated below. The actual position and other data for the valve can be entered in the Properties window for the Valve which now is in focus (to the right). By entering the data e.g. the PIPE and SECTIONBOUNDARY the valve will take its specified position on the Flowpath.

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Each graphic view has its own tab and if you click on the Case0-tab (see below) you get back to the Network view.

We shall show how you make a new Flowpath: Start with dragging a Node from the Components window and drop it on the canvas, see above.

Then you make a new Flowpath by following the instructions in the drawing below:

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The new Node and Flowpath also appears in the Model View window, see below:

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An alternative method for adding a Flowpath. Select the Components window

Select a FLOWPATH and drag it to the canvas. Then drag a new node to the canvas.

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Then do as illustrated below.

Re-configure the network:

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Connecting Nodes and Flowpaths can be done as follows: · Point to the red dot at one end of a Flowpath (the red dot indicates that this end of the Flowpath is not connected). · Hold down the right mouse button, initially pointing to the blue square that has appeared at the end of the Flowpath. · Move the mouse pointer to the Node which the Flowpath should be connected to and release. · Select connect from the pop-up box that appears. The dot at the end of the Flowpath turns green, indicating that a connection is established. Alternatively: · Right-click on the view background and select Network Connections. · Select the "from-to" nodes for each Flowpath and click OK. The network should appear as specified.

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Right-click within the blue square and move pointer towards NODE_0. Select Connect to and release mouse button.

Do the same with the other end of the Flowpath.

Disconnect a Flowpath from a Node by left-clicking on the Flowpath and then point to the green dot at the end of the Flowpath. Hold down the left mouse button while moving the end of the Flowpath away from the node and release. The dot at the end of the Flowpath should now be red, indicating that it is not connected.

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Left-click on Flowpath, select green dot (left-click) and drag endpoint away from Node.

Right-click while pointing to an object in the Network view brings up various menus depending on the object: - Add : Add items to the network object. - Verify : Checks input file and reports errors and missing input in the output window. - Copy : Copy selected item. - Paste : Past the copied item onto the currently selected item. - Delete : Delete selected object. - Properties : Starts property editor for selected object. For a Flowpath this would be to Geometry Editor while for other items it would typically be a time series editor. For example: pointing to a Flowpath gives the alternatives below.

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Text labels in the Network view (which reside in their separate text boxes) can be rotated and scaled in addition to moved (except those for Flowpaths). Move is the default edit mode. You can either select the edit mode on the toolbar

or you can type one of the following letters to change the edit mode for the selected text box.

s:

Scale: (left-click in the triangle and drag while keeping the mouse button down)

r:

Rotate: (left-click in the sector and drag horizontally)

m:

Move: (left-click in the square and drag)

You can add fixed points on a Flowpath by pressing Ctrl while double-clicking anywhere on it. A fixed point, indicated by a small square, appears on the Flowpath.

The fixed points can be moved to shape the Flowpath (this does not change the actual geometry of the Flowpath).

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More points are added by repeating the Ctrl double clicking. You remove the fixed points by Ctrl double click within its blue square. Right-click in the Network view activates a menu with the following items:

Copy as picture: Network Connections:

A "Case.jpg" file with the Network view is copied to the folder where the project resides. Opens the network overview/connection window

Network plot allows for a quasi-animated plotting of profiles in the Network view. Configure:

Allows for (re)configuration of e.g. colours and line interpolation.

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3D View

Changes to 3D view as described in Moving view in 3D .

Show directions

Direction arrows are displayed on each Flowpath.

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Flowpath view The actual profile of the geometry may be viewed by opening the Flow path; double click FLOWPATH in the ”Model View”. This opens a new tab in the Graphical Editor

showing the selected flow path only (including equipment). In the Flowpath view equipment may be added by drag and drop from the ”Components” window (the available components are now the ones that are located on a specific Flowpath).

Focus an object by a left mouse click to bring up the Property editor, and the properties of the object can be entered or modified.

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Focus is shifted away from selected objects by pointing to the background while holding down the Shift key. Zooming in and out is done by the mouse wheel and moving the mouse while the left mouse button is held down will move the layout within the window.

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Connection view The connection view is used for showing connections for a single component or all connections in a case. The connection view can also be used to create new connections. The connection view has two modes. The above figure shows connections for a selected component. When a component is selected, all terminals for the component is shown in left column in the view. The column "Connected NC" shows the name of the network component which is connected. The column "Connected terminal" shows which terminal is used on the connected network component. In a signal connection a variable is given. This variable is shown in the column "Variable". Creating a new connection for a selected component: 1. Select a network component from the column "Connected NC". Only network components with compatible terminals are shown in the list of available network components. 2. Select a terminal on the component from the column "Connected Terminal". After selecting a terminal, the connection is made. 3. Select a variable (only for signal connections) from the column "Variable". The other mode is for showing all connections in the case. In this mode it is easier to see the direction of the signals (see figure below) Creating a new connection when showing all connections: 1. Select a network component in the column "From". 2. Select the out-signal (terminal) from this component in the column "Out". 3. Select a network component to receive the signal in the column "To". 4. Select the in-signal (terminal) in the column "In" 5. Select a variable (only for Transmitters) from the column "Variable".

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Output window The output window (not to be confused with the OUTPUT keyword/OUTPUT File) gives information about the state of the cases, modeling and simulations. The information comes out three categories:

· Error messages (and task list) - : Cannot simulate o Errors in input o Errors from initialization phase o Errors during simulation o List of incomplete keywords. o Click on the symbol to go to the incomplete keyword. · Warnings - : The simulation may still be performed [1] · Information o Simulator state changes o Progress during simulation o Any messages during simulation (info previously directed to DOS window) The windows can be cleared from the context menu (right click). Text can be copied: · Mark text · Right click and copy

Which Output categories are active are indicated by the "orange" background around the category names in the top bar of the output window. A left mouse click on the text will activate and deactivate.

By default the output from the active case is shown. Output from other cases is selected from the pulldown menu at the top of the output window.

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[1] Warnings from the OLGA interpretation of fluid files which takes place when the simulation has started are categorized as Information See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Time series editor Input keys that have time series can be edited in a time series editor. The time series editor is accessed through the properties for the relevant keyword.

If there are several independent time-varying parameters within one keyword the graph of these can be displayed by checking them in the graph legend (which shows the minimum necessary input parameters).

You can insert columns in the spreadsheet by right-clicking on a column-header, see below.

Selecting "cancel" nullifies all actions performed within the time series editor.

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A trick: to fill in the same value for several time points: enter the value in the column for the last timepoint and then enter.

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Plotting Trend and profile plot output as defined by the user can be viewed during and after simulation. The plotting buttons on the top menu will show red lines when plot files are available for the active case.

TREND Plot PROFILE Plot Plot PVT file Multi-case plotting General features of the plotting tool Export/import data

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Active case trend plot Select trend plot with the buttons in the top menu. Trend plot gives you the menu below. Select the variables you want to plot. Move the selection over to the upper right hand side window where you may change units. Click OK to see the graph.

The default time unit for a Trend plot is Seconds which you change at the lower left.

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Active case profile plot You select the profile button and then select variable(s) to plot:

You may now "play-back" the profile plot, either by dragging the slide or by clicking the green triangle. You may also freeze a curve by clicking the "needle" button.

You get a frozen curve each time you click it. You "un-freeze" by disable the needle . The play-back is stopped by clicking the blue square. You may play-back several profiles simultaneously, but the speed will of course depend on your PC-capacity.

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Fluid properties You can use the plot-tool to plot fluid-properties. Select PVT file plot with the buttons in the top menu (.tab). You then select the property or properties you want to see and proceed as usual.

You may use the freeze-function as for profile plots. You click the nail and then the green triangle. You repeat clicking the nail to freeze more curves. The default x-axis is temperature. You can change this by moving the column header fields in the righthand side window to locate the "X-Axis" field (which is in the far right position by default) and select Pressure instead of Temperature.

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Multi-case plotting It is possible to plot results from several cases/projects simultaneously. For example you can plot data from all the cases in your project (use the Plot Project button in the select variables… dialog), the inactive as well as the one active. You can open several results files by the Tools -> Plot menu (select several files, either trend (.tlp) or profile (.plt) or from within the plot tool itself by adding files, see below. You plot as for single cases.

Note that for profile plots where different plotting intervals have been used in the different files the profile closest to the selected time will be used and no interpolation is currently applied.

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Some general features of the plotting tool The plotting tool is a quite sophisticated program and you have access to several functions for modifying your graph

· Add/remove data to plot: o Right click and select Dataset /Select or o Menu Options/Select Plot Variables · View values: Right click and select Track values · For profile plots: select plot time point with slider at bottom right · Collapse/expand axes: Right click and select o Axes/Collapse all or o Axes/Expand all · Display legend: Right click and select Show legend · Modify settings o Right click and select Configuration (window as below) or o Menu Options/Configuration · Zoom: o o o

Select upper left corner with left mouse button Drag to lower right corner while holding button Release

· Un-zoom: Do as for zoom, but drag to the left (any start and end point works) · Zoom in/zoom out/un-zoom buttons are also available

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Export/import data to/from MS Excel Export data: In the Select variable… dialog, mark the variables that you want to export and then press the Export button. The marked variable data are then copied to the clipboard and can easily be pasted into MS Excel. Some examples are shown below. Paste from Excel: Select data columns in and select copy. In Plot window right click and select Dataset->Paste. Trend:

All the variables marked in the selection dialog are copied to separate columns in the Excel-worksheet. Profile:

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When exporting profile variables, there are some options. First, choose the points in time that are of interest. Secondly, choose the output grouping. On time copies the variables sorted on time, while the On variable option copies the variables sorted on variables. See examples below:

Showing data sorted on time

Showing data sorted on variable

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Parametric Studies Parametric studies are defined through Tools-Studies, where new studies can be added or previously performed studies reopened.

The input screen for parametric studies is shown below.

The number of parameters is given in the field labelled "#Parameters”. At present studies can only be performed on the local machine, but the number of simultaneous simulation can be given (#Parallel simulations). This can be useful for machines with multiple processors or multithreading.

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The quick way to enter an equidistant parameter variation is given below:

Right-click in MASSFLOW below and select Set Value(s)

Set the e.g. the values below:

This results in the definition of 4 cases ready for running. You may save the study by clicking OK. The study is saved in a separate folder together with the Project/Case.

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Click Run Study and observe the progress:

For more information on XY-plot and Matrix see the Tutorial (accessed from the Help menu).

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Geometry editor Activating Enter a new profile Edit Geometries Edit the table Edit the graph Check angle distribution Filter the data Complete the data Define sectioning Use the new geometry Menus Limitations

See also Moving windows, Hot keys, Moving view in 3D, Menus, Toolbars or Properties and settings

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Activating Pipeline profiles are edited in the Geometry Editor. The tool can be started like this:

· Tools/Geometry Editor (opens with only default data) or · Select the Property page for the active geometry (opens with data for the selected geometry)

You may also select FLOWPATH (or GEOMETRY) in the Model-View and right click and then select Properties:

You will now see this graph of the default geometry for the single branch template:

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Enter a new profile You can work with an existing profile in the .xy-format by File/Import and opening the relevant xy-file with the browser (e.g. Profile-A.xy - this Geometry is given below).

You should save this new Geometry with a new label while in the Geometry Editor (e.g. GEOM-A. The saved geometry file has the extension .geo:

You must also give the new Geometry relevant sections, diameters, roughness and walls. How to do this is described below. You can also copy directly from an Excel –worksheet: Open the Geometry Editor and select Fileà New. You will get a new Geometry with one pipe and default values as given below. The geometry is now presented in a tabular format and you can toggle between this and the graphic format by clicking on the relevant tab.

Open the Excel-file with your profile-data, select the X-Y columns and copy.

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Select the Start Point 0, 0 in the Geometry Editor with the default geometry open and then Paste. You will get the question below. Answer yes and the data will be pasted directly over to your open geometry.

Please observe that if your excel geometry contains fewer pipes than the one you paste over you must delete the obsolete pipes. You can now save this Geometry (e.g. GEOM-B) and use it for one or several Flowpaths in any model. First you must of course complete it with sections, diameters etc., see below.

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Edit Geometries When opening the Geometry Editor you have seen that two views are available i.e. the graph of the profile and a table of pipes. The two windows can be viewed simultaneously by selecting the e.g. plot tab and drag it towards the bottom of the window (as has been done below).

See also Edit the table Edit the graph Check angle distribution Filter the data Complete the data Define sectioning Use the new geometry

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Edit the table New pipes are added, renamed or deleted, by right-clicking in the Pipe column and selecting the relevant action.

X and Y in the table give the data for the end point of the pipe. Changing Length-Elevation affects X-Y and vice-versa. Units are changed by right clicking in the title cell (e.g. ”r;Diameter [m]”) and selecting a unit.

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Edit the graph You can also edit the Geometry by the following actions under the Actions menu:

Normal (no change) A: Add a point M: Move a point D: Delete a point

Restrictions on the graphic editor can be imposed (Actions -> Restrictions):

X Fixed (X remains fixed, Y can be changed) X Bound (Point X-value can not be moved upstream or downstream neighbors) Y Fixed (Y remains fixed, X can be changed) Y Bound (Point Y-value can not be moved above or below neighbors) Recursive (all points downstream will follow the point that is being moved)

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Check angle distribution You can check the angle distribution of a Geometry by selecting Tools -> Check angle distribution. You can see the angle groups that are used by right clicking when in the output window from the angle distribution calculation. You can also change the angel groups. The colour of the bars and the % values in the output window indicate the difference between the average angle of the pipes within a group and the mean value of the angle group. Green (and a low % deviation) means a good relevance of the angle group. The % value is a numerically calculated standard deviation divided by half of the angle group span.

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Filter the data Select Tools/Filter. You have two options: a Box filter or a preservation of angle distribution / total flowpath length (the algorithm is identical to the one used in the OLGA 2000 Grid Generator).

Box filter: This filter is more relevant for removing relatively small disturbances from a pipeline survey. Enter the horizontal sample distance and the vertical sample height. These values define a moving rectangle (a box) within which all data points will be filtered out. The filtered data appear as a new geometry which may be further filtered/edited. Angel distribution: Enter the maximum pipe length that shall be used to filter the profile while maintaining the angle distribution and the total pipe length. When filtering has been completed it is a good idea to compare the angle distributions of the original geometry and the filtered ones. The filter with the best reproduction of the original geometry should be used – keeping in mind that the angel groups should be representative.

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Complete the data You may want to open the e.g. GEOM-A.geo file. All fields except the ”r;Length of sections” are editable directly, and copy/paste may be used for single cells. The "Length of sections" has its own input support-tools In contrast to OLGA2000 all Pipes must have a Diameter, a Roughness and a Wall (if relevant). You can use copy-paste functions to achieve this. If defined in the OLGA case, walls may be selected from the drop down menu. Within the Graph window the profile may be edited activating either of the four menu functions (found under Actions -> Graphical):

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Define sectioning The pipe sectioning can be performed in two ways: 1.

Manually enter number of sections in the ”r;# Sections” column. This gives you equally long sections for a given pipe.

2.

If you double click in the Length of Section list you enter a tool to distribute sections of various lengths over the pipe-length.

Change (the nominal) no of sections to 3 and enter 4.75 m in Section 1 and click OK.

You get 2 sections of 4.75 m and 1 0f 4.64214 m.

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The main rule is that the tool ensures that you get a sum of sections which is equal to the pipe length. Moreover, open section lengths mean that you repeat the value above. The "remaining of total" is the total pipe length minus length accumulated over the section lengths specified (including the open ones).

If you double-click in the Length of Sections field again

You get the window below and you see that the remaining now is very close to zero.

To start over again you can set # of sections to 0. 3.

Use the discretization tool (Tools/Discretize). Then all pipes are given the same selected number of sections.

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Use the new geometry A new geometry may be imported to a case as follows: Open the geometry files you want to use (you can open them from the Geometry editor or in explorer) Right click on FLOWPATH or Piping in the Model View, select ”r;Exchange Geometry” and pick the desired geometry. If you use the same Geometry file for several branches you must re-label the Geometries afterwards to secure that the labels are genuine. You can also exchange geometries between flow paths in the same case. Select the flow path and its Property Page of the Geometry you want to distribute to other flow paths. Then you select the flow paths that you want to import to and select Exchange Geometry. Select FLOWPATH and click on Properties. This opens the Geometry GEOM-1_2

Select destination FLOWPATH and click on Exchange Geometries and then on GEOM-1_2.

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Menus The Geometry Editor features the following menus: File New New geometry Import Import xy-data Open Open geometry file (*.geo) Close Close geometry Save Save geometry Save As Save geometry as new file Print Print active window Print Preview Print Setup Send Exit Edit Undo Cut Copy Paste Configure Configure graph window View Standard Restrictions Graph Status Bar Labels Actions Graphical Normal/Add/Move/Delete Restrictions X Fixed/X Bound/Y Fixed/Y Bound/Recursive Tools Angle groups Check Angle Distribution Check section lengths calculate the length ratio of adjoining sections. Discretize Automatic pipe sectioning (all equal) Filter Filter data Reset Pipe Labels Use default pipe labeling Reverse geometry Creates a geometry that is the mirror image of the original geometry (in xdirection). Window New window New window with active data (works on same data set) New window Select graph or table representation New Horizontal Tab Group New Vertical Tab Group More Windows Help Help Topics Not implemented About Geometry Version Information

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Limitations The following important limitation applies: 1. For export to Excel, dot (”r;.”) must be selected as decimal separator for Excel

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Moving windows Windows may be hidden and re-opened through the view menu. They may be detached from the frame (floating) and may be docked again by moving the window to the border of the frame. Double click on a floating window to move it back to the last docked position. In the picture below the blue area indicates where the window will end up if dropped at the current location. If the cursor is moved over one of the arrows towards the edge of the screen the window will dock on the corresponding border of the frame. If dropped on one of the four arrows in the centre of the screen the window will dock towards the corresponding side of the frame of the pipeline schematic window. Double clicking on the top bar of a docked window makes it float and double clicking on the top bar of a floating window makes it dock.

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Hot keys Ctrl+z z Leftshift+z Mouse wheel Delete

Undo Enable zoom in graphical editor; mark area with mouse Enable un-zoom in graphical editor; mark area with mouse Zoom in or out in graphical editor Deletes object

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Moving view in 3D The following illustration shows how to navigate the camera in fly mode. In Orbit Mode left mouse button + moving the mouse will make the camera orbit around the pivot point. If you release the left mouse button you can use the key combinations to move around. Camera maneuvering: · Mouse wheel · Arrows · Right shift · Left shift Left mouse button

Zoom in/out Move camera in/out/left/right Move up Move down (or: Insert move down) No selection: Rotate camera Network selected: Rotate network (see below)

Camera Movement Speed Slow to Fast Keys 1 – 9 Rotate/Move/Scale Rotate Move Scale

Select object + key R+ left mouse button + move mouse Select object + key M + left mouse button + move mouse Select object + key S + left mouse button + move mouse

Scene View Shortcuts Fly Mode Key F Orbit Mode Key O Field of View Mouse wheel, or key Z + left mouse button + mark area, or key Z + left mouse click (zoom in)’ Left Shift + key Z + left mouse click (zoom out) Space Deselect interaction mode Escape Deselect objects Q (in 2D View) Zoom to extent Delete [Del] Delete selected object.

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Graphic Configuration The graphical layout of individual flow paths can be changed through the Graphical configuration dialog. The choices made her will affect only the selected flow path.

If one want to change the layout of all the flow paths, this can be done in Tools -> Options ->Graphics.

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Menus File New > Project... New > Case... Open > Project... Open > Case... Save Case Save Case As... Duplicate Case... Save Project Close Project Print... Print Preview Print setup... Recent projects Recent cases Exit

Create new project Create new case Open project Open case Save case Save a new case Makes a copy of the selected case Save project Close (and save) project Disabled Disabled List of projects recently opened List of cases recently opened Exit

Edit Standard windows commands Undo Redo Cut Copy Paste Paste special...

Disabled Disabled

View Select what windows and toolbars to be visible.

Project Add New Item... Add Existing Item... Project Dependencies Close Project Simulation Run

Same as New Case Open an existing file e.g. an .opi file Option to specify the dependencies between the cases

Start simulation (Start simulation in batch- messages from simulation are sent to the Output window)

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Stop Pause Run Project Run Batch Run Project Batch

simulation are sent to the Output window) Stop simulation. Returns to initial state Pause simulation. Simulation may be resumed (Not implemented for OLGA). Start to run all cases in a project in a given order Start simulation in a DOS-control window. Start to run all cases in a project in a DOS-control window

Tools The tools available are listed below.

Windows Standard windows operations. Help Help topics GUI Manual Tutorial About OLGA

OLGA User Manual Opens OLGA GUI USer Manual (pdf). Starts OLGA 6 Tutorial Release information

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Toolbars Standard

New case Open case Save Save Project Copy Paste Undo Redo Model view Property editor Components File view Output view Connection view

Saves Case

Disabled

Simulate

Run Run Batch Verify

Start simulation Stop Pause Run batch in DOS window Verify case

Stop simulation. Returns to initial state. Disabled

Plot

Plot current trend plot Plot current profile plot Plot current PVT file View current Output File Layout

Fit window Move Scale Rotate Circular Grid

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Hierarchical type 1 Hierarchy Hierarchical type 2 Hierarchy Radial For systems with defined center V Layout algorithm direction is vertical. H Layout algorithm direction is horizontal. Layout of equipment Toggle between relative and sequential layout of inline equipment Snap to grid Toggle snap to grid

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Properties and settings The overall simulator settings are specified under Tools->Options; making it possible to work with different simulation engines under the same GUI (this includes OLGA 2000 versions as long as it accepts the keywords you actually use). Settings under the General tab are: My Project locations: Location where file dialogs will open. Show start page at start-up: If applied - start-page with recent projects will appear when starting the GUI. A sub-setting is "show the project list on the start-page". Use cached static data: This is set by default during installation. The GUI will then store certain data the first time the simulator is started. This speeds up file loading and is recommended to obtain the best performance from the program. The General tab can also be used to specify if the program shall execute auto-save at specified intervals. In the OLGA version tab one can specify which version to use by marking one of the displayed versions. External programs that should be available from the Tools menu can be specified under the External Tools tab. Some programs are set by default during installation and the user can specify additional programs like Excel, a text-editor etc. The Graphics tab is used to specify the pipeline layout view: Turn the background grid on and off and specify the colours of the gridlines. Set the canvas colour. Choose the interpolation method for the flowpath lines. Set flowpath colour.

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Simulation with bundles This description covers Fluid Bundles, Solid Bundles and Annuluses. In OLGA 6 these bundle types are network components. In this chapter the simulation of bundles is illustrated by a SOLIDBUNDLE example. To add a SOLIDBUNDLE right click the case level tab and choose Add > ThermalComponent > SOLIDBUNDLE (see figure below).

When the Solid Bundle is added, go to the property window and specify the required fields: DELTAT and DTPLOT. These parameters govern the frequency of updates of output from the FEMTherm computation (i.e. the computation of temperatures in the solid). The LABEL and MESHFINENESS fields may also be updated. A bundle in OLGA 6 consists of several components. The components of the bundle are flowpaths, shapes and possibly internal bundles. Note that all the components that constitute the bundle must be defined (added) elsewhere. Flowpaths and Lines must be defined as FlowComponents, Shapes must be defined under Library and bundles must be defined as ThermalComponents. Position labels to use for the specification of TO and FROM must be defined for each flowpath under "Piping". To add a component to a bundle (i.e. to specify that it is a part of the current bundle) choose Add > BundleComponents > COMPONENT in the Model View as shown in the figure below.

In the property window for the new component, specify the required fields:

· The type of the component (specify either a FLOWPATH, a LINE, a FLUIDBUNDLE, an ANNULUS or a SHAPE) · The start and stop position of the Bundle (TO and FROM) · The geometric center of the component (XOFFSET and YOFFSET) · The OUTERHVALUE of the component (optional) Note that the position of the origin of any cross-sectional coordinates is irrelevant as long as all coordinates within one and the same bundle refers to the same coordinate system. It is only the relative cross-sectional position that matters. 92 / 769

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coordinate system. It is only the relative cross-sectional position that matters.

About SHAPES A SHAPE in OLGA 6 defines the circumference of an area where a cross-sectional temperature profile may be computed by the FEMTherm module. Within this area heat is assumed to be transported by conduction in the radial direction. To add a SHAPE to a case right click the Library in the Model View and choose Add > SHAPE. In the property window for the new shape, fill out the type of the shape (CIRCLE, ELLIPSE, RECTANGLE, POLYGON) and the material. For any type of SHAPE the layout of the cross-section must also be defined. As illustrated by the property window to the right, a Circle requires the specification of a radius, an ellipse requires a width and a height, a rectangle requires the specification of coordinates of the lower left and upper right corners, and a polygon must be defined by a series of coordinates.

About LINES A LINE in OLGA 6 is a flowpath for which a simplified one-phase computation is performed. LINEs can be connected in networks, just as regular flowpaths can, but in a LINE network all the network components must have the parameter LINE set to YES. A complete case may contain several LINE-networks and several multiphase networks, but the two types of networks can not be coupled to each other. To add a line to a case in the GUI, right click the FlowComponent in the Model View and choose Add > FLOWPATH. In the property window for the new flowpath select LINE=YES. Then select FLUIDTYPE (gas, oil or water). Connect the LINE to a node in the same manner as other flowpaths are connected. Note, however, that the connected nodes must also have the parameter LINE set to YES.

About CROSSOVER nodes A CROSSOVER node in Olga 6 is a special type of single phase node which can be used in LINE networks only. The CROSSOVER node is a pressure boundary node with the following additional features: It must be connected to two LINES, and it imposes a given pressure difference (called MAXPRESSUREBOOST) between these two lines (at the connection point). A crossover node is added to a case in the same manner as any node is added: right click the FlowComponent in the Model View and choose Add > NODE. In the property window for the new node select TYPE=PRESSURE and LINE=CROSSOVER, then enter the rest of the required fields.

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Simulation with Controllers In OLGA 6 the controllers are signal components. Signal components are a special kind of network components, able to transfer signals between each other. Coupling in the signal network is possible between the following components (notice that a controller is always involved): · Pipeline section variable (via a transmitter) to controller · Inline component (ex. valve, pump, compressor etc.) to controller · Sources (source and well) to controller · Node variable to controller · Separator variable to controller · Controller to controller · Controller to inline component · Controller to separator · Controller to source This chapter describes how to connect signal components in the GUI.

Signal network terminology The following explanations of the terminology used for signal networks can make it easier to understand how controllers are connected to other components. A signal component is a component that can send and/or receive a signal. A signal component (e.g. a controller) is connected to other signal components (e.g. a flowpath) via terminals. Terminals are best explained with an example; A PID Controller has 3 terminals, 2 for receiving signals (the setpoint signal terminal and the measured signal terminal) and one for sending signals (the output signal terminal). Another signal component like a separator can send its holdup value as a signal to the PID Controller. The holdup will be sent via the measured signal terminal of the controller. The PID Controller will calculate an output signal based on the measured value and send it via the output signal terminal to e.g. a valve. A signal is just a value. There isn’t much difference between a signal in a signal network and a flow in a flow network. The flow represents a physical flow of oil, gas or water while the signal can represent anything. The meaning of the signal to the signal component depends on which terminal that is used to send the signal. In the example above the signal represented a measured value since it was sent via the measured signal terminal. A flowpath may send measured values as signals. To do this one must add a transmitter to the flowpath. The transmitter acts as an output signal terminal for the flowpath. Most inline process equipment added to the flowpath can act as a signal terminal for the flowpath in the same way as a transmitter (you may for example connect a controller directly to a valve).

Graphical configurations of controller connections Coupling of signal components is possible with two different techniques in the graphical user interface; i) Coupling with drag and drop - or ii) Coupling through the connection view

Drag and drop coupling The drag and drop coupling between two signal components is done in the same manner as between two multiphase network components: 1. Click a component and drag towards another component in the signal network (see list of legal couplings above) 94 / 769

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2.

Release on the second component. A context menu is shown with available terminals to connect from and to

3.

Choose one of the available terminals to connect from (only OUTSIG_1 is available in the figure above) and a terminal to connect to (MEASRD and SETPOINT is available in the figure above). A connection between the two components is created.

4.

Select variable to transmit. If the coupling is between a transmitter and a controller, a variable to be transmitted has to be given. Setting this variable must be done in the connection view

Coupling using the connection view The drag and drop technique for coupling components in the signal network is less practical when the case is large with many components. Dragging from one component to another may involve zooming to view both components, and thereby making the coupling difficult. It is possible to connect signal components using the connection view without seeing the other components. In the figure below the connections for a PID-controller is shown. All terminals (in-/out-signals) for controller CNTRL-1 are listed in column one (Terminal). Column two (Connected NC) and three (Connected terminal) lists which network components and terminals the controller is connected to. If a user-chosen variable is supposed to be transmitted column four (Variable) is used. 95 / 769

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The connection view has two modes. The above figure shows connections for a selected component. The other mode is for showing all connections in the case. In this mode it is easier to see the direction of the signals (see figure below)

Hiding and deleting connections If there are many controllers the case may be too complicated to get a good overview. In such cases you may hide the controllers and their connections. Do this by right clicking on a controller and select 'Hide'. To hide all controllers select 'Hide all of this type'. If you have connected a controller by mistake you may delete the connection by selecting it and pressing the 'Delete' button. NOTE: If you delete a controller the connection is not deleted automatically - you have to select the connection and press the 'Delete' button.

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Simulations with separators In OLGA 6 the separator is a network component. This means that it can not be inserted into a flowpath the same way as inline process equipment (like sources and valves). The separator has four types of terminals, INLET, GAS, OIL and WATER (only for three-phase separator). One or more flowpaths leads into the separator and are connected to the separator INLET terminals. It is required to connect at least one flowpath to each terminal type. All terminals allow both in and out flow from the separator. A separator is connected to flowpaths much the same way as nodes. Chapter 8.1 shows how a separator is coupled to flowpaths and nodes.

Graphical configuration and multiphase coupling of separator The multiphase coupling of a separator is made in the same manner as a multiphase coupling between a node and a flow path. Add a node and a separator to your case from the component view. Connect a flowpath from the node to the separator as follows: 1. Click the node and drag. 2. Release on separator. 3. A context menu will display which out-terminals on the node it is possible to connect from and which in-terminals on the separator it is possible to connect to. In the figure below the flow path is connected to the inlet terminal of the separator

Add another node to your case. Connect a flowpath from one of the separator outlets to the node as follows: 1. Click the separator and drag. 2. Release on the node. 3. A context menu will display which out-terminals on separator it is possible to connect from and which in-terminals on the node it is possible to connect to. In the figure below the flow path is connected from the gas outlet terminal of the separator to node 1. The oil outlet terminal of the separator is connected via another flowpath to node 2. 97 / 769

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2nd order scheme Mass equations can be solved with two different schemes in OLGA. The default is a 1st order scheme (upwind implicit) and the alternative is a 2nd order TVD scheme. The 1st order scheme is more robust and should be the preferred choice in most situations. The 2nd order scheme has less numerical diffusion and therefore keeps holdup fronts better. See also: When to use Methods and assumptions Limitations How to use

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When to use The 2nd order scheme for mass equations is to be used when it is important to track relatively sharp holdup fronts. Examples are: 1. Oil-Water fronts 2. Inhibitor fronts 3. Gas-Oil fronts

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Methods and assumptions The 2nd order method used for the mass equations is a combination of different numerical schemes in order to get a stable method which satisfies the TVD (Total Variation Diminishing) condition. For smooth gradients the method is 2nd order while for non-smooth flow (shocks) the method reduces to 1st order upstream. The smoothness of the data is measured on the control volume boundary like this

Where m is the mass and θ is the measure of smoothness. If θ < 0 the method reduces to first order upstream and if θ > 0 the method uses 2nd order methods. In the 2nd order region the numerical scheme is determined based on a 2nd order limiter. In OLGA the limiter known as the van Leer limiter is chosen.

Simulation differences between the 1st order and 2nd order schemes

Figure 2 Profile plot of an oil–water front showing the differences between the two schemes. The number of sections in the pipeline are 50, 100 and 500, respectively.

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Figure 3 Profile plots of a gas–oil front. The number of sections in the pipeline are 50, 100, 200, 500 and 1000, respectively.

Figure 4 Trend plot showing the hold-up at the top of a riser. The number of sections in the riser are 15, 30 and 60, respectively.

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Figure 5 The above figures show profile plots of an oil–water front. Inside the area filled with water, there are three areas containing MEG.

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Limitations The 1st order scheme diffusive behavior reduces unphysical numerical instabilities in the simulation if they occur. For simulations where instabilities are observed it is not recommended to use the 2nd order scheme. For such problems the 2nd order will only make matters worse because it enhances the numerical oscillations. Since the 2nd order method is only implemented for the mass transport equations the final result from the equation set will not converge to 2nd order accuracy. The improvement in the result will also differ depending on which physical phenomena which are of interest. For example simulations where pressure waves or temperature waves are of interest the improvement from the 2nd order method will be small. For simulations where propagation of holdup fronts is of interest the improvement can be significant. The 2nd order method only works if the CFL criterion is fulfilled. This means that it is not possible to violate CFL criterion by increasing MINDT when the 2nd order options is set.

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How to use The 2nd order scheme for the mass equations is activated by setting MASSEQSCHEME=2NDORDER in the OPTIONS keyword.

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Blackoil Blackoil modelling allows one to make a compositional model with a minimum of input. Compared to compositional tracking, the blackoil module is faster in terms of CPU cycles, and it treats shut-in cases more accurately than does the standard PVT table option. The module makes it possible to perform calculations with a minimum of information about the production fluids. Details about the fluid composition are not required for a blackoil simulation; specific gravity of gas and oil and the gas–oil ratio (GOR) at standard conditions are the only necessary data. If water is present, also the specific gravity of water must be input. Note that no fluid table is needed. A blackoil feed can consist of one gas, one oil and one water component. The gas component consists of hydrocarbon gas, and optionally H2S, CO2 and N2 components. It is possible to specify more than one blackoil feed, and for such a mixture each component of each feed is tracked, cf. the example network in Figure A below. Inside the OLGA engine, the blackoil module uses the framework of the compositional tracking module to track the components through the pipelines. Water properties are calculated by the standard OLGA routines. The physical properties of gas and oil are calculated from correlations belonging to a specific blackoil model – the user has a choice between four different blackoil correlations. To find the properties at a position in a pipe, the correlations use the pressure and the temperature, as well as the specific gravities of gas, oil and water, and the GOR, at that position. In the case of multiple feeds, the specific gravities and the GOR are mixture values. The mixture is the average taken over the constituting blackoils weighted by volume at standard conditions.

Figure A: Network case with several blackoil fluids (feeds) specified. Each component is tracked through the network. The fluid properties are calculated based on the fluid mixture. See also: When to use Methods and assumptions Limitations How to use

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When to use Due to the limited amount of input, the blackoil module can be a good choice when little is know about the production fluids. For instance, during planning or design one may use specific gravities and a GOR typical of the geographical area. Later when production is established, one may insert the actual values, and possibly make use of the module’s tuning mechanism to further improve the match between observations and the predictions made by OLGA. As mentioned above, the blackoil module is related to the compositional tracking module, and may be preferred as the computationally faster alternative. This is due to the fact that blackoil models are intrinsically crude, and cannot provide the detailed analyses of compositional tracking. It is however possible to include the effects of MEG in the density calculations by specifying a larger specific gravity for water. This method should also be used if salts are present.

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Methods and assumptions The following three assumptions are made for the blackoil module: 1. An oil component cannot exist as gas in the gas phase. As a consequence, the module is not suited for studying gas condensate systems. However, this assumption does not exclude the dispersion of oil and water, the existence of water/oil droplets in the gas or gas bubbles in the liquids. 2. Gas can dissolve in oil. 3. Gas cannot dissolve in the water phase, and water cannot exist as steam in the gas phase. (This assumption may change in a future version of OLGA.)

Blackoil Correlations To calculate the solution gas-oil ratio RSGO and the bubble point pressure Pb, four different correlations are available in OLGA. They are based on fluids from different areas, and have recommendation for use as mentioned in Table 1. The default correlation is Lasater. Table 1: Blackoil correlations and their recommended usage. Standing /28/ API < 15 Based on fluids from California Lasater /27/ API > 15 Based on fluids from Canada, U.S. and South America Vazquez & Beggs API > 15 Similar as Lasater /29/ Glasø /30/ API > 15 Based on fluids from the North Sea These correlations can be used to calculate the bubble-point pressure, Pb, for a given GOR or an equilibrium value of RSGO (< GOR) at any pressure below Pb. If measured values for GOR and the bubble point Pb(Tb) are available, it is recommended to tune the correlations for RSGO(P,T) and Pb(T). In the following, the four sets of correlations are presented with their tuning coefficients.

Lasater Correlation The basis for the Lasater correlation is the following relationships: (a) with , and

(b)

.

(c)

For the purpose of calculating the RSGO, the above equations are inverted with GOR replaced by RSGO, and Pb replaced with the actual pressure P. That is, find yg from Equation (c) with P instead of Pb, and invert Equation (c) to get RSGO, viz.: .

(d)

Please note that if P > Pb, then RSGO = GOR. In these equations we have that API = 141.5 / γo - 131.5 yg = mole fraction of gas γg = specific gravity of gas 108 / 769

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= specific gravity of oil Mo = effective molecular weight of tank oil GOR = gas-oil ratio f1(yg) = tabulated function of yg f2(API) = tabulated function of API CPb = tuning coefficient (default = 1) CRSGO = tuning coefficient (default = 1) γo

Pressure must be given with a unit of psia, temperature in 0R (degrees Rankine), and GOR and RSGO in scf/STBO.

Standing Correlation The bubble-point pressure at a given GOR is given by (e) where (f) Symbols have the same meanings as for the Lasater correlation. To calculate RSGO, replace Pb with the actual pressure P, and replace GOR with RSGO, and invert Equation (f) to obtain .

(g)

If the pressure is above the bubble-point pressure, then RSGO = GOR. With the Standing correlation, pressure is measured in psia, and temperature is measured in 0F.

Vazques & Beggs Correlation For API < 30: , and .

(h) (i)

, and .

(j) (k)

For API > 30:

If P > Pb, then RSGO = GOR. Symbols have the same meanings as for the Lasater correlation. Units for pressure and temperature are psia and 0R, respectively.

Glasø Correlations For known GOR, the bubble-point pressure is given implicitly by 109 / 769

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, and

(l)

.

(m)

Substitute RSGO for GOR and P for Pb to obtain .

(n)

If P > Pb, then RSGO = GOR. Symbols have the same meanings as for the Lasater correlation. Units for pressure and temperature are psia and 0F, respectively.

Treatment of Water Water is treated as inert in the current version, hence no water vapour enters the gas phase, and natural gas does not dissolve in the free water phase. With regard to the water density and viscosity, the blackoil module uses the same built-in routines for pure water property calculations as for the standard PVT table option.

Oil and Gas Density The oil density depends on pressure, temperature and the amount of gas dissolved in oil. At pressures below the bubble-point the procedure is as follows. First, the oil volume formation factor BO is calculated, see /28/, ,

(o)

where .

(p)

Now, the oil density is calculated as .

(q)

The density at the bubble-point, ρob, is given by the above equations with RSGO = GOR. At pressures above the bubble-point, the compressibility is taken into account, and the density is calculated by .

(r)

co is the isothermal compressibility of undersaturated oil. .

(s)

Units for Equations (o) to (s): Temperature is given in 0F, pressures in psia. BO is given in bbl/STB. The basis for calculating the gas density is the compressibility equation of state, viz.:

pV = znRT.

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When other variables have units of psia, ft3, lbm, moles and 0R, the gas constant R has the value 10.72. Now, the gas volume formation factor, BG, can be expressed as .

(u)

The gas density is obtained from (v) where ρgsc = 0.0764 γg. (The value 0.0764 is the density of air at standard conditions expressed as lbm/ft3). γg denotes specific gravity of gas at standard conditions. The gas compressibility z expresses the deviation of the real gas volume from the ideal gas behaviour. The assumption that real gas mixtures will have the same z-factor for the same values of pseudoreduced pressure Ppr and temperature Tpr, is used to determine the value of z. An algebraic relationship, cf. /28/, has been developed, and this relates z to Ppr and Tpr. The implicit set of equations that emerges, requires an iterative solution procedure. In order for OLGA to save CPU CYCLES, THE Z-VALUES HAVE BEEN PRE-COMPUTED, AND TABULATED AS A FUNCTION OF PPR AND TPR. Values for Tpr and Ppr are found from the pseudocritical temperature Tpc and the pseudocritical pressure Ppc:

Ppr = P/Ppc and Tpr = T/Tpc.

(w)

Empirical equations exist for Ppc and Tpc, /28/, and we use them: , and

(x)

.

(y)

As already mentioned, the units are psia and 0R. The presence of CO2 and H2S is accounted for by correcting the pseudocritical values Ppc and Tpc. Nitrogen, N2, is assumed to have no significant effect on the z-factor. The corrected values become

Tpc’ = Tpc - ε, and Ppc’ = Ppc Tpc’ / (T pc + B(1-B) ε),

(z) (aa)

where

A = yCO2 + yH2S, B = yH2S (yCO2 and yH2S are mole-fractions), ε = 120 (A0.9 - A1.6) + 15 (B0.5 - B4.0).

(ab) (ac)

Oil and Gas Viscosity Dead oil viscosity is calculated using the following equation: 111 / 769

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(ad) Now, the live oil viscosity μo is found by modifying the dead oil viscosity according to the gas dissolved in the oil, i.e., ,

(ae)

where , and

.

(af)

Note that Covisc is a tuning coefficient; its default value is 1. If the pressure is above the bubble pressure Pb, the above expression corresponds to the viscosity at the bubble point μob, where RSGO = GOR. For these pressures the viscosity is modified, viz.: , with

.

(ag)

Units: Pressures are measured in psia, temperatures in 0F, viscosities in cp and RSGO in scf/STB. The gas viscosity is calculated, according to /27/, from the correlation ,

(ah)

with

A = (9.379 + 0.016Ma)T1.5 / (209.2 + 19.26Ma + T ) B = 3.448 + 986.4 / T + 0.01009Ma C = 2.447 - 0.2224B Ma = 29γg (Ma is the apparent molecular weight)

(ai) (aj) (ak) (al)

Units: ρg given in g/cm3; T in 0R; μg in cp. Liquid viscosity is calculated as for the standard pvt table option with oil viscosity as above. Surface Tension The expression for the gas-oil surface tension needs to be simple without the information about the fluid composition. Given values of API, T (0R) and P (psia), we can use (am) for dead oil, and then correct the value for saturated oil at saturation pressure: .

(an)

For undersaturated oil, the corresponding saturation pressure for P(T,RS) is used. The unit of a surface tension σ is dynes/cm (1 dyne/cm = 0.001 N/m). The expression used for the gas-water surface tension is .

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For oil-water surface tension empirical data are scarce, and a preliminary relation is used: ,

(ap)

with default coefficients A1 = 30.0, A2 = 0.0 and A3 = 0.0. The above correlations are based on data from /31/ and /33/.

Thermodynamic Properties of Blackoil SPECIFIC HEAT OF GAS The specific heat or heat capacity of gas cpg will be tabulated as a function of temperature and specific gravity of gas. The data are taken from /31/, Figure 4-49. It is assumed that the specific heat of a gas mixture corresponds to the specific heat of a pure gas with the same specific gravity. SPECIFIC HEAT OF OIL The specific heat of oil, cpl, can be calculated using the following equation, cf. /32/: , (aq) where γo = specific gravity of oil

T = temperature in 0C The unit of cpl is kJ/kg0C. ENTHALPY OF GAS The enthalpy of gas, Hg is calculated from the equation (ar) The term (dH/dP)T can be expressed as -(RT2/P)*(dz/dT)P . From tabulated values for cpg and z, a table for Hg can be generated; 00C and 1 bara is used as the zero point. The compressibility factor z is tabulated as a function of Tpr and Ppr. Thus the term (dH/dP)TdP in Equation (ar) can be expressed in terms of Tpr and Ppr: .

(as)

ENTHALPY OF OIL The enthalpy of oil Ho is calculated directly by integrating cpo from zero to the actual temperature. Modifications of Ho at elevated pressures are ignored. ENTHALPY OF GAS DISSOLVED IN OIL The latent heat for gas dissolved in oil ΔHgo will be used to calculate the enthalpy of liquefied gas Hgo. We have 113 / 769

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We have

Hgo = Hg - ΔHgo

(at)

The term ΔHgo can be approximated by a simple correlation from /32/. First, the latent heat is estimated at 1 bara.

ΔHgosc = 4.19 Tabp (8.75 + 4.57 log(Tabp)) / M,

(au)

where Tabp is the atmospheric boiling point measured in K. The unit of the latent heat thus becomes kJ/kg. Second, the latent heat is extrapolated for pressures above 1 bara, according to

ΔHgo = ΔHgosc - 1.7 (P - 1)

(av)

Tabp is tabulated as a function of oil specific gravity and molecular weight, cf. /32/, see Table 2 below. Table 2: Tabp as a function of specific gravity of oil and molecular weight. Atmospheric boiling point, Tabp (0C) M 70 80 90 100 120 140 160 180 200 220 Spec grav. Tabp 0.6 27 42 60 79 104 128 146 165 190 205 0.9 66 93 116 132 165 202 222 252 274 294

Thermal conductivity Data for the thermal conductivity of gas as a function of M and T is plotted in /31/. A function has been developed that gives a reasonable approximation to these data, and this function is used by OLGA. Little data are available for oil, and so a simple linear function is used, viz.: ,

(aw)

The default values for the coefficients are:

, and

.

(ax)

Blackoil Tuning It is possible to tune the correlations for gas dissolved in oil RSGO, bubble pressure Pb and oil viscosity to measured data. Tuning of the correlations use data for a single fluid or a mixture. If there are several blackoil feeds (e.g., a network case), one must either tune to one of the fluids or to a mixture of the fluids. If the measurements are from a separator, the data available will typically be for the mixture. Please note that the tuned correlations are used for the whole network. See the description of the correlations for how the tuned parameters enter the calculations.

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the tuned parameters enter the calculations. Tuning is specified through the BLACKOILOPTIONS keyword.

Converting to mass flow rate When converting the volume flow rate at the standard conditions to the mass flow rate, the densities of gas, oil, and water that are used are taken from the corresponding blackoil components as given in BLACKOILCOMPONENT. When converting the in-situ mass flow rates to the volumetric flow rate at the standard conditions, the densities at the standard conditions are calculated from the blackoil correlations. The density from the blackoil correlations does not give the same density as the input. Therefore, the standard volumetric flow rates that are calculated by flashing the in-situ mass flow rate to the standard conditions differ from the standard volumetric flow rates given in the input. The difference is however within the uncertainty of the blackoil correlations.

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Limitations The blackoil module has the same limitations to its usability that the compositional tracking module.

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How to use Set the following keywords to use the blackoil module: OPTIONS to set COMPOSITIONAL = BLACKOIL BLACKOILOPTIONS to set GORMODEL (optional) BLACKOILCOMPONENT to set the properties of the gas, oil and/or water components BLACKOILFEED to combine the gas/oil/water blackoil components into feeds, and specify GOR and WATERCUT. NODE/SOURCE/WELL to set flow rates or volume fractions of the feeds to enter the pipeline system The steady state pre-processor may be used with the blackoil module. If one chooses to start from INITIALCONDITIONS, the initial volume fractions for the feeds must be given. See also: Sample case for Blackoil

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Complex Fluid Complex fluids are liquids with high viscosity, yield stress, or liquids exhibiting shear thinning. Such properties might arise in waxy oil or emulsions which often exhibit shear thinning and high viscosity, whereas a slurry of hydrate crystals in oil may have a yield stress depending on the particle concentration. Hydrate is a snow like substance formed by water and natural gas that might occur in hydrocarbon transport lines at ambient temperatures well above the normal freezing point of water at elevated pressure. Fluids that demonstrate both shear thinning and a yield stress, e.g., gelled waxy crude, can only be approximated using complex fluid models. The presence of yield stress or shear thinning in the liquid might result in a decreasing pressure drop with increasing production rates up to a certain point where the pressure drop is at a minimum, even for horizontal pipes. For production rates below this minimum, unstable operation might occur depending on the boundary conditions of the transport line. These instabilities can interact with other, more well known, multiphase flow phenomena such as terrain slugging and give rise to a wider range of unstable operational conditions. The purpose of the complex fluid model is to predict such behavior. See also: When to use Methods and assumptions How to use

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When to use The complex fluid module should be used whenever a fluid exhibits significant deviation from Newtonian behavior, either by shear thinning (e.g., heavy oils) or influence of yield stress (e.g., waxy oils). For Newtonian liquids, the module should be used when modeling fluids with viscosity above 50 cP and it has been tested up to 1000 cP.

License requirements The Complex Fluid Module requires a separate license.

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Methods and assumptions The complex fluid model utilizes the Bingham model for fluids exhibiting yield stress, while the Power law is used for shear thinning fluids. As opposed to the complex viscosity model, the complex fluid model includes numerous modifications to the physical models for both separated and distributed flow taking into account the non-Newtonian behavior of the fluids. Non-Newtonian behavior can be modeled for the liquid hydrocarbon phase, the water phase or both. The Newtonian option is included to capture the peculiarities of higher viscosity liquids. Bingham plastic model (a) where

Power law model (b) where K = consistency factor Newtonian fluid (c) where μ = viscosity When running standard OLGA, i.e., without slug tracking activated, the use of complex fluid yields an important improvement since the slug flow model includes the effects of the above rheologies and at the same time as it covers the range of Reynolds numbers from laminar to turbulent flow. This affects the bubble front velocity, and, consequently, the liquid accumulation. Furthermore, it yields a better model of the liquid flowing below the slug bubble as well as a better prediction of the slug fraction. Using this as basis for pressure drop predictions is a major difference from the complex viscosity model, which is very important for more viscous liquids. For stratified flow, the wall friction calculations should yield better results than when using an equivalent viscosity.

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How to use The Complex Fluid module is activated in the FLUID keyword by setting the key TYPE=COMPLEXFLUID. The fluid viscosity model to be used is determined by the keys CFLUML and CFLUMW for the liquid hydrocarbon phase and water phase, respectively. Except for the default Newtonian modeling, fluid viscosity can be modeled using either the Bingham model or the power law model. The parameters of the viscosity models can be given in two ways. If the key FULL=YES, the fluid viscosity parameters (yield stresses/power exponents) are read from the fluid property file as functions of pressure and temperature. If, on the other hand, FULL=NO, the yield stresses YIELDSRL and YIELDSTW or power exponents POWEXPL and POWEXPW have to be given if the liquid hydrocarbon or water viscosity model is set to BINGHAM or POWERLAW respectively. For both options, the viscosity given in the fluid file is interpreted as the plastic viscosity for Bingham fluids and as the consistency factor for Power law fluids.

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Compositional Tracking The compositional tracking model combines the powerful multiphase capabilities in OLGA with customised calculations for fluid properties and mass transfer. Part of this module is a software package developed by Calsep. With the compositional tracking model, every single fluid component is accounted for throughout the calculation, enabling simulation of scenarios such as start-up and blowdown with a high level of detail and accuracy. See also: When to use Methods and assumptions Limitations How to use

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When to use It is important to acknowledge that the extra level of detail given by compositional tracking compared to table-based approach is CPU-intensive and will increase the simulation time. Note that a higher number of components will also increase the simulation time. Standard OLGA will in many cases, such as for single pipeline flow and networks where the fluids in the pipelines are similar, give satisfactorily accurate results. Typical cases where compositional effects may have influence are: Networks with different fluids Changes in composition at boundaries Blowdown Gas injection / gas lift Start-up Shut-in and restart

License requirements The Compositional Tracking Module requires a separate license.

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Methods and assumptions The standard OLGA model uses a fluid table with material properties calculated for a predefined composition, and this composition is assumed to be constant throughout the whole simulation. Different compositions can be used for each branch in a system, but with compositions that are constant with time. In reality the composition may vary along the pipeline due to slip effects (velocity differences between phases), interphasial mass transfer, merging network with different fluids, elevated geometry, and changes in fluid composition at the inlet. In the Compositional Tracking model the mass equations are solved for each component (e.g. H2O, C1, C14-C22) in each phase (e.g. gas, liquid droplets, bulk hydrocarbon liquid and bulk water). Thus, the model will keep track of the changes in composition in both time and space, and will ensure a more accurate fluid description compared to using the standard OLGA model. Instead of using a fluid file with pre-calculated material properties, a so-called feed file must be generated (by PVTsim) and given as input to OLGA. The feed file contains information about the feeds (fluid composition used in a source or well and as boundary or initial conditions) that the user wants to use in the simulation, and about the components comprising the feeds. In addition, the user may define additional feeds through the FEED keyword. These feeds may only contain a set of the components defined in the feed file. It is not possible to define additional components outside the feed file.

PVT package The material properties of the fluid along the pipeline will be calculated continuously during the simulation, based upon the current conditions (i.e. local pressure, temperature and composition). These calculations are part of a PVT package delivered by Calsep. This PVT package uses functions that are similar to the ones used by PVTsim, although they are optimised for increased computational speed. PVTsim must also be used to characterize the fluid and generate the feed file to be used as input to the model. Moreover, the molar fractions and their derivatives with respect to the current conditions at phase equilibrium are also delivered by the package. Based on these results, the mass transfer between the phases needed for the mixture to be at equilibrium is calculated. Physical limits for the temperature and pressure used in the PVT calculations are introduced and can not be changed by the user (as it can with fluid tables). The temperature range is from -200 to 500 C and the pressure range is from 0.05 to 1000 bara. If the temperature or pressure goes out of range, they are reset to the upper or lower limits. These reset values are used in the PVT calculations only and are not fed back to the overall calculations of temperature and pressure. The phase equilibrium calculations in PVTsim are based on either the Soave-Redlich-Kwong (SRK) or the Peng-Robinson (PR) equation of state (EOS) [Soave (1972) and Peng and Robinson (1976)]. The fluid data in the feed file are based on one of these equations, with or without the Peneloux volume correction [Peneloux et al. (1982)], and the same EOS will be adopted in the OLGA simulation.

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Limitations Maximum number of components allowed in a feed file is 30. Except for this, there are no special limitations associated with the Compositional Tracking model. However, as described, be aware of the additional CPU-intensive calculations that are performed.

Other considerations Steady state pre-processor A compositional steady state pre-processor is implemented in OLGA. Process equipment The system can include process equipment such as critical and sub-critical chokes, compressors with controllers, check valves, valves, separators, heat exchangers, pumps, and controlled mass sources and sinks. Combination with other models The compositional tracking model can not be combined with other compositional models such as slug tracking, inhibitor tracking, blackoil or wax. Flow model The descriptions of the flow regimes, friction factors and wetted perimeters etc in the compositional tracking model are as in the standard OLGA model. Restart The Compositional Tracking model is available with full restart functionality. However, it is not possible to switch from or to the compositional model in a restart case.

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How to use Input In order to use the Compositional Tracking model, follow the steps below;

Step 1: Use PVTsim to characterize the fluids to the same pseudo components and generate the feed file with all the necessary compositional data for the fluid. The ”Plus” and ”No-plus” fluid types only require mole or weight fractions, mole weights and liquid densities. For the ”Plus” fluid, PVTsim will generate pseudo-components based on the last (plus) component. The ”Characterized” fluid type is used when the fluid characterization has been performed in another PVT tool, and requires all fluid properties such as critical temperature, accentric factor, etc. Choose ”Interfaces” from the Main Menu in PVTsim, and then choose ”Compositional Tracking”. In this window the feed file that is an input to the Compositional Tracking module is generated. The feeds defined in the feed file will then be available as feeds in OLGA, with the name specified in the Well column in the Fluid box in PVTsim as feed name.

Step 2: Prepare the OLGA input using the following keywords; OPTIONS; COMPOSITIONAL set to ON. FILE; FEEDFILE to specify the feed file name. FEED; to define additional feeds and their composition (use components from the feed file) COMPOPTIONS; to define calculation options to be used by the PVT routines. INITIALCONDITIONS; to specify initial feeds. SOURCE; to specify feeds and feed flows in the mass source. WELL; to specify feeds in the well stream. NODE; to specify feeds and feed flows in mass flow and pressure nodes.

Step 3: Specify output variables for detailed plotting of simulation information. OUTPUTDATA to print compositional information to output file (*.out). TRENDDATA to print compositional variables to trend file (*.tpl). PROFILEDATA to print compositional variables to profile file (*.ppl). PLOTDATA to print compositional variables to OLGA Viewer file (*.plt). Plot data for individual components can be specified with the addition of the COMPONENTS=() key to each plotting keyword. If COMPONENTS is not specified, it will be plotted for all components for the specified variable. Note: Output variables for rates at standard conditions (e.g. QGST) are CPU demanding since a flash must be performed, and should be used with care for Compositional Tracking simulations.

Special considerations In the keyword COMPOPTIONS the user should evaluate what flash algorithm to use, what kind of viscosity correlation to use, if any of the fluid components should be assigned delay constants, and if needed specify the density limit for the dense phase region. The user can also choose to use the default values, in which case none of these parameters have to be specified. 126 / 769

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Flash algorithms (key FLASHTYPE) The FLASHTYPE key specifies the flash algorithm to be used. FLASHTYPE = TWOPHASEFLASH treats water as an inert component. Hydrate inhibitors such as MeOH and glycols in the water phase will also be inert. A two-phase flash is carried out for the hydrocarbon components. There will not be any aqueous components in the hydrocarbon phases and no hydrocarbon components in the water phase. Classical mixing rule is used for all component pairs for the two-phase flash calculation. This is the only option allowed when performing simulations with fluids consisting purely of nonaqueous components. It may also be used with fluids containing aqueous components when high simulation speed is wanted, provided the amount of free water is believed to have little impact on the conclusions. It should not be used if: Hydrate control is important and MeOH or another component more volatile than H2O is used as inhibitor. Tracking of hydrocarbons and inorganic gasses dissolved in the aqueous phase is important. Tracking of aqueous components dissolved in a hydrocarbon liquid phase or a dense gas phase is important. FLASHTYPE = SIMPLETHREEPHASE means that the water components are treated as an inert phase initially. A two-phase flash is performed for the hydrocarbon components. Then aqueous components are added to the hydrocarbon phases, and hydrocarbon components and inorganic gasses are added to the aqueous phase until the fugacity is the same for all the phases. Classical mixing rule is used for all component pairs throughout the calculation. This approach involves two simplifications relative to full three phase flash The change in phase equilibrium due to dissolution of components in a phase is not taken into account, i.e. the result is not rigorous equilibrium but approximated equilibrium. A simplified model for the solubility of hydrocarbon components and inorganic gasses in the aqueous phase and vice versa is used. This is the default option when at least one aqueous component is defined in the feed file, and is expected to provide accurate results for most simulations involving fluids consisting of both hydrocarbons and aqueous components. Full three phase flash is recommended for rigorous simulations if Hydrate control is important and MeOH or another component more volatile than H2O is used as inhibitor. Tracking of hydrocarbons and inorganic gasses dissolved in the aqueous phase is important. Tracking of aqueous components dissolved in a hydrocarbon liquid phase or a dense gas phase is important. Note that simplified three phase is the recommend option for performing screening/approximate simulations where high accuracy may not be required even in the aforementioned cases. This is due to the full three phase option being significantly slower than the simplified three phase option. FLASHTYPE = FULLTHREEPHASE means that a full three-phase flash is performed for the total composition. The fugacity of all the components in all the phases is the same. All the phases are in rigorous equilibrium, i.e. any component can dissolve in any phase. Classical mixing rule is used for component pairs not involving aqueous components while the Huron-Vidal mixing rule is used for all component pairs involving aqueous components. 127 / 769

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This option is significantly slower than the simplified three phase flash option. It is recommended as an option to make a final check of whether the accuracy obtained using the simplified three phase flash is adequate for the given case. Full three phase flash is also recommended if Hydrate control is important and MeOH or another component more volatile than H2O is used as inhibitor. Tracking of hydrocarbons and inorganic gasses dissolved in the aqueous phase is important. Tracking of aqueous components dissolved in a hydrocarbon liquid phase or a dense gas phase is important. Note that simplified three phase is the recommend option for performing screening/approximate simulations where high accuracy may not be required even in the aforementioned cases. This is due to the full three phase option being significantly slower than the simplified three phase option. This is the only option allowed when performing simulations with fluids containing salts.

Viscosity correlations (key VISCOSITYCORR) The VISCOSITYCORR key can be used to specify the viscosity calculations. The viscosity calculations can be based on the corresponding states principle (CSP) or the LohrenzBray-Clark (LBC) correlation (1964). If the fluid has been tuned to one of the correlations in PVTsim, it is not possible to choose a different correlation in OLGA Compositional tracking module (an error will be given if the other correlation is chosen). The default viscosity correlation is CSP. When using CSP the PVT code executes 2-3 times slower than when LBC is used. Since 10-90% of the calculation time in an OLGA simulation is spent in the PVT code, the cost of using CSP instead of LBC may vary a lot. However, the LBC model is not reliable as a predictive model. The following steps should therefore be taken when using LBC: Tune LBC to experimental or simulated CSP viscosity data in PVTSim. Check if tuned oil viscosity data match reasonably well with the experimental data. If a good match cannot be obtained, use the CSP viscosity model in OLGA Compositional Tracking module (a mismatch is more likely for heavy oils). Substantial tuning of the a-coefficients in the LBC-model can affect the gas viscosity. Evaluate gas viscosity before and after tuning if the a-coefficients are changed considerably. In case the CSP viscosity model is chosen, it is still recommended to tune to experimental viscosity data if available. The predictive capability of the CSP model is within 10% up to viscosities of approximately 1 cP. For higher viscosities the capability is more uncertain. It is further recommended to consider if oil viscosities at temperatures below approximately 20-40 C are influenced by precipitated wax. The CSP and LBC viscosity models cannot account for the influence of precipitated wax, nor the non-Newtonian effects associated with the precipitation. The CSP and LBC models may still be forced to follow the apparent oil viscosities. Since the Compositional Tracking module does not account for wax precipitation/ deposition, viscosities will follow the apparent oil viscosity.

Dense phase specification (key DENSITYLIMIT) The DENSITYLIMIT key specifies the limit for the dense phase region density. 128 / 769

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In the dense phase region (see Figure A below), there are no good criteria to distinguish gas from oil, and the "chosen" phase does not affect the fluid properties for simulations with Compositional Tracking. This can be a problem especially for INITIALCONDITIONS where a user specifies e.g. voidfraction=0 for an entire branch, but gets an error saying that this is not valid input since there is no liquid for parts of the branch. The user then has to specify voidfraction pipe-wise, which can be a lot of work. Also, PVTsim might predict another phase than Compositional Tracking since a different and more time demanding approach is used, which adds to the confusion.

Figure A. Dense phase region. In the dense phase region, a fluid with higher density than the given DENSITYLIMIT value is defined as liquid and a fluid with lower density is defined as gas. If the user gets an error saying there is no gas for this branch the DENSITYLIMIT should be increased. The DENSITYLIMIT should preferably be set equal to the density found in PVTsim when performing a flash at the critical point. If not specified, internal routines will be used to decide phase (which may cause instabilities when crossing bubble/dew point). Note: The use of DENSITYLIMIT can also reduce oscillations, such as for cases with decreasing pressure where different sections cross from the dense phase region to the two phase region on each side of the critical temperature.

Delay constants (keys TCONDENSATE/TVAPORIZATION) The keys TCONDENSATE and TVAPORIZATION are non-equilibrium delay constants for the mass transfer from liquid phase to gas phase and vice versa. The keys can be introduced for each component, and the equilibrium state reached in the flash calculations will be delayed. The default is no delay. In the non-equilibrium model the convective mass transfer terms are calculated according to: (a) where u is the superficial velocity of the mixture flowing into the section calculated for the equilibrium conditions at the section and DZ is the section length. is the convective mass transfer term calculated by the equilibrium model for component fc. TDELAY,fc is the non-equilibrium delay factor for component fc, which has the dimension seconds. The user must specify the value of this factor, and separate values can be given for vaporization (TVAPORIZATION) and condensation 129 / 769 (TCONDENSATION).

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(TCONDENSATION). The local non-equilibrium mass transfer term is derived from the following equation:

(b)

where is the local mass transfer term calculated by the equilibrium model and is the delay factor for component fc for condensation or vaporization dependent on the sign of the equilibrium mass transfer term. This yields:

(c)

Output The keywords OUTPUTDATA, TRENDDATA, PROFILEDATA and PLOTDATA in the input file specify the data collection from the simulation. The output file (*.out), trend file (*.tpl), profile file (*.ppl) and plot file (*.plt) can be used to show detailed compositional information: Mass flow rate for each component in each phase (oil droplets, oil film, total oil phase, water droplets, water film, total water phase, and gas) Mass rate of flashing for each component to gas phase, oil phase and water phase Specific mass for each component in each phase Mole fraction for each component in gas phase, oil phase and water phase Equilibrium mole fraction for each component in gas phase, oil phase and water phase Mass fraction for each component in gas phase, oil phase and water phase Equilibrium mass fraction for each component in gas phase, oil phase and water phase Total mole fraction (all phases) for each component Total mass in branch for each component The output file shows information textually and is structured for easy reading. The trend file and profile file are ASCII files that can be plotted graphically in the OLGA GUI. The plot file is a binary file that is viewed in a separate plotting tool called the OLGA Viewer. Due to the binary format, which reduces the file size, this form of data collection can use a shorter plotting interval and is useful for detailed analysis.

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Controller introduction: Controllers is in OLGA terms a network component labeled “signal component” which mean that they can communicate with other network components by sending and receiving signals. Other network components may be other signal components or flow components (i.e. a branch). Controllers are typical signal components but also other types of network components may be signal components. All controllers have one common key; LABEL, which are used to identify the controller. There are 13 different types of controllers: Algebraic Controller ASC Controller Cascade Controller ESD Controller Manual Controller Override Controller PID Controller PSV Controller Scaler Controller Selector Controller STD Controller Switch Controller Table Controller

Both analog and digital controllers can be simulated in OLGA (see Analog vs. digital controllers for further details). A controller can be set to one of five different modes operation either by using time series in the MODE sub-key or hooking a defined controller up to the MODE terminal (see Controller modes for further details). In addition to implementing the possibility to switch the controller mode, the current version of OLGA also implements the possibility to “activate” and “deactivate” the controllers by hooking an external controller up to the ACTIVATE terminal (see controller activation/deactivation for further details). The controller output is constrained; see constraining the controller output for further details. In the most advanced usage of the OLGA controllers utilizes the possibilities of interconnecting controllers by the use of terminals. A description to the different terminals is given in controller details.

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Analog vs. digital controllers For all the controller types, the digital controller option can be selected by using the key SAMPLETIME. The difference between analogue and digital sampling in an OLGA simulation is as follows: The analogue controller collects input and gives a corresponding output at each simulation time step. The MAXCHANGE sub-key specifies the maximum allowed change in controller output from one time step to the next. The default value is 0.2. The automatic integration time step mechanism ensures that the relative change in the output signal of the controller from one time step to the next will never exceed MAXCHANGE. The digital controller collects input and generates a corresponding output at time points separated by time intervals given in sub-key SAMPLETIME. There may be one or more OLGA integration time steps in between each sample time point. The automatic time step control assures that a simulation time point always agree with a sample time point (to the accuracy specified in the MAXCHANGE sub-key). The output signal from the controller is kept constant during the sample time interval.

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Controller mode A controller in OLGA can be set in one of the five different modes:

Automatic In MODE = AUTOMATIC, the controller behaves according to the controller function as specified for the different controller types. For those controllers that make use of setpoint the value in MODE = AUTOMATIC is taken from the SETPOINT key.

Manual In MODE = MANUAL, the controller function is bypassed and the controller output is set according to the time series definition of key MANUALOUTPUT.

External signal In MODE = EXTERNALSIGNAL, the controller function is bypassed and the controller output is set according to the external controller connected to the SIGNAL terminal.

External setpoint The controller MODE = EXTERNALSETPOINT is similar to MODE = AUTOMATIC except that the setpoint is taken the controller connected to the SETPOINT terminal.

Freeze In MODE = FREEZE, the controller function is bypassed and the controller output is kept constant (equal to the previous output value). The controller MODE can be manipulated either by time series or by another controller. To manipulate the mode of a controller by time series, specify the sequence in the MODE sub-key. The predefined literals: AUTOMATIC

value 1

MANUAL

value 2

EXTERNALSIGNAL

value 3

EXTERNALSETPOINT value 4 FREEZE

value 5

are used when specifying the MODE through MODE sub-key in the GUI and input file. The MODE subkey is interpreted together with the TIME sub-key. When using the terminal to change the mode of a controller one need to connect an external controller to the MODE terminal. E.g. to manipulate the mode of controller A by a controller labeled A.MODE connect controller A.MODE to the MODE terminal of controller A. The mode of controller A id the dependent on the output value of A.MODE A.MODE

<

1.5

gives AUTOMATIC

1.5

<=

A.MODE

<

2.5

gives MANUAL

2.5

<=

A.MODE

<

3.5

gives EXTERNALSIGNAL

3.5

<=

A.MODE

<

4.5

gives EXTERNALSETPOINT

4.5

<=

A.MODE

gives FREEZE

All controllers except “Table” and “Scaler” have MODE implemented. The definition on MODE through the use of the MODE terminal overrules the definition of MODE given by the MODE sub-key. 133 / 769

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Controller activation/deactivation In addition to implementing the possibility to switch the controller mode, the current version of OLGA also implements the possibility to “activate” and “deactivate” the controllers by hooking an external controller up to the ACTIVATE terminal. A controller A might be deactivated and activated by connecting an external controller A.ACTIVATE to the ACTIVATE terminal of controller A. Then controller A is active if the output of A.ACTIVATE is greater or equal to 0.5. When a controller is “deactivated” (A.ACTIVATE < 0.5) the controller function is bypassed and the controller output is kept constant (equal to the previous output value). When a controller is activated the output is calculated according to the controller function and any specification of MODE. The deactivation of controllers takes precedence over controller function and mode. For further details see the description of the controller details.

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Constraining the controller output The controller output is constrained in two steps. First controller output is checked against signal constrains; secondly the controller output is checked against rate of change constraints. The signal constraints are specified in the keys MAXSIGNAL and MINSIGNAL. If the controller output is greater or equal to MAXSIGNAL then the output signal is set equal to MAXSIGNAL and the SAUTRATED output is set equal to 1.0 to signal “high saturation”. If the controller output is less or equal to MINSIGNAL then the output is set equal to MINSIGNAL and the SATURATED output is set equal to -1.0 to signal “low saturation”. If the rate of change in the controller output violates the OPENINGTIME (or STROKETIME) the controller output is set equal to the maximum allowed output satisfying the rate of change constraint and the RATELIMITED variable is set equal 1.0 to signal a “high rate of change saturation”. If the rate of change in the controller output violates the CLOSINGTIME (or STROKETIME) the controller output is set equal to the minimum allowed output satisfying the rate of change constraint and the RATELIMITED variable is set equal -1.0 to signal a “low rate of change saturation”.

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Controller details Figure A below shows a block diagram of how different inputs and outputs relate to different part of the controller implementation.

Figure A: Overall block diagram for controller implementation. In Figure A above and Figure B below: inputs in terms of sub-keys are given in boxes framed by an orange line, inputs given through terminals are given in boxes framed by a green line and internal calculation boxes are framed by a black line and gray background color. The larger block “Controller function + Controller mode” in Figure A, implements the controller functionality given by the controller type, the controller modes and the controller activation deactivation. Output A from the “Controller function + Controller mode” block represents the unconstrained output. The unconstrained output is checked against sub-keys MAX/MINSIGNAL and forms the constrained output B. Finally, output B is checked against rate of change constrains (OPENINGTIME and CLOSINGTIME) to form the final constrained output CONTR. Note, the additional outputs SATURATED and RATELIMITED. These are used to signal saturation and rate of change limitation to other controllers.

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Figure A: Implementation of controller modes and activation/deactivation mechanisms. Figure B shows the implementation of modes and activation/deactivation mechanisms. Depending on the controller type the controller function block may or may not need the setpoint sub-key. Controller type PID is an example of a controller type that makes use of the setpoint sub-key, whereas controller type OVERRIDE does not use the setpoint sub-key. The controller function block may also use additional terminals and sub-keys not shown in Figure B. If mode is AUTOMATIC (mode value one) the setpoint is taken from the sub-keys and if mode is EXTERNALSETPOINT (mode value four) the setpoint is connected to the setpoint terminal. This is illustrated by the upper left switch in Figure B. The lower left switch in the figure determines how MODE is set. This switch cannot be changed during runtime. If a controller is connected to the MODE terminal, it is value obtained through the terminal that determines the mode of the controller irrespective of what is set in the MODE sub-key. If no controller is connected to the MODE terminal then it is MODE sub-key that determines the mode of the controller. If MODE is AUTOMATIC or EXTERNALSETPOINT then the output of the controller function (CF) block is routed through the larger switch in the figure (position one or four at the input of the switch) and the corresponding setpoint is connected to the controller function. If MODE is MANUAL the manual output signal is routed through the switch (position two at the input of the switch). When the MODE is EXTERNALSIGNAL the SIGNAL TERMINAL is connected to the output of the switch (position three at the input of the switch). When MODE is FREEZE the lower memory block is connected to the output of the switch (position five at the input of the switch). The memory blocks hold the previous output value. Thus the output is frozen (kept constant).

-

The activation/deactivation mechanism is illustrated by the switch with two inputs and memory block on the right in the figure. If the controller is activated (ACTIVATE = true, or value greater or equal to 0.5) the activate switch is in position two connecting the controller to the output A. If the controller is deactivated (ACTIVATE = false, or value less than 0.5) then the activate switch is in position one connecting the output A to the previous value, thus the output is frozen (kept constant).

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Controller Terminals Most of the controller types will have the following input terminals: MODE – used to set the mode of a controller SIGNAL – used to override the output of the controller when MODE = EXTERNALSIGNAL SETPOINT – used to override the setpoint key when MODE = EXTERNALSETPOINT, e.g. cascaded controllers ACTIVATE – used to activate deactivate the controller function All controllers will have the following output terminal: OUTSIG_1..N – Used to connect the controller output to another input signal terminal. In the controller output terminal OUTSIG a number of output variables are available. The variable transmitted is set-up (specified) in the signal connection. See controller details for further information.

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Actuator time of controlled device There are no restrictions on the rate of change of the output from the controller algorithms. The output from the controller frequently changes faster than the device is capable of following. This situation is taken care of by passing all output from the controllers through an actuator filter that computes a 'real' output (as observed by the devices) according to the rule:

(d) or (e) where tact,open - is the actuator time when increasing U tact,close - is the actuator time when decreasing U Dt - is the time step Uold - is previous output signal from the controller U - is output signal from the controller Umax - is the maximum output signal from the controller Umin - is the minimum output signal from the controller The actuator time is specified as stroke time or the time required to open/close. The user specifies minimum and maximum controller output signal, Umin and Umax. These two parameters determine the operating range of the controller. Normally the operating range is from 0 to 1., i.e., an output of 0 from a controller operating on a valve means that the valve is closed, whereas an output of 1 means that the valve is fully open.

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Connecting the controllers All the controllers have a set of input and output signal terminals. The output terminals (OUTSIG) can be distributed to several receiving terminals. When connecting output signals the first available terminal will be named OUTSIG_1. The next terminal will be named OUTSIG_2 etc. In general it is written OUTSIG_1..N, to show that the terminal OUTSIG can be connected an arbitrary number of times. It is required that some of the input terminals are connected. The required input is different for the different types of controllers. Connecting the output terminals is optional. The controller output can be connected to process equipment (Valve, Pump etc.). The controller input is connected to output from another controller, a transmitter or some process equipment. Example: PID pressure control The PID controller has the following terminals: MEASRD (Required input) SETPOINT (Optional input) OUTSIG_1..N (Optional output) The input terminal MEASRD is required, while the input terminal SETPOINT is optional. The PID controller has internal setpoint given as key input. But the user can connect an external setpoint to the controller. In order to use the external setpoint the SETPOINTMODE must be set to EXTERNAL.

Figure A: Pressure control example In Figure A the measured pressure is taken from a transmitter (PT). The controller (PC) output is connected to the valve opening. Connection (1): TRANSMITTER OUTSIG_1 → CONTROLLER MEASRD A variable and unit must be defined for the output from the transmitter. Ex. ”PT bara” Connection (2): CONTROLLER OUTSIG_1 → VALVE INPSIG

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Controller Setpoint Most controllers take a setpoint as input. The setpoint can be connected as an input terminal or given as a time series. If it is given as a time series the keywords SETPOINT and TIME must be given. Figure B shows how the controller setpoint is changed for the following SETPOINT/TIME input: SETPOINT = (0, 1, 0.5) TIME = (0, 1, 2) Note that the setpoint change in a step wise manner.

Figure B: Setpoint vs. time

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Controller measured variable Most controllers take an input signal in terms of a measured variable, see terminal MEASRD and/or terminal INPSIG. The measured variable can be delayed by specifying the DELAY key on the controllers (avaiable on most controllers). If the DELAY key is set to 10 seconds, the measured variable is delayed 10 seconds before it is taken into account in the control algorithm.

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Algebraic Controller The algebraic controller is used to combine input signals to form algebraic equations and logical expressions. The algebraic controller issues a control signal to a device (e.g. a valve) or as an input signal to other controllers. See also: When to use Methods and assumptions How to use

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When to use Use to change a variable in a process unit (e.g. Valve, Pump) or an input to another controller according to an algebraic function or a logical expression. Ex. Make the valve opening dependent on more then one signal and an algebraic expression. Ex. Make the valve opening dependent on a logical expression. Ex. Activate deactivate controllers according to a logical expression. Ex. Non-linear transformation a measured signal to a controller.

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Methods and assumptions The algebraic controller takes a number of input signals and combine these according to the specified VARIABLEFUNCTION key. The computed output signal is affected by maximum, minimum constraints and by rate of change constraints (opening, closing time or stroke time), see Constraining the controller output and Actuator time of controlled device.

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How to use Connect the required input signal(s) to the INPSIG_1..N terminal(s). Specify the operators to act on the input signal(s) in the VARIABLEFUNCTION key. Connect the controller output signal OUTSIG_1..N to a device variable. The figure below shows how multiple controller blocks can be combined in one algebraic controller.

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ASC Controller The main purpose of the ASC unit, is to prevent a compressor from operating to the left of the Surge Line in a compressor performance map, see Figure A: Compressor characteristic diagram, Figure B: Recirculation loop and Figure A: Anti Surge Controller. See also: When to use Methods and assumptions How to use

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When to use Use to control the recycle flow for compressors, and to avoid compressor surge.

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Methods and assumptions An ASC should be able to open the recirculation valve very fast to prevent a dangerous surge condition. This can be achieved by choosing a high amplification factor for the ASC and selecting a recycle valve with a short stroke time. But the ASC must also be capable of managing a situation where the compressor inlet or discharge is closed. The high amplification factor could give excessive compensation, which would cause the recirculation valve to hunt between open and closed position and aggravate the surge due to pressure and flow pulsation. Therefore it is necessary to have a controller that can operate on a non-linear control algorithm. In essence, the controller shall apply one level of amplification and integral action to a positive error input signal and a different level of amplification and integral action to a negative error input signal. In this way the recycle valve can be opened rapidly while an inertia is imposed when it is closed again. The ASC unit uses a standard PID controller formula except that it allows for two different controller amplifications (AMP1 and AMP2) that are necessary when operating on a non-linear control algorithm. AMP1 is used when the deviation parameter (e) is negative (left of anti surge control-line in the compressor performance map) and AMP2 when it is positive. The anti surge control-line is the setpoint for the ASC unit and is calculated by multiplying the compressor surge flow at different RPM's with a constant security factor specified by the user through the compressor input group, COMPRESSOR (i.e. a security factor of 1.2 means that the set point for the ASC unit is 20% higher than the surge flow). The surge flow at different RPM's, is specified in the compressor data file. The surge flow increases with increasing RPM, which means that the setpoint for the ASC unit is not constant. By using a large AMP1 and a (corresponding) small AMP2, the anti surge control valve is forced to a rapid opening whereas the closing operation is more relaxed. Figure A shows the ASC application.

Figure A: Anti Surge Controller The cascade controller uses the PID algorithm, see Proportional Integral Derivative (PID) Algorithm. The ASC controller have the same functionality as the PID controller, in addition to the functionality described in this section. See PID Controller Methods and assumptions (Jump to: PID controller Methods and assumptions).

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How to use See Connecting the controllers for an example on how to connect a controller. Connect the compressor output (QGSURGE) to the ASC controller setpoint (SETPOINT). (Connect the compressor OUTSIG to the ASC setpoint and specify QGSURGE as variable.) This is the volume flow (default unit m3/s) at predicted surge multiplied with a security factor. The security factor is given in the compressor SECURITYFACTOR key. Put a transmitter at the same section boundary as the compressor. Connect the gas volume flow QG to the ASC controller measurement terminal (MEASRD). Make sure QG and QGSURGE have the same units. The MEASRD terminal must be connected. Connect the ASC controller output to the Compressor ASCSIG input terminal. Figure B shows the connection possibilities of the ASC controller.

Figure B: ASC controller connection terminals

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Cascade Controller The purposes of a cascade control loop are: 1. To reduce the effects of some disturbances. 2. To improve the dynamic performance of the control loop. To achieve this cascade control utilize multiple feedback loops. See also: When to use Methods and assumptions Limitations How to use

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When to use Cascade control is used when there are disturbance associated with the manipulated variable, or when the final control element exhibits nonlinear behaviour. Examples of use is: Level control in a separator. The separator holdup changes are slow compared to flow dynamics. See Figure A: Cascade control. Temperature control when two fluid flows are heat exchanged. The temperature dynamics are slow compared to the flow dynamics.

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Methods and assumptions As illustrated below in Figure A a cascade control uses two (or more) controllers with the output of the primary controller changing the setpoint of the secondary controller. The output of the secondary controller regulates the control device, here the drain valve.

Figure A: Cascade control The OLGA cascade controller will represent the inner loop. That is; the secondary controller shown in Figure A. The cascade controller uses the PID algorithm, see Proportional-Integral-Derivative (PID) Algorithm. See also the PID Controller Methods and assumptions. The Cascade controller have the same functionality as the PID controller, in addition to the functionality described in this section. The cascade controller can be in normal or extended mode. The difference between the two is how the setpoint of the secondary controller are determined. For the normal cascade controller, the setpoint of the secondary controller is determined by the output of the primary controller: (a) Where S the setpoint of the secondary controller Smin minimum setpoint Smax maximum setpoint Cp output from the primary controller For the extended cascade controller, the setpoint is calculated differently: (b) Where (c)

Sn Sn-1 Cp Cp,min

C = C1

if

|PM - Ps| > Cswitch

(d)

C = C2

if

|PM - Ps| £ Cswitch

(e)

setpoint of the secondary controller at the current time point setpoint of the secondary controller at the previous time point output from primary controller minimum of output from primary controller 154 / 769

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Cp,max Ps Dt PM Tav C C1 C2 Cswitch

maximum of controller output from primary controller setpoint of the primary controller numerical time step (tn - tn-1) moving averaged of the primary controller variable P user defined (moving) averaging time period constant that can take two different values user defined constant user defined constant user defined constant

For the level control as illustrated above, suppose the separator pressure increases. The pressure drop over the drain valve will be larger, so the liquid flow will increase. With a single level controller, the drain flow rate will not be corrected until the increased drain flow decreases the liquid level. Thus the separator pressure disturbs both the liquid level and the liquid drain rate. With the cascade control loop, the flow controller (secondary controller) will immediately see the change in the flow rate and correct the valve opening to return the drain flow rate to the setpoint set by the level controller. Thus it gives a better control on the liquid level and a smoother liquid drain rate.

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Limitations Secondary loop process dynamics should be at least four times as fast as primary loop process dynamics.

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How to use See Connecting the controllers for a example on how to connect a controller. The cascade control loop is built as two separate PID controllers, where the output from the primary controller is used as a setpoint of the secondary controller. The cascade controller require that the measurement terminal (MEASRD) and the setpoint terminal (SETPOINT) are connected. Figure B show the connection possibilities of the Cascade controller.

Figure B: Cascade controller connection terminals

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ESD Controller Emergency-Shut-Down (ESD) logics are used to avoid damage on the process equipment and the pipeline. A ESD controller closes, output goes from 1 to 0, when a measured process variable rises above (or fall below) a safety limit. See also: When to use Methods and assumptions How to use

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When to use Use to model safety control system. Example of use: Shutdown of a pump downstream a separator. If the liquid level in a separator becomes to low, gas might flow in the pump feed. Gas in the feed might damage the pump.

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Methods and assumptions The controller will monitor one or more variables (normally pressure). As soon as any of the variables becomes less than or greater than the setpoint value, depending on opening mode, a controller signal activates a valve that will close within a certain time. If a reset value is specified, the ESD valve will open again when all of the controlled variables become greater or less than the reset value. The output signal is limited with stroke time. See Actuator time of controlled device.

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How to use See Connecting the controllers for an example on how to connect a controller. Connect the measured value (e.g. a pressure). The MEASRD terminal must be connected. The ESD output is typically connected to some process equipment or a pressure driven source/leak. Set the setpoint where the controller should close. If the controller should automatically open, enter a reset value. Include sufficient hysteresis for the reset value compared to the setpoint value. In this way a situation where the ESD output oscillates will be avoided. That is; a situation where the ESD closes in one time step, opens the next, closes again in the next etc. Figure A show the connection possibilities of the ESD controller.

Figure A: ESD controller connection terminals

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Manual Controller The manual controller is used to simulate the actions of an operator. The manual controller issues a control signal to a device (e.g. a valve). See also: When to use Methods and assumptions How to use

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When to use Use to change the process unit (e.g. Valve, Pump) inputs manually. Ex. Simulate a manual change in valve opening. Ex. Simulate a manual ramp-up of a choke. Ex. Simulate a starting leak from the pipeline.

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Methods and assumptions The manual controller take a setpoint as an internally defined time series, or as a input signal. The changes in setpoint will be applied immediately, that is; the setpoint will change in a step wise manner. The input signal is filtered through with stroke time limitations. This can be avoided by setting a low stroke time. See Actuator time of controlled device.

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How to use Give the required setpoint changes, and connect to a device variable. The manual controller don’t require any of the signal terminals to be connect. Figure A shows the connection possibilities of the manual controller.

Figure A: Manual controller connection terminals

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Override Controller The Override controller acts as a minimum or maximum operator on its input. It can be configured to select the lowest or highest value among several inputs. See also: When to use Methods and assumptions How to use

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When to use When there are fewer variables to manipulate than there are variables to control. The controllers (or measurements) of the controlled variables need to share the manipulated variables.

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Methods and assumptions The override controller can be a low select or high select operator. The override controller requires one or more input signals. The input signals can come from any other output terminal. In low select mode the minimum input signal is selected as the final output signal from the unit. A typical application of the controller unit in a process module is shown in Figure A.

Figure A: Double PID controller used as a turbine speed controller Here the output signal from two pressure controllers (PC) are connected as input to the override controller. One of the pressure controllers is controlling the suction pressure before the first compressor stage, and the other is controlling the pressure downstream of the second compressor stage. In normal operation, the speed is controlled by the suction pressure controller, but in situations where the outlet pressure approaches the maximum operating pressure, the speed is controlled by the high pressure controller. Figure B shows a typical application of the override controller (OC) with input signal from three controllers in a process module. The override controller is in low select mode. The flow controller (FC) is controlling the flow downstream of the control valve (choke) while the pressure controllers (PC) are controlling the pressures upstream and downstream of the control valve. In normal operation, the valve is controlled by the flow controller. In situations where the pressure downstream of the control valve approaches the maximum operating pressure (set-point for downstream pressure controller), the valve is controlled by the high-pressure controller. In situations where the pressure upstream of the control valve approaches the minimum operating pressure (set-point for upstream pressure controller), the valve is controlled by the low-pressure controller.

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The output signal is limited with stroke time. See Actuator time of controlled device.

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How to use See Connecting the controllers for an example on how to connect a controller. Select the mode of operation by setting SELECTIONMODE. Connect the signals the override controller should operate on. The Override controller require that at least one input terminal is connected. Figure C shows the connection possibilities of the Override controller.

Figure C: Override controller connection terminals

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PID Controller The main function of a PID controller is to maintain process parameters within specified bounds by controlling process equipment parameters like valve opening and compressor speed. See also: When to use Methods and assumptions How to use

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When to use To stabilize a process variable, or to stabilize an entire pipeline. To model actual control functionality used to stabilize pipe flow. A typical application of the controller unit in a process module is to control a separator level (Figure A) and it is then called a level controller. Input process parameter is liquid level in the separator and the output signal from the controller is used to control the opening of a drain valve. The controller may alternatively have flow, pressure etc. as input signal, and is then called a flow controller, a pressure controller etc.

Figure A: PID controller used as a level controller

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Methods and assumptions The PID controller uses the Proportional-Integral-Derivative (PID) Algorithm, see below. The PID controller limits the output with the stroke time of the connected device (e.g. Valve). See Actuator time of controlled device. The controller uses Anti-Windup. When the controller reaches maximum/minimum output (saturates) the integral is kept to a proper value, so that the controller is ready to resume action, as soon as the control error changes. The anti-windup used is a tracking/back calculation scheme. Transfer between setpoint modes are made bumpless. When the setpoint mode change, the integral term is corrected to remove a sudden jump in the controller output. If the PID controller output is connected to a Selector or a Override controller it might become inactive. See Selector and Override controllers. There are four different modes for the controller when it becomes inactive. The Selector or Override controller will automatically set the PID controller in a active/inactive state. Actions taken when the controller becomes inactive (keyword INACTIVEMODESUBC): ONHOLD Restore old values, everything is on hold. INTERLOCK The PID controller get feedback on the output signal used (uused) from the connected controller (Selector or Override). If the PID controller becomes inactive it will use uused to back calculate its integral error. DEFAULTINPUT Compute output signal based on default input, given in key DEFAULTINPUT. NORMAL No action for normal mode. Proportional Integral Derivative (PID) Algorithm A PID algorithm may be mathematically formulated as:

(a) (b) where: x = input process parameter (pressure, level, etc.) = time constant u = output signal from controller t = time bias = initial value Subscripts: stp = set point (or reference point) i = integral d = derivative 0 = time at start of simulation 173 / 769

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The amplification factor Kc is a dimensioned quantity. If the option with normalised amplification factor is used, the program will calculate Kc using the range given with the following expression: (c) For non-linear controllers, KC, i, d can be given in tabular form as a function of the error signal e. An error is then given as a vector (keyword input). The PID parameters keys for KC, i and d must be specified as vectors with the same dimension as . The controller parameters are found by linear interpolation in the actual controller error, e. The non-linear controller option is activated when the PID parameters are given as vectors, and not as single values. By using this general formula, simpler controllers as P and PI controllers can be defined by giving proper values to the time constants in the PID formula. The table below shows time constants for simpler controllers. Table 1: Time constants for P, PI and PD controllers Time constants d i P controller 0.0 109 PI controller 0.0 < 108 PD controller > 0.0 109 This controller formula is frequently referred to as a standard PID controller in the manual.

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How to use See Connecting the controllers for an example on how to connect the PID controller. The PID controller require that a measurement value is connected to the controller. (Signal terminal MEASRD). The setpoint must be given in the key SETPOINT, or connected to the SETPOINT input terminal. Figure B shows the connection possibilities of the PID controller.

Figure B: PID controller connection terminals PID controller example Three parameters are at our disposal for tuning a PID controller, Kc, td and ti. However, for petroleum applications td is rarely used (td = 0), since there is usually quite a lot of noise on the input process signal. This results in rapid oscillations in the derivative of the signal, and if the derivative term in the controller equation were included this would result in oscillations in the controller output, which is not desirable. We have the following relation between the symbols used in this description and the OLGA input variables in the CONTROLLER keyword: Kc td ti bias x xstp

= AMPLIFICATION = DERIVATIVECONST = INTEGRALCONST = BIAS = VARIABLE = SETPOINT

Note that the stroke-time of the controller valve (defined through STROKETIME) does not directly influence the controller output as discussed here. However, the opening and closing speed of the controller valve is limited by the stroke-time. That is, if the stroke-time is given as 100 s the opening of the valve will at maximum change by 1% per second. Level control A typical application of a level controller is shown in the Figure A: PID controller used as a level controller. The change in the liquid volume fraction in the vessel (b) is given by (a)

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where Qin [m3/s] is the liquid volume flow into the vessel, Qout [m3/s] is the liquid volume flow out of the vessel and V [m3] is the volume of the vessel. The flow out of the vessel can be written (b)

where Qmax is the maximum flow when the controller is fully open. For the current case, the error (e) is defined as liquid volume fraction minus the volume fraction at the setpoint, and the derivative time constant is set to zero. Taking the time derivative of the above two equations with the use of the control equation (Jump to: Equation a in the following differential equation is obtained

(c) Where f(t) is a disturbance that the control system should compensate for. Casting it into the standard form (d) we get the time constant of the control loop

(e) and the damping coefficient

(f) Kc must be positive for tp and z to be real numbers. The figure below shows the performance of control loop for different damping constants for a step disturbance at t = 0 (f(t) has a step increase). This could for instance be that the setpoint of the level control is changed.

Figure C: Response of level control to step disturbance. 176 / 769

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From this figure, one can see that a damping coefficient from 0.5-0.7 will give satisfactory results for level control. Therefore, one may use the following procedure to select the parameters for level control: 1. Size the drain valve so that it can deliver Qmax = two times the normal drain rate for the pressure difference between separator pressure and backpressure of the drain valve. 2. Set Kc < 2 and choose ti (the integral time constant) to make the damping coefficient between 0.5 and 0.7. Flow control Assuming constant upstream and downstream pressure over the valve, the flow rate can be written as: (g) where: F = flow rate (mass or volumetric flow rate) Fmax = max flow rate through the fully open valve at the given pressure drop u = output signal from controller Taking the time derivative of the above equation and using the control equation we obtain

(h) or (i) For the solution to be stable, Kc must be negative. The time constant of the solution is (j) Figure D shows the response of the flow to a step change in for example setpoint (f(t) has a step increase).

Figure D: Response of flow control to step disturbance. The shorter the time constant, the faster the response goes to the setpoint. One could use the following procedures to select the controller parameters for flow control. 1. Estimate the upstream and downstream pressure over the control valve at the design flow rate. If 177 / 769

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the pressure difference is less than e.g. 0.2 bar, adjust the upstream or downstream pressure so that the difference is at least 0.2 bar. This is considered a convenient pressure drop over a valve being used for flow control. 2. Size the valve so that it can deliver maximum flow rate = 2 times the designed value for the same pressure drop over the valve. 3. Set with A ranging from 1 to 10. 4. tp can be selected from the above chart, depending on how fast you want the flow rate to reach e.g. 90% of the set point. When tp has been chosen ti is found from the definition of tp. 5. By choosing a different A, the same tp can be obtained for a different ti.

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PSV Controller A Pressure-Safety-Valve (PSV) typically opens fast when the pressure rises above a defined value. When the valve is opened the pressure is relieved. The safety valves are included to avoid damage on the process equipment and the pipeline. The PSV controller and a valve (or source) simulates the behaviour of the Pressure-Safety-Valve. See also: When to use Methods and assumptions How to use

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When to use Use to model pressure safety valves. Use together with a valve or pressure driven source.

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Methods and assumptions The controller will compare one or more input variables (normally pressure) with a setpoint. If any one of the variable values becomes higher than or less than the setpoint, the controller will open a selected PSV-valve. This could be the valve defined as a source valve. If all of the variables become greater or lower than the reset value, this valve is closed again. The output signal is limited with stroke time. See Actuator time of controlled device.

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How to use See Connecting the controllers for a example on how to connect a controller. Connect the measured value (e.g. a pressure). The MEASRD terminal must be connected. Connect the PSV controller output to a valves, pressure driven sources or leaks. Set the setpoint where the controller should open. If the controller should automatically close, enter a reset value. Include sufficient hysteresis for the reset value compared to the setpoint value, to avoid a situation where the PSV output oscillates. That is; a situation where it opens in one time step, closes the next, opens again in the next etc. Change the default OPENMODE to BELOW if the controller should open when the measurement falls below the setpoint. Figure A shows the connection possibilities of the PSV controller.

Figure A: PSV controller connection terminals

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Scaler Controller The scaler controller is used to scale input signals linearly from an input range to an output range. The scaler controller issues a control signal to a device (e.g. a valve) or as an input signal to other controllers. See also: When to use Methods and assumptions How to use

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When to use Use to scale a variable in a process unit (e.g. Valve, Pump) or an input to another controller. Ex. Scale controller ouptput signal from range 0 - 100% to input valve signal range 0 - 1. Includ a scaler controller between main controller and valev Ex. Scale signal from transmitter range to controller input range. Include a scaler controller between transmitter and main controller. Ex. Limit transmitter signal to stay in configured range.

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Methods and assumptions The scaler controller scales the input signal linearly from the input range (LOWLIMIT to HIGHLIMIT) to the ouput range (MINSIGNAL to MAXSIGNAL). u = (MAXSIGNAL-MINSIGNAL) / (HIGHLIMIT - LOWLIMIT) * (y - LOWLIMIT) + MINSIGNAL where y - measured variable u - unconstrained output The computed output signal is affected by maximum, minimum constraints and by rate of change constraints (opening, closing time or stroke time), see Constraining the controller output and Actuator time of controlled device.

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How to use Connect the required input signal to the MEASRD terminal. Specify input range and the output range by setting LOWLIMIT, HIGHLIMIT and MINSIGNAL, MAXSIGNAL keys. Connect the controller output signal OUTSIG_1..N to a device variable. The figure below shows transformation of input to output through a scaler controller C.

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Selector Controller A SELECTOR controller is a controller that uses two sub-controllers that are selected based on the value of selected variables relative to low and high limits of these variables. The controller operates as a kind of hysteresis controller, selecting the signal from one of the sub-controllers, and using this sub-controller until the low (or high) variable limit is reached. Then the controller selects another sub-controller, and keeps it until the high (or low) variable limit is reached. See also: When to use Methods and assumptions How to use

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When to use When there are fewer variables to manipulate than there are variables to control. The controllers (or measurements) of the controlled variables need to share the manipulated variables.

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Methods and assumptions The controller algorithm is best described by an example: Figure A shows a system consisting of a pipeline with a separator. The separator has liquid and gas valves attached to it, in addition to an emergency liquid drain valve. In addition there is a separator inlet valve having a fixed opening. Upstream of the separator, at some distance from it, is a gamma densitometer used for measuring the local liquid volume fraction.

Figure A: Separator using SELECTOR controller to control the liquid outlet valve. We want to control the separator level by controlling the liquid level in the separator with a level PID controller. As long as the liquid level is below a given value we want the controller to act slowly / moderately fast. If a liquid slug arrives we want the level control on the separator liquid outlet to be faster to prevent the level from increasing to very high levels. This means that for normal operation we have a moderately fast PID level controller, and for transient operation (when a slug arrives) we have a fast PID operation. In addition, a gamma densitometer is placed at some distance from the separator inlet. When the time averaged signal from the meter reaches a certain limit, a slug is expected to arrive. We also want this to trigger a faster operation of the separator liquid valve. Our control structure for the separator liquid outlet valve will then be: Normal operation: 1. Slow separator liquid level controller used to control the liquid outlet valve. 2. If the separator liquid level reaches a given high level, or the time averaged gamma densitometer signal becomes higher than a given limit, the fast separator liquid outlet valve controller takes over. Transient operation: 1. The fast liquid valve controller that is controlled by the separator liquid level is acting. 2. If the separator liquid level drops below a given low limit, the slow / normal separator liquid level controller starts controlling the liquid outlet valve. The operation is back to normal. There is no restriction on the number of variables that can be used for switching between the subcontrollers. The variables and their low and high limits are given as input to OLGA. If the sub-controllers are PID controllers the integral term of the non-acting controller can be saved (interlocked), reset to zero, or still be integrated. This will be determined in the input to the OLGA subcontrollers by the user. 189 / 769

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How to use See Connecting the controllers for an example on how to connect a controller. Connect one or more limit signals (HIGHLIMITSIG/LOWLIMITSIG). Define the controller used at start of simulation (keyword INITIALCONTROLLER). Define the limits where the Selector controller changes its output (LOWLIMIT, HIGHLIMIT). Connect the controller used below LOWLIMIT (SUBCONLOW), and the controller used above HIGHLIMIT (SUBCONHIGH). Figure B show the connection possibilities of the Selector controller.

Figure B: Selector controller connection terminals

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Purpose The controller converts mass flow rate to volumetric flow rate at standard conditions.

See also: When to use Methods and assumptions Limitations How to use

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When to use Use to control a volumetric flow rate at standard conditions.

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Methods and assumptions The controller converts mass flow rate to volumetric flow rate at standard conditions. Fluid properties are calculated from the given fluid table (FLUID), or composition (FEEDNAME) at standard conditions. Standard conditions; pressure = 1 atm and temperature = 60 °F (~15.5 °C). If neither of GOR/CGR/WGR/WATERCUT/MOLWEIGHT are given, the fluid table/composition phase distribution at standard conditions will be used to calculate the overall mass flow rate.

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Limitations Standard conditions, pressure = 1 atm and temperature = 60 °F (~15.5 °C), must be included in the fluid table.

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How to use To convert from mass flow at to volumetric flow rate at standard conditions: Set correct phase in PHASE key. Specify the fluid in the FLUID or FEEDNAME keys. Specify the wanted GOR/CGR/WGR/WATERCUT/MOLWEIGHT, and the volumetric flow rate at standard conditions will be calculated. Connect the STDController output terminal OUTSIG to an PID controller MEASRD terminal.

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Switch Controller The main purpose of the switch controller is to switch between alternative inputs values. The output of the controller is selected based on the setpoint in MODE = AUTOMATIC or SETPOINT terminal if MODE = EXTERNALSETPOINT. See also: When to use Methods and assumptions How to use

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When to use Use to select between alternative inputs to controllers or valves. Ex. Alternative inputs to valves. Ex. Alternative measured signals to controllers.

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Methods and assumptions The output of the switch controller is selected based on the setpoint in MODE = AUTOMATIC or SETPOINT terminal if MODE = EXTERNALSETPOINT. SP < 1.5

unconstrained output A is set equal to controller at terminal INPSIG_1

1.5 <= SP < 2.5

unconstrained output A is set equal to controller at terminal INPSIG_2

2.5 <= SP < 3.5

unconstrained output A is set equal to controller at terminal INPSIG_3

.... (N-0.5) <= SP

unconstrained output A is set equal to controller at terminal INPSIG_N

Where N is the number of connected input terminals INPSIG_1..N

The computed output signal is affected by maximum, minimum constraints and by rate of change constraints (opening, closing time or stroke time), see Constraining the controller output and Actuator time of controlled device.

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How to use Connect the required input signal(s) to the INPSIG_1..N terminal(s). Specify the SETPOINT key or connect the SETPOINT terminal. Connect the controller output signal OUTSIG_1..N to a device variable. The figure below shows how INPSIG_1..4 is connected to OUTSIG.

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Table Controller The table controller make it possible to tabulate a relation between the controller input and the controller output. See also: When to use Methods and assumptions Limitations How to use

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When to use Use to define a non-linear relation for a process variable.

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Methods and assumptions A table controller uses the input variables as lookup variable, x, in a table, u = f(x). The controller output is u. It is possible to use nested tables, that is; u = f(g(x)). This is done in the table definition, where one table can reference another. The result from interpolating one table is used to interpolate in another.

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Limitations The table controller is limited to one variable tables. It is only possible to calculate u = f(x1), and not u = f(x1,x2) etc.

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How to use Define a table, with XVARIABLE and YVARIABLE set to NOTGIVEN. Reference the table in the controller definition. Make the input signal available (from e.g. a transmitter) with the correct units, and connect to the controller. The table controller require that the input signal (INPSIG) terminal is connected. Figure B shows the connection possibilities of the table controller.

Figure B: Table controller connection terminals

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Transmitter Transmitters are used to measure flow path variables and transmit them to controllers etc. through an output signal terminal. See also: When to use Methods and assumptions Limitations How to use

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When to use The transmitters are used together with the controllers.

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Methods and assumptions The transmitter creates a trend object and update the signal terminal every time step. That implies that every variable available for trending is available from a transmitter. The signal is converted to user specified units. If no unit is given, the default unit is used. One transmitter can measure and transmit an arbitrary number of variables (from a single position).

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Transmitter - Limitations The transmitters can only be connected to the flow path. For process equipment (Valve, Pump etc.) variables, connected the equipment directly.

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How to use The transmitter is positioned on the flow path, using pipe and section/section boundary or absolute position. It is possible to use one transmitter to for both PT (volume variable) and UL (boundary variable). Make the connection between the transmitter, and the receiving signal terminal. Use the Connections view to set variable name and unit. After making a connection from the transmitter (ex. OUTSIG_1), a new terminal will be made available (ex. OUTSIG_2). One transmitter can measure and transmit an arbitrary number of variables (from a single position).

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Corrosion The purpose is to calculate standard uniform CO2 corrosion and Top Of Line (TOL) CO2 corrosion. See also: When to use Methods and assumptions Limitations How to use

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When to use CO2 corrosion should be expected whenever CO2 and water is present.

License requirements The Corrosion Module requires a separate license.

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Methods and assumptions The basic chemical reactions in CO2 corrosion are: (a) which dissociates in two steps: (b) (c) In CO2 corrosion when the concentrations of Fe2+ and CO32- ions exceed the solubility limit, they combine to form solid iron carbonate films according to: (d) These films can be more or less protective for further corrosion. Currently, three CO2 corrosion models; the NORSOK model , the de Waard 95 model and the IFE topof-line corrosion model have been implemented in the OLGA three-phase flow model /5/, /8/, /18/. The de Waard 93 corrosion model was included in earlier versions, but has now been replaced with the topof-line corrosion model. Corrosion dominated by H2S is at present not covered by the corrosion module. The NORSOK and de Waard 95 models are both regarded as conservative models as they include only limited effects of protective corrosion films. Protective corrosion films can form especially at high temperature (above 60 °C) and at high pH (above pH 5.5). The corrosion rate will increase with temperature for both models up to a limiting temperature where formation of protective corrosion films are predicted. Both models are tuned to a large set of experimental data, but the NORSOK model takes somewhat larger account for protective corrosion films at high temperature and high pH than the de Waard 95 model, as more recent high temperature data also have been used. The NORSOK model gives the corrosion rate as function of pH, temperature, CO2 partial pressure and wall shear stress: CR = f(pH, T) * g(T) * h(PCO2, t)

(e)

The de Waard 95 model gives the corrosion rate according to the following formula: CR = (1 / (1 / Vr + 1 / Vm)) * Fscale

(f)

where Vr is the maximum corrosion rate based on the limiting reaction rate given as a function of temperature, CO2 partial pressure and pH: Vr = f(T, pH, PCO2),

(g)

Vm is the maximum corrosion rate based on the limiting mass transfer rate given as a function of CO2 partial pressure, liquid flow velocity and hydraulic diameter: Vm = C * PCO2 * UL0.8 * DH0.2,

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and the scale protection factor Fscale is a function of temperature and CO2 partial pressure: Fscale = g(T, PCO2)

(i)

In the IFE top-of-line corrosion model the top-of-line corrosion rate is limited by the amount of iron that can be dissolved in the condensed water: CR = a * Rcond * CFe * (b - T)

(j)

where Rcond is the water condensation rate calculated by OLGA and the solubility of iron in the condensing water CFe is a function of CO2 partial pressure and temperature: CFe = f(T, PCO2)

(k)

The flow field at each section along the pipeline/network is used to calculate the corrosion rate.

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How to use For Top Of Line (TOL) corrosion the water condensation rate is needed. This is not available when using the Black oil model. When using the PVT table option it is only available for a three phase table and when specifying: FLASHMODEL = WATER in OPTIONS. When using compositional tracking (COMPOSITIONAL=ON IN OPTIONS). TOL can only be used when specifying: FLASHTYPE= FULLTHREEPHASE or SIMPLETHREEPHASE in COMPOPTIONS. The NORSOK and de Waard models can be used for all PVT calculation options (Black oil, PVT table and Compositional Tracking). The input parameters for the corrosion models are specified in the keyword statement CORROSION. Input parameters for each branch of the network are as follows: CO2 mole % in the gas (key: CO2FRACTION) Bicarbonate concentration in the water phase (BICARBONATE) Total ionic strength in the water (IONICSTRENGTH) Inhibitor efficiency (INHIBITOREFF) Glycol concentration in the aqueous phase (GLYCOLFRACTION) The water cut limit where water droplets in oil will wet the wall (WCWET). If the water cut is higher than this value, the water droplets will wet the wall, even if no continuous water film is present. The default value is 30 %. This parameter is only used for the water wetting test in the corrosion module. It has no influence on the flow conditions. An option for calculating pH based on saturated iron carbonate concentration in water (PHSAT) Maximum CO2 partial pressure in single phase liquid flow (PCO2MAX) Bubble point pressure , from which the CO2 partial pressure for single phase liquid flow will be calculated (PTMAX) Currently, the bicarbonate, glycol concentrations, ionic strength and water wetting limit are given as constants for a given branch. The glycol concentration can either be set manually or be determined by the MEG tracking function if available to the user. If the manual option is used, the glycol concentration is constant through the whole pipeline. If the MEG tracking option is used, the glycol concentration will be diluted in accordance with water condensation rates. The water chemistry has a significant influence on the calculated corrosion rates. Experience in CO2 corrosion evaluation is therefore important to prepare input and evaluate simulation results properly. For both the NORSOK and the de Waard 95 models the pH value in the bulk water phase is calculated as a function of CO2 partial pressure, temperature, bicarbonate content and ionic strength by the formulas given in the NORSOK model. The input parameters BICARBONATE and PHSAT can be used to choose between different water chemistry conditions when calculating the pH value: Condensed water without corrosion products: BICARBONATE = 0, PHSAT = OFF Condensed water saturated with corrosion products: BICARBONATE = 0, PHSAT = ON Water with specified bicarbonate content (e.g. formation water): BICARBONATE > 0, PHSAT = OFF The pH calculation is based on the CO2 partial pressure calculated as the CO2 mole % in the gas phase multiplied by the total pressure. For a situation with no free gas phase the CO2 content will be constant for pressures above the bubble point pressure. The user must then manually supply the bubble point pressure (PTMAX), which may be found by running OLGA. The maximum CO2 partial pressure is

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point pressure (PTMAX), which may be found by running OLGA. The maximum CO2 partial pressure is then calculated by the code for all pressures higher than PTMAX: CO2FRACTION * PTMAX. This is done even though free gas is present; the code only checks if the pressure is above PTMAX or not. Alternatively, the user may set the maximum CO2 partial pressure directly, (PCO2MAX). If no free gas exists in the pipeline at all, PTMAX or PCO2MAX can be found from measurements or calculations in a separator or in a pipeline further downstream where a free gas phase exists. In the de Waard 95 model, corrosion reduction due to protective films is not accounted for when formation water is present. For ionic strengths larger than 0.2 M, formation water is assumed and there will be no corrosion reduction due to scaling. For ionic strengths lower than 0.2 M, condensed water conditions are assumed, and the scaling reduction factor is then dependent on the CO2 partial pressure and temperature. The presence of glycol will reduce the corrosion rate. The same glycol reduction factor is used for both the NORSOK and the de Waard 95 models. The effect of corrosion inhibitors can be specified through the key INHIBITOREFFICIENCY. Parameters calculated by the three phase flow model OLGA, which are used by the corrosion models, are pressure (plot variable PT), temperature (TM), water velocity or mixture water/oil velocity, wall shear stresses in water or alternatively liquid mixture (boundary variables TAUWWT, TAUWL), water volume fraction (BEWT), oil film volume fraction (BEHL) and the near-wall water cut (WCWALL, which is given as a fraction). WCWALL is defined to be 1.0 if there is any continuous water film at the wall. If water is present only as droplets in the oil film, WCWALL is equal to the liquid film water cut. The liquid film water cut can be expressed as USLWT/(USLWT+USLHL) where USLWT is the superficial velocity of water in the liquid film, and USLHL is the superficial velocity of oil in the liquid film. The water wetting conditions are determined as follows: First, the water-oil flow regime is determined by the flow model. There are mainly two flow regime conditions of concern for the corrosion model: 1.

A continuous water film exists (WCWALL = 1.0). A continuous water film may be a result of stratification, or due to a water cut above the flow model's water-oil inversion point. The water-oil inversion point has a default value of 0.5 (water cut = 50%), but may be changed through the keyword WATEROPTIONS, INVERSIONWATERFRAC. The OLGA code has been verified with 0.5 as inversion point. Please note that changing this value might change the flow predictions significantly. 2. Water only existing as droplets in a continuous oil film. For such cases, the water cut must be below the flow model's inversion point (0.0 < WCWALL < INVERSIONWATERFRAC < 1.0) This flow information is sent to the corrosion module where tests are performed to determine if water wetting occurs: Condition 1 will always give water wetting of the wall. Condition 2 will give water wetting if the water cut (and WCWALL converted to %) is above the water wetting limit, WCWET, given in the CORROSION keyword (default value 30 %). For slug flow (output variable ID = 3), both conditions might be occurring intermittently, i.e. a passing slug bubble might be in condition 1, while the liquid slug might be in condition 2 or vice versa. Such cases are treated as full water wetting (condition 1). To sum up, the case of no water wetting can only occur in condition 2 when the liquid film water cut (and WCWALL in %) is less than the water wetting limit (WCWET). In that case, zero corrosion rate follows. Full water wetting will always occur if WCWALL (in %) is larger than or equal to WCWET. 216 / 769

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In addition, the corrosion rates assuming full water wetting are always calculated. See also: CORROSION Keys Corrosion Output Variables Sample case for Corrosion

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Limitations The corrosion models are not valid if pH > 6.5 or if T > 150° C. In cases where corrosion control by pH stabilisation is applied, the pH value might exceed the upper pH limit of the corrosion models. The implemented corrosion models are not suitable for such cases. The corrosion models should not be used for CO2 partial pressures above 10 bar. In addition, the NORSOK model is presently not valid for pH < 3.5 or T < 20° C. The user must ensure that these limits are not exceeded. The top-of-line corrosion model does not account for increased corrosion due to presence of acetic acid in the gas, which can increase the solubility of iron in the condensed water and hence the top-of-line corrosion rate. If the gas contains acetic acid this should be evaluated separately. The CO2 corrosion models are not valid when the ratio between CO2 and H2S partial pressure (or the ratio between CO2 and H2S molar fraction in the gas phase) is lower than 20. The models should not be used when the H2S partial pressure is higher than 100 mbar. For partial pressures ratios of CO2 and H2S between 20 and 500, the models will give an upper bound for the corrosion rate, but may be conservative since iron sulphide films may be formed.

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Drilling fluid The Drilling Fluids option was developed to describe different fluids that are used in a drilling operation. For example, muds of different densities can be pumped into the well during the drilling operation. This option is also useful to simulate well clean-up operation or initial startup of a well after completion or workover. Drilling fluids are tracked in addition to production fluids from the well. It is possible to combine MEG tracking and drilling fluids. The drilling fluid can either be in oil, water, or gas phase. It is assumed that a drilling fluid is completely miscible with the phase it is specified to and immiscible with the other phases. Therefore this option is suitable for displacement of different fluids of low volatility. See also: When to use Methods and assumptions How to use

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When to use The Drilling Fluid option can be used when it is desired to track one or more fluid in additional to the produced oil, water, and gas in simulating the process of one fluid displacing another. This option is often used to simulate drilling operations, well clean-up, deal oil ciculation and start-up with a mud filled well.

License requirements Drilling and its associates are parts of the Wells Module that requires a separate license.

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Methods and assumptions There are two methods for determining the physical properties of the drilling fluids: use of built-in correlations or interpolation from the PVT table. Only one method can be used in the same case. When the built-in correlations are used, the code uses the following fictitious components to keep track the amount of mixing of different drilling fluids. Sixteen fictitious components are used: Component ID 1 2 3 4

Component name HC H2O MEG GDENMIN

5

GDENMAX

6

GVISMIN

7

GVISMAX

8

ODENMIN

9

ODENMAX

10

OVISMIN

11

OVISMAX

12

WDENMIN

13

WDENMAX

14

WVISMIN

15

WVISMAX

15

CUTTING

Description Hydrocarbon mixture Aqueous mixture Hydrate inhibitor Min gas density tracer for drilling fluid (WATER/OIL) Max gas density tracer for drilling fluid (WATER/OIL) Min gas viscosity tracer for drilling fluid (WATER/OIL) Max gas viscosity tracer for drilling fluid (WATER/OIL) Min oil density tracer for drilling fluid (WATER/OIL) Max oil density tracer for drilling fluid (WATER/OIL) Min oil viscosity tracer for drilling fluid (WATER/OIL) Max oil viscosity tracer for drilling fluid (WATER/OIL) Min water density tracer for drilling fluid (WATER/OIL) Max water density tracer for drilling fluid (WATER/OIL) Min water viscosity tracer for drilling fluid (WATER/OIL) Max water viscosity tracer for drilling fluid (WATER/OIL) Cuttings

The masses and physical properties of the individual drilling fluids are tracked along the flow paths. The solubility of the drilling fluid into other phases than the miscible phase is neglected. Furthermore, the drilling fluids do not affect the phase behaviour of the produced fluids. The ideal mixing is assumed when different drilling fluids of the same phase are mixed with each other and with the production fluid. When the PVT table is used for a drilling fluid, the non-Newtonian behavior is accounted for through the apparent viscosity for flow calculations.

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How to use In order to invoke the Drilling Fluids, the key DRILLING in the OPTIONS keyword must be set to ON. Once the DRILLING option has been turned on, it cannot be turned off in a subsequent restart from a RESTART file. In addition at least one DRILLINGFLUID keyword must be defined on Library level, a type must be set to any of OILMUD, WATERMUD, or GASMUD. Since these labels are arbitrary identifiers, up to three drilling fluids may be specified in a simulation. The drilling fluid properties can be identified through a fluid property table in the *.tab file, use the FLUIDTABLE key to refer to the *.tab file that contains the drilling fluid properties. The fluid properties table referred must contain all liquid properties normally present in a *.tab file. As a result, a drilling fluid FLUIDTABLE is generally generated using PVTsim. Alternatively, and simpler, the drilling fluid density and viscosity can be specified using the keys, MAXDENSITY, MINDENSITY, MAXVISCOSITY, and MINVISCOSITY. These keys denote the drilling fluid density and viscosity at standard conditions. Based on these standard properties, the density and viscosity at in-situ temperatures and pressures are calculated by correlations. Units conversions of these drilling fluid properties are supported, so a valid density unit (such as LB/FT3) or viscosity unit (such as CP) must follow the density and viscosity specifications. The primary means of getting drilling fluids into the system is through the SOURCE. Drilling Fluid inflow rates must be specified in mass units, generally kg/s. Time series of mass inflow rates are allowed. Normally GASFRACTION and TOTALWATERFRACTION must be set to zero so the MASSFLOW specified refers to drilling fluid mass flow. In addition, the drilling fluid used must be identified by label, along with its density and viscosity. This label, density, and viscosity must be consistent with the label, density, and viscosity specified in the DRILLINGFLUIDS keywords. If drilling fluid backflow is possible at a pressure BOUNDARY, the drilling fluid used must be identified by label, just as for a SOURCE. As with the SOURCE, the label, density and viscosity in the must be consistent with the label, density, and viscosity specified in the DRILLINGFLUID keywords. A number of drilling mud variables can be plotted as either TREND or PROFILE variables. A comprehensive list can be found on Drilling output variables In addition the keywords below are useful: · ANNULUS to specify the annulus configuration (thermal interactions) · POSITION to specify initial bit position and leak-to positions · LEAK to specify TOPOSITION (useful for simulating well unloading valves)

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HydrateCheck This module is used to get information on possible formation of hydrates. The user can specify hydrate formation curves for each flowpath that should be investigated. See also: When to use Methods and assumptions Limitations How to use

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When to use HydrateCheck should be used when there is a risk of reaching the temperature/pressure region where water can form hydrates.

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Methods and assumptions The program does the following: 1. For a given pressure and inhibitor concentration in a section, the temperature below where hydrate may form is determined from the hydrate formation curve. The difference between the hydrate formation temperature and the fluid temperature is then calculated, i.e. the volume variable DTHYD is updated. 2. For a given pressure and inhibitor concentration in a section, the pressure above where hydrate may form is determined from the hydrate formation curve. The difference between the fluid pressure and the hydrate formation pressure is then calculated, i.e. the volume variable DPHYD is updated. 3. The positions and the values of the maximum temperature and pressure differences for hydrate formation are calculated, i.e. the branch variables MDPHYD, MDPPOS, MDTHYD and MDTPOS are updated. Interpolation and extrapolation of the hydrate curves: An imaginary square is formed to define the limits of the hydrate curve(s). When hydrate curves for different inhibitor concentrations (HAMMERSCHMIDT = OFF) are used, the four sides are the highest/lowest temperature and highest/lowest pressure of the hydrate curves. All hydrate curves are extrapolated so they reach two of the square sides as illustrated in the figure below for INHIBCONC = 0%, INHIBCONC = 20% and INHIBCONC = 40%. For HAMMERSCHMIDT = ON the highest/lowest pressure is defined by the hydrate curve for the inhibitor concentration of 0%, while the highest/lowest temperature depends on the actual inhibitor concentration (Hammerschmidt).

Figure 1 Hydrate curve square with different pressure/temperature conditions. Condition 1 and 2 has an inhibitor concentration of 40%, while Condition 3 has 0%. When OLGA computes DPHYD and DTHYD it uses the inhibitor concentration and the pressure and temperature in the section. See Condition 1 in the figure above. If the Hammerschmidt equation is used (HAMMERSCHMIDT = ON), the hydrate temperature is calculated based on the actual inhibitor concentration. 225 / 769

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on the actual inhibitor concentration. If HAMMERSCHMIDT = OFF it is checked whether the inhibitor concentration in a section is within the range given by the hydrate curves. If it is above the highest inhibitor concentration, the hydrate curve for the highest inhibitor concentration is used. If is below the lowest inhibitor concentration, the hydrate curve for the lowest inhibitor concentration is used. If the inhibitor concentration in the section is between two hydrate curves, OLGA interpolates the two hydrate curves to generate a new hydrate curve for the inhibitor concentration in the section. When DPHYD is computed the temperature in the section is used to find the hydrate pressure for the given inhibitor concentration. If the temperature in the section is inside the square and no match is found, the highest hydrate pressure is used if the temperature is to the right of the hydrate curve (Condition 2) and the lowest is used if it is to the left (HAMMERSCHMIDT = OFF only; hydrate pressure always defined within the square with ON). If the temperature in the section is to the right of the square (Condition 3) the highest pressure in the square is used as the hydrate pressure. When the temperature in the section is to the left of the square the lowest pressure in the square is used as the hydrate pressure. When DTHYD is computed the pressure in the section is used to find the hydrate temperature for the given inhibitor concentration. If the pressure in the section is inside the square and no match is found, the highest hydrate temperature is used if the pressure is above the hydrate curve (Condition 3) and the lowest is used if it is below (HAMMERSCHMIDT = OFF only; hydrate temperature always defined within the square with ON). If the pressure in the section is above the square (Condition 2) the highest temperature in the square is used as the hydrate temperature. When the pressure in the section is below the square the lowest temperature in the square is used as the hydrate temperature. It should be noted that if the section pressure is above the highest pressure in the square the reported DPHYD will always be a positive value that indicates hydrate formation. This can be misleading, especially if the section temperature also is higher than the highest temperature in the square, in which case DTHYD < 0 and the section temperature in reality may be far above the hydrate formation temperature, see Condition 4. To remove this source of error all hydrate curves should include both the minimum and maximum pressure in the pipeline. That is, the hydrate curves in Figure 1 are not well defined for conditions 2, 3 and 4 (especially the hydrate curve for 0%). Also, it is recommended to always include the hydrate curve for an inhibitor concentration of 0% to avoid underestimating the hydration formation temperature. Using DEBUG = ON in OPTIONSOPTIONS, a warning is given the first time the fluid temperature is above or below the maximum temperature in the ”hydrate curve” square to alert the user. This goes for pressure above/below the square and inhibitor concentrations above/below the given values, as well.

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Limitations For Compositional Tracking, the INHIBITOR must be defined in the FEEDFILE before it can be selected in the HYDRATECURVE. The Hammerschmidt equation (used when HAMMERSCHMIDT = ON) is only valid for inhibitor concentrations below 70%. The inhibitor concentration can be verified by plotting e.g. MEGMFR.

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How to use Define the hydrate formation curves with the HYDRATECURVE keyword in the Library section. In each flowpath, use the HYDRATECHECK keyword to specify a list of hydrate curves to apply. Each HYDRATECURVE specified in a flowpath must have a unique inhibitor concentration (INHIBCONC). The hydrate formation curve can be specified either with keys PRESSURE and TEMPERATURE, or from an ASCII file where the hydrate formation curve is given. The effect of an inhibitor on the hydrate formation temperature can be calculated. This requires the Inhibitor tracking module or the Compositional tracking module with an inhibitor defined in the FEEDFILE. Note that changes in the composition (except the specified inhibitor) does not affect the hydrate curve calculations. This effect can be calculated in two ways: 1.

2.

HAMMERSCHMIDT = OFF: One hydrate curve per inhibitor concentration (INHIBCONC) must be given. OLGA will then interpolate between the curves defined in the HYDRATECHECK. One HYDRATECURVE keyword must be defined for each curve and concentration. HAMMERSCHMIDT = ON: The Hammerschmidt equation (see ”The Inhibitor tracking module” ) will be used based on the hydrate curve for no inhibitor. The equation is valid for inhibitor concentrations between 0% and 70%.

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Hydrate Kinetics The hydrate kinetics model (CSMHYK) allows for the prediction of where and approximately where hydrate plugs will form in oil and gas pipelines. The current version of CSMHYK model (version 1) is more suitable for systems with small mass and heat transfer resistances inside of the pipeline. See also: When to use Methods and assumptions Limitations How to use

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When to use Include the hydrate kinetics if the pipeline temperature is close to the hydrate formation temperature. If the temperature drops sufficiently below the hydrate equilibrium temperature hydrate will be nucleated. The formation of hydrate will affect both the temperature of the pipeline and the pressure drop due to increased viscosity of the hydrate-oil slurry relative to oil viscosity.

License requirements The Hydrate Kinetics Module requires a separate license.

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Methods and assumptions The hydrate kinetics module combines the hydrate kinetics and rheological model developed by Colorado School of Mines with the flow equations of the OLGA model. The hydrate kinetics model determines the amount of gas and water consumed by hydrate formation and the effective viscosity of the hydrate particle laden oil phase. The flow model integrates the mass consumption rate to obtain the amount of hydrate phase and uses the effective viscosity for the flow calculations.

Hydrate reaction The model assumes that induction time of gas hydrate is instantaneous after sufficient sub-cooling (SUBCOOLING). The default sub-cooling is 6.5°F. Therefore the nucleation is currently assumed independent of any other thermodynamic properties except for the hydrate equilibrium temperature at the given system pressure. It is assumed that structure II hydrates are formed. The hydrate formation reaction will by default react gas (methane) hydrocarbons with liquid water to form hydrate particles (OILGUESTFRACTION=0 and GASGUESTFRACTION=1). The HYDRATEKINETICS key GASGUESTFRACTION is the mass fraction of gas available for hydrate formation to all the gas in a section, mg, i.e., (a) The HYDRATEKINETICS key OILGUESTFRACTION is the mass fraction of oil available for hydrate formation to all the oil in a section, m0. The hydrate reaction rate is limited to the mass available to react. First the gas mass will react, then the oil mass will react.

Flow model modifications By default the hydrate particles will flow with the oil film. That is; the hydrate velocity will be the same as for the oil film (COIL=1 and CWATER=0, denoted Co and Cw, respectively). But it is possible to relate the hydrate velocity to both the oil and water velocity, uof and uwf, respectively,according to (b) An effective hydrate oil slurry viscosity, γhos, is calculated by the Colorado School of Mines code: (c) It is possible to force a drift flux relation between the gas velocity, ug, and the volume average liquid velocity, ul by using the DRIFTFLUX, VELOCITYRATIO and DRIFTVELOCITY keys: (d) It is also possible to increase the drag between gas and liquid by using the FOGEXPONENT key:

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are present. By using the FULLDISPERSION key, no slip between oil film and water film is used in the simulation.

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Limitations The model is still in the research phase, and the initial emphasis has been on flowing liquid dominated systems with excess of water and gas for hydrate formation. Future versions will likely also address gas dominated systems and include a deposition mechanism. Special care should be taken when using the model since the model has only been validated against limited data sets. Further, it is not designed for shut-in and depressurization studies. The hydrate particles are uniformly distributed in the oil phase. The hydrate equilibrium is pre-calculated and the kinetic model developed for methane is adapted. No deposition on wall is activated. Immediate nucleation of the hydrate particles (no induction time).

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How to use The hydrate kinetics model is activated through the HYDRATEKINETICS keyword. HYDRATEKINETICS keyword is a FlowPath FA-Model (Flow Assurance Model). The HYDRATEKINETICS references a HYDRATCURVE that describe the hydrate equilibrium temperature.

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Inhibitor Tracking Module The Inhibitor tracking module allows for tracking of the contents of a hydrate inhibior in the pipeline. The module allows the choice between three inhibitors; MEG (mono-ethylene glycol), MEOH (methanol) or ETOH (ethanol). See also: When to use Methods and assumptions Limitations How to use

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When to use An important application of this module within flow assurance, is using it to ensure that the amount of hydrate inhibitor throughout the pipelines is sufficient to prevent the formation of hydrates. In the standard three-phase model of OLGA, the pipeline may contain water and inhibitor, but information regarding the inhibitor concentration along the line is not available.

License requirements The Inhibitor Tracking Module requires a separate license.

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Methods and assumptions Although similar, there are some differences in the assumptions used for MEG vs MEOH/ETOH tracking. The following assumptions are made for MEG tracking: MEG is only present in the aqueous phase. Water will be in both gas and aqueous phase. The only properties of the aqueous phase affected by MEG are the viscosity, the density, and the density’s derivatives. The water vapour content in the gas phase is adjusted by the mole fraction of MEG in the aqueous phase. There is no diffusion of MEG in the aqueous phase. The inhibitor tracking module is not aware of any special physics the user may have activated, and hence may not work properly in combination with e.g. Wax or Corrosion. However, it should work with all the features of basic OLGA. The inhibitor tracking module must be used with a two-phase fluid table or with a three-phase fluid table that has only H2O in the water phase. The following assumptions are made for MEOH/ETOH tracking: MEOH/ETOH does not effect flashing between gas and oil. This flash is calculated based upon the gas mass fraction from the PVT table. There is no hydrocarbon component dissolved in the water. The mole fraction of MEOH/ETOH in gas is equal to the vapor pressure divided by the system pressure. The active coefficients of MEOH/ETOH and H2O from UNIFAC correlations are used to calculate the chemical potentials of MEOH/ETOH and H2O in the aqueous phase. The Inhibitor tracking module uses a fluid of three components, namely 1. HC Hydrocarbon in oil and gas phase 2. H2O Water, which can be in the gas and the aqueous phase. 3. Inhibitor (MEG, MEOH or ETOH). At each time step the properties of the aqueous phase are calculated from the local pressure and temperature, and also from the fluid composition in each section of the pipeline. The effects of the inhibitor are included in the calculation of the density and viscosity of the aqueous phase. The method of Grunberg and Nissan is used to calculate the viscosity of the inhibitor-water mixture, and the HankinsonBrobst-Thomson (HBT) technique yields an estimate of the liquid density. Descriptions and formulae for the Grunberg and Nissan method and the HBT technique can be found in the open literature, see /35/. The effect of inhibitor can also be included in the calculation of the hydrate formation temperature. The user can either specify a hydrate curve for each inhibitor concentration and let OLGA interpolate between the values, or the Hammerschmidt formula for hydrate depression (/19/) can be used (the equation is valid for inhibitor concentrations between 0% and 70%):

(2.199)

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DT M H W TMEGCONC TMEGCONC=0

= Hydrate depression, oF = Molecular weight of inhibitor (MEG: 62.069 g/mol, MEOH: 32.042 g/mol, ETOH: 46.069 g/mol) = Hammerschmidt constant, default value is 2335 delta F = Weight per cent of the inhibitor in the liquid = Calculated hydrate temperature = Hydrate temperature for no inhibitor

For the other properties of the aqueous phase, the effects of the inhibitor are neglected and pure water properties from the three-phase fluid table or from OLGA are adopted.

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Limitations Inhibitor tracking is turned on through the COMPOSITIONAL keyword and cannot be used in conjunction with the other modules available through this keyword (e.g. Blackoil or Compositional Tracking). Furthermore, it cannot be used with Wax tracking. Please also see the list of assumptions in Methods and assumptions.

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How to use With the Inhibitor tracking module, one can specify a hydrate inhibitor (one of MEG, MEOH, or ETOH) to see the effect this will have on the formation of hydrates in the pipeline. Specify the following keywords to use the Inhibitor tracking module: OPTIONS to set COMPOSITIONAL = MEG/MEOH/ETOH SOURCE to specify INHIBFRACTION in the mass source INITIALCONDITIONS to specify INHIBFRACTION at initial time (if STEADYSTATE = OFF in OPTIONS) NODE to specify INHIBFRACTION at the boundary TRENDDATA/PROFILEDATA/OUTPUTDATA to print compositional variables for given components HYDRATECURVE and HYDRATECHECK to calculate the effect on the hydrate formation temperature Note that either INHIBFRACTION or TOTALINHIBFRACTION can be given. The former is the mass fraction of the inhibitor in the total aqueous phase; the latter is the mass fraction of the inhibitor in relation to the total aqueous phase + water vapour.

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Leak The leak is a negative mass source. It removes mass from the pipeline. The leak can transport mass between two pipelines. The leak outlet must then be connected to another pipeline. See also: When to use Methods and assumptions Limitations How to use

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When to use Use to simulate leaks and pipe ruptures. It is also used for gas lift valve (GLV) modeling.

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Methods and assumptions A leak or a pipe rupture is described as a negative mass source (mass out of the pipeline). The leak area can be controlled by the control system. Both sub-critical and critical flow is supported in OLGA. For sub-critical leak flow, the flow rate is governed by the difference between the internal and the external pressures, the conditions in the pipe and the leak area. For critical leak flow, the flow rate is governed by the conditions in the pipe and the leak area only. The leak flow is always limited to critical flow. The leakage flow area is calculated from:

where us = controller signal ( 0 ≤ us ≤ 1). The leak uses the valve model. See Choke Methods and assumptions. It is possible to route the flow through the leak to any pipe section in any branch by using the subkey TOPOSITION, in which case backflow is allowed. A leak can also be used to simulate a gas lift valve (GLV).

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Limitations The leaks are not included in the steady state pre-processor. Backflow is not allowed when the BACKPRESSURE key is used, that is, there will be no backflow if the section pressure is lower than the given backpressure. The leak uses the valve model. See valve limitations.

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How to use Position the leak. Leaks can be placed anywhere along the pipeline. A LEAK has two main functionalities: 1) 2)

It can be used to model a valve or rupture where the mass out of the pipe is removed from the simulated system, that is, the mass is lost to the surroundings (requires the key BACKPRESSURE) It can also be used to model interconnections in the model, where the mass out of one section is transferred to mass into another section (requires the key TOPOSITION). BACKPRESSURE cannot be defined in this case as the backpressure is equal to the pressure in the section defined in TOPOSITION.

Backflow is not allowed for functionality 1, that is, there will be no backflow if the section pressure is lower than the backpressure. For functionality 2 backflow is not allowed if GASLIFTTABLES is used. GASLIFTTABLES defines the gas lift valve (GLV) response curve. Backflow is allowed if CD/DIAMETER or TABLE/PHASE/CF is used instead. Note: GASLIFTTTABLES can also be used for functionality 1. See Gas Lift Valve (GLV) for information about GLV’s. If the flow through the leak is calculated using CD/DIAMETER or TABLE/PHASE/CF, the flow area of a leak can be manipulated by a controller. Connect a controller to the leak input signal terminal INPSIG. If no controller is connected to the leak, the entire flow area is used. See Valve How to use for details.

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Near-Wellbore Module Conventional dynamic well flow models use steady-state IPRs (Inflow Performance Relationship) to describe the influx of oil and gas from the reservoir, ignoring the transients in the near-wellbore area. Furthermore, reservoir models use steady-state lift curves to represent the TPRs (Tubing Performance Relationship), which ignores the wellbore flow dynamics. Neither the well models nor the reservoir models can account for the dynamic wellbore/reservoir interactions. In OLGA the IPR is described with the WELL keyword. With this model some transient phenomena in the well are not accurately predicted while others are not predicted at all. To bridge this modeling gap, the near-wellbore reservoir model Rocx has been developed and linked to OLGA. See also: When to use Methods and assumptions Limitations How to use

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When to use This link should be used when transient phenomena in the wellbore/reservoir are studied. Typical examples are: Well Shut-in/start-up Onset of instability Dynamic gas/water coning Well loading and back seepage Cross flow

License requirements Near wellbore is part of the ROCX Module that requires a separate license.

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Methods and assumptions The reservoir model is considered as a plug-in to the OLGA model, and the integrated simulation is fully controlled by OLGA. During the simulation, OLGA provides the wellbore pressure to the reservoir model and the reservoir model calculates the flow rate of each phase at the interface. The flow rates can be positive or negative depending on the flow directions corresponding to production and injection respectively. In case of injection or back seepage, the phase mass fractions in the wellbore section that the reservoir model interfaces to are converted to saturations in order to calculate the fractional injection rate for each phase. The near-wellbore reservoir model, Rocx, is capable of simulating three-phase Newtonian Darcy flow in porous media. The flow equations are solved in three dimensions, giving saturations and pressures varying in space and time as output in addition to the flow rate of each phase at the boundary. The numerical coupling between OLGA and Rocx is implemented in an implicit scheme. The concept of the implicit coupling here is that Rocx calculates a sensitivity coefficient for the production rate with respect to the wellbore pressure at each time step and makes it available for OLGA. At the next time step, OLGA uses this sensitivity coefficient to determine the new wellbore pressure. The sensitivity coefficient is extracted from the Jacobian matrix of the reservoir model in the last iteration. The size of the near-wellbore domain contributing to the rate-pressure sensitivity calculation is specified by the coupling level that can be given as a simulation input. The principle of the implicit coupling can be summarized as follows: 1. Assuming the models have been integrated up to time step n, the wellbore model begins integration to time step n+1 by requesting the reservoir model to calculate the sensitivity coefficients and , which are used in this relation: (a) where PP is the pressure in the wellbore, MP is the mass flow rate for each phase and the subscript p refers to a given phase, i.e. gas, oil or water. 2. The wellbore model uses the above relation as a boundary condition and solves for the complete wellbore. The wellbore model has now completed time step n+1 and sends and to the reservoir model. 3. The reservoir model completes its time step n+1 calculation by using the wellbore model supplied boundary condition.

The sensitivity coefficient

is calculated by (b)

which can be analytically derived from the reservoir model equations.

is simply given by

(c) With this implicit coupling implementation, the integrated model can run simulations with relatively long time steps while maintaining numerical stability.

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Limitations OLGA Rocx is not compatible with these fluid property models Compositional option Black oil module Rocx uses the OLGA PVT table for looking up fluid properties. Currently, only the three-phase fixed format OLGA PVT table can be used. The steady-state pre-processor in OLGA can not be applied in the integrated simulation. The simulation can be initialized by initial conditions or restart files. Rocx has its own restart file with the extension .rrs. Other limitations on the Rocx reservoir simulator are given in the ”Rocx User Manual”.

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How to use Rocx is linked to OLGA through the NEARWELLSOURCE keyword. Rocx supports both radial and rectangular grids. The numerical and physical kernel code is not affected by the choice of grid. The flow and thermal equations of Rocx are solved fully implicitly, using the Newton-Raphson iterative method at each time step. Input data to Rocx are permeability and porosities of the porous medium, fluid transport properties, and thermal properties of the rock and fluids. Necessary boundary and initial conditions must be given to enable simulation. Like in OLGA, the boundary conditions of the reservoir model can also be specified in time series. Rocx reserves the skin option for the situation when the inflow deviation from its ideal can not be properly accounted for by the reservoir model itself, e.g. the perforation skin. The simulation input information is stored in a keyword based text file. Standard industry file formats are used for output. More details of the Rocx model can be found in the ”Rocx User Manual”.

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Phase split node The phase split node is based upon the functionality of an INTERNAL NODE, but the phase fractions can be specified in the outgoing branches. For a normal internal node the composition flowing out of each terminal connected is equal to the total composition in the node itself, but for a phase split node there will be different distributed phase flows through each of the outgoing branches according to the actual type of terminal chosen. In a way the behaviour of the phase split node might be seen as a simple type of network SEPARATOR where there are no level controls and no internal separator efficiencies included. See also: When to use Methods and assumptions Limitations How to use

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When to use The phase split node is recommended to be used in a finger type separator and in nodes where the in/over pipe connections where the phases tend to have an uneven split.

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Methods and assumptions The phase split node has an arbitrary number of inlets/outlets. It has six different types of terminals: GAS, OIL, WATER, LIQUID, DRYGAS and MIXTURE. Terminal = GAS - gas +droplets Terminal = OIL - oil bulk Terminal = WATER - water bulk Terminal = LIQUID - oil and water bulk Terminal = DRYGAS - gas only Terminal = MIXTURE - all phases within the node itself(default) When the volume fraction of the connected phase(s) is sufficiently low(0.01), the flow in the outgoing branch will be as from an internal NODE.

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Limitations The phase split node is not intended for design purposes. It only distributes the phase fractions in the outgoing branches according to the user defined type of terminals chosen: • The phase split node is only treated as a simple volume tank with no internal separation equipment • There are no level controls and no separator efficiencies • No heat exchange with the surroundings

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How to use Input Connections to external pipelines The following connections are defined: · MIXTURE_1, … MIXTURE _N inlets and outlets · GAS_1, … GAS_N outlets · OIL_1, …OIL_N outlets · WATER_1, …WATER_N outlets · LIQUID_1, ... LIQUID_N outlets · DRYGAS _1, … DRYGAS _N outlets Internal volume If the volume is not given, it will be default assigned a value by OLGA. In some cases it might be more useful to give a larger value for the key VOLUME in order to get more stable node conditions during the simulations. Output All of the output variables specified under section “VOLUME VARIABLES” that are available for the internal NODE are also available for the phase split node.

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Pig A pig is a mechanical device which is inserted into a pipline that moves with the flow. Such devices can be used for, e.g., inspection, internal cleaning, or pushing liquid out of the pipe. When running a pigging operation, parameters of interest are 1. 2. 3. 4. 5. 6.

the pressure drop over a pig. the rate and total volume of liquid pushed out of a pipeline ahead of a pig. the liquid content of a pipeline before and after pigging. the flow restriction caused by a pig. the velocity of a pig. the time for a pig to traverse a pipeline.

See also: When to use Methods and assumptions Limitations How to use

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When to use The Pig keyword is used to simulate various pigging scenarios.

License requirements Tracking of the liquid slug in front of a pig (TRACKSLUG=ON) is part of the Slugtracking Module that requires a separate license.

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Methods and assumptions Friction forces and pigs The friction forces acting on a pig are described in the following sections. Static friction force The static force between the pig and the pipe wall is denoted F0. For a static pig, this is the force that needs to be overcome in order for the pig to start moving. Thus, a pig only starts moving if the pressure difference over the pig yields a large enough force. Wall friction force The wall friction force due to contact between the pig and the pipe wall is given by (a) where F0 = static friction force [N] fw = wall friction factor [Ns/m] Up = pig velocity [m/s] As the pig velocity, Up, increases, the wall friction force decreases due to less contact between the pig and the pipe wall. This effect is approximated by the wall friction factor. Viscous friction force — the frictional pig model When a pig is moving, the flow of the fluid film around the pig results in a viscous friction force. This force is calculated through (b) where f1 = linear friction factor [Ns/m] f2 = quadratic friction factor [Ns2/m2] Up = pig velocity [m/s]

Leakage There are two different types of leakage. Pressure drop induced leakage Due to the pressure drop over the pig, liquid can be pushed from behind the pig to in front of it. The pressure drop induced volumetric flux is given by

(c) where cpl = leakage factor [-] ΔPpig = pressure drop over the pig [Ns2/m2] ρ = density [kg/m3] Slip induced leakage (back leakage) 259 / 769

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Due to slip between the pig and the fluid surrounding it, some fluid ahead of the pig will not be carried along by it but rather leaks between the pig and the pipe wall. When the gap between the pig and pipe wall is very narrow, the effects of gravity and the pressure gradient can be neglected when calculating the flow of the fluid film that passes around the pig. Assuming laminar flow, the average film velocity becomes (d) where Up = pig velocity [m/s] Using this, the volumetric flow rate is then given by (e) where D = inner pipe diameter [m] Dp = outer diameter of pig [m] By default, the gap between the pig and pipe wall is equals two times the pipe roughness. The user can override this setting by specifying the pig diameter using the key DIAMETER. The total volumetric leakage flow rate is split over the oil, water, and gas phases. For stratified flow, the total leakage of gas, oil, and water is proportional to the hold-up each respective phase at that position. For all other flow regimes, gas leakage is not allowed and the total leakage is split over water and oil in proportion to the local water and oil hold-up, respectively.

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Limitations The calculation of the volume of wax dislodged by a pig and the additional forces required to push accumulated wax ahead of a pig is not available. It is not possible to simulate the melting of a hydrate plug since the pig mass is constant. It is not possible to simulate a pig traversing through a pipeline at the same time as slug tracking is enabled.

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How to use General A pig is added to the simulation by declaring the PIG keyword on the flow-path where it is to be inserted.

Launch and trap position of the pig A pig is launched and trapped at the boundaries closest to the positions given by the keys LAUNCHPOSITION and TRAPPOSITION, respectively. The trap position is optional, and if not specified, the pig traverses through the flow-paths until it exits through a terminal node and is removed. The behavior of launching and trapping is the same as that of the PLUG model (TYPE=SHORT) in OLGA5. It should be noted that this differs from the OLGA5 PIGTRACKING model where pigs are launched 25 percent into the section and trapped at the section boundary.

Routing — Pig in network In a network with bifurcations, the pig will enter the flow-path having the largest volumetric flow unless its routing is specified by the key ROUTING. N.B., when routing is given, the flow-path where the pig is launched has to be included in the routing.

Leakage factor The leakage factor, cpl, used in determining the volumetric flux of liquid from behind the pig to in front of it can be specified in three different ways in order to override the default value: 1. Specify the leakage factor directly through the key LEAKAGEFACTOR. 2. Specify the relative leakage opening Aleak/Apipe through the key LEAKOPENING and evaluate the leakage factor according to 3. Using the pressure loss coefficient, Fpig, specified through the LEAKDPCOEFF key, the leakage factor is given by The pressure loss coefficient can calibrated by letting fluid flow past a stationary pig.

Tracking the liquid slug In order to track the liquid slug in front of a pig, set TRACKSLUG=ON.

Output Pig specific plotting variables are found in the subgroup Pig of the group Basic. In addition, slug related plotting variables (group SlugTracking or group Compositional, subgroup Slug) apply when the liquid slug in front of a pig is tracked.

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Check valve A check valve prevents the total flow from flowing in the wrong direction. See also: When to use Methods and assumptions Limitations How to use

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When to use Use to model check valves, and to prevent the flow from flowing in an undesirable direction.

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Methods and assumptions The check valve closes if the total volume flow is in the wrong direction, e.g., there can be a negative flow of liquid and positive flow of gas through the check valve. They remain closed until the pressure differ ence across them is sufficiently large to give flow in the desired direction.

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Limitations A check valve close if the total volume flow is in the wrong direction, but there can be a negative flow of liquid and positive flow of gas through the check valve.

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How to use Position the check valve at any section boundary in the pipeline. If ABSPOSITION is used the check valve will be moved to the closest section boundary. Set the allowed flow direction in the DIRECTION key.

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Compressor A compressor is included to increase the pressure of the gas. The compressor is described by compressor characteristics that give the pressure and temperature increase over the compressor as a function of flow through the compressor and the rotational speed of the compressor. The compressor characteristics also give information about the minimum inlet flow (surge flow) that the compressor can operate on. If the inlet flow drops below the surge flow multiplied by a safety factor, a recirculation loop around the compressor is opened. The recirculation loop secures stable conditions for the compressor. A heat exchanger (cooler) can be included in the recirculation loop. See also: Methods and assumptions Limitations How to use

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Methods and assumptions The compressor is modelled as a flow-dependent and rotational-speed-dependent pressure jump and energy source. Any recirculation around the compressor is treated by a source into the section upstream of the compressor, and a sink out of the section downstream of the compressor, as OLGA cannot handle recirculation directly. The compressor characteristics and the surge volume flow are given in the form of tables. The compressor surge volume flow is the lowest volume flow the compressor can operate on without becoming unstable. Compressor data needed for the model are found by linear interpolation in the compressor tables. Pressure increase and derivatives of pressure increase are calculated from the pressure characteristics and are used for setting new coefficients in the momentum equations. Temperature increase is calculated from the temperature characteristics and is used for setting new coefficients in the energy equation. The compressor speed and the recirculation around the compressor are governed by the control system. In addition, the compressor speed is limited by a user-specified range. The surge volume flow calculated from the compressor tables is used together with an optional security factor to establish a set point for the controller that controls the recirculation around the compressor. It is assumed that during operation the control system keeps the compressor within the bounds of validity of the characteristics. Compressor pressure step evaluation The compressor pressure characteristics give compressor pressure ratio as a function of reduced rotational speed and reduced mass flow, Equation (a) below. (a) where p1 p2 G

= = = =

(-) is the pressure ratio (N/m2) is the inlet pressure (N/m2) is the outlet pressure (kg/s) is the mass flow

Figure A shows a typical compressor characteristic diagram.

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Figure A: Compressor characteristic diagram The pressure increase over the compressor is calculated from the compressor pressure characteristics. For calculation of the operating point, the compressor speed is necessary. The speed is governed by the control system and is limited by a user-specified range. The range is normally determined by the speed range in the compressor tables. r = (rmax - rmin) u + rmin

(b)

where r is the compressor speed, and u is the signal from the control module. u is in the range from 0 to 1, where u equal to 1 means that the compressor speed is at its maximum. Compressor temperature calculation In order to calculate gas temperatures, the power supplied by the compressor, PWC, is added as an enthalpy source to the enthalpy balance for the pipe section following a compressor boundary. The temperature resulting from this balance is used for calculating fluid properties, while the compressor outlet temperature is only used for informative purposes. Polytropic compression is assumed. The enthalpy source due to the compressor is: (c) where W is the mass flux through the compressor and Dz is the section length of the section downstream of the boundary where the compressor is located. For an inlet at pressure p1 and a density of r1, the power required for compression to an outlet pressure p2 is:

(d) The relation between pressure ratio, temperature and the polytropic exponent n is:

(e) The compressor temperature characteristics are also given in the form of tables, and the temperature ratio is found by linear interpolation.

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ratio is found by linear interpolation. The polytropic factor (n-1)/n is calculated from pressure ratio and temperature ratio using Equation (f).

(f) Calculation of surge volume flow The surge flow is in the form of tables, with reduced surge mass flow as a function of reduced compressor speed, see Figure A. The surge volume flow is used together with an optional security factor to establish a set point for the anti-surge controller (ASC) that controls the recirculation around the compressor, preventing unstable compressor operation. Reduced surge mass flow as a function of compressor speed is found by linear interpolation. For a compressor located at boundary j the surge volume flow is calculated as follows:

(g)

Recirculation flow modelling Recirculation flow around a compressor is modelled as a set of negative and positive sources, since OLGA cannot handle recirculation directly. The flow is controlled by a choke with the choke opening governed by the control system. The recirculation is between two neighbouring sections with a compressor on the common boundary, see Figure B. Only gas is allowed to flow in the recirculation loop. The recirculation flow is treated as a source into the section volume ahead of the compressor boundary, and a source out of the section volume after the compressor boundary.

Figure B: Recirculation loop The pressure drop across the restriction is equal to the pressure difference between the sections downstream and upstream of the compressor. The recirculation flow is restricted by the critical pressure difference. If the pressure difference between the section upstream and downstream of the compressor is higher than the critical value, the critical value is used. The pressure drop over the restriction is: (h) Solving for W: (i) where the positive sign relates to a positive source, and the negative sign relates to a negative source. W is the mass flux, ρg is the gas density in the section it is flowing out of (section after the compressor), 271 / 769

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W is the mass flux, ρg is the gas density in the section it is flowing out of (section after the compressor), D is the diameter of the section with the source, and Do is the orifice diameter of the controlled choke. For subcritical flow through the controlled choke the pressure difference between the section upstream and downstream of the compressor is used in equation (i). For critical flow through the controlled choke, the critical pressure difference is used for calculating the recirculation flow. Critical pressure difference is based on single phase gas flow with constant specific heat ratio, g. Specific heat ratio of 1.3 is used.

(j) (k) where g is specific heat ratio pcrit is critical pressure ratio p is the pressure in the section it is flowing out of Dpch, crit is critical pressure difference The energy leaving the section downstream of the compressor and entering the section upstream of the compressor through the recirculation loop is calculated as follows. (l) hg is the specific gas enthalpy in the compressor downstream volume, Wrec,g is the mass flux based on the section area of the section with a source and Dz is the section length of the section with a source. A heat exchanger may also be included in the recirculation loop. The aim of the heat exchanger is to extract energy to obtain a desired heat exchanger outlet temperature. In this case, the temperature of the recirculation source entering the section upstream of the compressor has to be specified. The heat exchanger is modelled as an ideal heat loss. The energy source entering the upstream section in a situation with a heat exchanger in the recirculation loop is calculated as:

(m)

is specific gas enthalpy based on the desired heat exchanger outlet temperature and pressure in the section where the source is entering. is specific enthalpy decrease in the heat exchanger. The energy extracted through the heat exchanger is limited by the heat exchanger capacity. The orifice opening of the controlled choke is governed by the control system. The control module also takes care of the stroke time of the controlled choke. The orifice opening is calculated as: (n) where u is the signal from the control module, and is in the range from 0 to 1. u equal to 1 means that the controlled choke is fully open.

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the controlled choke is fully open.

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Limitations Only gas flows in the recirculation loop. Critical flow calculations are based on single-phase gas flow with a constant specific heat ratio of 1.3. If the pressure in the section upstream of the compressor exceeds the pressure in the section downstream of it, the recirculation flow is set to zero. The compressor may not be positioned at the first or last section boundary of the pipeline. In that position, the controlled bypass is unrealisable since it is defined as going from the downstream section to the upstream section. It is recommended that a separator is located upstream of the compressor in order to avoid liquid flow through it. Numerically, the compressor model works with liquid phase present but the results make no sense.

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How to use To use a compressor, one needs to add a compressor and two controllers (speed controller and antisurge controller). There must be one compressor table for each compressor. If the controllers are omitted the speed will be kept at minimum speed (MINRPM) and the recycle loop will be closed.

Controlling rotational speed Compressor minimum rpm, MINRPM, and maximum rpm, MAXRPM, are specified by the user. These two parameters determine the operating range of the compressor and they must be within the rpm range of the compressor tables. A controller can be used to regulate the speed within the operating range. The speed is calculated by Equation (b) above. If the speed controller is omitted the controller signal will be zero and the compressor will use its minimum speed. Recycle loop The anti-surge security factor, SECURITYFACTOR, determines the anti-surge control line. To protect the compressor against surge conditions, always select a security factor > 1. A typical value for security factor is from 1.1 to 1.3. A security factor of 1.2 means that the control valve in the recirculation loop starts to open at a compressor inlet flow that is 20% higher than the surge flow specified in the compressor tables. The anti-surge controller (ASC) should be configured as a PI controller. The ASC is a kind of non-linear controller that have two amplification factors, AMP1 and AMP2. AMP1 is used if the inlet flow to the compressor is less than the surge flow, and AMP2 if the inlet is greater than the surge flow. Both AMP1 and AMP2 have to be negative, and the absolute value of AMP1 should be higher than the corresponding absolute value of AMP2 in order to rapidly open the recycle valve and to impose an inertia to close it again. A short stroke time for the recycle valve should also be selected. Select also the controller initial output signal (BIAS), equal to zero. To send information from the compressor to the ASC about surge flow, connect the OUTSIG_n out-signal from the compressor to the MEASRD input-signal of the controller. Then select QGSURGE as the measured variable. If the anti-surge controller is omitted the controller signal will be zero which will cause the recycle choke to be closed, i.e. there will be no flow in the recycle loop. To add a cooler to the recirculation loop, set COOLER=ON and also set the COOLCAPACITY.

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Gas Lift Valve In the gas lift process, either continuous or intermittent, relatively high pressure gas is injected downhole through a gas lift valve (GLV) into the production string to lift the fluid to the surface. The bottom hole pressure after shut-in is often much higher than the bottom hole pressure at normal production conditions. Several gas lift valves (unloading valves) are spaced along the depth of the well to lower the compressor discharge pressure required during startup phase of gas lift after a shut-in operation. Properly spaced and designed, these unloading valves should close one after the other from top to bottom as the lift gas reaches the deeper valves. The unloading valve opens or closes depending on the casing pressure and tubing pressure. The opening pressures are affected by downhole temperature as the temperature changes the forces acting on the valve stem. The characteristics of a GLV are usually given by several sets of curves with each curve shows the gas injection rates at different production pressures at a constant injection pressure. The keyword TABLE provides the channel for users to specify the GLV characteristics. The keyword LEAK allows users to use the GLV characteristics and specify the lift gas injection position. As many leaks can be given as the actual gas lift well configuration requires. Combining the functions that are provided by the keywords TABLE, LEAK, and ANNULUS, it is possible to simulate different gas lift configurations and various operations such as startup, shut-in, and steadystate operation. Gas lift distribution systems and production networks of wells can be simulated with the network capability of OLGA. See also: When to use Methods and assumptions Limitations How to use

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When to use Whenever the gas-lifted well contains GLV of which the opening depends on the production and injection pressure, the characteristics of the GLV should be used through the keyword TALBE in the simulation model. Such a model can be used to: Dimension and space the unloading valves along the wellbore. Calculate compressor discharge pressure required to unload the well. Check the possibility of flow instability such as casing heading, density wave instability. The GLV dynamics have major impact on the flow stability of gas lift systems. Trouble shoot problems such as interference of unloading valves during normal operation (simultaneous gas injections through more than one GLV). Find various remedies to flow instability.

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Methods and assumptions A gas lift valve (GLV) is used to inject gas into the tubing from the annulus/casing. Typically more than one GLV is placed after each other down the annulus. The intention is that the GLV closest to the wellhead opens first, and as the tubing pressure decreases this GLV shall close and the next one open (might already be open depending on the response curve). This cycle will be repeated till the injected gas reaches the operating GLV (lowermost active GLV). Once the gas lift gas reaches the operating GLV, gas is continuously injected through this GLV and stable production is optimised by regulating the optimum amount of gas (injection gas rate). At constant injection pressure (casing pressure) all GLV’s above the operating GLV should be closed. If the tubing pressure is increased for any reason (e.g. choke back production at the wellhead, a big liquid slug coming from the productive formation, etc), this may cause the opening of some GLV’s. This opening is the automatic response of the GLV’s to stabilise the flow. The injection of gas will reduce the liquid head pressure in the tubing until the GLV’s are closed again. Figure A shows an example of these “response curves” where tubing pressure is along the x axis, standard volume gas rate along the y axis, and there is one curve for each casing pressure.

Figure A:

Example of GLV Response Curves

The GLV is constructed to respond on both the casing pressure and tubing pressure, see Figure B. The casing and tubing pressure work together to open the valve, while the gas (typically nitrogen) charged dome works in the opposite direction. The curve for the casing pressure of 730 psig illustrates the behaviour. For low tubing pressures the combined force is not enough to open the valve (Pt < 330 psig). For tubing pressures above the “opening pressure” of 330 psig the valve starts to open; the “Throttling region” from 330 to approximately 600 psig is where the valve goes from closed to fully open. For a tubing pressure approaching the casing pressure the flow decreases as the differential pressure decreases, and above 730 psig (Pt > Pc) there is no flow as there is a check valve that stops the flow going from the tubing to the casing. In the input to OLGA the terms “injection pressure” and “production pressure” is used instead of “casing pressure” and “tubing pressure”, respectively, since the injection gas may be injected in the tubing instead of the casing, and the well fluid flows up the casing. The intention of the GLV is to allow flow from the injection to the production side, so using the terms injection/production makes the input more general.

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Figure B:

Sketch of typical casing (injection) pressure operated GLV (with gas charge)

The GLV in Figure B is characterized as an Injection or Casing Pressure Operated GLV since the injection/casing pressure works on the large part of the bellows (AINJ) while the tubing pressure works on the small part (APROD). The force balance for the point where the GLV starts to open is then: (a) where R = ASEAT / ABELLOW. PINJ and PPROD switch places in the equation for a Production or Tubing Pressure Operated GLV. Calculation of flow from curves The standard volume gas rate through the GLV is found by linear interpolation in the user-given response curves (defined in LEAK/GASLIFTTABLES) using the calculated injection pressure (upstream the GLV) and production pressure (downstream). First, the code finds the two response curves with injection pressures that are closest (higher and lower) the current injection pressure. One gas rate is found for each curve by interpolating using the current production pressure, and then the resulting gas rate is found by interpolating between these two rates using the current injection pressure. If the current injection pressure is below the lowest given injection pressure, the curve for the lowest injection pressure is used directly and vice versa for injection pressure above the highest given injection pressure. That is, no extrapolation for injection pressures. Extrapolation is performed in the direction of decreasing production pressure to find the opening production pressure, if not given (allowed with a negative extrapolated value, as would be the case for the injection pressure of 790 psig in Figure A). It is required that the last point in a response curve (the point with highest production pressure) has a gas rate of 0. It is possible to create a curve with only one point for which this is not a requirement (a way to specify constant standard volume flow for all production pressures below the injection pressure). Associated liquid (in case of liquid on the injection side) through the GLV is calculated by setting the total mass flux WTOT [kg/(m2s)] as:

(b) where WG is the gas mass flux derived from the response curves, rG is the gas density and rmix the volume averaged density. For each phase, P, (gas, oil, water, etc.) the mass flux through the GLV is: 279 / 769

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(c) where xP is the mass fraction of the phase upstream the GLV (in the section where the GLV is placed). Temperature effect In the case of a gas charged dome (a GLV might have a spring instead) the pressure in the dome will increase with increasing temperature as the gas is contained in the dome. This means that the required force from the production and injection side to open the GLV also increases with increasing temperature. According to Winkler and Eads /20/ the increased pressure in a nitrogen charged dome/bellows (based on reference temperature TREF of 60 F) is expressed like:

(d) where TB is the bellows temperature, and the pressures and temperature are given in psia and F. These equations have been implemented in OLGA, but with a user given reference temperature. That is, it has been assumed that the equations give reasonable results also for other reference temperatures than 60 F. The bellows temperature will depend on the production temperature, injection temperature, flow conditions, geometry of GLV, placement of GLV, etc. The user must give a parameter a where the bellows temperature is a linear interpolation between the injection and production temperature: (e) From the force balance equation (a) we get the following expressions for the increase in required production pressure to open the GLV (assuming constant injection pressure): (f) where DPB is calculated in equations (d). This effect can be very significant. For a sufficiently high temperature above the given reference temperature the GLV might never open: PPROD, open + DPPROD > PINJ. In OLGA this effect is included with a right-shift of all the response curves associated with the GLV. The point with maximum gas rate (for each of the curves) is identified, and the points to the left of this maximum point are shifted with the calculated DPPROD. The new response curve will then consist of the adjusted left side of the curve, the original right side of the curve, and a new maximum point where they cross each other. This procedure is a simplification of how the response curves are affected in the dynamic region; only the opening point is correctly calculated (except for the uncertainty in using equations (d) for a reference temperature different from 60 F). E.g., the curve for a casing/injection pressure of 850 psig in Figure A will not be affected by temperature with this procedure. This is not physically correct.

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Limitations The temperature effects on the opening/closing of a GLV are mainly uncertainties in using the GLV characteristics. The average of the temperatures on the production and injection side is used as temperature inside the valve body. In reality, the temperature distribution within the valve is more complex because of interaction between the production string and the injection string, the expansion of lift gas through the valve, and axial heat transfer along the pipes. It is also assumed that the maximum flow rate point of the GLV performance curve corresponds to the flow rate of a fully opened valve. For the curves which do not have the maximum point, the effects of temperature on the closing of the valve are not considered.

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How to use Use the keyword TABLE to specify the curves of gas flow rate as a function of production pressure for different injection pressures. Use the keyword LEAK to specify the gas injection position and the name of the table the GLV performance curves are given. Use ANNULUS keyword to configure the injection and production strings.

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Heat Exchanger A heat exchanger is included to raise or lower the temperature in the fluid. There are two different types of heat exchangers in OLGA;’Setpoint Heat Exchanger’ and ’Controlled Heat Exchanger’. Both can be configured to give practically the same results, but each is configured differently and this allows for different usages. See also: When to use Methods and assumptions Limitations How to use

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When to use When a heat exchanger is used in the anti-surge recirculation loop of a compressor, it is specified through the keys of the COMPRESSOR keyword (keys COOLER and COOLCAPACITY). Otherwise, use this HEATEXCHANGER keyword to create a heat exchanger.

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Methods and assumptions The setpoint heat exchanger is an idealised heat source/sink, and no description of the real heat transfer process is included. It simply provides a way of specifying a temperature at the heat exchanger outlet, consistent with the energy equation in OLGA. In the setpoint heat exchanger, a heat source/sink is estimated that will give the specified fluid temperature for a particular section. More specifically, the heat exchanged is equal to the enthalpy difference corresponding to the difference between the inlet temperature and the specified outlet temperature of the heat exchanger. The controlled heat exchanger has a simpler model. In the controlled heat exchanger, the effect of the heat exchanger is determined by the controller system. The heat source/sink is not estimated as the heat exchanger has no knowledge of any target temperature. The CONTROLLER for the heat exchanger knows the current temperature and the target temperature and adjusts the effect of the heat exchanger to obtain the target temperature.

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Limitations A heat exchanger can not be positioned at the first or last section boundary of a pipeline.

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How to use To select between a setpoint heat exchanger and a controlled exchanger, simply set the TYPE. To use a setpoint heat exchanger, specify the position, an outlet temperature and an upper limit of the heat source, the capacity. To use a controlled heat exchanger, specify the position and the capacity, but instead of setting the outlet temperature, connect the heat exchanger to a controller. The controller will typically measure the temperature at a specified position along the pipeline and compare the measured temperature to a setpoint. Based on the difference between the setpoint and the measured temperature, the controller will deliver a signal to the heat exchanger which determines how large a fraction of the heat exchanger’s capacity will be applied. Different types of controllers can be used, making the input of a controlled heat exchanger more flexible than that of the setpoint heat exchanger. For example, one can measure the average temperature over several sections by using a Linear Combination Controller.

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Pump The PUMP keyword is used to model specific pump types of common commercial interest. Real commercial pumps may be classified into the following categories; 1. Rotodynamic pumps 2. Positive displacement (volume) pumps 3. Other types (jet pump, water hammer pump, etc). OLGA currently offers four different pump models; the centrifugal pump and the simplified centrifugal pump which belong to category 1 above, as well as the displacement pump and the pump battery which belong to category 2 above. No explicit OLGA models are yet implemented for the less-common types of specialized pumps listed in category 3 above. See also: When to use Methods and assumptions Limitations How to use

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When to use If the inlet pressure of a pipeline is too low to drive the fluid to the outlet of the pipeline, or if we want to increase the oil production, a pump can be installed to increase the flow rate in the pipeline.

License requirements The centrifugal and displacement pumps are part of the Multiphase Pump Module that requires a separate license. The pump battery model is used for drilling applications, and is only available with the Wells Module. The simplified centrifugal pump requires no additional license.

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Methods and assumptions Centrifugal pump Theory and multiphase dynamics For a generalized multiphase centrifugal pump, the pressure increase over the pump, DP, is dependent on the flow rate Q, pump speed N, inlet gas volume fraction aI, and the pump inlet pressure PI: (a)

For the liquid (assuming incompressible), the specific work delivered from the pump into the fluid is: (b) where PO is the pump outlet pressure, PI the pump inlet pressure and rl the liquid density. For a compressible gas, and assuming a polytropic process, the work done by the pump is:

(c) Where n is the polytropic constant and rg, I the gas density at pump inlet. The work input to the gas is equal to the increase in the gas enthalpy. When the gas is assumed to be ideal Win can be written as:

(d) The polytropic efficiency is defined as the ratio of the work done by the pump divided by the work input to the gas. If the adiabatic constant k for the gas and the compressor efficiency hp are given, the polytropic constant n can be calculated. For a two-phase mixture, the pump power to the fluid is weighted by mass fractions (αm = gas mass fraction) as follows:

(e) With W calculated from the pump characteristics, Equation (e) can be solved for PO/PI. The relationship between head H and specific work W is W = gH = ghHR, where HR is rated head and h is the head ratio. For a two-phase mixture (except for very high gas fractions) an isothermal compression of the gas may be assumed (i.e. n=1.0) to account for rapid vapor-phase heat loss to all of the associated liquid, the pump impeller / case, and the surroundings. Assuming n = 1.0, equation (e) can then be rewritten by a series expansion to:

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(f)

Modeling in OLGA OLGA's transient calculations for centrifugal pump performance utilize multi-dimensional interpolation across four separate (default, or user-specified) quadrants of performance curves. Each quadrant is defined in a specific normalized / homologous format (see Pump Data Table for Centrifugal Pumps for an exact definition of all quadrant formats). Together, these four quadrant curve sets give OLGA advanced capability to model all possible transient combinations of Positive and Negative Normalized Speed Ratios and Flow Ratios (including transient backflows that often occur during pump startup and shutdown, in combination with either weak forward impeller rotation or actual reverse impeller rotation). However, most pump manufacturers do not publish performance curves directly in this normalized / homologous format required by OLGA. Nor do they typically offer any curves at all for the operating quadrant representing Positive Speed with Negative Flow (where the pump is transiently unable to overcome external backpressure, typically during Startup/Speedup) or the operating quadrant representing Negative Speed with Negative Flow (where the centrifugal impeller is physically rotating backwards, either due to reverse power input or overwhelming external backpressure). Instead, most manufacturers publish one Head versus Flowrate Curve (with Power or Torque overlaid) for the case of Gas Volume Fraction (GVF) = ZERO, plus additional curves for increasing GVF's, up to a "Degraded Performance Limit" (often GVF=60-70%, but variable by manufacturer and model).

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In order to incorporate such manufacturer curves into an OLGA pump model, the user must first convert the manufacturer curves into homologous curves where the head and torque ratios (actual value to rated value) are functions of the pump speed and flow rate ratios, as defined in Equations (g) below. OLGA's special homologous centrifugal pump curves utilize the following non-dimensional variables: - head ratio

- speed ratio

- flow ratio

- torque ratio

(g)

where subscript R means rated value. OLGA interpolates over four quadrants of homologous curve sets, all defined in terms of the above nondimensional variables. Each quadrant curve set includes: Single phase head HS Two phase head HT Single phase torque THS Two phase torque THT The two-phase head HT and two-phase torque THT curves should be based on fully-degraded twophase conditions. The transfer from single-phase conditions to fully-degraded two-phase conditions is described by a two-phase multiplier. The pump head H and hydraulic torque TH under two-phase conditions are determined as:

(h) where HM(a) is the two-phase head multiplier, TM(a) is the two-phase torque multiplier and a the gas volume fraction at the pump inlet. Each set of homologous curves consists of four curves. These are defined in Table 1 and Table 2. 292 / 769

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A complete default set of homologous curves is tabulated in the code (and also documented in an external file that is linked to the example centrifugal pump in the pump.opi sample case installed with OLGA) . These built-in default centrifugal pump curves are based on experimental data, and are representative for typical centrifugal pumps. However, users can change these data easily by specifying their own experimental data through the pump data table. An example of a graphical presentation of the tabulated pump characteristics is shown in Figure A. This figure shows the single phase homologous head curves. Because the homologous curves are dimensionless, one set of curves can be used to describe a variety of different pumps (i.e., within a single OLGA model) by specifying the desired rated density, head, torque, flow rate and speed for each pump. In calculating the hydraulic torque, TH, the difference between actual fluid density and rated density must be corrected as: (i)

Table 1: Dependence of Pump Head on Pump Speed and Flow Rate

Curves

Range

Independent variables

Dependent variables

1

w > 0,

q/w

h/w 2

2

q > 0,

w /q

h/q2

3

q < 0,

w /q

h/q2

4

w < 0,

q/w

h/w 2

Table 2: Dependence of Pump Torque on Pump Speed and Flow Rate

Curves

Range

Independent variables

Dependent variables

1

w > 0,

q/w

b/w 2

2

q > 0,

w /q

b/q2

3

q < 0,

w /q

b/q2

4

w < 0,

q/w

b/w 2

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Figure A: Single Phase Homologous head curves The OLGA centrifugal pump model also includes embedded numerical models for typical recycle and bypass lines, including user-specified orifices that may be linked to OLGA controllers. For more detail, see the heading Recycle and bypass flow below. For details of the energy balance across the OLGA Displacement Pump, see the heading Energy balance below.

Displacement pump Theory and multiphase dynamics For the displacement pump, the pump flow rate is the theoretical flow rate minus the backflow through the pump. The theoretical flow rate is a function of the pump speed and the characteristics of the pump, expressed through the specific flow rate. The backflow rate is a function of several parameters and is tabulated in a backflow table. This can be summarized as follows:

(j)

where Q0 Qb Qspc N DP aI nl PI

- theoretical flow rate - back flow rate - pump specific flow rate - pump speed - pressure increase across the pump - void fraction at the pump inlet - liquid kinetic viscosity - pressure at the pump inlet

Modeling in OLGA For a given displacement pump, the specific flow rate Qspc is a constant. Qb is tabulated in the backflow table as a function of N, DP, aI, nl and PI. A default implementation of the backflow table is implemented in the displacement pump (and also documented in an external file that is linked to the example displacement pump in the pump.opi sample 294 / 769

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documented in an external file that is linked to the example displacement pump in the pump.opi sample case installed with OLGA). Other backflow tables may be given by using the TABLE keyword.(See Pump Data Table for Displacement Pumps.) The OLGA displacement pump model also includes embedded numerical models for typical recycle and bypass lines, including user-specified orifices that may be linked to OLGA controllers. For more detail, see the heading Recycle and bypass flow below. For details of the energy balance across the OLGA Centrifugal Pump, see the heading Energy balance below.

Pump Battery Accurate simulation of the pumps used for a standard drilling operation is important for the overall estimation of the pump power needed as well as the volume of mud/water required during the operation. Defining the total flow rates proportional to the rate of pump strokes simulates the battery of positive displacement pumps. We define the pump battery through a proportionality factor for the volume delivered at a certain pump rate: (k) where QP = PFAC = SPES =

Volume delivered by the pump battery Pumping factor Strokes per time unit

The pump rate is normally controlled by the following set of controllers: Controller on the maximum hydraulic horsepower allowed Controller on the maximum pump rate Controller on the minimum pump rate Controller on the maximum pump pressure allowed If any one of these controllers is set into action the pump rate is adjusted automatically. The number of controllers can be extended above the number shown above and different variables (e.g. fluid rate, inflow rate) can be used to control the pumps. The total hydraulic horsepower, HHP, is calculated from the following definition:

(l) where Qinj = Pump injection rate of mud or water (bbl/min) WHP = Pump injection pressure (bara)

Recycle and bypass flow Recycle and bypass flows are only defined for centrifugal (not simplified) and displacement pumps. The recycle flow, GR, is considered as the flow through a controlled choke. The flow is calculated with a 295 / 769

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recycle flow, GR, is considered as the flow through a controlled choke. The flow is calculated with a given pressure difference between the two sides of the choke, DPch, and the choke upstream conditions. The choke upstream condition is taken from the pump downstream section (pump pressure side). The choke flow can be regulated by a controller. If the recycle flow is in subcritical condition, GR is calculated by: (m) where Cd is the choke discharge coefficient and Ach the choke opening area. If the mass flow through the choke exceeds the critical flow rate, critical flow conditions will be used. The flow rate through a critical choke is governed by the choke upstream conditions and the choke opening. No forward flow is allowed in the recycle loop. The bypass flow, Gb, is controlled by a choke and calculated in the same way as for the recycle flow. If the bypass flow line is opened, the fluid flows from the pump inlet to the pump outlet in the normal pumping flow direction without going through the pump. Back flow is not allowed through the bypass line.

Simplified centrifugal pump Theory and multiphase dynamics The simplified centrifugal pump in OLGA is intended for quick, approximate modeling. It models a linearized approximation to the local behaviour of a real centrifugal pump, and is therefore only accurate for use across small excursions from its specified local operational point (where the tangent to the real nonlinear operating curve does not change significantly). These simple algebraic expressions are used to calculate the pressure increase over this simplified pump, as well as its pump efficiency:

DPo = DPr ( 1 + D1 ( N - Nr ) + D2 ( Q - Qr ) ) ( 1 - D3 a ) =

r ( 1 + E1 ( N - Nr ) + E2 ( Q - Qr ) ) ( 1 - E3 a )

DP = DPo

r

(n) (o) (p)

where:

DPo DP N Q a

= Pump pressure increase at rated density ( bar ) = Pump pressure increase ( bar ) = Pump speed ( rpm ) = Flow rate ( m3/s ) = Gas volume fraction = Pump efficiency ( adiabatic ) = Specific density ( kg/m3 ) D1,2,3 = Input coefficients for pressure increase E1,2,3 = Input coefficients for efficiency Subscripts:

r = rated

The power to the fluid is calculated in the following manner: a. Inlet enthalpy (Hs) (J/kg) and entropy (Ss) are found from the fluid file. The enthalpy at discharge 296 / 769

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pressure is found assuming isentropic conditions (Hiso). The actual enthalpy change is then calculated by following formula: (q) b. Outlet enthalpy is calculated from: Hd = Hs + ΔH

(r)

c. The power input to the fluid is calculated from: Wfluid = GT×ΔH

(s)

where Wfluid is in W, and GT is the total mass flow in kg/s. Total shaft power: Wtot = Wfluid / η M

(t)

Pump torque: = Wtot /

(u)

Pump hydraulic torque: TH = Г η M

(v)

where = 2 N / 60, and M the pump mechanical efficiency. Modeling in OLGA Note that by setting the coefficients D1,2,3 and E1,2,3 = 0.0, a pump with a constant pressure increase will be simulated. If the user wants to obtain a certain flow rate in a simple way, one can either iterate on the input value for Pr or assume some value for D1 and let a controller determine the necessary speed.

Energy balance Centrifugal and Simplified Centrifugal pumps The total power input to the fluid from any pump (including the OLGA centrifugal, displacement, and simplified pumps described above) is: (w) where TH is the pump hydraulic torque, w the pump speed and M the pump mechanical efficiency. Displacement pump For the displacement pump, the hydraulic torque, TH, may not be available, and it is therefore difficult to calculate the term QPt. In this case, the total power input to the fluid is calculated by summing the mechanical work on the fluid and the different losses as following: 297 / 769

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The power used for mechanical work on the fluid, QPM, is calculated as: (x) where, Wl Ql rl Wg Qg rg

- specific work delivered from pump into liquid - liquid flow rate - liquid density - specific work delivered from pump into gas - gas flow rate - gas density

Mechanical friction loss: (y) Viscous friction loss: (z) where, a - experiment coefficient for mechanical friction loss b - experiment coefficient for viscous friction loss Nref - pump reference speed QPmf,ref - mechanical friction loss at the pump reference speed QPvis,ref - viscous loss at the pump reference speed Then, the total power input to the fluid is calculated as: (aa)

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Limitations The recycle flow and bypass flows around the OLGA centrifugal and displacement pumps are considered as flows through controlled chokes. Each flow is calculated with the given pressure difference between the two sides of the choke and the choke upstream conditions. The pipeline effect of the recycle flowline and bypass flowline is not considered. The recycle flow can only flow from the pump downstream section to the upstream section, and the bypass flow can only flow from the pump upstream section to the downstream section. It is impossible to insert any component in the recycle flowline or bypass flowline, because no pipeline is considered. Pumps can not be positioned at the first or last section boundary of a flow path.

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How to use General setup (all pump types) 1 Add the PUMP keyword to the desired flowpath 2 Specify pump location by one of ABSPOSITION (length), PIPE & SECTIONBOUNDARY, or POSITION (an alias) 3 Choose a desired PUMPTYPE from the list below: A Simplified Centrifugal to roughly simulate multiphase transient dP and efficiency with only three algebraic coefficients, as either constant or linearly sensitive to transient fluctuations in speed, flowrate, and void fraction. B Centrifugal to more rigorously model the real nonlinear transient operation of a particular multiphase centrifugal pump (including recycle and bypass). OLGA calculations are based on either built-in nonlinear curves for a "typical" pump, or user input of special dimensionless OLGA curves for a particular pump that must usually be derived from given dimensional curves before OLGA entry. C Displacement to rigorously model the real nonlinear transient operation of a particular multiphase positive displacement pump (including recycle and bypass). OLGA calculations are based on either built-in nonlinear curves for a "typical" pump, or detailed manufacturer's curves expressing that multiphase displacement pump's internal backflow rate as a 5-dimensional tabular function of speed, dP, multiphase void fraction, inlet pressure, and liquid-phase viscosity. D Pump Battery to simulate the special case of a battery of positive displacement liquid-phase drilling mud pumps. by specifying a proportionality constant relating operating speed to total volumetric flowrate, subject to specified control limits for minimum and maximum flowrate, as well as maximum hydraulic horsepower and outlet pressure. NOTE: The related topic Pump - When to use documents the differing OLGA module license requirements for each PUMPTYPE described above. 4 Choose any applicable means of controlling the pump speed, as described in detail at the bottom of this section.

Simplified Centrifugal setup 1 In addition to the General Setup above, you must specify DPRATED, FLOWRATED, SPEEDR, and MAXSPEED. Allso override the (900 kg/m3) default of the required DENSITYR with your actual rated liquid density, if significantly different. 2 You may also specify related sensitivity of pump DP to varying speed, flowrate, and void fraction via the linear departure coefficients DCOEFF1 - DCOEFF3. NOTE: Without these optional user inputs, the OLGA simplified centrifugal pump defaults to a constant DP = DPRATED regardless of any transients. 3 You may also override the default (0.5) adiabatic efficiency by entering EFFRATED, then make that efficiency sensitive to speed, flowrate, and void fraction if desired by also entering ECOEFF1 ECOEFF3. NOTE:Adiabatic efficiency of the Simplified Centrifugal Pump affects OLGA calculations for fluid heating, hydraulic horsepower, total shaft horsepower and torque, through the relations documented in Pump - Methods and assumptions. 4 If more accurate estimation of Total Shaft Power is also required, you may also override the default (0.7) EFFIMECH.

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1 Like the Simplified Centrifugal Pump discussed above, the OLGA Centrifugal Pump also requires DENSITYR (same 900 kg/m3 default, or specified), plus FLOWRATED, and SPEEDR. 2 However, OLGA's full Centrifugal Pump model also requires you to specify HEADRATED and TORQR as a minimum, in order to scale the general transient response surface of either the built-in default or user-specified Homologous Centrifugal Pump Curves to your actual pump. 3 You may optionally enter custom transient centrifugal pump performance curves to precisely represent the exact transient response surface for your actual pump. However, note that most manufacturers do not publish pump curves directly in this format, and it may also be difficult to obtain degraded multiphase performance curves up to the maximum degraded Gas Volume Fraction (GVF) for your particular hardware and application (often somewhere in the range of 30 - 70% vapor volume).For more specific information about the theoretical basis of these special OLGA input requirements, consult Table 1, Table 2, and Figure A of the Pump - Methods and Assumptions topic. 4 The OLGA Centrifugal Pump will run without any further inputs, already representing a much more realistic transient modeling upgrade to the Simplified Centrifugal Pump model at only slightly greater modeling cost in setup time and runtime. 5 This PUMPTYPE also includes additional provisions for simple "branch-less" Bypass and Recycle modeling to further increase the realism of OLGA's transient responses for typical pump packages. The setup procedures and modeling assumptions for these Built-in Bypass and Recycle features are described in detail below.

Displacement setup 1 The OLGA Displacement Pump requires significantly different types of inputs than the Centrifugal or Simplified Pumps. For example, none of DENSITYR, FLOWRATED, HEADRATED, SPEEDR, or TORQR are used. 2 You must enter SPECAPACITY (the total specific volume displaced per revolution or displacement cycle). as well as MAXSPEED. OLGA will then multiply these two inputs to determine the (gross) theoretical volumetric flowrate displaced (before subtracting internal bypass). 3 The OLGA Displacement Pump will run without any further inputs, although equipment manufacturers or others with detailed knowledge may wish to override the defaults for one or more of ACOEFFICIENT, BCOEFFICIENT, MDISSIPATION, VDISSIPATION, etc in order to tune the model very precisely. 4 You may optionally enter custom transient displacement pump backflow (performance) curves to precisely represent the exact transient response surface for your actual pump. However, note that the required input format is a complex 5-dimensional matrix of internal backflow rates as a function of pump speed, head, void fraction, inlet pressure, and liquid viscosity - information normally only available from the manufacturer's experts, perhaps even requiring new eperimental work on a prototype pump for your particular fluid and operating conditions..For more specific information about the theoretical basis of these special OLGA input requirements, consult the Displacement Pump Theory topic in the Pump - Methods and Assumptions section. 5 Like the Centrifugal pump, this PUMPTYPE also supports additional provisions for simple "branch-less" Bypass and Recycle modeling to further increase the realism of OLGA's transient responses for typical pump packages. The setup procedures and modeling assumptions for these Builtin Bypass and Recycle features are described in detail below.

Pump Battery setup 1 Setup of and use of the special Pump Battery model (for a battery of dtilling mud pumps) is primarily described within the Pump Battery topic of the Pump - Methods and Assumptions section. 2 Required inputs include MAXSPEED, MINCAPACITY, MAXCAPACITY, MAXPRESSURE, and HPMAX. MINSPEED is optional. 3 These inputs are used to simulate simple limit controls on horsepower, flowrate, and pressure.

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To activate OLGA's simplified Bypass feature for any Centrifugal or Displacement Pump, specify BYDIAMETER and connect a bypass controller of your choice. No other bypass inputs are offered or required. To activate OLGA's simplified Recycle feature for any Centrifugal or Displacement Pump, specify at least RECDIAMETER and MAXRECYCLE, plus any non-default values for RECPHASE, MINRECYCLE, and ACCECOEFF. Then connect a recycle controller of your choice. Further details about the internal workings of these simplified Bypass and Recycle features are provided in the following text, equations, and block flow diagrams. A common multiphase transportation system with pump is shown in Figure B.

Figure B: Multiphase Transportation System with Pump Within OLGA, this system will be simplified as shown in Figure C. Note that in this implementation the pump is abstracted into a volume-less element on the section boundary J between section J-1 and section J. The recycle flow is out of section J and into Section J-1, and the bypass flow out of section J1 and into section J. No-slip flow is assumed for all of gas, liquid, and droplets moving through section boundary J, as: Ug = Ud = Ul = U OLGA also permits the user to add a separate VALVE keyword at the same section boundary where a centrifugal pump is located. The user may then close that optional OLGA Valve to block any possible backflow transients (that may otherwise occur due to higher downstream pressure at any moment when the centrifugal pump is shut down).

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Figure C: Multiphase Transportation System modelled in OLGA The centrifugal pump model requires a pump table with the characteristics of the pump. The displacement pump model requires a backflow table. The pump manufacturers generally characterize their pumps by pump operating characteristics. There is a default implementation of such tables in OLGA. If other tables are needed they should be given with the TABLE keyword. Each of the characteristics is assigned a label, which is referred to in the PUMP keyword. The user can choose the recycle flow as gas only, liquid mixture, water only, or fluid mixture.

Controlling the pump speed The following options are available for controlling the pump speed: 1. Pump speed regulated by controller (All pump models): a. Controlled manually by specifying time and speed series in the controller definition. b. Regulated by a physical parameter. The speed is calculated by: (ab) where Nmax is the maximum pump speed (defined by user), Nmin is the minimum pump speed (defined by user) and u the signal from the controller.

2. Controlled by an override controller (Only for centrifugal and displacement pumps): To adapt the pump to the production change (because the recycle flow is at upper or lower limits), the pump speed will be changed automatically according to the required speed variation (speed acceleration). The speed variation may be given in form of:

where A is a constant pump speed variation rate (acceleration). The speed variation will stop once the recycle flow is within a defined range below MAXRECYCLE and above MINRECYCLE.

3. If the maximum pump torque has been given by users (Only for centrifugal and displacement pumps): The effective pump torque is calculated from the total power input to the fluid, QPt : (ac) where QPt is the total power input to the fluid. If the pump shaft torque is over the limit the pump speed is reduced, and a warning message will be given in the output file.

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Separator The network separator is not intended to accurately model separation phenomena, but is meant to include the influence of a separator on transient pipeline dynamics. The behaviour of the separator is mainly based upon user given input for the separation efficiency (gas/liquid, oil/water), and set critical levels for oil and water drainage. See also: When to use Methods and assumptions Limitations How to use

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When to use It is recommended to use the separator model whenever a ”real” separator is present in the flow network and the effect of the downstream flow pattern is of interest. If it is only interesting to look at the upstream flow pattern, it sometimes is appropriate to replace the separator with an ordinary pipe with large diameter to stabilize the boundary conditions and in that way avoid the needs for more complex specification of outgoing pipes, valves and controllers linked up to the separator. It can also be useful to employ a separator as a downstream boundary condition for controlling the boundary pressure. This may reduce unwanted flow oscillations in the network compared to using a constant pressure boundary condition.

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Methods and assumptions Separator type The separator may be two-phase or three-phase and the geometry orientation is horizontal, vertical or table specified. Connections to external pipelines The separator has an arbitrary number of inlets/outlets. Two phase separators must have connected at least one inlet, one gas-outlet and one oil-outlet to pipes. Three phase separators must in addition also have one water-outlet connected. Valves/controllers The separator has no internal valves and controllers, so they have to be specified on the outgoing pipes. Level control The separator levels are controlled by the valves and controllers in the outlet pipes. For a three-phase separator, the water level limit for when the water will be drained together with the oil can be specified in the separator keys: HHWATHOLDUP or HHWATLEVEL

Separation efficiencies a)

Liquid carryover in gas outlet. The gas-liquid separation efficiency is defined as one minus the volume fraction of the liquid droplets in the gas outlet stream. By default, the gas-liquid separation efficiency is equal to one, that is, no liquid carryover in the gas outlet. The user can, however, specify a constant gas-liquid separation efficiency, effg by the key EFFICIENCY in the keyword SEPARATOR. The liquid droplet volume fraction in the gas stream is then equal to one minus the value assigned to EFFICIENCY. For three phase flow the liquid droplet volume fraction is distributed to water and oil droplet volume fractions according to the water and oil volume fractions in the settled liquid in the separator. To prevent instabilities in the separator when the liquid holdup becomes very large, it is possible to specify two input keys, EFFLOW and EFFHIGH, to assure a continuous transition from effg = EFFICIENCY to effg = 0.0. EFFLOW is the liquid volume fraction when efficiency is being reduced and EFFHIGH is the liquid volume fraction when efficiency becomes zero and the gas outlet is treated as a normal flow path. The gas-liquid separation efficiency, effg is modified by the following set of rules: The liquid volume fraction, αl ≤ EFFLOW:

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αl > EFFLOW and αl < EFFHIGH:

(b)

αl ≥ EFFLOW: (c)

b)

Oil in water drain. The oil volume fraction in the water drain is determined by the following relation for separation efficiency:

(d) where Kso is the time constant, OILTCONST, for separating oil from water and Trsp is the residence time which is defined as the separator liquid volume / liquid volume flow into the separator. The oil volume fraction in the water drain is then 1 eff0. c)

Water in oil drains. The water volume fraction in the oil drains is determined by an equation similar to the one above:

(e) where Ksw is the time constant, WATTCONST, for separating water from oil. If the water level is above a certain limit, HHWATHOLDUP or HHWATLEVEL, the water above this limit is assumed to be drained together with the oil and the separation efficiency for separating water from oil is modified as follows:

(f) where Hof is the ratio of the water layer height above the limit to the liquid height above the same limit. The water volume fraction in the oil stream is then 1effw.

Heat transfer The heat transfer, qtr into the separator or out from the separator is given by: 307 / 769

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(g) where U is the overall heat transfer coefficient, A is the surface area, T sep is the separator temperature and Tamb is the ambient temperature. If adiabatic temperature option is given for the total flow network, U is set to zero for all separators in the network.

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Limitations The network separator is not intended for design purposes. It only simulates a predefined behaviour of a ”real” separator. The separator is only treated as a simple volume tank with no internal separation equipment The separator efficiencies is user given No wall temperatures is calculated There are no time restrictions for calculation of the flash contributions. The total mass internally is taken into account and treated as at equilibrium. Due to the internal geometry of the separator, this might give incorrect results if the separator pressure or temperature suddenly changes.

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How to use

Figure A An illustration of a three-phase separator

Input Connections to external flow paths For a two phase separator, the following connections are defined: INLET_1, …INLET_N inlets GAS_1, … GAS_N outlets (Use GAS_2 to model flare outlet) OIL_1, …OIL_N outlets(Use OIL_2 to model emergency outlet) For a three phase separator, the following connections are defined: INLET_1, …INLET_N inlets GAS_1, … GAS_N outlets (Use GAS_2 to model flare outlet) OIL_1, …OIL_N outlets(Use OIL_2 to model emergency outlet) WATER_1, …WATER_N outlets(Use WATER_2 to model emergency outlet) Initial conditions Key INITTEMPERATURE gives initial value for the separator temperature Key INITPRESSURE gives initial value for the separator pressure Key INITWATLEVEL gives initial value for the water level Key INITOILLEVEL gives initial value for the oil level Geometry There are two ways to specify the geometry of the separator. One method is to specify the separator length, LENGTH and the separator diameter, DIAMETER. The surface area and volume is then calculated by using the knowledge of the cylindrical form. The other method is to define a specific level table LEVELTABLE, a set of user defined values giving the volume as a function of the level (height). Using this method the surface area, SURFACEAREA also has to be given. Separator valves/controllers The separator has no internal valves and controllers. All valves must be defined on the outgoing pipes and might be positioned at the first section boundary of the pipes. The controllers are connected to the valves and must also be defined outside the separator. It is recommended that the water valve opening is controlled by a water level controller, the oil valve opening is controlled by a oil level controller and the gas valve opening is controlled by a separator pressure controller. 310 / 769

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Output Many of the plot variables specified under volume variable are available for the separator. In addition a number of separator specific plot variables also are available: Mass flow rates for each mass field for each pipe connection Separator levels (oil, water) Separator efficiency

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Valve The valve models the pressure drop for flow through chokes and valves. See also: When to use Choke — Methods and assumptions Valve — Methods and assumptions Limitations How to use

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When to use Use to model orifices, chokes and different types of valves. For high velocities in the pipeline, a fully open valve can be used to limit the flow to critical flow. Use a choke with choke diameter equal to the pipeline diameter. Position the Valve at the last section boundary of the pipe where the flow rate should be limited.

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Methods and assumptions The choke model uses mixture balance equations for mass, momentum and energy. Compression of gas into the narrow throat is accounted for in the model. A circular-symmetric flow geometry and steady-state over the choke is assumed. See Selmer-Olsen et al. for the full model description [34]. The choke model describes the effects of both subcritical and critical chokes. The choke opening may be controlled by the control system, by a predefined time series, or be fixed. The choke has finite opening and closing time (stroke time) specified by the user. A subcritical choke is represented through its pressure drop as a function of flow rates and choke openings. The flow rate through a critical choke is governed by the upstream conditions and the choke opening (choke flow area). The choke flow rate is limited to critical flow.

Figure A: An illustration of a choke. Fluid is flowing from position 1 to position 2.

Choke model The flow through the choke is assumed frictionless, homogeneous and adiabatic. The flowing phase fractions are frozen at inlet conditions. Phase change occur after the throat, and the fluid reaches equilibrium in position 2. The choke model in OLGA describe the pressure drop from upstream (position 1 in Figure A) to downstream (position 2 in Figure A) an orifice or other constriction in the pipeline. The model include pressure drop from position 1 to throat (position t in Figure A) and pressure recovery when the fluid expands from the throat to position 2. The pressure drop to throat — Bernoulli and continuity equation Bernoulli Equation:

(a) where um ρm P

mixture velocity (m/s) momentum density (kg/m3) pressure (Pa)

Momentum density: (b) Flowing gas mass fraction: 314 / 769

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(c) where M is the overall mass flow through the choke and Mg is the gas flow through the choke. Continuity equation: (d) where A is the cross sectional area. Recovery after throat — Momentum and continuity equation Momentum equation: (e) The overall pressure drop over the choke is found by combining equations (a) through (e). Critical flow The critical flow through the choke is found at the maximum of equation (a). Differentiating equation (a) w.r.t. pressure and combining with equation (d) yields the following relation for the critical flow, MC,

(f) The throat area, At, is corrected with the choke discharge coefficient, Cd, to find the minimum flow area. Simplified fluid property calculations The liquid properties are calculated in position 1 and treated as constant, while the gas is compressed/expanded isentropically. Gas density:

(g) where γ is the isentropic gas expansion coefficient,

(h) The reported throat temperature (TVALVE) is the gas temperature

(i) The liquid is assumed isothermal and the liquid throat temperature is therefore the same as the inlet temperature. 315 / 769

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Critical flow options Two options are available when calculating the critical flow through a choke: 1. Frozen: No mass transfer, isentropic expansion of gas. (Homogeneous frozen critical flow model) 2. Henry–Fauske: The Homogeneous frozen critical flow model corrected for mass transfer in the throat [3]. If the Henry–Fauske model is used and entropy values are given in the fluid property tables file (with the word ENTROPY in the heading of the fluid file), the entropy values in the fluid file will be used. Otherwise, the entropy changes will be calculated from enthalpy, mass fraction and density by integrating the following equation from the upstream conditions (position 1) to the throat conditions (position 2): (j) The integration is performed in two steps, from P1 to P2 at T1 and from T1 to T2 at P2.

Controlled choke In the case of a controlled choke, the choke area, Ao, is varied according to the controller signal us : (k) where (l) Do is the choke diameter and Amax is the maximum choke area. In the case of an uncontrolled choke, the choke flow area is varied according to the time tables of the relative choke area, orel, (m) In the case of a fixed choke, the choke flow area is constant; (n) Note that it is possible to simulate a choke without a controller; the choke area is then given by a time series.

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Methods and assumptions In the valve model the pressure drop and critical flow are calculated according to a valve sizing equation. The valve model uses a table (keyword TABLE) that contains the valve sizing coefficients, Cv or Cg, versus valve opening. It is possible to give a table representing the valve sizing coefficients either for gas flow or for liquid flow. It is not possible to give a table for two/three-phase flow. The sizing coefficients are tabulated as functions of the relative valve opening. The liquid valve sizing coefficient can also be given as a function of both relative valve opening and pressure drop over the valve. Note: The input data for the valve sizing coefficients must be consistent with the units specified together with the valve sizing equations below. A valve can be located anywhere in a pipeline. Liquid Valve sizing equation If a liquid sizing table is given, the valve flow rate (even three-phase flow) will be calculated using the choke model in OLGA. The liquid sizing table should be used for liquid flow, near incompressible gas flow and two/three-phase flow. The pressure drop through a valve is calculated as follows: Liquid sizing equation:

(o) where

Q Cv G DP

Flow rate (gallons/min.) Valve sizing coefficient (gal/min / psi 1/2) Specific gravity (-). Water = 1. Pressure difference across the valve (psi)

OLGA converts Cv for liquid to the choke flow area, Ao, used in eq. (p). Equations (p) and (o) will produce a relation between Cv and Ao. Setting CD=1.0, the choke area can be calculated. The pressure drop and the critical flow rate are calculated using the choke model, regardless if the flow is gas, liquid, or multiphase flow. The mixture density is used in the calculation. Orifice equation:

(p) where Cd A

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Ao Wtot Ui αi ΔPorf

Choke (orifice) flow area Total mass flux Velocity of flow field i, (film velocity, droplet velocity etc.) The volume fractions of flow field i Pressure drop over the orifice

See Cv to area conversion for the details of the conversion from Cv to orifice area. Gas valve sizing equation If the MODEL key is set to HYDROVALVE, the gas sizing equation is used in the same manner as the liquid valve sizing. Combining equations (p) and (q), a choke area can be calculated. The critical flow will then be determined by the choke model. If instead the model option GASSIZING (keyword MODEL) is used, the gas sizing equation will be used for both subcritical and critical flow. The choke model will not be used. Gas sizing equation: (q) where Qm rg p1 Cg DP Cf

Mass flow rate (lb/hr.) Gas density (lb/ft3) Upstream pressure (psi) Gas sizing coefficient (lb/hr / (psi × lb/ft3)1/2) Pressure drop (psi) Coefficient ratio, Cg/Cv (-)

The critical flow rate is obtained by setting the sine-term equal to one. The upstream density is used in the calculation.

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Conversion between liquid valve sizing coefficient (Cv) and orifice area The orifice equation for an incompressible fluid:

(a)

rFluid Q αi Ui A AOrifice Cd ΔPOrifice

Is the fluid density Is the volumetric flow rate Volumetric fraction of mass field i Velocity of mass field i Pipeline area Orifice area Orifice discharge coefficient Orifice pressure drop

The valve sizing equation:

(b)

Cv Q ΔPSizing G ρRef ρFluid

Valve sizing coefficient (gal/min/psi1/2) Is the volumetric flow rate (gal) Sizing pressure drop (psi) Specific gravity (-) Water density at 39ºF/4ºC and 1 atmosphere (998.840 kg/m3) Fluid density at reference conditions

Setting ΔPOrifice = ΔPSizing and solving for Cv or orifice area (AOrifice):

(c) Above we have assumed that the orifice equation is given with the same units as the sizing equation. Converting to SI units:

CvSI = Cv · (d)

(m3/s/Pa1/2)

Using SI units for the area, m, and inserting the reference water density we get the following equation:

(e)

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Limitations Friction and gravity forces are neglected in the choke model. See Selmer-Olsen et al. for limitations in the choke model /34/. When using the Henry-Fauske critical flow model (CRITFLOWMODEL = HENRYFAUSKE) make sure the entropy is given in the thermo tables. Otherwise the entropy must be integrated from the enthalpy and density data in the thermo tables. In some cases, this will slow down the simulation. Further, it is not allowed to position a valve at the first section boundary in a flowpath next to a closed node in OLGA 6. OLGA 5 does not have this restriction.

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How to use Position the valve. Valves can be inserted anywhere in the pipeline. Choose which valve model to use from available information in data sheet etc. If no Cv/Gg is given, use the choke model. The choke is used when the model option HYDROVALVE (keyword MODEL) is set. A discharge coefficient, CD and maximum choke diameter must be defined for the choke. If the discharge coefficient is unavailable, use the default value. Consider using the CRITFLOWMODEL option HENRYFAUSKE for two/three-phase simulations with flashing fluids. Otherwise use CRITFLOWMODEL = FROZEN. If Cv data are available, use the model option HYDROVALVE, and specify the Cv vs. valve opening in a table. The valve Cv can also be described as a function of valve pressure drop (DELTAP) and valve opening. If Cg data are available, use the model option GASSIZING (key MODEL). Specify the Cg vs. valve opening in a table. It is also possible to use the HYDROVALVE (MODEL key) to simulate a gas valve. To control the valve flow in the choke, or the pressure drop over it, connect a controller to the input signal terminal INPSIG. When connected, INPSIG will be used as the valve opening. Otherwise, the key OPENING will set the valve opening. The given OPENING can be constant, or a function of time. To limit the rate of change in valve position, set the valve stroke time. Set CLOSINGTIME/ OPENINGTIME or STROKETIME. Setting STROKETIME will give CLOSINGTIME = OPENINGTIME = STROKETIME. It is possible to tune both the choke and valve model. The input signal CVTUNINGSIG will scale the choke CD, or the valve Cv/Cg.

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Single component The single component module allows for tracking of a single component, e.g., H2O or CO2, that crosses the saturation line in time or space in a pipeline. Standard OLGA cannot deal with single component systems if the saturation line is crossed due to the explicit coupling between volume balance and energy balance equations and the lack of a two phase region (two phase envelope) for single component systems. In order to circumvent this limitation, time constants, or delays, are introduced in the evaporation/condensation process. The difference between the saturation temperature and the fluid temperature serves as a potential for phase mass transfer. Multiplying this temperature difference with a certain heat or energy transfer coefficient yields an energy transfer rate that can be used to estimate the mass transfer rate. An asymptotic approach to equilibrium occurs where the speed at which equilibrium is reached is determined by the size of the energy transfer coefficient. See also: When to use Methods and assumptions How to use

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When to use The single component module should be used for all single component fluids. Special options exist for H2O and CO2, for which the fluid property calculations have been hard coded into OLGA. For other single component fluids, it is necessary to specify input parameters to the fluid property calculations. The numerics in standard OLGA have been designed for multi component hydrocarbon fluids. A consequence of the chosen approach is that standard OLGA become unstable when simulating single component fluids that cross the saturation line in time or space. The same can happen for multi component fluids with very narrow phase envelopes, for example a fluid composed predominantly of one component, but with a small amount of impurities. Since the behavior is very case dependent, it is hard to give general guidelines on the exact amount of impurities required before standard OLGA can be expected to yield reasonable results. One should, however, be careful when using standard OLGA to simulate fluids consisting of 90% or more of one component. Besides the numerical issues, it is important to make sure that the fluid property calculations are accurate for the particular fluid composition to be simulated. As implied by the name, the single component module can only be applied to pure single component fluids. At present, OLGA is thus not able to simulate single component fluids with small amounts of impurities.

License requirements The Single Component Module requires a separate license.

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Methods and assumptions The following assumptions are made in the single component model: the gas and liquid phases have the same temperature. the pressure of the gas and liquid phases is the same. if the fluid temperature is higher than the saturation temperature, flashing or boiling of liquid will take place. if the fluid temperature is lower than the saturation temperature, condensation of vapor takes place. The inner pipe wall surface can be superheated or subcooled as compared to the saturation temperature. Such situations might lead to surface boiling or surface condensation in cases where the liquid or gas is in direct contact with the pipe wall. The resulting, additional, mass transfer term is not explicitly included, but it can be accounted for by an enhanced heat transfer due to surface boiling/condensation.

Generation of gas and liquid properties The equations used to calculate the H2O properties are taken from ref. 1. For CO2, the thermodynamic equations are taken from ref. 4. The transport properties are calculated through the equations given in ref. 2. For other components, the Soave–Redlich–Kwong (SRK) cubic equation of state (Appendix 1) is used to calculate the saturation line and the physical properties of the vapor and liquid phases. Temperature dependent volume translation is applied to improve the accuracy of phase density. The transport properties are determined by the corresponding state method by Pedersen (ref. 2). The evaluation of the fluid property equations is time consuming, and, therefore, they are only evaluated at the start of the simulation. The properties are evaluated at a grid of pressure/temperature values that is limited by the minimum and maximum values of pressure and temperature given in the input. An equidistant grid is used with a minimum of 50 and maximum of 100 grid points for both pressure and temperature. During the simulation, linear interpolation is used to evaluate the properties in between grid points.

Saturation line for a single component The saturation line is determined by solving the equal fugacity of gas and liquid from the equation of state (EOS). Below the critical point, determined by the critical pressure, PC and the critical temperature, TC, the saturation pressure, Psat(T), and saturation temperature, Tsat(P), at a given grid point (P,T) are determined from the saturation line. Above the critical point, the saturation line is extrapolated with the slope of the saturation line at the critical point.

Liquid properties for a single component For pressures below the critical pressure liquid properties are determined by the EOS in the liquid region. In the gas region, the liquid properties are extrapolated from the saturation point — the enthalpy equals the gas enthalpy minus the latent heat at the saturation temperature and the density is integrated from the vapor saturation pressure to actual pressure using the compressibility at the saturation temperature. All the other properties are from the saturation temperature. For pressures above the critical pressure, liquid properties are calculated from the EOS.

Gas properties for a single component For pressures below the critical pressure, the gas properties in the gas region are acquired from the EOS. In the liquid region and a pressure below the critical pressure, the gas properties are extrapolated from the saturation line — the enthalpy equals the liquid enthalpy plus the latent heat at the saturation temperature corresponding to the pressure and the density is acquired by linear interpolation between the value at critical pressure and the saturation pressure. All other properties are taken at the saturation temperature corresponding to the pressure. For pressures above the critical pressure, gas properties 324 / 769

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temperature corresponding to the pressure. For pressures above the critical pressure, gas properties are calculated based on the EOS. Using this procedure, the gas and liquid properties are continuous across the fictitious gas-liquid (V–L) division line when the pressure is above the critical one. At the critical point and its vicinity, the thermal capacity and density derivatives show extreme sensitivity to temperature and pressure changes, even to the extent where discontinuities occur. Therefore, a buffer zone is introduced near the critical temperature as shown below. Within this zone, the liquid density derivative and thermal capacity are given the values calculated at a temperature, Tlow, less than the saturation point. Similarly, for the vapor phase, the gas density derivative and the thermal capacity are given the values calculated at a temperature, Thigh, above the saturation point.

The buffer zone is bounded by the coordinates [Tlow, Psat(Tlow)], [Tlow, Pc], [Thigh, Pc], [Thigh, Psat(Thigh)].

Saturation line for H2O Below the critical point, (PC,TC), the saturation pressure, Psat(T), and saturation temperature, Tsat(P), at a given grid point (P,T), are determined from the saturation line. Above the critical point, PC=221.2 bar and TC=647.3 K, and up to T=676 K and P=250 bar, a straight line is used to divide the single-phase or dense-phase region into gas and liquid. Above 676 K and 250 bar, the boundary line between region 2 and region 3 is used as the division between gas and liquid. The definition of the regions is found in ref. 1.

Liquid properties for H2O For pressures below 225 bar in region 1, the water properties equations found in ref. 1 are used for water in the water region. 325 / 769

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In the gas region, the properties for water are extrapolated from the saturation point — the enthalpy is based on thermal capacity at the saturation temperature corresponding to a given pressure. The density, on the other hand, is calculated using the density derivative w.r.t. pressure at the saturation pressure corresponding to the given temperature. All the other properties are evaluated at the saturation temperature. For pressures above 225 bar, water properties are calculated based on equations for the different regions specified in ref. 1. The thermal capacity and enthalpy for water are singular near the critical point. To avoid numerical problems in region 3, the water properties from region 1 are used instead of those for region 3 when the pressure is below 225 bar. The same procedure is used for steam (gas).

Gas properties for H2O For pressures below 225 bar, steam property equations for region 2 are used for gas in the gas region. In the water region, the gas properties are extrapolated from the saturation point. Enthalpy is based on thermal capacity at the saturation temperature corresponding to the given vapor pressure and the density according to the density derivative w.r.t. pressure at the saturation pressure corresponding to the given temperature. All other properties are evaluated at the saturation temperature corresponding to the vapor pressure. For pressures above 225 bar, vapor properties are calculated based on equations for the different regions. Using this procedure, the vapor and water properties are continuous across the vapor-liquid (V–L) division line when the pressure is above 225 bar.

Flashing/Condensation The driving force for flashing of liquid or condensation of gas is the difference between the saturation temperatures and the fluid temperature. The effect of local boiling on a hot wall surface or condensation on a cold one are not explicitly included in the mass balance of liquid and gas, but can be accounted for through an enhanced heat transfer at the pipe wall. The total energy available for generating gas or condensing it to obtain saturated conditions is (a) where mg = specific mass of gas [kg/m3] ml = specific mass of liquid [kg/m3] cpg = specific heat of gas [kJ/kgC] cpl = specific heat of liquid [kJ/kgC] h S V

= heat transfer coefficient at inner wall surface [kJ/m2sC] = inner surface area per unit volume of pipe [1/m] = section volume [m3]

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(b) where hsat,g = enthalpy of saturated gas [kJ/kg] hsat,l = enthalpy of saturated liquid [kJ/kg] In order to reduce numerical problems, it is assumed that this mass transfer occurs over a time Tψ. This yields the mass transfer rate (c) The mass transfer per time step must not be larger than the available component mass of the diminishing phase.

References 1.

Revised Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, The International Association for the Properties of Water and Steam, Lucerne, Switzerland, August 2007 2. K. S. Pedersen et al. Properties of Oils and Natural gases. Gulf Publishing Company, 1989, Houston, Texas. 3. B.E.Poling, J.M.Prausnitz, J.P.O’Connell: The properties of gases and liquids. 5th Edition. McGRAW-HILL 2000. 4. R. Span and W. Wagner: A New Equation of State for Carbon Dioxide Covering the Fluid Region from the Triple-Point Temperature to 1100 K at Pressures up to 800 MPa. J. Phys. Chem. Ref. Data, Vol. 25, No. 6, 1996

Appendix 1 The Soave–Redlich–Kwong (SRK) equation of state: (A.1) where

The SRK equation of state can be written on the form: 327 / 769

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(A.2) where

The solution, Z, to the above equation is found by iteration. As initial guess, the pressure is given by the Antoine equation except for CO2 where the Wagner equation is used. Coefficients for these equations can be found in ref. 3. The solution for Z can be adjusted by a volume tuning factor (A.3) according to (A.4) where XV1 and XV2 are given through the keys VOLX(1) and VOLX(2), respectively, and Pr = P/Pc. The specific heat, CP, is calculated through the equation (A.5) where the coefficients, CPi, are given through the input by CPIC(i+1).

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How to use The single component model is activated by setting the key COMPOSITIONAL=SINGLE under the OPTIONS keyword. The time constants for condensation and boiling are specified by the keys TCONDENSATION and TBOILING, respectively, under the keyword SINGLEOPTIONS. These keys are available as time series if desired. Large values of the time constants will slow down the mass transfer leading to a fairly large non-equilibrium. Small values will speed up the mass transfer and thereby reduce the thermal nonequilibrium. Too small values might however cause instabilities which in turn can result in nonphysical results. The keyword SINGLEOPTIONS specifies options for COMPOSITIONAL=SINGLE. COMPONENT can have the values H2O, CO2, or OTHER. H2O is set by default. N.B., if COMPONENT=OTHER, it is required to specify additional fluid properties such as viscosity tuning factor, VISX critical temperature, TC [C] critical pressure, PC [bara] acentric factor, OMEGA molecular weight, MW volume tuning factors, VOLX(2) coefficients in equation for specific heat, CPIC(5) For many different components values of these coefficients can found in ref. 3. The keys MINPRESSURE, MAXPRESSURE, MINTEMPERATURE and MAXTEMPERATURE in SINGLEOPTIONS are used to generate a PVT tables for the single component properties, i.e., no external PVT file is needed. 51 to 52 pressure and temperature points are used when generating the tables and the griding is adjusted so that a grid point is close to the critical point. During the simulation, linear interpolation between the grid points (P,T) is applied. For boundaries, sources and wells, the gas fraction will be either gas or liquid, all depending on the specified temperature as compared to the saturation temperature at the specified pressure. For sources without any given pressure, the pressure of the source receiving position is used. The output variables TSAT, TSV, PSAT, PVAP (see output variables description) are used to retrieve the vapor data. TSV equals TM and PVAP equals PT for single component simulations (no partial pressure since only a single component is considered). Other data can be obtained by specifying compositional variables. Under OPTIONS, the key WRITEPVTFILES=[NO]/YES controls whether the program will write the single component properties that are being used to file or not. For YES, a tab file _pvt.tab (fixed format) will be generated. Furthermore, the saturation line will be written to a file _pvt.env. Both these files can be visualized in the GUI.

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Slug Tracking In the standard OLGA model, physically sharp fronts in liquid hold-up are smeared out by the numerical scheme, a phenomenon that is more pronounced in horizontal or near horizontal high velocity transient flow cases. In situations where slug flow is identified by the flow model, hydrodynamic slugs are accounted for only in an average manner that does not give any information about slugs, their properties, or how they affect the flow. However, many flow parameters are highly dependent on the slug pattern, e.g., the pressure drop in a flow-path. Thus, it is necessary to be able to explicitly account for the occurrence of slugs. The slug tracking model is designed to initiate, maintain, and track physically sharp fronts such as those constituted by start-up slugs and hydrodynamic slugs. Among other things, the model gives information about position, velocity, length, and other characteristic quantities of each individual slug. In turn, this information is used to give better estimates of the actual properties of the overall flow. See also: When to use Methods and assumptions Limitations How to use

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When to use The slug tracking model have two different options initiating slugs (keyword SLUGTRACKING). These options are: 1. Level slug initiation, which initiate slugs when changes in liquid hold-up are detected from one section to another. The change in hold-up might be caused by a start-up situation, liquid sources, or boundary conditions changing with time just as well as geometry effects. This option is activated through the LEVEL key and is mainly to be used for well-defined start-up slugs. 2. Hydrodynamic slug initiation, which is the recommended slug initiation method for hydrodynamic and terrain slugging. Hydrodynamic slugs can be initiated when OLGA predicts transitions from either stratified or annular flow to slug flow. This option is activated by the key HYDRODYNAMIC. In addition to these two options, there is manual hydrodynamic slug initiation. This option is activated through the HYDRODYNAMIC key and requires that all slugs initiated are given as user input. Thus, in order to use this option, detailed knowledge about the slugging is required since the user has to specify the number of slugs to set up, at which positions to set them up, and at which times.

License requirements Slug tracking is part of the Slugtracking Module that requires a separate license.

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Methods and assumptions Initiation of level slugs

Figure A Schematic visualization of a pipeline shut-in situation where liquid has been accumulated at low points. The pipeline consists of a well, a transport line, and a riser. Level slug initiation may be carried out at any time in the user specified time interval given by STARTTIME and ENDTIME. The detection of level slugs is based on differences in the gas fraction. SLUGVOID is used to specify the maximum void allowed in a slug whereas BUBBLEVOID determines the minimum void in a bubble. When a section is found with void less than SLUGVOID, a level slug might be initiated, all depending on the void in the neighboring sections. If the void increases and exceeds BUBBLEVOID within two upstream sections, a tail is initiated. If, on the other hand, the void increases and exceeds BUBBLEVOID within two downstream sections, a front is initiated.

Initiation of hydrodynamic slugs

Figure B Schematic visualization of the initiation of a hydrodynamic slug. If OLGA predicts slug flow (ID=3) at boundary J, a hydrodynamic slug may be initiated in section J, J-1, or over both sections, see Figure B. Initiating a new slug implies redistribution of masses which might lead to discontinuities in pressure in inclined or vertical pipes. To avoid such discontinuities, the new slug is set up with an as short slug length as possible. These short hydrodynamic slugs will then grow into larger slugs as they propagate through the pipe if the conditions are favorable. When OLGA predicts slug flow, two criteria must be met before a hydrodynamic slug is initiated in a section: The distance to the closest slug must exceed a minimum distance. The time elapsed since a slug was either generated in or passed through the section must be larger than a specified minimum time. The minimum distance between slugs is specified through the INITFREQUENCY key (slug initiation frequency, Fi). Using the slug initiation frequency, the minimum distance is calculated as UB/Fi, where 332 / 769

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frequency, Fi). Using the slug initiation frequency, the minimum distance is calculated as UB/Fi, where UB is the bubble nose velocity of the new slug. Per default, the minimum distance is 10 pipe diameters. The idle time required before generating a new slug at any section boundary is specified through the DELAYCONSTANT key. The delay constant,DC, is given as the minimum number of pipe diameters between the new slug and the slug that last occupied the same section. The idle time is calculated according to (a) where D = pipe diameter [m] Ul = average liquid velocity [m/s] The default value for the delay constant is 150.

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Limitations Model limitations The model currently used for hydrodynamic slug initiation uses a slug frequency and a delay constant to determine when to set up new slugs. The slug frequency determines how close to an existing slug a new slug can be initiated whereas the delay constant determines the shortest time allowed between setting up two consecutive slugs at the same boundary or setting up a new slug after a slug has passed.

Compatibility limitations At present, it is not possible to run slug tracking in combination with Pig. The combination is not allowed. Complex fluid. The simulation will run, but as far as slugging goes, the results will be the same as if complex fluid had not been used.

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How to use General 1. Add the SLUGTRACKING keyword and choose a slug initiation method. 2. Add trend and profile plot variables to see differences between running the simulation with and without slug-tracking, e.g., PROFILEDATA VARIABLE=(PT, TM, ID, HOL, HOLHL, HOLWT, UL, UG) TRENDDATA PIPE=PIPE5, SECTION=3, VARIABLE=(QLT, QLTHL, QLTWT, ACCLIQ, ACCOIQ, ACCWAQ) The accumulated flow rates (ACCLIQ) can be used to estimate slug sizes. 3. Add global trend to get overview of the simulation. TRENDDATA VARIABLE=(LIQC, OILC, WATC) TRENDDATA VARIABLE=(RMERR, VOLGBL, HT, NSLUG)

Slug identification number When initiated, each slug is assigned a unique identification number. The first slug initiated gets identification number, and then 1 is added for each new slug initiated. This unique number enables the possibility to follow the development of individual slugs as they move through the pipeline. It is possible to plot, e.g., slug length, front and tail velocities, etc. Plotting individual slug data is useful mainly when there are few slugs is the system. When hydrodynamic slugging generates lots of slugs, it is difficult to identify which slug to consider.

Illegal slug section An illegal section is a section where no slugs are initialized and through which no slugs are allowed to pass (keyword SLUGILLEGAL). A slug front may enter into the illegal section, but it will be trapped inside it until the slug tail reaches the section and the slug is removed. The first section in a flow-path is by default an illegal section and so is the last one. This implies that slugs cannot propagate through networks. If stability problems are encountered when using in-line process equipment together with slug-tracking, it is recommended that illegal sections are introduced around the process equipment. Furthermore, if there are large changes in pipe diameter, e.g., when modeling a separator at the end of a pipeline as a pipe with big diameter, instabilities can be avoided by setting illegal sections on each side of such boundaries. With long pipelines mainly operating in the slug flow regime, the number of slugs can become very large which in turn results in long simulation times. In such situations, it is recommended to only allow for slugs close to the pipeline outlet, say the last 5-10 km. Yet again, this can be accomplished by using the keyword SLUGILLEGAL. In cases where terrain effects are predominant and large slugs develop far away from the outlet, illegal sections should not be used to prevent such slugs from developing.

Flow regime When slug tracking is activated, the flow regime indicator (ID) should be used with caution since the flow regime is forced to bubbly inside liquid slugs whereas it is forced to stratified in slug bubbles. Thus, the flow regime indicator will never indicate slug flow when slug tracking is activated.

Vertical riser at the end of a pipeline Problems might be encountered when slug tracking is activated and the pipeline has a vertical riser at the end. The problems are usually caused by back-flow in the riser. If such problems are encountered, the following actions might reduce them: Set the gas fraction on the outlet node equal to one. Now, if back-flow occurs at the outlet, only gas will enter the pipeline. Unless the flow in the riser is expected to influence slug patterns significantly, set the riser pipeline sections to illegal (SLUGILLEGAL). 335 / 769

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If possible, add a couple of horizontal sections at the top of the riser.

Startup slugs not detected If all start-up slugs are not detected, it is possible to specify the void limits used for initializing start-up slugs. This is done by modifying the void limits given by the keys BUBBLEVOID and SLUGVOID.

Hydrodynamic slug initiation The slug model might initiate slugs too often or too seldom as compared to the expected slug pattern. In order to tune the model to mimic the expected pattern, it is recommended that only the DELAYCONSTANT key is varied first. If it is not possible to achieve the slug pattern sought by varying DELAYCONSTANT alone, INITFREQUENCY can be modified as well. Hydrodynamic slug initiation: the delay constant The delay constant, DC, is the number of pipe diameters a slug must travel before the slug model tries to initiate a new slug at the same boundary. Thus, the time between two consecutive slug initiations on any given boundary or the time between a slug passes a boundary and a new slug can be set up is given by (a) where D = pipe diameter [m] Ul = average liquid velocity [m/s] Using the Shea correlation for the slug frequency (b) where D = pipe diameter [m] L = pipeline length [m] Usl = superficial liquid velocity [m/s] it is possible to get an estimate of the delay constant. Tuning on the delay constant should be performed such that the resulting slug frequency is in the same order of magnitude as Fsl. It should be noted that this correlation is based on experimental data and field data for systems dominated by hydrodynamic slugging. Thus, if terrain effects are predominant, one should not use the Shea correlation. The default value of 150 has been found to yield good results for a number of cases.

Profile plots, trend plots, and slug statistics When specifying, e.g., the hold-up (HOL) in TRENDDATA or PROFILEDATA, it is important to note that the hold-up plotted is the section average. It is not possible to resolve the hold-up of individual slug and bubble regions inside sections, but these are used to calculate the section average. In order to visualize the hold-up of individual slugs/bubbles, specify HOLEXP under TRENDDATA. This will show the instantaneous hold-up at the boundary specified. It is possible to plot properties of individual slugs using their identification number. This feature is mainly of use when there are few slugs in the system and the slugs of interest are easily identified. In cases with severe slugging, the large number of slugs will make it virtually impossible to single out a particular slug. However, it might be of interest to look at a statistical sample of slugs in order to get an idea of the general slug properties. The syntax for addressing individual slugs is TRENDDATA SLUGID=1, VARIABLE=(LSL, LSB, JSLT, JSLF, USF, UST, ZFSL, ZTSL, PTJF, PTJT) 336 / 769

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Slug statistics The trend plot variables LSLEXP and LSBEXP show the length of a liquid slug or slug bubble currently residing at a given section boundary. TRENDDATA PIPE=PIPE-1, SECTION=10, VARIABLE=LSLEXP Using the OLGA GUI, these variables can be used to plot slug statistics. The slug statistics is generated by post-processing of the .tpl-file and is accessed by selecting the variables LSLEXP_STAT and LSBEXP_STAT in the trend plot dialog. These two plot variables represent the statistical distribution of slug and slug bubble lengths at the boundary considered. The properties of these plots can be set through 'Slug Statistics...' under the Edit menu.

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Slug tuning The SLUGTUNING keyword makes it possible to tune parameters in the slug model. See also: When to use Methods and assumptions Limitations How to use

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When to use The SLUGTUNING keyword is used for tuning the OLGA slug tracking model to specific sets of measurement data or sensitivity studies. SLUGTUNING should be applied with great care, as it might cause the validation and verification of the OLGA model to no longer be valid.

License requirements Slug tuning is part of the Tuning Module that requires a separate license.

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Methods and assumptions The slug tuning coefficients are multiplied by the related values calculated by OLGA. The exception is slug length which is interpreted directly as slug length in number of diameters. The Taylor bubble velocity is calculated as (a) where CUB1 = CUB2 = C0 = Umix = U0 =

tuning coefficient 1 given by the key UBCOEFF1 tuning coefficient 2 given by the key UBCOEFF2 distribution coefficient mixture velocity, i.e., sum of the superficial velocities drift velocity

The slug front pressure drop is given by

(b) where CDP = CDP0 = Lslug = f(α,ρl) = Ucrit =

tuning coefficient for slug front pressure drop given by key DPFACT tuning coefficient for onset of slug front pressure drop given by key DPONSET slug length additional pressure drop cutoff velocity at which the slug front pressure drop is switched on

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Limitations The slug tuning coefficients are given globally, i.e., it is not possible to specify different sets of tuning parameters for different flow-paths.

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How to use Specify the desired slug tuning coefficients and where they should be applied. N.B., the slug tuning coefficients are global.

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Source A source can be used to model pipeline inflow and outflow of gas and liquid. OLGA use mass flow rate for internal calculations, but input flow rate may also be given as volumetric flow at standard conditions. Wells and nearwells are more specialized types of modelling pipeline inflow and outflow. See also: When to use Methods and assumptions How to use

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When to use The SOURCE key can be used when a flow needs to be inserted into the pipeline. For more advanced flow simulations the WELL or NEARWELL keys can be used.

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Methods and assumptions Two types of sources can be specified; the mass source and the pressure driven source, which is also known as a controlled mass source or source controlled by valve (SOVA). Each type of source can be either positive (flow into the pipeline) or negative (flow out of the pipeline). The upstream (for positive source) or downstream (for negative source) pressure and temperature can be specified. When the upstream/downstream pressure is given, the expansion from the given pressure to the pressure inside the pipe section will be taken into account for the temperature calculations. A mass source need not specify the upstream/downstream pressure, and this will then be set to the pressure inside the pipe section where the source is introduced. A SOVA must always specify the upstream/downstream pressure. The external pressure and temperature can be constant or given as a time series. Phase fractions can be specified in the input for a positive source. For a negative source, the phase fractions in the connected section will be used.

Mass source The mass source is the simplest model and has a given mass flow rate specified by the user. Phase fractions for gas and water can be specified, from which the oil phase fraction will be calculated. The default value for gas is -1, which means it will be read from the PVT file. The default value for water is 0. If a controller is used, the actual mass flow rate into the section (positive source) or out of the section (negative source) is a fraction of the mass flow rate given as input, with the fraction regulated by the controller. Note that the mass flow node covers the functionality of a mass source in the first section after a closed node.

Pressure driven source (SOVA) The flow for a SOVA will be calculated from a flow equation for mass flow through an orifice, where the orifice area can be governed by a controller. The figure below illustrates this.

Figure A. Illustration of a pressure driven source

Controlling the flow The flow area of the SOVA is governed by the control system, where the valve has finite opening and closing time (stroke time) specified by the user. Both sub-critical and critical flow is described. For sub-critical flow the flow rate is governed by the 345 / 769

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Both sub-critical and critical flow is described. For sub-critical flow the flow rate is governed by the difference between the internal and external pressures, the upstream conditions and the flow area. For critical flow the flow rate is governed by the upstream conditions and the flow area only. The pressure difference determines the direction of flow in or out of the pipe. The orifice area is calculated from: (a) where us = controller signal

Valve functionality The valve-specific functionality is further described in the Valve section.

Calculating mass flow at standard conditions The following equations show how the total mass flow is calculated from volumetric flow given at standard conditions. Symbols used in the equations are given in the list below:

wc

r

Water cut, volume of water divided by volume of liquid at standard condition Gas oil ratio, volume of gas divided by volume of oil at standard condition Gas liquid ratio, volume of gas divided by volume of liquid at standard condition Volume flow Mass flow Density

Indexes: tot ST g o liq w *

Total At standard condition Gas phase Oil phase Liquid phase (water + oil) Water phase Equivalent phase

GOR GLR Q

The density in the equations below is taken from the PVT table. It is necessary that the properties at standard condition are included in the PVT table. If WATERCUT, GOR and volume flow of gas at standard condition ( PHASE = GAS and STDFLOWRATE =

) are known, use:

(b)

If WATERCUT, GOR and volume flow of liquid at standard condition ( PHASE = LIQUID and STDFLOWRATE =

) are known, use:

(c)

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If WATERCUT, GOR and volume flow of oil at standard condition ( PHASE = OIL and STDFLOWRATE =

) are known, use:

(d) If WATERCUT, GOR and volume flow of water at standard condition ( PHASE = WATER and STDFLOWRATE =

) are known, use:

(e) If WATERCUT, GLR and volume flow of gas at standard condition ( PHASE = GAS and STDFLOWRATE =

) are known, use:

(f) If WATERCUT, GLR and volume flow of liquid at standard condition ( PHASE = LIQUID and STDFLOWRATE =

) are known, use:

(g)

If WATERCUT, GLR and volume flow of oil at standard condition ( PHASE = OIL and STDFLOWRATE =

) are known, use:

(h)

If WATERCUT, GLR and volume flow of water at standard condition ( PHASE = WATER and STDFLOWRATE =

) are known, use:

(i) Specified GOR or GLR will shift the values of gas mass fraction in the PVT table with use of the following equation (2 phase) (j) where Gas mass flow at given pressure and temperature Gas mass flow at standard condition - calculated from given GOR or GLR Oil mass flow at standard condition - calculated from given GOR or GLR Gas mass fraction at given pressure and temperature - value from the PVT table Gas mass fraction at standard condition - value from the PVT table 347 / 769

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(k) If the equivalent gas volumetric flow rate at standard condition ( ) and the mol weight of the total flow, , are known, use: PHASE = GAS, STDFLOWRATE = and MOLWEIGHT = The density of the equivalent gas at standard conditions will then be calculated from ideal gas law, and the total mass flow will be given from the following equation on condition that GOR or GLR is greater then 1010 (infinitely in OLGA) (l) If GOR or GLR is less than 1010 the total mass flow will be calculated from the equations described earlier for PHASE = GAS with = and = . Note: There are limitations on how much the value of GOR/GLR can be changed when using a PVT table. One can check the source input by plotting the volume flow rates through the source at standard conditions (e.g. QGSTSOUR). E.g. if a source using default GOR/GLR has no gas at the in-situ conditions, one cannot give a lower GOR/GLR for this source. Removal of gas that is not present is impossible.

Steady state pre-processor Both source types can be used with the steady state pre-processor. However, there are certain limitations: With a closed node, the sum of all flows into the adjacent section (including contributions from all sources, wells, and nearwells) can not be 0

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How to use To define a SOURCE, follow the steps described below. Each SOURCE must have a unique LABEL. The position along the branch must be given; either by use of the POSITION key, ABSPOSITION key, or a combination of the PIPE and SECTION keys. Phase fractions can be given either directly with the GASFRACTION and WATERFRACTION/TOTALWATERFRACTION keys or at standard conditions with the GLR/GOR/WATERCUT keys. The upstream/downstream PRESSURE and TEMPERATURE can be specified. See Capabilities for further description. Each source type is also available for use with the compositional models (i.e. Compositional Tracking, Blackoil, MEG, Wax). All input variables can be defined as time series with the TIME key. See keyword SOURCE for more details.

Mass source There are several keys available to define the mass source. When the mass flow rate is to be specified at the source temperature and pressure without compositional tracking use the key MASSFLOW. With compositional models the keys FEEDMASSFLOW, FEEDMOLEFLOW or FEEDSTDFLOW may be used. When the volumetric flow rate at the standard conditions is given, the key STDFLOWRATE should be used. See keyword SOURCE for more details.

Pressure driven source (SOVA) The SOVA massflow is defined by the valve specific input data. For further descriptions, see the Valve section. See keyword SOURCE for more details.

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Steady State Processor The steady state pre-processor in OLGA computes a steady state solution for a pipeline or an entire flow network. Steady state pressures, temperatures, mass flows, liquid hold-ups and flow regimes are calculated along the pipelines. The steady state pre-processor is primarily intended for generation of initial values for dynamic computations, but may also be used as a standalone steady state tool. See also: When to use Methods and assumptions Limitations How to use

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When to use The steady state pre-processor may be used in order to 1. eliminate the need for user given initial conditions 2. get a consistent initial state as a basis for dynamic simulations 3. perform screening studies The steady state pre-processor can be used for flow networks with any combination of boundary conditions at inlets and outlets. Both merging and diverging networks can be calculated. Except for displacement pumps and pump battery, the steady state pre-processor incorporates the effect of process equipment. For PID controllers the bias settings are used as the controller outputs.

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Methods and assumptions The steady state pre-processor finds a consistent solution for flow networks by iteration. Networks where all inlet flows and outlet pressures are known are solved by the following sequence of computations: 1. Phase transitions are computed using old values of pressures and temperatures. The combination of phase transition and inlet flows gives consistent flow rates along all the pipelines in the entire network. 2. Using the newly computed flows, old temperatures, and the pressure boundary conditions at the outlet, new pressures are computed along all the pipelines in the network. The point model OLGAS THREE-PHASE is used in this step. 3. The temperatures along all the network components are computed. Iteration on the sequence 1) to 3) is performed until the change between two iterates is smaller than a tolerance. If the inlet flows and/or outlet pressures are not known, an outer iteration is needed in addition to the one shown above. In this iteration the initial guesses for inlet flows/outlet pressures are refined until the residuals are smaller than a given tolerance.

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Limitations The solution computed by the steady state pre-processor and the solution obtained when simulation with the dynamic solver until a steady state is achieved may not be equal. This is mainly due to the two following reasons: 1. For unstable systems (for instance slugging cases) the steady state pre-processor may find a solution that differs from the average value in the transient solution as there is no truly steady-state condition. 2. The steady state pre-processor has some small residual errors that are removed by the transient simulation. In some sensitive cases this can cause a difference in pressure, temperature and holdup profiles. Therefore, if the slug flow regime is detected in the simulation, it is recommended to perform a dynamic simulation with the slug tracking model (not available in OLGA 6.1). The steady state pre-processor is not as robust as the dynamic OLGA. This is particularly the case for simulations with pressure or well (productivity index) as inlet boundary conditions, or negative sources. In such cases, if the pre-processor does not converge to a reliable solution, the pre-processor must be turned OFF (STEADYSTATE=OFF under OPTIONS), and INITIALCONDITIONS must be applied to all the FLOWPATHS instead. The steady state pre-processor cannot handle counter-current flow (such as for instance positive gas flow and negative liquid flow). The steady state pre-processor cannot handle zero flow in the pipeline, therefore it should not be used with closed valves in the flow path or with mass sources that sum up to zero flow rate at start time. For flow networks with one or more separators the steady state pre-processor uses a simplified approach. The separator is treated as a simple node with mixture properties and the phase flow fractions of any phase are assumed to be equal for any of the outlets of a separator. This approach may lead to discontinuities between the steady state and dynamic solution. The steady state pre-processor may be run with wax deposition or hydrate kinetics activated, but the pre-processor does not consider the wax phase or hydrate formation.

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How to use To activate the steady state pre-processor from the OLGA GUI do the following: In the property window for OPTIONS. Choose STEADYSTATE=ON to get a full steady state computation including calculations of temperatures. Choose STEADYSTATE=NOTEMP to avoid the temperature calculation. In this case initial temperature profiles must be given for all the flow components in the network. The latter option can be useful if the pre-processor has problems finding a solution. This implies that the simulation must be run dynamically for some time in order to achieve a true thermal steady state solution. The steady state pre-processor can sometimes fail to find a solution if flows are negative, i.e. if the flow goes from the outlet to the inlet of a pipeline. For such pipelines it is therefore recommended to set INIFLOWDIR=NEGATIVE in the BRANCH input group. In order to do some fast studies (screening studies), one can use the steady state pre-processor results. In this case use STEADYSTATE = ON under OPTIONS and STARTTIME equal ENDTIME under INTEGRATION. If input parameters (boundary conditions, valve openings, etc.) are given as time series, the steady state pre-processor uses the values at the start time.

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SteamWater-HC The availability of the steam module depends on the User's licensing agreement with SPT Group. The SteamWater-HC module is an improved way of tracking when there is a considerable amount of H2O in the fluid. There are some basic limitations when not using this module: 1. The standard table based version of the code assumes that the gas phase is always saturated with

steam (no mass balance for steam). Does not apply for MEG/MeOH/EtOH Tracking and Compositional Tracking as they have a steam mass balance. 2. There must be a gas phase otherwise water can not be evaporated. 3. OLGA can not deal with a single component system if the saturation line is crossed. This is due to the explicit coupling of volume balance and energy balance equations and the lack of a two phase region (two phase envelope) for a single component system. The second limitation is not a real limitation as there will usually be some HC gas in situations where water is evaporating. The only situation where this limitation is real is if only water is present in the fluid and temperature and pressure conditions are such that the saturation line is crossed. The third limitation is related to the way the conservation equations are solved with an explicit coupling between volume (pressure) balance and energy (temperature) balance. This is solved by introducing time constants or delays in the evaporation/condensation process. The difference between the saturation temperature and the fluid temperature serves as a potential for phase mass transfer. Multiplying this temperature difference with a certain heat or energy transfer coefficient gives a certain energy transfer rate that can be used to estimate the mass transfer rate. In that case an asymptotic approach to equilibrium occurs. How fast this approach is depends on the size of the energy transfer coefficient. Also, this module gives more correct water/steam properties around the critical point and also in the supercritical region. See also: When to use Methods and assumptions How to use

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When to use The SteamWater–HC module should be used when there is a considerable amount of water in the fluid, or when it is important to limit the rate of boiling/evaporation/condensation, e.g., when simulating drying of a pipeline with hot gas.

License requirements SteamWater–HC is part of the Single Component Module that requires a separate license.

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Methods and assumptions The following assumptions are mode in the model: Oil, gas, water and vapor (steam) will all have the same temperature, TM. The pressure of the water phase will be equal to the total pressure. The pressure of vapor will be equal to the partial pressure of vapor in the gas phase and will be calculated assuming an ideal mix of vapor and hydrocarbon gas. Water saturation temperature, TSATW, will be calculated from the total pressure. Vapor saturation temperature, TSATV, will be calculated from the partial pressure of vapor. If the fluid temperature, TM, is higher than TSATW, flashing or boiling of water will take place. If TM is higher than TSATV but lower than TSATW, evaporation of water will take place. If TM is lower than TSATV, condensation of vapor will take place. Note that TSATV will always be less or equal to TSATW. The inner pipe wall surface may be superheated or subcooled compared to TSATW or TSATV. Such a situation may lead to surface boiling or surface condensation in cases where water or vapor is in direct contact with the pipe wall. This additional mass transfer term will not be directly included but can be accounted for by an enhanced heat transfer due to surface boiling/condensation.

Generation of steam and water properties. The equations used to calculate the steam and water properties are taken from ref. 1. These equations are time consuming to solve and will therefore be used only at the start of a simulation. The properties will be calculated at pressure/temperature values corresponding to the pressure/temperature grid points specified in the PVT table prepared for the simulation. After the saturation points and the physical properties are calculated for all the P/T grid points that correspond to the PVT table for the HC mixture, linear interpolation between the grid points is applied during the simulations. For simulation cases where the pressure may cross the critical pressure, it is important that the HC PVT table contains a grid point that is close to the critical point in order to obtain accurate crossing of the saturation line. For all the cases, a pressure interval less than10 bar and a temperature interval less than 10 K are recommended in order to maintain acceptable accuracy of the linear interpolation.

Saturation line Below the critical point, PC and TC, (pressure and temperature), the saturation pressure, Psat (T), and saturation temperature, Tsat (P), at a given grid point, P,T, is determined from the saturation line. Above the critical point, PC = 221.2 bar and TC = 647.3 K, and to 676 K and 250 bar, a straight line is used to divide the single-phase or dense-phase region into vapor and liquid. Above 676 K and 250 bar, the boundary line between region 2 and region 3 is used as the division between vapor and liquid. The definition of the regions is described in ref. 1.

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Physical properties. Water properties: For pressures below 225 bar, water property equations for region 1 (see ref. 1) are used for water in the water region. In the vapor region, the properties for water are extrapolated from the saturation point: Enthalpy is based on thermal capacity at saturation temperature corresponding to a given pressure and the density according to the density derivative to pressure at the saturation pressure corresponding to a given temperature. All the other properties are from the saturation temperature. For pressures above 225 bar, water properties are calculated based on equations for the different regions specified in ref. 1. Thermal capacity and enthalpy for water is singular near the critical point. To avoid numerical problems in region 3 the water properties from region 1 instead of those for region 3 when the pressure is below 225 bar (the equations are very similar except when you are closer than <1C and 0.1 bar). The same is done for steam. Vapor properties: For pressures below 225 bar, vapor property equations for region 2 are used for vapor in the vapor region. In the water region, the vapor properties are extrapolated from the saturation point. Enthalpy is based on thermal capacity at saturation temperature corresponding to the given vapor pressure and the density according to the density derivative to pressure at the saturation pressure corresponding to the given temperature. All the other properties are from the saturation temperature corresponding to the vapor pressure. For pressures above 225 bar, vapor properties are calculated based on equations for the different regions. With this procedure, the vapor and water properties are continuous across the vapor-liquid (V-L) division line when pressure is above 225 bar. Vapor pressure: 358 / 769

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PVAP = P*Mvap/(Mvap + Mhc) where Mvap = MGVAP/MWH2O, kmoles of vapor/unit volume(m3) Mhc = MGHC/MWhc, kmoles of HC gas/unit volume(m3) MGVAP = Mass of vapor/unit volume MGHC = Mass of HCgas/unit volume MWH2O = Molweight of vapor = 18 kg/kmol MWhc = Molweight of HC gas

Flashing/Condensation The driving force for flashing of water or condensation of vapor will be the difference between the saturation temperatures and the fluid temperature. The vapor saturation temperature will be directly related to the partial pressure of vapor assuming an ideal mixing of HC-gas and vapor. With the presence of HC-gas in the fluid, a gradual transfer of mass of H2O will take place as the partial pressure of vapor changes. With no HC-gas in the fluid the partial pressure of vapor will be equal to the total pressure and no bulk mass transfer takes place until either sub-cooled water reaches saturation temperature or superheated steam cools down below saturation temperature. The effect of local boiling on a hot wall surface or condensation on a cold wall surface will not be included directly in the mass balance of water and vapor but can be accounted for through an enhanced heat transfer at the pipe wall. The total energy available for generating vapor or condensing vapor to obtain saturated conditions is HTOTV. HTOTV = (mghc*cpgh + mlhc*cplh +mlwt*cpwt + mgv*cpv) *(TM-TSATV) where mghc mlhc mlwt mgv cpgh cplh cpwt cpv

= specific mass of HC-gas (kg/m3) = specific mass of HC-liq (kg/m3) = specific mass of water (kg/m3) = specific mass of vapor (kg/m3) = specific heat of HC-gas (KJ/kgC) = specific heat of HC-liq (KJ/kgC) = specific heat of water (KJ/kgC) = specific heat of vapor (KJ/kgC)

The total mass transfer to obtain saturated conditions is: PSIVTOT = HTOTV / ( HSATV - HSATW ) In order to reduce numerical problems it will be assumed that this mass transfer will take a certain time TPSI. The mass transfer rate will then be: PSIV = PSIVTOT / TPSI ( kg/ m3sec ) The mass transfer per time step must not be larger than the available mass of the diminishing phase component.

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References 1. Revised Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, The International Association for the Properties of Water and Steam, Lucerne, Switzerland, August 2007

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How to use In order to activate the SteamWater-HC model, the input key COMPOSITIONAL under keyword OPTIONS must be set to STEAMWATER-HC. TCONDENSATION, TVAPORIZATION and TBOILING in keyword COMPOPTIONS can be used to specify the time constants for condensation, evaporation and boiling, respectively. They are available as time series if desired by using the subkey TIME (but not for Compositional Tracking). Large values will slow down the mass transfer leading to fairly large non-equilibrium. Small values will speed up the mass transfer thereby reducing the thermal non-equilibrium. Too small values may however cause instabilities and probably nonphysical results. For initialconditions, boundaries, sources and wells, the specified water fraction will be either steam or liquid depending on the specified temperature compared to the water saturation temperature at the specified pressure when STEAMFRACTION is set to -1 (default). For sources without any pressure given, the pressure of the source receiving position will be used. STEAMFRACTION can be set between 0 and 1 to give both water and steam. New output variables for presenting vapor data have been implemented: TSAT, TSV, PSAT, PVAP (see output variables description). Other data for vapor can be obtained by specifying compositional variables. After the saturation points and the physical properties are calculated for all the P/T grid points that correspond to the PVT table for the HC mixture, linear interpolation between the grid points is applied during the simulations. For simulation cases where the pressure may cross the critical pressure, it is important that the HC PVT table contains a grid point that is close to the critical point in order to obtain accurate crossing of the saturation line. In OPTIONS the subkey WRITEPVTFILES=[NO]/YES controls if the program will write to file the water/steam properties that are being used. For YES, tab files (fixed format) will be written for each HC mixture PVT table, using the same P/T grid. The name of the file(s) will be _pvt_.tab. Also, the saturation line will be written to a file with the name _pvt.env. Both can be viewed in the GUI. For all the cases, a pressure interval less than 10 bar and a temperature interval less than 10 K are recommended in order to maintain acceptable accuracy of the linear interpolation.

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Thermal Components The basic functionality in OLGA computes an axial temperature distribution in pipelines taking into account radial heat transfer through pipe walls. In addition to this functionality, OLGA has three types of thermal components that also take crosssectional heat transfer between different pipelines into account. This is useful for, e.g., pipeline bundles, buried pipelines and drilling configurations. The Bundle model should be used for pipeline bundles when the effect of heat transfer between different pipelines is important. The Annulus model is similar to the Bundle model, but it is specially designed for well and drilling configurations. The FEMTherm model should be used when pipeline configurations are surrounded by a solid medium. It computes a three-dimensional temperature distribution by combining computation of radial and angular heat storage and heat transfer in the medium surrounding the pipelines, with the onedimensional axial computation for the pipeline fluid.

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Annulus In well- and drilling-configurations such as the one illustrated in Figure 1 below, there will be cross sectional heat transfer between the different pipelines. If the temperature distribution in one pipeline changes, it will affect the temperatures in all the other pipelines. The annulus model treat such heat couplings in a more explicit and dynamic manner than the basic OLGA model.

Figure 1 Example of an annulus configuration. See also: When to use Methods and assumptions Limitations How to use

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When to use The annulus model should be used for pipeline configurations like the one shown in Figure 1 below in order to account for cross sectional heat transfer between the different pipelines. The annulus model is very similar to the bundle model, but it is specially designed for well- and drilling-applications. In the annulus model diameters are allowed to vary in the axial direction.

Figure 1 Example of an annulus configuration. The annulus model may be used to model gas-lifted wells where gas is injected into the annulus between the casing and tubing and recovered in the tubing together with the production fluid. The annulus model has no purpose if all U-values (overall heat transfer coefficients) and temperatures are known.

License requirements Annulus is part of the Wells Module that requires a separate license.

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Methods and assumptions The annulus model computes temperatures in annular pipeline configurations by coupling the basic temperature computation in the axial direction to a temperature computation in the cross sectional direction. This is achieved by the following two-step procedure: 1. In each cross section of the annulus, the fluid temperature and wall layer temperatures of all the enclosed pipelines are solved simultaneously. 2. A regular one-dimensional temperature calculation is performed for each pipeline, in which the fluid temperatures and wall layer temperatures in the whole pipeline are solved simultaneously. The combination of 1-dimensional fluid and wall layer temperature calculations in the axial direction and the 2-dimensional calculation in each bundle cross section results in a 3-dimensional temperature field. The annulus model is based on the following assumptions: The heat transfer from an outer wall surface of one pipeline to the surrounding fluid in a carrier line is based on free/forced convection unless a user given heat transfer coefficient is given. No additional girding is used in the annulus model as compared to solving each pipeline thermally decoupled from each other.

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Limitations All pipelines that are contained within the same annulus must have the same section lengths and elevations. The annulus model requires the WALL or FASTWALL temperature calculation option to be used. The annulus must cover entire pipes.

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How to use To use the Annulus model, in the OLGA GUI do the following: From the Case level, right click and choose: Add→ThermalComponent→ANNULUS In the OLGA GUI, an annulus consists of a carrier line enclosing one or several flow-paths. The carrier line itself is a regular flow-path. To populate the annulus, the following has to be repeated for each participating component: From the newly created annulus, right click and choose: Add→AnnulusComponents→COMPONENT In the property window for the newly created component, fill out the required fields. In particular, the FLOWPATH identifier have to be specified. N.B., no flow-path is created by this procedure, and, thus, the flow-path specified have to either exist beforehand or be added to the case later. The properties FROM and TO define the part of the flow path that is enclosed in the annulus (axial direction). They refer to position labels which must be defined under Piping for the FLOWPATH. The properties XOFFSET and YOFFSET are X- and Y-direction offsets for the FLOWPATH center from an arbitrary reference point. All flow-paths contained in the same annulus must have the same reference point. The property OUTERHVALUE may be used if the heat transfer coefficient from the outer wall surface to the carrier line is known, otherwise forced/free convection will be applied. Flow-paths that are contained within the same annulus have to have the same section lengths and elevations. Pipe diameters may vary in the axial direction. The WALL or FASTWALL temperature calculation option must be specified when an annulus is present in a case.

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FEMTherm FEMTherm may be used to calculate the thermal performance of the following systems: Bundled pipelines Buried pipelines Complex risers

Figure A A hot water insulated and buried bundle FEMTherm covers the functionality of the Soil module implemented in earlier versions of OLGA, with several differences: Easier input: Discretization: just one value is required (MESHFINENESS) Predefined shapes (circle, ellipse, rectangle) in addition to a user-defined polygon Better visualization of cross section, grid and results (FEMTherm Viewer) More accurate discretization around the circular pipe wall (unstructured triangular mesh) Radiation is included See also: When to use Methods and assumptions Limitations How to use

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When to use The FEMTherm model is designed to simulate the thermal interactions between parallel pipelines enclosed in a solid medium. In situations with buried pipelines, the model is capable of predicting the transient thermal behavior of the surrounding soil. Therefore, the model is very useful when the immediate surroundings of a pipe cannot be treated as a constant thermal reservoir. The model is also very flexible with respect to geometry definitions and is well suited for analyzing complex risers with temperature variations that are not axi-symmetric. However, the FEMTherm calculations can be timeconsuming, and, thus, this model is not recommended for systems where the ambient heat transfer boundary conditions can be defined sufficiently well using the concentric wall layer model.

License requirements The FEMTherm model is part of the FEMTherm Module that requires a separate license.

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Methods and assumptions FEMTherm consists of a grid generator and a Finite Element Method (FEM) equation solver. The grid generator makes a 2D finite element mesh in accordance with the Delaunay criterion. The finite element equation solver determines the transient 2D temperature distribution of any user defined cross section, which can have several shapes, i.e. CIRCLES, ELLIPSES, RECTANGLES and POLYGONS. Figure A illustrates the grid system used for solving the 2-dimensional heat transfer equation in a rectangular cross section with two interior pipelines. The simulation model consists of stacks of such cross sections along the pipeline.

Figure A: Cross section grid In a FemTherm calculation, OLGA solves the following equations in two steps: 1. Energy equation for the fluid in the pipe and the heat transfer equation for the layers of the pipe WALL. These equations are solved for each of the pipe sections along the pipelines, giving the profiles of the fluid temperature along the pipeline and in the pipe WALL. 2. FEMTherm establishes the thermal coupling of the pipelines and solves the 2-dimensional heat transfer equation in the solid medium surrounding the pipe WALL, giving the temperature distribution over the cross sections as well as the interaction between fluid temperatures in embedded pipes. The combination of 1-dimensional fluid and WALL temperature equations along the pipelines and the 2dimensional heat transfer equations for the media in each of the cross sections along the pipeline results in a 3-dimensional temperature field. Consider the pipe cross section in Figure B.

Figure B: Cross section grid and concentric pipe with a single wall layer In the situation of an incompressible fluid in the pipe visualized above, the governing equations for this system are: 370 / 769

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(a) (b) (c) , In the more general case, equations (a) and (b) are solved for each component and for each wall layer. Equation (a) describes the energy conservation of the fluid, Equation (b) the energy conservation of the pipe WALL and Equation (c) the energy conservation with heat conduction in the interior of the solid medium. In addition to these, a set of boundary and initial conditions are required for the calculation. The temperature, = ( , , , ), is the central variable in FEMTherm and the parameters in the model are: Area of the pipe cross section Af Temperature of the fluid Tf Density of the fluid rf Heat capacity of the fluid

Tw rw

Temperature of the first wall layer Density of the first wall layer Heat capacity of the first wall layer

Aw

Cross sectional area of first wall layer Flow rate of fluid Heat transfer between fluid and first layer Heat transfer between first layer and FEM domain boundary Heat flux across FEM domain boundary Conductivity of the solid interior of the bundle Density of the solid interior of the bundle Heat capacity of bundle Heat flux at the FEM domain boundary

Unit outward normal at the FEM domain boundary The weak form of Equation (c) according to classical functional analysis is: (d) where is the interior of the FEM domain, is the boundary subject to non-essential boundary conditions and is the test function. The last term in this equation is used to impose the boundary condition for the Newton’s law of cooling of external boundaries: (e) where the heat transfer coefficient, , and the ambient temperature, , are user-defined constants. The finite element domain is discretized using linear triangular elements, while the evolution in time is modeled using a backward Euler scheme. By factoring out the ambient temperature, , and the temperature in the last wall layer, , the following system of discrete equations is obtained. (f) This can now be used to solve the vector of nodal temperatures, , as a function of the ambient temperature, the last wall layer temperatures of each component and the temperature at previous time step, . The wall layer temperatures are not yet known, and therefore the equation system (f) is coupled to and solved simultaneously with the equations for the fluid and wall temperatures for all embedded 371 / 769

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to and solved simultaneously with the equations for the fluid and wall temperatures for all embedded components. The linearization needed for this coupling is derived in the following manner: The ”ambient” temperature, , of the last wall layer of each component is obtained by taking the average temperature in the FEM domain along the boundary of thei’th component, . This average temperature of discrete nodal temperatures is defined by the function (g) where is the length of boundary i and the function is evaluated element by element along the boundary. By the linearity of the solution, using superposition this can be written as: (h) where is a vector of nodal temperatures resulting from the boundary condition at perimeterj, and is a scaling of the nodal temperatures at timen. Given that the temperature, ,within the FEM domain is a linear function of the nodal temperatures, the constantsaijcan easily be obtained from: , With the exception of the term, , these integrals are evaluated once. This is possible because FEMTherm operates with a fixed time step, decoupled from the temperature calculations in the pipes. The inertial term, however, must be evaluated for each section and each FEMTherm time step. Numerical considerations In OLGA the fluid temperature varies in the axial (z) direction only. Therefore the heat conduction in the first WALL layer is always in the radial (r) direction. In the cross section below, two OLGA pipes are placed within a circular cross section. The temperature of the fluid and the temperature of the pipe WALL are solved with the OLGA model (finite difference method) on the assumption that radial heat conduction is predominant. Thus the pipe WALL outer surface (see Figure C) serves as an external boundary to the finite element equation. The heat conduction in the rest of the cross section is in both spatial directions (x and y). It is possible to include more than one radial conduction WALL layer in the model.

Figure C: Two OLGA pipes in a cross section One needs to determine the number of nodes that is required to obtain a suitable grid and time step in order to obtain numerical solutions to the heat transfer Equation (c). The FEMTherm model should be used with optimized spatial and temporal discretizations which gives a step-size independent solution. In the figure below we see a close-up of the region between the two pipes in Figure C for three examples 372 / 769

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the figure below we see a close-up of the region between the two pipes in Figure C for three examples of the spatial discretization. The numerical accuracy is strongly dependent on the number of internal nodes (N) between external boundaries.

Figure D: Different discretizations for the area between two OLGA pipes Due to the linear interpolation functions in the finite element calculation, we recommend that N should be at least 4 to get a good approximation for the temperature field. In (a) N=0, in (b) N=3 and in (c) N=4. Thus the grid in (c) is the only acceptable grid for high precision calculations. The MESHFINENESS[*] key in the SOLIDBUNDLE keyword sets the spatial resolution of the grid by determining the number of nodes on the outermost shape. The number N can be checked after the simulation has been performed by looking at the grid in FEMTherm Viewer, or alternatively using FEMTherm Tool. Thermal calculations with the finite element method are computationally expensive and are not carried out for every single time step in OLGA. We recommend that the time step for thermal calculations The key DELTAT in the SOLIDBUNDLE keyword should be below the smallest characteristic time constant in the system. For complex pipes this constant may be difficult (if not impossible) to calculate, but a fairly valid approximation is: (a) where , and are the density, specific heat capacity and thermal conductivity of a pipe layer thickness . Thus, one should determine this time constant for all the layers in a pipe and use a time step that is below the smallest of these. It should be noted that the thermal masses in the solid medium can be very large and it may require very long simulation times to obtain thermal equilibrium when integrating the energy balance equation. To account for this, without using the steady state pre-processor, it is possible to switch the TEMPERATURE option from FASTWALL to WALL between restarts. This is in principle the procedure used in the steady state pre-processor. The FASTWALL option is equal to setting the heat capacity parameter to zero and can be used when there are no thermal transients. The increase in computational speed may be significant when compared to using the WALL option. However, for transient analyses this option should only be used to initialize the simulations. The results from an OLGA simulation where the FEMTherm module has been applied can be visualized using FEMTherm Viewer. Note that the FEMTherm code makes a triangle mesh also for the OLGA WALLS (radial conduction layers) and the fluid within. This is for the purpose of visualization only. The temperature is not calculated separately for these dummy nodes (e.g., the nodes in the WALL layers have the same temperature for a given radius). See Figure E that shows an inner OLGA WALL with two outer walls defined by SHAPE.

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Figure E: Left: Grid visualized in FEMTherm Viewer (the fluid in the middle will also have a mesh). Right: Grid used in FEMTherm calculation. The plotting frequency is determined by the key DTPLOT in the SOLIDBUNDLE keyword and should be set judiciously. For very fine discretization and/or long bundle sections, the amount of data may become exceedingly large for long simulations. By increasing the value of DTPLOT, the amount of data may be limited.

[*] MESHFINENESS is the number of nodes, which are evenly distributed on the outer boundary of the SHAPE with the longest circumference within a SOLID BUNDLE, which is not a POLYGON. The density of nodes (nodes divided by circumference) on the SHAPE with the longest circumference determines the number of nodes on all other non-POLYGON SHAPES in order to obtain a mesh with uniform node spacing.

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Limitations All pipelines that border to a solid shape must have a constant diameter in the axial direction. Thus, if an annulus borders to a solid shape the diameter of the outermost pipeline of the annulus is not allowed to vary. Multiple outer shapes as well as overlapping shapes are allowed. However, shapes inside an outer shape are not allowed to partially overlap, or to be adjacent as shown in Figure A. Note that the model is constructed with the use of rectangles and circular pipes only.

Figure A Illustration of allowable FEMTherm/SOLIDBUNDLE configurations in OLGA. The FEMTherm calculations are based on linear theory which assumes fixed geometry and material properties. All materials are assumed to be homogeneous and isotropic. The integration in time is performed using a fixed time step (no time step control) for the temperature distribution in the cross section. The model can only handle parallel pipes and pipes of a constant diameter.

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How to use FEMTherm is activated through the SOLIDBUNDLE keyword. To include a SOLIDBUNDLE/FEMTherm computation in the simulation, the following must be done in the OLGA GUI: From the Case level, right click and choose: Add →ThermalComponent → SOLIDBUNDLE. Configurationwise, a SOLIDBUNDLE consists of an outer SHAPE that encloses one or several FLOWPATHS, LINES and/or FLUIDBUNDLES. In the following these are referred to as bundle components. For each bundle component do the following: From the newly created solid bundle, right click and choose: Add → BundleComponents → COMPONENT. In the property window for the newly created bundle component, fill out the required fields. In particular, a reference to either a FLOWPATH, a LINE a FLUIDBUNDLE or a SHAPE must be specified. Note that no new component is created by this procedure, and that the specified component must exist beforehand or be added later. The properties FROM and TO define the part of the component that is enclosed in the bundle (axial direction). They refer to position labels. The thermal computations are only affected by the relative position of one object to another. To give better control of the cross section, without having to adjust the pipeline geometry, the coordinate system of the bundle cross section is decoupled from the rest of the model. All components are by default placed concentric around the origin and may be independently moved to its correct location with the keys XOFFSET and YOFFSET. The only exception to this rule is for SHAPES of type RECTANGLE and POLYGON. In this case, the x and y coordinates of the shape are given explicitly, but XOFFSET and YOFFSET may still be used for an additional offset. The property OUTERHVALUE may be used if the heat transfer coefficient from the outer surface of the bundle component to the carrier line is known, otherwise forced/free convection will be applied. The length and elevation of each section of a pipeline that is contained within a SOLIDBUNDLE must be maintained. A SOLIDBUNDLE/FEMTherm simulation requires that the WALL or FASTWALL temperature calculation option is selected For every SOLIDBUNDLE a finite element triangle mesh is generated. The fineness of the mesh is set by the MESHFINENESS key. The value of this key denotes the number of nodes on the SHAPE with the largest circumference. The higher the MESHFINENESS, the finer the mesh. However, the grid is not very sensitive with respect to MESHFINENESS as the value of this parameter is being rounded off to multiples of 32. The typical values for this key is between 128 and 640. To select this parameter wisely, it is recommended to read about numerical considerations in Methods and Assumptions. The ambient conditions for the bundle may vary both in the vertical axis of the cross section and along the length of the bundle. It is defined through the use of the AMBIENTDATA keyword. If this keyword is not given, the ambient conditions defined in the HEATTRANSFER keyword in the largest flow component of the bundle is used.

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Fluid bundle For pipeline configurations like the one shown in Figure 1 below, there will be cross sectional heat transfer between the different pipelines. If the temperature distribution in one pipeline changes, it will affect the temperatures in all the other pipelines. The bundle model treat such heat couplings in a more explicit and dynamic manner than the basic OLGA model.

Figure 1 Example of a fluid bundle configuration. See also: When to use Methods and assumptions Limitations How to use

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When to use The bundle model should be used for pipeline configurations like the one seen in Figure 1 below when accuracy in temperature is important.

Figure 1 Example of a fluid bundle configuration.

License requirements Fluid bundle is part of the FEMTherm Module that requires a separate license.

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Methods and assumptions The bundle model computes temperatures in bundled pipelines by coupling the basic temperature computation in the axial direction to a temperature computation in the cross sectional direction. This is achieved by the following two-step procedure: 1. In each cross section of the bundle, the fluid temperature and wall layer temperatures of all the enclosed pipelines are solved simultaneously. 2. The combination of 1-dimensional fluid and wall layer temperature calculations in the axial direction and the 2-dimensional calculation in each bundle cross section results in a 3-dimensional temperature field. The Bundle model is based on the following assumptions: The heat transfer from an outer wall surface of one pipeline to the surrounding fluid in a carrier line is based on free/forced convection unless a user given heat transfer coefficient is given. No additional griding is used in the bundle model as compared to solving each pipeline thermally decoupled from each other.

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Limitations The diameters of the carrier line and all the interior pipelines have to be constant in the axial direction. All pipelines that are contained within the same bundle have to have the same section lengths and elevations. The bundle model requires the WALL or FASTWALL temperature calculation option to be used. The bundle must cover entire pipes

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How to use To use the Bundle model, in the OLGA GUI do the following: From the Case level, right click and choose: Add→ThermalComponent→FLUIDBUNDLE In the OLGA GUI a fluid bundle consists of a carrier line enclosing one or several flow components (flowpaths, lines, and/or bundles). The carrier line itself is either a regular flow-path or a line. To populate the fluid bundle, the following has to be repeated for each participating flow component: From the newly created fluid bundle, right click and choose: Add→BundleComponents→COMPONENT In the property window for the newly created bundle component, fill out the required fields. In particular, a reference to the flow component (FLOWPATH, LINE or FLUIDBUNDLE) have to be specified. N.B., no new flow component is created by this procedure, and, thus, the component specified have to either exist beforehand or be added to the case later. The properties FROM and TO define the part of the flow path that is enclosed in the bundle (axial direction). They refer to position labels which must be defined under Piping for the FLOWPATH. The properties XOFFSET and YOFFSET are X- and Y-direction offsets for the component center from an arbitrary reference point. All components contained in the same fluid bundle must have the same reference point. The property OUTERHVALUE may be used if the heat transfer coefficient from the outer wall surface of the bundle component to the carrier line is known, otherwise forced/free convection will be applied. Flow-paths that are contained within the same bundle have to have the same section lengths and elevations. Pipe diameters must be constant in the axial direction. The WALL or FASTWALL temperature calculation option must be specified when a fluid bundle is used in a case.

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LINE A LINE is a type of FLOWPATH for which simplified one-phase calculations are performed. In OLGA 6, a LINE also takes into consideration frictional effects and will give a pressure drop along the pipeline. Thus, it needs fluid properties as a function of both pressure and temperature. These fluid properties are given as usual with the PVTFILE and FLUID keys. The former way of giving constant fluid properties with MATERIAL=FLUID is not supported in OLGA 6. Note that this also applies when running component tracking (e.g. CompTrack, Blackoil). Example 1phase fluid files are provided with the Sample cases. See also: When to use Limitations How to use

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When to use Lines are typically used in bundles, for injection lines and auxiliary lines where the pipeline hydraulics may be neglected.

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Limitations LINES cannot be connected to multiphase nodes. LINES can form networks but these networks must be hydrodynamically decoupled from multiphase networks.

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How to use The implementation of a LINE in the OLGA GUI is as follows: From the Case level right click and choose Add → FlowComponent → FLOWPATH. In the property window for the FLOWPATH choose LINE=YES. Fill in the required fields in the property window. For further instructions on FLOWPATH properties see the keyword description for FLOWPATH. LINES must be connected to nodes just as FLOWPATHS do. These nodes must also be defined as singe-phase by selecting LINE=YES or LINE=CROSSOVER in the property window for the node. A CROSSOVER node is a node that allows flow recirculation; see the keyword description of NODE for details.

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Thermal computations Temperature is an important parameter in flow assurance analyses and is a key prediction in the analysis of phenomena such as hydrate and wax formation propensities. Thus, temperature can influence the production capacity of a network and therefore, a reliable prediction of the temperature profile in a pipeline is important. In OLGA, a homogeneous temperature is calculated for the fluid which can be multiphase. In addition, it calculates the heat transfer across the pipe wall by determining the average temperature of each wall layer. The pipe wall may comprise of multiple layers of materials of different types, which are aligned concentrically. Ambient conditions for an area can vary significantly in winter and summer seasons or during a day. This may cause freezing or melting of the soil surrounding a pipeline. OLGA can simulate phase changing materials and give detailed modelling of the soil taking the latent heat of fusion and differences in thermal properties for frozen and unfrozen materials into account. See also: Methods and assumptions Limitations How to use

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Methods and assumptions Thermal calculations for the wall rest on the assumption that radial heat conduction through the concentric walls is the dominating phenomenon. The heat flux may be calculated in two ways: The heat flux through the pipe wall layers is calculated by the code with user-defined thermal conductivities, specific heat capacities and densities for each wall layer. The heat flux is determined by a user-defined overall heat transfer coefficient. The former is recommended since the heat storage capacity in the wall is often significant. It is preferred to include a dynamic calculation of the temperatures of individual wall layers in a transient simulation. The latter option will save some CPU time, but should be used with care and preferably in steady state situations only.

Figure A: Illustration of a buried pipe Buried pipelines may be modelled with the soil as the outermost wall layer. The first method of calculating the heat flux (where heat flux is a function of wall properties) should then always be used due to the large thermal mass of the soil. The thickness of the composite soil layer is based on an equivalent heat transfer coefficient for the soil for a pipeline burial of a particular depth. Theoretically, the equivalent heat transfer coefficient from the outer surface of a buried pipeline to the top of the soil can be calculated to be:

(a) where: D H lsoil hsoil

= outer diameter of buried pipe = distance from centre of pipe to top of soil = soil heat conductivity = overall heat transfer coefficient for soil

The term cosh-1 (x) can be expressed mathematically as follows: cosh-1 (x) = ln ( x + ( x2 - 1 ) 0.5 )

for x ³ 1

The thickness of the composite soil layer can be determined using the expression below for a known value of the soil thermal conductivity:

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(b) where: Rsi = inner radius of soil layer (=outer radius of pipe wall) Rso = outer radius of soil layer ksoil = input value of soil conductivity The specific heat capacity of the soil may be adjusted as follows in order to predict the transient heat transfer accurately:

(c) where: Cp input = input value of soil thermal capacity Cp soil = soil thermal capacity Heat transfer at steady state conditions depends only on the outer soil layer radius Rso and on ksoil. However, for dynamic situations, a good soil discretization is important in order to obtain a reliable temperature profile across the wall layer. Alternatively, the Solid Bundle module may be used in such a situation. Phase changing materials The model for simulating phase changing materials accounts for latent heat of fusion and the difference in thermal properties for unfrozen and frozen materials. Thermal conductivity and heat capacity are given for three ranges, above the melting point, below the melting point and in the transition phase. For heat capacity, the value specified in HEATTRANSFER is used for all temperatures above the melting point. A multiplier ( HCAPMULT) is used below the melting point. If the FUISIONMULT key is different from 0, a step wise function is used for heat capacity having the value equal to FUSIONMULT in the phase changing region. If the FUSIONMULT key is 0, linear interpolation is performed between 1 and HCAPMULT. The FUSIONMULT key takes the latent heat of fusion (additional energy added or withdrawn for a phase change) into consideration. The exmple below describes how the latent heat of fusion is caluated. The phase changing region is from 0 to -1 C. Then, one multiplier is used between 0 and -1 C, while another multiplier is used below -1 C. The multiplier between 0 and -1 C also takes into consideration the latent heat of fusion. As an example soil with dry density 1900 kg/m3. With 10% water weight/dry soil weight the moist unfrozen heat capacity is 1067 J/(kgC) (0.255 btu/(lbF) and the frozen heat capacity is 876 J/(kgC) (0.209 btu/(lbF). The latent heat of fusion is (190 kg/m3*333 kJ/kg)/(2090 kg/m3) = 30.27 kJ/kg. This gives a multiplier of 29.4 in the range from 0 and -1 C. Thermal conductivity given in HEATTRANSFER is used directly for temperatures above the melting point. A conductivity multiplier (CONDMULT) is used for temperatures below the melting point. Linear interpolation is used in between.

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Limitations Wall Layer Thickness The numerical solution for the temperatures in the wall layer depends on the discretisation of the layer. It is sufficient to undiscretize the wall layer for steady-state calculations. A finer discretisation of the wall layers may be necessary for transient calculations, when the heat storage in the pipe walls can be important (cool down or warm up), A wall layer should, as a rule of thumb, not be thicker than approximately 30% of the outer radius of the layer. The change in thickness, δ, between two neighbouring layers should be 0.2 ≤ δ(i)/δ(i-1) ≤ 5 to obtain a good accuracy. If ELECTRICHEAT is defined in the WALL definition, it is preferable to have at least three layers and define the electric heating in the middle layer. Very thin layers, such as paint etc., should be included in a neighbouring layer by adjusting the thickness and conductivity of that layer. Only the thickness needs to be adjusted if the thermal conductivity of the thin layer is fairly close to the conductivity of one of it's neighbours.

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How to use In the OLGA GUI the method for the temperature calculation is set from the OPTIONS card on the Case level. In the OPTIONS property window the TEMPERATURE can be set either to: OFF

No temperature calculation – initial temperatures must be specified with the INITIAL keyword statement ADIABATIC No heat transfer to surroundings UGIVEN A user-defined overall heat transfer coefficient is used for the entire wall WALL The heat flux through the pipe wall layers is calculated by the code with user-defined thermal conductivities, specific heat capacities and densities for each wall layer FASTWALL Similar as WALL but heat storage is neglected in the wall User-defined heat transfer parameters for the chosen temperature option must be given for each pipeline. In the OLGA GUI under Boundary&InitialConditions for each FLOWPATH , one or several HEATTRANSFER cards may be added. In the property window for each HEATTRANSFER card, the required fields must be filled out. In a temperature calculation the homogeneous temperature profile along the pipeline should be critically examined. Large discontinuities are often unphysical, although if large pressure differences occur between two neighbouring sections the Joule-Thompson effect may give a substantial temperature difference. Furthermore, if there is a great difference in hold-up between two adjacent sections, temperature differences can be expected depending on the thermal properties of the gas, liquid, and pipe walls, as well as the surrounding medium. In order to simulate a phase changing material, TYPE must be set to PCM in MATERIAL keyword. An upper and lower temperature limit for melting and freezing must be specified, PHCHMAX and PHCHMIN. Further, the three multipliers for properties below the melting point and in the phase changing region must be given.

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Tracer tracking Tracer tracking simulations together with measurements of tracer output from real fields provide a means to obtain valuable information about flow conditions in reservoirs, wells and pipelines. The tracer tracking functionality in OLGA can be used to track tracers which have such a purpose of investigation/examination, and it can be used to track tracers of inhibitor type (for instance kinetic hydrateor corrosion inhibitors). OLGA predicts the distribution in space and time of mass, age and residence time for tracers being inserted into wells/pipelines. The results may be used by for instance hydrate kinetics- and corrosion models to take into account the effect of the inhibitors.

See also: When to use Methods and assumptions Limitations How to use

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When to use Tracer tracking should be used when one wants a distribution in space and time of mass, age and residence time of tracers of such small amounts that their influence on the flow is negligible. Examples of such tracers are KHI inhibitors, corrosion inhibitors and radioactive tracers.

License requirements Tracer tracking is part of the Inhibitor Tracking Module that requires a separate license.

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Methods and Assumptions The Tracer Tracking model in OLGA computes a distribution in space and time of tracer mass, residence time and age (if the key AGING=ON). If aging is on, ages are divided into age groups (defined by the key AGEBOUNDARIES), and the average age within each group is computed. The computation of all these variables is based on simple conservation equations, here represented by the equation for mass: Here G represents the sum of regular sources as well as the influence of entrainment and deposition of droplets. The age- and residence time-equation has an additional source term, which, in the case of aging, takes into account the amount of time the tracer is subject to sub-cooling relative to an equilibrium temperature (for instance the hydrate formation temperature in case of KHI tracking). The following assumptions are used: The presence of tracers is assumed to have no effect on the flow, i.e. tracers usually exist in amounts so small that the effect on the flow of the production fluids is negligible. The tracers/inhibitors are assumed to be carried in a carrying phase (condensate, water or gas). Partitioning of tracers/inhibitors to other phases than the carrying phase is not included in the current version of the model.

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Limitations The current corrosion model and hydrate kinetics model in OLGA do not take into account the inhibition effect of any tracer. · Partitioning of tracers is not implemented in the current version. · The distribution of ages (when applicable) is divided into a given number of groups. Each group has a user given low and high bound of age. All the inhibitors within each group are assumed to have the same age (average age). · It is not possible to specify an initial condition (by the keyword INITIALCONDITIONS) containing tracers, but the steady state preprocessor will compute an initial steady state tracer distribution. · It will not be possible to specify the tracer content in negative sources. The amount of tracer going out will be based on the concentration of the tracer in the section from which the source originates. · Production flows from wells will not contain any tracer. The injection flows will be treated in the same manner as negative sources. · The tracer does not follow the water vapor phase. Any vaporization/condensation does not affect the tracer mass, but the concentration changes. If a section is totally emptied of the carrying phase, e.g. water, by vaporization, the remaining tracer is removed.

·

Tracer tracking can be combined with all other modules, but some limitations exist: · Tracer tracking can be combined with slug tracking, but the tracer output variables are average values for a section. · Tracer tracking can be combined with pig tracking (which is a special version of slug tracking), but distribution of tracer on each side of the pig might in some cases be inaccurate. · Tracer functionality is not implemented in the near well module Rocx.

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How to use The following keywords and keys must be set to use tracer tracking. In the property window for the keyword OPTIONS choose: · TRACERTRACKING=ON Specify one TRACERFEED for each tracer: · In the OLGA GUI, at the library level right click and choose Add->TRACERFEED. In the property window for each TRACERFEED set the following keys: · LABEL choose a label · AGING must be set to ON to track age distribution of the tracer · CARRIERPHASE specify the fluid phase on which the tracer is based · AGEBOUNDARIES must be set when AGING=ON (numbers separated by comma) · LOWLOWBOUND age below LOWLOWBOUND is not plotted · HIGHLOWBOUND age below HIGHLOWBOUND is not plotted under certain conditions Tracers may be fed into pipelines either via a SOURCE or via a MASSFLOW node. In the property window for a SOURCE or a node of type MASSFLOW set the following keys: · SOURCETYPE select TRACER ·

TRACERFEED

set the name of the tracer feed in this source/node

·

TRACERMASSFLOW

specify the tracer mass flow

·

TRACERAGE

specify the age of the tracer

·

TRACERRESIDENCETIME

specify the residence time of the tracer

To compute aging of a kinetic hydrate inhibitor, specify the HYDRATECHECK keyword. Some output variables are available for plotting per tracer feed and per age group.

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Tuning The TUNING keyword makes it possible to tune the fluid properties, friction, phase mass transfer and entrainment of liquid droplets into the gas phase. See also: When to use Methods and assumptions How to use

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When to use The TUNING keyword can be used for adjusting the OLGA model to specific sets of measured data or for sensitivity studies. TUNING should be applied with great care, as it might cause the validation and verification of the OLGA model to no longer be valid.

License requirements The Tuning Module requires a separate license.

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Methods and assumptions The tuning coefficients are multiplied by the related values which are either calculated by OLGA or set in the input file depending on whether the tuned parameter is dynamically calculated by OLGA or case invariant, e.g., geometry information.

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How to use Specify the desired tuning coefficients and where they apply. The tuning coefficients AREA, DIAMETER and ROUGHNESS can only be specified for an entire pipe or an entire branch. It is not possible to specify these coefficients using the section key. The keys POSITION, PIPE and SECTION will be processed in a nested manner. The number of entries must either be one or a multiple of the listed number of combinations of pipes, sections or positions.

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Water The purpose of the Water model is to let the user specify the parameters and model used for oil/water dispersion viscosities and to specify the approach used to determine the water distribution between liquid and gas phases. See also: When to use Methods and assumptions Limitations How to use

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When to use Changes to the dispersion model are recommended when experimental data shows that the default options do not give a good description of the fluid. The module may also be used for sensitivity analysis with respect to dispersion e.g. the water volume fraction at inversion point.

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Methods and assumptions Calculation of velocity difference between water and liquid hydrocarbon ("slip velocity") Two different options can normally be used for calculating the velocity difference between liquid water and hydrocarbon liquid (we term the latter "oil" for simplicity). This velocity difference is termed the "slip velocity" or just "slip". The liquid droplets flowing in the gas phase are not included in this context. By turning the water slip option off (WATERSLIP = OFF), the user assumes that there is no velocity difference between the oil and water flow fields. In this case oil and water are always assumed to flow as a homogeneous mixture with average properties. The fluid mechanical model reduces to a two-phase gas-liquid model. However, water enthalpies are accounted for in the temperature calculations. Water droplets are entrained in the oil if the water cut in the liquid film is less than the phase inversion point, and vice versa. Phase inversion is assumed to occur at a water cut given by the user through the key INVERSIONWATERFRAC (default value of 0.5). The degree of mixing of oil and water can vary from fully separated to fully dispersed, depending on the phase velocities and the material properties. This applies to all gas/liquid flow regimes. It is also possible to specify an intermediate dispersion range. Between a lower critical water cut (given by FWLOW) and the inversion point (given by INVERSIONWATERFRAC), the flow is assumed to be a water-in-oil dispersion flowing above a free water layer. The degree of mixing of water into oil is predicted by the standard OLGA model, but the maximum fraction of the total water stream that can be mixed into the oil is given by EMAX: (Volume flow of water in oil)/(Total volume flow of water) ≤ EMAX. With the default values of FWLOW and EMAX, 0.0 and 1.0 respectively, no such intermediate range is defined. A third option is also available: The user may specify a constant velocity difference between oil and water. This is a special option that should only be used with great care in special cases for tuning purposes.

Dispersion viscosities With the dispersion viscosity option turned on (DISPERSIONVISC= ON), six different viscosity models can be chosen: Pal & Rhodes, Rønningsen, Pal & Rhodes correlated with experimental data, Woelflin, Barnea & Mizrahi or table based model. The mixture viscosity for oil continuous dispersions (mhw) and water continuous dispersions (mwh) are expressed as: (a) (b) where mh [cP] is oil viscosity, mw [cP] is water viscosity and mrel [-] is relative viscosity (dispersion viscosity / viscosity of continuous phase). Pal & Rhodes and Pal & Rhodes correlated with experimental data: One correlation for relative viscosities of liquid/liquid dispersions was developed based on a generalization of Einstein’s equation to also be valid for high concentrated dispersions. The correlation was published by Pal and Rhodes (1989) /15/ and is primarily developed for dispersions where coalescence and deposition has negligible influence on the pressure drop (and the apparent viscosity). The equations below show the Pal & Rhodes correlations for relative viscosity of an oil continuous dispersion (m ) and a water continuous dispersion (m ): 402 / 769

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dispersion (mrel,h) and a water continuous dispersion (mrel,w): (c)

(d)

where

is the concentration of water droplets in the oil continuous dispersion, and is the concentration of oil droplets in the water continuous dispersion. mrel is limited

upwards to 10000. The parameter is the dispersed phase volume fraction for which the relative viscosity mrel equals 100. Based on pipe flow experiments on stable oil continuous emulsions for different crude oils and formation waters, the parameter is set equal to 0.765 (Søntvedt et al., 1994). In the present version of the model, this correlation and the correlation parameters are also applied for water continuous dispersions using the analogous quantities. It is still left to investigate how to discriminate between oil and water continuous dispersions. With an experimental point, F rel (F h or F w depending on the inversion point) and mrel (mrel,w or mrel,h) specified, the Pal & Rhodes method in Equations (c) and Equation (d) is rearranged to calculate the value: (e)

Equation (c) will then be used to calculate the water in oil dispersion viscosity. For oil in water dispersion, Equation (d) is used. F rel is defined with the key PHIREL, mrel with the key VISCREL, and the inversion point with the key INVERSIONWATERFRAC. Rønningsen: Another correlation for relative viscosities of an oil continuous dispersion is the correlation by Rønningsen recommended for a shear rate of 500 1/s (2003) /17/: (f)

where

mrel,h = Relative viscosity (dispersion/oil) T = Temperature (deg C) Fw = Volume % of water dispersed in oil Above the inversion point, the viscosity of the oil in water dispersion is assumed equal to the pure water viscosity, when the Rønningsen method is applied. The possibility to use a simple volume weighting with a tuning factor is also available.

mmix = (moil*(1-WATERCUT) + mwater* WATERCUT)*VISCMOD (g) where the tuning factor VISCMOD can be specified through input as a tabulated function of WATERCUT. 403 / 769

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Woelflin: A third option for the relative viscosity is given by

Defined by WATEROPTIONS DISPMODEL = WOELFLIN. Two parameters can be set with this model: AWOELFLIN (default value 4.2) and BWOELFLIN (default value 2.5). Barnea & Mizrahi: For the Barnea & Mizrahi correlation, the relative viscosity is given by where

Here µc and µd are the viscosities for the continuous and dispersed phases, respectively. The model is activated with WATEROPTIONS DISPMODEL = BARNEA. Table based model: The final way of giving a dispersion viscosity correlation is to use the bable based model. This can be defined by WATEROPTIONS DISPMODEL = INPUTVISC. The input is used as in this example: WATEROPTIONS DISPMODEL=INPUTVISC, \ VISCMOD=(1,1.05,1.2,1.4,1.9,2.8,2.7,1.3,1.15,1.05,1)\, WATERCUT=( 0,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1),\, WATERFLASH=ON, WATERSLIP=ON Note that the "Table base model" should use WATERFLASH=ON and WATERSLIP=ON.

Flashing/condensation of water With the water flash option turned on for standard simulations with PVT tables (FLASHMODEL = WATER in the OPTIONS keyword) the amount of water that evaporate or condense is calculated by OLGA under the assumption that the gas phase is always saturated with water vapour. The pressure and temperature dependent mass fraction of water vapour in the gas phase at water saturation is determined from the fluid properties table. If water properties are calculated by OLGA itself, water vapour in the gas phase is assumed to be zero and FLASHMODEL = WATER is disregarded. If the inhibitor tracking module is used (which uses PVT tables), it is not assumed that the gas phase is saturated with water vapor, that is, the gas might be dry if there is no available water. In some instances, therefore, inclusion of the inhibitor tracking option may provide more accurate calculation of the distribution of water between phases. WATERFLASH has no effect on Compositional Tracking simulations, in which case flashing of water is decided by FLASHTYPE in COMPOPTIONS.

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Limitations The three phase flash option is only valid when a three phase fluid property file is used.

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How to use The following sections describe how to use the keys in the WATEROPTIONS keyword.

Calculation of velocity difference between water and liquid hydrocarbon By default OLGA calculates the velocities of the oil and water fields separately (WATERSLIP = ON). If WATERSLIP = OFF, oil and water are always assumed to flow as a homogeneous mixture with average properties. Finally, the user may specify a constant velocity difference between oil and water with WATERSLIP = CONSTANT. The velocity difference is the specified by the key VELOCITYDIFFERENCE. This is a special option that should only be used with great care in special cases for tuning purposes. Dispersion viscosities The water volume fraction at inversion point is determined by the key INVERSIONWATERFRAC (default: INVERSIONWATERFRAC = 0.5). If DISPERSIONVISC = ON, the dispersion viscosities are calculated according to the model specified in the DISPMODEL key. If DISPERSIONVISC = OFF, the viscosities are read from the fluid property file directly if WATERSLIP = ON. When WATERSLIP = OFF | CONSTANT, viscosities of liquids are weighted according to volume fraction. If DISPMODEL = PALRHODES, PHI100 must be given (default: PHI100 = 0.765). PHIREL and VISCREL are required for the EXPERIMENT option (default: PHIREL = 0.765 and VISCREL = 100). The default values for the EXPERIMENT option correspond to the standard PALRHODES model. If DISPERSIONVISC = OFF and WATERSLIP = OFF, the volume weighting calculation of viscosities can be tuned using the keys VISCMOD and WATERCUT. WATERCUT must be given as a list ascending values for the water cut. For each value in WATERCUT a corresponding value for the viscosity tuning factor must exist in the VISCMOD key.

Hints and tips Water fractions in sources, wells and at boundaries (when using PVT tables) are specified either as the mass fraction of liquid water relative to the total mass (flow) with the keyword WATERFRACTION or as mass fraction of total water (liquid water plus the water vapour in the gas phase) with the keyword TOTALWATERFRACTION. The water vapour fraction of the gas phase is taken from the fluid properties table. If TOTALWATERFRACTION is set to -1, its actual value is taken from the fluid properties table. With FLASHMODEL = WATER this value is split into free water and water in gas according to the water mass fraction in gas values from the fluid table, while with FLASHMODEL = HYDROCARBON the value is interpreted as only free water (resulting in more free water than with FLASHMODEL = WATER). The relations between the various mass fractions and mass flow for e.g. a mass source at a specific temperature and pressure are then by definition: Rs Rswt Rswv Rsw where Rs Rswt Rswv Rsw

= Ggas/Ghc = Gw/Gtot = Gwv/Ggas = GwL/Gtot - gas mass fraction - total water mass fraction (TOTALWATERFRACTION) - water vapor mass fraction (always from fluid table) - liquid water mass fraction (WATERFRACTION) 406 / 769

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Gtot Ghc Gw GwL Ggas Gwv

- source total mass flow rate - source total mass flow rate exclusive of liquid water - mass flow rate of total water (vapor + liquid) - mass flow rate of liquid water - mass flow rate of total gas (including any water vapor) - mass flow rate of water vapor in the gas phase

Example: Assume a flowing mixture consisting of 50 kg/s gas (saturated with water), 30 kg/s of oil and 20 kg/s of aqueous phase. Furthermore, let the saturated gas flow include 1 kg/s of water. The various mass fractions then become: Rs = 50/(50+30) = 0.625 Rswt = (20+1)/(50+30+20) = 0.21 Rswv = 1/50 = 0.02 Rsw = 20/(50+30+20) = 0.20 Please observe that either TOTALWATERFRACTION (Rswt) or WATERFRACTION (Rsw) can be specified for the same e.g. source. If WATERFRACTION is specified all the water in the e.g. source is considered to be liquid water. When modeling a three-phase mixture using PVT tables where you want to include the mass transfer between the free water and the gas phase, the water option in OLGA must be used with FLASHMODEL = WATER. This option is more important for gas production systems than for "normal" oil production systems. When using two-phase PVT tables in OLGA simulations, internal routines are used for the calculation of water properties. The water vapour mass fraction, however, will be set to zero; all water in the calculations will be free water. If the fluid temperature becomes sub-zero, the enthalpy and entropy are extrapolated, meaning that the fluid is in thermal but not in chemical equilibrium (sub-cooled water, not ice). This is consistent with the 3-phase PVT tables created by PVTsim. The user should be aware that when performing standard simulations with PVT tables there is no separate water vapour mass balance equation. For three phase simulations, the gas phase is assumed to be saturated with water. The amount of water vapour is determined by the water vapour mass fraction from the PVT table. Therefore, the total water mass could be in error for cases where e.g. the inlet total water mass flow rate is not sufficient to saturate the gas at the water vapour mass fraction from the PVT table. However, MEG tracking has a water vapour mass balance equation that makes it suitable for simulating three phase systems where a detailed analysis of the water distribution is necessary (can be used with no MEG). When using compositional tracking, the water vapour will be taken into account depending on FLASHTYPE in COMPOPTIONS. For multiphase transport systems where liquid accumulation could represent a problem, it is recommended to perform three phase flow computations with the water slip switched on.

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Wax deposition The wax deposition module allows for modeling of wax precipitation and deposition of wax on the wall. Wax precipitation is calculated based on a pre-calculated wax table containing data on each of the wax forming components. The format of this file is described in Wax table file. The wax file can be generated in PVTSim. Wax deposition will be calculated for all flow paths, but different wax data can be given for each flow path. See also: When to use Methods and assumptions Limitations How to use

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When to use When case laboratory experiments indicates the presence of wax, and the wax appearance temperature is within the temperature envelope encountered during pipeline operation. Example cases: a.

b.

During a system shut-in, when the temperature may fall under the wax appearance temperature and wax solids starts to precipitate. This may cause both a reduction in effective pipe diameter and a severe increase in oil viscosity. Gelling of the oil may occur at zero fluid velocity and sufficiently low temperatures, making it difficult to restart the pipeline. Production cases where low fluid temperatures occurs in the pipeline, where wax both deposits at the wall and precipitates as particles suspended in the oil. Both diameter reduction due to the wax layer at the wall and the effect of suspended wax particles on oil viscosity may significantly increase pipeline pressure drop and thereby reduce the production capacity of a pipeline.

License requirements The Wax Deposition Module requires a separate license.

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Methods and assumptions The model takes into account the thermal-hydraulic effects of the wax in the following way: 1. Mass conservation equations are solved for a. Wax dissolved in oil b. Wax precipitated and dispersed in oil c. Wax deposited at wall 2. Pipe diameter and roughness for each section is adjusted depending on the thickness of wax deposited on the wall. 3. Heat balance for precipitation, deposition and melting of wax. 4. Volume change due to precipitation, deposition and melting of wax. 5. Wall heat transfer is adjusted to take the wax layer into account 6. Oil viscosity is adjusted to take into account any suspended (dispersed) wax Wax precipitation and dissolution in bulk Precipitation and dissolution/melting of dispersed wax are calculated from variations of the wax component solubility with pressure and temperature. The solubility variations are taken from the wax property tables. Transport mechanisms from bulk to wall Wax deposition can occur in two ways, either by diffusion of dissolved wax due to a temperature difference between fluid and wall, or by transfer of precipitated wax due to shear. The wax deposition rate due to molecular diffusion may be described by: (a) Where G [kg/(cm2s)] is the mass transfer rate of wax deposited and D [cm2/s] is the molecular diffusion coefficient. The RRR and HEATANALOGY models are using the Hayduk & Minhas correlation. The MATZAIN model is using the Wilke & Chang correlation. mfr [-] is the mass fraction of wax components, roil [kg/cm3] is the oil density, and L [cm] is the thickness of the boundary flow layer. The boundary layer is calculated differently for the different models activated through the key MODEL. In the RRR model, the laminar velocity boundary layer is used. The HEATANALOGY model uses a laminar concentration boundary layer based on the laminar thermal layer and the ratio of thermal vs. mass diffusivity (Lewis number). The MATZAIN model uses the laminar thermal boundary layer and an adjustment constant to enhance diffusion. It is assumed that the precipitation rate at the wall is much quicker than the rate of wax transported to the wall, so that all wax transported from bulk to wall immediately precipitates. It is possible to adjust the diffusion coefficient for the wax components by using the key DIFFCOEFFMULT. The value is directly multiplied with the diffusion coefficients calculated by the code. The key may be applied for all deposition models. Wax layer porosity (volume fraction of trapped oil in wax layer), φ [-], is taken into account when calculating the wax layer thickness. A model for shear stripping of wax is used as a wax deposition limiting effect in the MATZAIN and HEATANALOGY models. The shear stripping terms are taken from the Matzain model /12/. The equation for the rate of change in wax layer thickness is as follows: 410 / 769

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(b)

where C2 and C3 are the constants given in /12/. Values: C2 = 0.055 and C3 = 1.4. is the change rate due to diffusion, and porosity effects. The constant C1 = 15.0 from /12/ is included in for the MATZAIN model only. NSR is a flow regime dependent Reynolds number /12/:

Where is the oil density [kg/m3], is the oil velocity [m/s], is the wax layer thickness [m], is the oil viscosity kg/(m s), is the average density of the gas-oil mixture and is the liquid velocity. It is possible to adjust the constants related to the shear stripping model by using the keys SHEARMULTC2 and SHEARMULTC3. These are tuning parameters multiplied directly with C2 and C3 , respectively. Shear deposition effects may be included by applying the key COEFSHEAR when using the RRR or HEATANALOGY models. The deposition rate constant K* (=COEFSHEAR) determines the volume rate of precipitated wax deposited due to shear by the following formula:

(c) Where Cwall is the volume fraction of precipitated wax in the oil at the inner wall temperature, is the shear rate at the wall [1/s], A is the surface area available for deposition [m2] and is the average 3 density of the wax [kg/m ]. Transport mechanisms from wall to bulk (dissolution of wax layer) Dissolution/melting of wax deposited on the wall may be activated separately through the keys DISSOLUTION, DISSOLPRESS, DISSOLTDIFF and DISSOLRATE for the RRR model. The melting process is calculated by the following method: 1. The dissolved wax concentration derivative with respect to temperature is found at the cloud point for the pressure in the section. 2. The dissolved wax concentration at the wall is adjusted when the wall surface temperature is above the dissolution temperature (found by applying DISSOLTDIFF). The adjustment is as follows:

where Cwax is the concentration of wax, TWS is wall surface temperature, is the concentration derivative with respect to temperature at the cloud point (see point 1), WDT is the dissolution temperature: WDT = WAP + DISSOLTDIFF WAP is from the wax tables, while DISSOLTDIFF may be a constant or a function of the section pressure (through the given DISSOLPRESS). 411 / 769

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pressure (through the given DISSOLPRESS). 3. The adjusted Cwax,wall is used in the normal diffusion equations where Cwax,bulk- Cwax,wall is the driving potential of the diffusion process. When Cwax,wall > Cwax,bulk , melting will occur. 4. The total dissolution and diffusion rate of wax from wall to bulk, DISSOLRATE (kg/(m2s )):

, is limited upwards by

where is the mass diffusion rate based solely on the wax concentration differences between wall and bulk (see point 3). The default value of DISSOLRATE is 1.0e+12, which means that there is no limitation of the dissolution and molar diffusion rate. The reduction to DISSOLRATE is done so that the mass fraction of the wax components transported by diffusion is kept constant. Viscosity of wax/oil dispersions: Calculation of the viscosity of the wax/oil dispersion is done by using a model supplied by Calsep A/S, when using the key VISCOPTION = CALSEP. The current model is the same as used in PVTSIM 16. The apparent viscosity of oil with suspended wax particles is calculated as follows:

(d) where

is the viscosity of the oil not considering solid wax and

the volume fraction of precipitated

wax in the oil-wax suspension. is the shear rate. The parameters D, E and F have the following values (viscosities in Pa s and shear rates in s-1) D= E= F=

18.12 405.1 7.876*106

In the PVTsim program from Calsep, it is possible to tune the wax-oil dispersion viscosity model to measurements. The resulting tuning parameters may be given directly as input to OLGA when using the Calsep viscosity model. Keys: VISCMULTD, VISCMULTE, VISCMULTF. These are multiplied with the D, E and F parameters, respectively. The shear rate used in the equation is limited to be 10 s-1 or larger to avoid division by zero. The resulting viscosity, , is limited to be or larger. The influence of dispersed wax on the oil viscosity may also be given as a table (keys: VISCOPTION = TABULAR, VISMULTIPLIER, WAXVOLFRACTION). Wax layer properties: One may also give information about the porosity (oil volume fraction) of the wax layer, the roughness due to deposited wax (keys: WAXROUGHNESS and MAXROUGHNESS) and the thermal conductivity of pure wax. The conductivity may be set manually in the input file by using CONDUCTOPT = MANUAL and set CONDUCTIVITY, or it may be taken from the wax tables (CONDUCTOPT = TABLE). The instantaneous porosity of wax added to the wax layer may be set as a constant (INSTPOROSITYOPT = MANUAL, WAXPOROSITY between 0.0 and 1.0), or be calculated by the code 412 / 769

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(INSTPOROSITYOPT = MANUAL, WAXPOROSITY between 0.0 and 1.0), or be calculated by the code (INSTPOROSITYOPT = AUTOMATIC, minimum and maximum limit given by MINPOROSITY and MAXPOROSITY). The instantaneous porosity equation used by the code is as follows /12/:

(e) where is the porosity (volume fraction of oil in the wax film), is the oil density [kg/m3], is the liquid velocity [m/s], is the inner pipe diameter including the wax layer [m] and is the oil viscosity kg/(m s). The effect of ageing may also be included by using the keys AGEINGOPT=AGEING, AGEINGTIME, INITPOROSITY and HARDPOROSITY. This activates a linear ageing model where the entries for AGEINGTIME, INITPOROSITY and HARDPOROSITY are used to determine the derivative of porosity with time. The porosity is averaged over the new layer and the old, aged layer at each time step. The porosity of the wax layer is taken into account when calculating the thermal conductivity of the wax layer. The conductivity is found by using the following equation [ref.13]

(f) Where kdep is the overall thermal conductivity of the wax film, kwax is the conductivity of pure wax (=CONDUCTIVITY in input), koil is the conductivity of oil and is the weight fraction of solid wax in the wax film. .

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Limitations Note: The wax deposition model cannot be used together with the slug tracking, compositional tracking or the inhibitor tracking models. The steady state pre-processor will not consider the wax phase.

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How to use Input To use the wax deposition module, follow the steps below; Step 1: Generate a wax file and an OLGA PVT table in PVTsim. When generating the OLGA PVT table, multiphase flashing (gas, oil, wax) should be used. The wax phase will, however, normally not have a significant effect on the properties of the oil phase, apart from the viscosity of the oil/wax dispersion, which is taken into account in the model. Step 2: Prepare the OLGA input using the following keywords; OPTIONS to set WAXDEPOSITION = ON OPTIONS TEMPERATURE = WALL FILES WAXFILE to specify the file containing the wax data WAXDEPOSITION to specify wax specific data for each flow path. Wax deposition may be calculated by using one of the three following models: RRR model /6/ HEATANALOGY model /14/ MATZAIN model, as described by Matzain et. Al, /12/ The required model is chosen by using the key MODEL in keyword WAXDEPOSITION. BOUNDARY, WELL and/or SOURCE to specify WAXFRACTION. A scaling factor for determining the amount of wax forming components relative to a HC mixture. The value must be in the range [0,1]. If all inflow boundaries have WAXFRACTION = 1 (default value), the amount of wax in the inflow will be according to equilibrium (specified in the wax data file). TREND to print wax variables for given positions to a trend plot file OUTPUT to print wax variables for a branch at given times to an output file PROFILE to print wax variables for a branch at given times to a profile file

Output The keywords TRENDDATA, PROFILEDATA and PLOT in the input file specifies the output from the simulation. The trend file (*.tpl), profile file (*.ppl) and plot file (*.plt) are used for plotting several variables related to wax deposition: The different was deposition variables are described in Waxdeposition Output Variables. The trend file and profile file are text files that can be viewed in the OLGA GUI. The plot file is a binary file that is viewed in a separate plotting tool called the OLGA Viewer. Due to the binary format this file can use a shorter plotting interval and is useful for detailed analysis. A sample case for wax deposition is described in Sample: Waxdeposition.

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Wells Module The wells module provides the possibility of building virtual wells that can be used to analyse ”what if” case scenarios. This is especially useful for analyzing transient well behaviour such as start-up/shutdown, unstable flow, rate changes, well clean-up, well testing, liquid loading and chemical injection. It also enables a full-field integrated modelling approach, where a combination of reservoir, well bore, pipeline network and facilities simulators are used to construct an analytical model of the full field production system. An Wells Module is available for well flow applications where the reservoir properties and the inflow relationships play an important role in the modeling. See The Wells Module for more details. Please also see /36/ which covers different topics where the OLGA wells module could be used. See also: When to use Methods and assumptions Limitations How to use

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When to use The Wells module is suited for the following applications: Start-up and shut down of production and well testing Complicated production from several reservoir zones Reservoir injection, e.g., water alternating gas injection (WAG) Analyzing cross flow between different reservoir zones Water cut limit Flow from multilateral wells Flow stability Flow assurance (hydrates) Gas lift requirements Production optimization Well test equipment sizing

License requirements Production or injection flow equations other than linear, quadratic, or tabular are enabled by the Wells Module that requires a separate license.

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Methods and assumptions Well placement options A well can be placed at the mid-point or the inlet (bottom) of the well section. When it is placed at the inlet, the inlet or bottom hole flowing pressure is calculated by adding the hydrostatic pressure drop to the pressure in the well section. If the well is placed at the mid-point of the section, the bottom hole flowing pressure is equal to the pressure in the well section. Phase fractions For flows from the well section into the reservoir, the total mass flow is calculated with the gas mass flow fraction equal to the gas mass fraction within the well section. For the flow from the reservoir into the well section, the gas mass fraction of the oil and gas mixture of the well fluid, GASFRACTION, and water mass fraction in the total mixture of the well fluid, WATERFRACTION (or TOTALWATERFRACTION) are given. If GASFRACTION < 0 is given, the equilibrium gas mass fraction will be used. If the water option is not used, WATERFRACTION should be zero (default value).

Options for calculating flow rate Flow from reservoir into well Two thermal options for calculating enthalpy inflow are available. The isothermal option assumes that the fluid enters the well at the reservoir temperature, and reservoir fluid enthalpy is calculated on the basis of reservoir temperature and well pressure. If the adiabatic option is used, the reservoir fluid enthalpy is calculated on the basis of reservoir temperature and reservoir pressure. The fluid temperature may change as the pressure decreases from the reservoir pressure to the pressure at the well section due to constant enthalpy expansion and flashing. The following three options are available for specifying the relationship between the mass flow rate and the pressure difference (with the Wells Module seven new options are available – see The Wells Module). 1. Linear formula:

Gw = A + B( pR - pwf )

where Gw is the mass flow rate, pR the reservoir pressure, and pwf the bottom hole flowing pressure. Constant B is defined as the productivity index. Constant A allows for a minimum pressure difference required for the fluid to start to flow from the reservoir to the well and it must be less or equal to zero. The inflow model Constant productivity index, Equation (g) in the Wells Module, can also be used for linear inflow. This model is available for all users and is described in section Constant productivity index. 2. Non-linear formula:

A + BGw + CGw2 = pR2 - pwf2

where A, B and C are constants. Constant A allows for a minimum pressure difference required for flow to start from the reservoir to the well. 3. Tabular form (see keyword TABLE): The table input option is made to support gas and water coning. The relationship between the flow rate (or other well parameters) and the pressure difference is given by a table. If the user does not give a zero flow point in the input, the program will automatically add a zero point at zero pressure difference. For pressure differences within the range of the table, the flow rates are calculated by a polynomial interpolation of second degree. For pressure differences larger than the maximum value in the table, the flow rates are determined by a linear extrapolation using the tangent to the quadratic curve at the end point of the table.

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the quadratic curve at the end point of the table.

Flow from the well into the reservoir For negative flow from the well to the reservoir, the negative enthalpy source will correspond to the pressure and temperature conditions in the well section. The following three options are available for specifying the relationship between the mass flow rate and the pressure difference. 1. Linear formula:

Gw = A + B( pwf - pR )

where Gw is the mass flow rate into the reservoir and constant B is the injectivity index. Constant A represents the minimum pressure difference required for the fluid to start to flow from the well into the reservoir and it must be less than or equal to zero. The inflow model Constant productivity index, Equation (g) in the Wells Module, can also be used for linear inflow. This model is available for all users. 2. Non-linear formula:

A + BGw + CGw2 = pwf2 - pR2

where A, B and C are constants. A is the minimum pressure required for flow to start from the well into the reservoir. 3. Tabular form (see keyword TABLE): The table input option is made to support gas and water coning. The relationship between the flow rate (or other well parameters) and the pressure difference is given by a table. If the user does not give a zero flow point in the input, the program will automatically add a zero pressure difference. The interpolation and extrapolation procedure is the same as for flow from the reservoir to the well. Note: If equivalent pipe is used and there are wells in each parallel pipe, there are two ways to prepare the data for these wells: Give input data for each individual well. Use a single equivalent well. Use one of the following procedures to construct data for the equivalent well: 1. If the linear equation is used, the constants A and B for the equivalent well are: A = NAi B = NBi where Ai and Bi are constants for each parallel well. N is number of parallel wells included in the equivalent well. 2. If the non-linear equation is used, the constants A, B and C for the equivalent well are: A = Ai B = Bi/N C = Ci/N2 419 / 769

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where Ai, Bi and Ci are the constants for each parallel well. 3. If the well performance is given by a table, the flow rate in the table is the sum of the flow rates of all the parallel wells at the same pressure difference. With the Wells Module seven new models for calculating the reservoir inflow are available. For these models the reservoir performance can be specified through reservoir variables or from draw-down/buildup tests from the actual well, see The Wells Module for further information.

Dynamic Well Inflow An option is available for simulating the dynamic characteristics of a well. For positive well flow, the instantaneous flow rate for each phase, f, is calculated by

(a) where qf is the instantaneous flow rate for phase f, qf¥ is the steady-state flow with the bottom hole flowing pressure at time t, and Tf is the time constant for the flow of phase f. The steady-state flow for each phase is calculated by: (b) when the flowing pressure, Pwf, is less than a given threshold pressure, Plim,f. When Pwf is above Plim,f, Pwf.

will be set to zero. The productivity index, PIf, as well as the time constant Tf can change with

Numerically, Equation (b) is solved by

(c) (d) As an option, a transport delay can be modelled by specifying a certain distance that the front of phase f must travel before the actual inflow can be started. This distance, hf,o, will be user determined.

(e)

(f) If hf > hf,o, the flow rate into the well section is set to qf; otherwise, the flow rate into the well section is set to zero. The transient option is switched on if one or both of the time constants are greater than zero. The transient option is only applied for positive flow (from the reservoir to the well section). For the negative flow, the constants are assumed to be zero. 420 / 769

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negative flow, the constants are assumed to be zero.

The Wells Module The Wells Module is designed for well flow applications where the reservoir properties and the inflow relationships play an important role in the modelling. The Wells Module will be especially well suited for the following applications: Start-up and shut down of production and well testing. Complicated production from several reservoir zones. Reservoir injection, e.g. water alternating gas injection (WAG). Analysing cross flow between different reservoir zones. Flow from multilateral wells.

Reservoir inflow In the Wells Module the reservoir performance is specified through permeability, extension of the reservoir, fluid properties etc. or from draw-down/build-up tests from the actual well. The reservoir inflow can be specified in a number of different ways depending on the type of reservoir simulated. The different inflow performance models are presented below.

Constant productivity index The linear form is used for the production of a typical oil reservoir, or as a first estimate when the production curve for the well is not properly defined: (g) where pR is the static reservoir pressure, pwf is the flowing bottom hole pressure and J is the constant productivity index given by: Linear productivity (typical oil reservoir) (h) in oilfield units (stb/d/psi) where J kh

n Bo re rw s

Productivity index [stb/d/psi] Effective permeability x net pay [mD ft] Oil viscosity [cP] Oil formation volume factor [Rft3/Sft3] Reservoir extension [ft] Wellbore radius [ft] Mechanical skin

Forchheimer and Single Forchheimer model When the full production curve can be estimated and a constant PI is not applicable a quadratic form of the relation between inflow and draw-down can be used, for example the Forchheimer model (see ref. /1/): 421 / 769

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(i) where B and C are the linear and non-linear part of the productivity index respectively defined by: [psi2/(scf/d)]

(j)

[psi2/(scf2/d2)] Where: T mg z re rw s D k h

(k)

reservoir temperature [°R] (RESTEMPERATURE) gas viscosity at reservoir conditions [cP] (VISGRES) Gas z-factor at reservoir conditions (ZFACT) reservoir extension [ft] (RESEXT) wellbore radius [ft] (HOLES/2) mechanical skin [-] (SKINS) non-Darcy or turbulence skin [1/Sft3/d] (SKIND) reservoir permeability [mD] (KPERM) well effective net pay [ft] (HPAY)

For high pressure gas wells with limited draw down, pressure can be used instead of pressure-squared, in which case the Single Forchheimer equation is written: ,

(l)

where B and C are defined by: [psi/(scf/d)] [psi/(scf2/d2)]

(m) (n)

where pav is defined as pav= (pR + pwf)/2.

Vogels equation The following IPR equation, known as Vogels equation, was traditionally used for oil-well performance in saturated oil reservoirs (see ref. /1/ ).

(o) where q0,max is the theoretical maximum oil rate when flowing bottom hole pressure equals zero.

Backpressure and normalized backpressure equations For gas wells the following simple equation is often used for the inflow performance (see ref. /1/ ). ,

(p) 422 / 769

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where C is defined by: [scf/d/psi2n]

(q)

This equation is often referred to as the backpressure equation. The exponent n ranges in value from 0.5 to 1.0. A normalised form of this equation can be used for saturated oil wells:

(r) where q0,max is the maximum oil rate when flowing bottom hole pressure equals zero.

Undersaturated oil wells For oil wells producing from reservoirs with static reservoir pressure above the bubble point pressure, the bottom hole flowing pressure might drop below the bubble point pressure during production. In these cases the linear inflow relationship will not be sufficient alone to describe the inflow under varying flowing pressures. The following two equations are therefore introduced: for

(s)

for

(t)

where pb is the bubble point pressure. Tabulated inflow performance curve If neither of the above inflow performance curves nor the linear and non-linear option presented in this section is applicable for the reservoir, a tabulated inflow curve can be specified by the user. See the description in the beginning of this section. Variable reservoir reference pressure When a reservoir has been flowing for some time at high rates the reservoir pressure close to the well can be reduced significantly. The initial static reservoir reference pressure is no longer applicable for specifying the inflow from the zone and a reduced reference pressure is introduced. For the model to take these local drawdown and build-up effects into account, the reservoir reference pressure can be specified as a function of time by the user. Injectivity index The injectivity index is used for modelling of flow from the wellbore into the reservoir zone of gas, hydrocarbon liquid or water. This option is for example used for pushing the gas back into the reservoir during a work-over operation. The injectivity index is adapted to specify the relation between the flow from the well into the reservoir and the pressure build-up in the well. That is, when the bottom hole pressure exceeds the static reservoir pressure an inflow into the reservoir will start depending on the injectivity index. The inflow into the reservoir can be specified on the same form as the well production, but a different relationship can also be used. In addition, a separate linear injectivity index can be used for the oil phase or the water phase. 423 / 769

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or the water phase. Fracture pressure When the pressure in the wellbore exceeds a certain value above the static reservoir pressure the formation will break down. The pressure required to burst the formation is called the fracture pressure. When the pressure inside the wellbore exceeds this pressure small fractures will be created in the formation resulting in a significant increase in injectivity, and the fluid in the wellbore will flow into these fractures instead of flowing into the reservoir matrix. By specifying the fracture pressure the user defines the maximum allowable pressure inside the wellbore. In the Wells Module this is modelled by an "infinite" inflow into the reservoir zone.

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Limitations The steady state pre-processor does not handle injection wells. For these cases a solution with source close to 0 is found as input to the dynamic solver.

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How to use Standard and advanced well feature There are two ways of specifying the data for flow between the reservoir and the well. You may either specify the coefficients used in the inflow correlations directly, or you may specify traditional well/reservoir variables like permeability and net pay. In the standard well for OLGA the coefficients used in the inflow correlations is specified directly. Three options are available for specifying the relationship between the mass flow rate and the pressure difference, a linear formula, a non-linear formula and a tabular form. Please see Methods and Assumption description for more details. The Wells Module is designed for well flow applications where the reservoir properties and inflow relationships play an important role in the modeling. In the Wells Module the reservoir performance is specified through permeability, extension of reservoir, fluid properties etc. The well/reservoir variables are translated into the coefficients used in the inflow correlations. The volume flow q is a function of the bottom hole pressure pwf, the reservoir pressure pR, and the computed coefficients used in the inflow correlations. The coefficients used in the inflow correlations may also be given directly. There are several different inflow models implemented in the Wells Module e.g. Forchheimer, Vogels and Backpressure. Please see Methods and Assumption for more information.

Input The keyword ”WELL” is used to define required data for calculating the flow performance of wells. Keyword dependencies: BRANCH, GEOMETRY, OPTIONS, POSITION, FEED Required keys: LABEL, INJOPTION, PRODOPTION, RESPRESSURE, RESTEMPERATURE, ISOTHERMAL, LOCATION (Default values can be used if specified) Either the key ABSPOSITION or POSITION or the keys PIPE and SECTION is used to locate the well. The production and the injection models are specified through the keys PRODOPTION and INJOPTION with the following values available: LINEAR QUADRATIC TABULAR FORCHHEIMER (The Forchheimer model) SINGLEFORCHHEIMER (Forchheimer with pressure instead of pressure squared) VOGELS (The Vogels equation for saturated oil reservoirs) BACKPRESSURE (The Backpressure equation for oil and gas wells) NORMALIZEDBACKPR (Normalized backpressure for saturated oil wells) UNDERSATURATED (Under saturated oil wells) For advanced well inflow types the coefficients could be given directly by using the keys BINJ, CINJ, BPROD, CPROD and EXPONENTN or by setting the reservoir variables through using some of the keys BOOIL, BPPRESSURE, FRACPR, GASINJ, HOLES, GASINJ, HPAY, INJECTIVITY, INJPOSTFRACFACTOR, INJPREFRACFRATOR, INJTHRESHOLD, KPERM, OILINJ, PHASE, PRODI, PRODPOSTFRACFACTOR, PRODPREFRACFACTOR, QMAX, RESEXT, SKIND, SKINS, VISGRES, VISLRES, WATINJ and ZFACT. Which key to use for the different well flow models will be highlighted in the GUI interface.

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When using the standard well in Olga the key GASFRACTION, and WATERFRACTION or TOTALWATERFRACTION is the one to use since AINJ, BINJ, APROD and BPROD then are mass based. Values from PVT table is used when GASFRACTION and TOTALWATERFRACTION is set to -1 in the input. With the advanced well inflow types the key GORST and WATERCUT is appropriate to use since AINJ, BINJ, APROD and BPROD then are volume based. WATERCUT is calculated from PVT table if set to -1 in the input. If COMPOSITIONAL = ON in OPTION then either the key FEEDMASSFRACTION or FEEDMOLEFRACTION is used. If COMPOSITIONAL = BLACKOIL in OPTION then the key FEEDVOLFRACTION is used. Be aware of that you may not get as output the fractions or water cut specified for the well since this depend on that there are enough content of the specified phases in the well. Please see the keyword Well description for more details.

Output The keywords TREND and PROFILE in the input file specify the output from the simulation. The resulting trend file (*.tpl) and profile file (*.ppl) are used for plotting several Well variables (same variables for Advanced and Standard well): Mass rates for each phase (gas, oil and water) Steady-state mass rates for each phase Total mass rate for the liquid phase and all phases Cone front for each phase Enthalpy for the well Please see the Well variables for more details.

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REFERENCES Referenced papers 1. H.B. Bradley: Petroleum Engineering Handbook. Society of Petroleum Engineers, 1987 2. A.T. Bourgoyne, K.K. Millheim, M.E. Chenevert, and F.S. Young: Applied Drilling Engineering. Society of Petroleum Engineers, 1991 3. R.E. Henry and H.K. Fauske: The two-phase critical flow of one-component mixtures in nozzles, orifices and short tubes. Journal of Heat Transfer, May 1971, p. 179-187 4. Terje Straume, Magnus Nordsveen and Kjell Bendiksen: Numerical simulation of slugging in pipelines. ASME Symposium on Multiphase Flow in Wells and Pipelines, Anaheim, CA (1992) 5. M. Nordsveen, R. Nyborg, L. Hovden: Implementation of CO2 corrosion models in the OLGA three-phase flow code. BHR Group 1999 Multiphase ’99, ISBN 1 86058 212 5 6. O.B. Rygg, A.K. Rydahl and H.P. Rønningsen Wax Deposition in offshore pipeline systems BHRGroup Multiphase Technology, Volume 31, Banff, Canada, June 1998 7. Calsep: PVTSIM Method documentation: Modelling of wax formation -> Viscosity of oil-wax suspensions. 8. Rolf Nyborg, Peter Andersson and Magnus Nordsveen: Implementation of CO2 Corrosion Models in a Three-Phase Fluid Flow Model. CORROSION/2000, Paper No. 48 (Houston, TX: NACE International, 2000) 9. E.F. Caetano, O. Shoham and J.P. Brill: Upward Vertical Two-Phase Flow Velocity and Flow Through an Annulus. Part I: Single-Phase Friction Factor, Taylor Bubble Rise Velocity and Flow Pattern Prediction. Part II: Modelling Bubble, Slug and Annular Flow. BHRA, Multi-Phase Flow - Proceedings of the 4th International Conference, Nice, France, pp. 301-362, 1989 10. O.B. Rygg, J. D. Friedmann and J. Nossen: Advanced well flow model used for production, drilling and well control applications. IADC Well Control Conference for Europe, Aberdeen, May 1996 11. A. H. P. Skelland: Non-Newtonian Flow and Heat Transfer. John Wiley & Sons, New York, 1967 12. Matzain, Zhang, Volk, Redus, Brill, Apte and Creek: Multiphase flow wax deposition modelling. Proceeding ETCE, February 2001, Houston USA 13. Singh,Venkatesan,Fogler, Nagarajan: Formation and Aging of Incipient Thin Film Wax-Oil Gels. 428 / 769

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AIChE Journal, Vol. 46, No. 5. 14. Incropera & DeWitt: Fundamentals of Heat and Mass Transfer. 4th ed., ISBN 0-471-30460-3 15. Pal, R., Rhodes, E.: Viscosity/Concentration Relationships for Emulsions. J. of Rheology, Vol. 33, no. 7, pp. 1021-1045 (1989) 16. Rønningsen, H. P.: Correlations for Predicting Viscosity of W/O Emulsions based on North Sea Crude Oils. SPE Paper 28968, presented at the SPE International Symposium on Oilfield Chemistry, San Antonio, Texas, US, February 14-17, 1995 17. Rønningsen, H. P.: Viscosity of ’live’ water-in-crude-oil emulsions: experimental work and validation of correlations. J. of Petroleum Science and Engineering 38, pp. 23-26 (2003) 18. Stein Olsen and Arne Dugstad: Corrosion under Dewing Conditions CORROSION/91, Paper No.472, NACE, 1991 19. Hammerschmidt, E.G.: Gas Hydrate Formations: A Further Study on Their Prevention and Elimination from Natural Gas Pipe Lines. GAS, Vol. 15, no. 5, pp. 30-35, May 1939 20. Winkler, H.W. and Eads, P.T.: Algorithm for More Accurately Predicting Nitrogen-Charged Gas-Lift Valve Operation at High Pressures and Temperatures. SPE 18871, March 1969 21. Pedersen, K. S., and Rønningsen H. P.: Effect of precipitated wax on viscosity Presentation at AIChE Spring National Meeting, Houston, TX, March 14-18, 1999. 22. Darby R., Melson J.: How to predict the friction factors for flow of Bingham plastics Chemical Engineering, December 28, 1981 23. White, F.M.: Fluid Mechanics 2nd ed., ISBN 0-07-066525-7 24. Turian, R.M., Hsu, F.L. and Ma, T.W.: Estimation of the Critical Velocity in Pipeline Flow of Slurries Powder Technology, 51, pp 35-47, 1987 25. Krieger, I.M. and Dougherty, T.J.: A mechanism for Non-Newtonian Flow in Suspensions of Rigid Spheres Trans. Soc. Rheol. III 137-152., 1959 26. Thomas, A.D.: Slurry Pipeline Rheology 429 / 769

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2nd Conference on Rheology, Sydney, Australia. 27. Lasater, J. A.: Bubble Point Pressure Calculation Trans. ANIME (1958), 379. 28. McCain W. D.: The properties of petroleum fluids. PennWell P. C. 1990 29. Vazquez and Beggs: Correlations for Fluid Physical Property Prediction M.S. Thesis, Tulsa Univ. 1976. 30. Glaso, Oistein.: Generalized Pressure-Volume-Temperature Correlations Journal of Petroleum Technology, pp. 785-795, May 1980. 31. Katz D. L. Handbook of natural gas engineering. McGRAW-Hill 1959 32. Campbell J. M. Gas conditioning and processing, vol 1. John M. Campbell and Company, 1966-1998 33. Baker O. and Swerdloff W.: Finding surface tension of hydrocarbon liquids. Oil and Gas Journal, Jan. 2., 1956. 34. Selmer-Olsen, S., Holm, H., Haugen, K., Nilsen, P. J. and Sandberg, R., Subsea Chokes as Multiphase Flowmeters. Production Control at Troll Olje. Proc. 7th Int. Conf. on Multiphase Production, BHR Group, Wilson, A. (ed.) Cannes 7-9 June 1995, pp. 441-446 35. The Properties of Gases & Liquids Fourth Edition, Reid, R.C., Prausnitz, J.M. and Poling, B.E. 36. Juan Carlos Mantecon, SPT Group: SPE 109829: The Virtual Well: Guidelines for the Application of Dynamic Simulation to Optimise Well Operations, Life Cycle Design and Production Non-referenced papers describing the OLGA model: Bendiksen, K.H., Malnes, D., Moe, R. and Nuland, S.: The Dynamic Two-Fluid Model OLGA: Theory and Application. SPE Production Engineering, May 1991, pp. 171-180 Rygg, O.B. and Ellul, I.R.: The Dynamic Two-Phase Modeling of Offshore Live Crude Lines Under Rupture Conditions. OTC 6747, presented at the 23rd annual Offshore Technology Conference, Houston, U.S.A (May 16-9, 1991) Shea, R.H., Rasmussen, J., Hedne, P. and Malnes, D.: Holdup predictions for wet-gas pipelines compared. Oil & Gas Journal, May 19, 1997 Non-referenced papers describing applications of the OLGA model: Burke, N.E. and Kashou, S.F.: Slug Sizing/Slug Volume Prediction, State of the Art Review and Simulation, OTC 7744, presented at the 27th annual Offshore Technology Conference, Houston, U.S.A (May 1-4, 1995) 430 / 769

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Burke, N.E., Kashou, S.F. and Hawker, P.C.: History Matching of a North Sea Flowline Startup. Journal of Petroleum Technology, May 1993, pp. 470-476 Courbot, A.: Prevention of Severe Slugging in the Dunbar 16" Multiphase Pipeline. OTC 8196, presented at the 28th annual Offshore Technology Conference, Houston, U.S.A (May 6-9, 1996) Erickson, D.D. and Mai, M.C.: A Transient Multiphase Temperature Prediction Program. SPE 24790, 1992, Presented at the 6th Annual Technical Conference and Exhibition of the SPE, Washington, D.C., October 4-7, 1992 Flaten, G., Nunes, G.C. and Assayaga, S.: Evaluation of the dynamic flow behavior for the Petroboost system. Presented at the 8th Int. Conf. on Multi-Phase Production, Cannes, 1997, BHR Group Conference Series No. 24, pp. 185-198 Hustvedt, E.: Determination of Slug Length Distribution by the Use of the OLGA Slug Tracking Model. Presented at the 6th Int. Conf. on Multi-Phase Production, Cannes, 1993, BHR Group Conference Series No. 4, pp 147-163 Hærdig, A. and Moe, R.: Dynamic simulations of multiphase flow in flowline bundles on Åsgård. Presented at the 8th Int. Conf. on Multi-Phase Production, Cannes, 1997, BHR Group Conference Series No. 24, pp. 275-289 Klemp, S., Meland, B., and Hustvedt, E.: Operational experiences from multiphase transfer at Troll. Presented at the 8th Int. Conf. on Multi-Phase Production, Cannes, 1997, BHR Group Conference Series No. 24, pp. 477-496 Lingelem, M.N.: TOGI Multiphase Flow From Troll to Oseberg. OTC 6670, presented at the 23rd annual Offshore Technology Conference, Houston, U.S.A (May 16-9, 1991) Mazzoni, A., Villa, M., Bonuccelli, M., De Toma, G., Mazzei, D., and Crescezi, T.: Capability of the OLGA Computer Code to Simulate Measured Data From AGIP Oil Field. Presented at the 6th Int. Conf. on Multi-Phase Production, Cannes, 1993, BHR Group Conference Series No. 4 Mazzoni, A. and Bonuccelli, M.: OLGA and WOLGA dynamic codes validation with Trecate test loop three-phase transient data. Presented at the 8th Int. Conf. on Multi-Phase Production, Cannes, 1997, BHR Group Conference Series No. 24, pp. 257-274 Rygg, O.B., Friedemann, J.D. and Nossen, J.: Advanced Well Flow Model Used for Production, Drilling and Well Control Applications. Presented at The IDAC Well Control Conference for Europe, Aberdeen, May 22-24, 1996 Straume, T., Nordsveen, M. and Bendiksen, K.: Numerical Simulation of Slugging in Pipelines, ASME Int. Symp. On Multiphase Flow in Wells and Pipelines, Anaheim, 8-13 Nov., 1992 Xu, G.Z., Gayton, P., Hall, A. and Rambaek, J.: Simulation study and field measurement for mitigation of slugging problem in The Hudson Transportation lines. Presented at the 8th Int. Conf. on Multi-Phase Production, Cannes, 1997, BHR Group Conference Series No. 24, pp. 497-512 Xu, Z.G.: Solutions to Slugging Problems Using Multiphase Simulations.

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OLGA 7

Keywords ABCDEFGHIJKLMNOPQRSTUVWXYZ

A ALGEBRAICCONTROLLER AMBIENTDATA ANNULUS ASCCONTROLLER

B BLACKOILCOMPONENT BLACKOILFEED BLACKOILOPTIONS BRANCH

C CASCADECONTROLLER CASE CHECKVALVE COMPOPTIONS COMPRESSOR COMPONENT CORROSION

D DRILLINGFLUID DTCONTROL

E ESDCONTROLLER

F FEED FILES FLOWPATH FLUID FLUIDBUNDLE

G GEOMETRY

H HEATEXCHANGER HEATTRANSFER HYDRATECHECK 432 / 769

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HYDRATECURVE HYDRATEKINETICS

I INITIALCONDITIONS INTEGRATION

L LEAK LOSS

M MATERIAL MANUALCONTROLLER

N NEARWELLSOURCE NODE

O OPTIONS OUTPUT OUTPUTDATA OVERRIDECONTROLLER

P PHASESPLITNODE PIDCONTROLLER PIG PIPE PLOT POSITION PROFILE PROFILEDATA PSVCONTROLLER PUMP

R RESTART

S SCALERCONTROLLER SELECTORCONTROLLER SEPARATOR SHAPE SINGLEOPTIONS SLUGILLEGAL 433 / 769

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SLUGTRACKING SLUGTUNING SOLIDBUNDLE SOURCE STDCONTROLLER SWITCHCONTROLLER

T TABLE TABLECONTROLLER TIMESERIES TOOLJOINT TRACERFEED TRANSMITTER TREND TRENDDATA TUNING

V VALVE

W WALL WATEROPTIONS WAXDEPOSITION WELL

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CASE (on CASELevel) Description ( See also: Keys) Defines information about a simulation.

CASE (on CASELevel) Keys ( See also: Description ) Key AUTHOR DATE INFO PROJECT TITLE

Type

Parameter set

Unit:( )

Default:[ ]

String String String String String

Description Author of the input file. Date. General information about the case. Project name. Case title.

Link to: CASE (on CASELevel) Description Keys

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DTCONTROL (on CASELevel) Description ( See also: Keys) This statement defines a switch for stability control. See restrictions and limitations for more information.

DTCONTROL (on CASELevel) Keys ( See also: Description ) Type

Parameter set

Unit:( )

Default:[ ]

CFL

Symbol

OFF | [ON]

CFLFACTOR

Real

[0.8]

Key

GRADPRESSURE Symbol

ON | [OFF]

PREFACTOR

Real

[0.8]

PRESSURE

Symbol

ON | [OFF]

SOUND_CFL

Symbol

ON | [OFF]

Description The Courant-Friedrichs-Lewy (CFL) criterion based on the flow velocity. Tuning factor for the CFL time-step. Time-step control based on the first-order derivative of pressure w.r.t. time. Tuning factor for pressure criterion. Time-step control based on the secondorder derivative of pressure w.r.t. time. Time-step control based on the speed of pressure waves.

Link to: DTCONTROL (on CASELevel) Description Keys

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OLGA 7

FILES (on CASELevel) Description ( See also: Keys) This statement defines the additional input files, e.g., PVT table files for fluid properties, pump data table files, compressor table files, feed file for the compositional tracking model and wax file for the wax deposition model. Note: several files can be listed for COMPRESSORFILE, PUMPFILE and PVTFILE. For definition of a restart file, click here. If drilling fluids are used and the fluid properties are given in files, these are specified as additional files in the PVTFILE key.

FILES (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

COMPRESSORFILE StringList

FEEDFILE

String

PUMPFILE

StringList

PVTFILE

StringList

WAXFILE

String

Description Name of COMPRESSOR file(s). The files can contain several compressors each. Name of FEED file (used by the compositional tracking module). Note that only one file may be specified, however one file can contain several feeds. Name of PUMP file(s). Each file can contain only one pump. Name of the file(s) containing fluid properties. Name of the file containing the WAX table. Note that only one wax table can be specified for the time being. See user manual for details.

Link to: FILES (on CASELevel) Description Keys

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INTEGRATION (on CASELevel) Description ( See also: Keys) This statement defines the start and end times of the simulation. It also defines the start value, the maximum value and the minimum value of the time step. A controller can be used to setup a conditional stop of the simulation before the specified end time. The simulation stops when the signal from the controller is zero.

INTEGRATION (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

DTSTART

Real (s)

ENDCONTROLLER

Symbol

ENDTIME

Real (s) RealList (s) RealList (s) RealList (s) RealList (s)

MAXDT MAXTIME MINDT MINTIME

RUNTIMESTEPAGAIN Symbol STARTTIME

Real (s)

Description Initial time-step. Label of the controller determining conditional termination of the simulation. Simulation end time.

[1.0]

Largest time-step allowed.

[0.0]

Timetable for changing MAXDT.

[0.001]

Smallest time-step allowed.

[0.0]

Timetable for changing MINDT.

FALSE | [TRUE]

Select whether or not to recompute the time-step if the first-stage solution is unsatisfactory. Simulation start time.

Link to: INTEGRATION (on CASELevel) Description Keys

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OPTIONS (on CASELevel) Description ( See also: Keys) This statement specifies the different calculating options to be applied in the simulation. OPTIONS is a required keyword.

OPTIONS (on CASELevel) Keys ( See also: Description ) Type

Parameter set

Unit:( )

Default:[ ]

COMPOSITIONAL

Symbol

ON | MEG | MEOH | ETOH | BLACKOIL | STEAMWATER-HC | SINGLE | [OFF]

DEBUG

Symbol

ON | LIMITED | [OFF]

DRILLING

Symbol

ON | [OFF]

FLASHMODEL

Symbol

HYDROCARBON | [WATER]

HYDSLUG

Symbol

OFF | [ON]

MASSEQSCHEME

Symbol

2NDORDER | [1STORDER]

NOSLIP

Symbol

ON | [OFF]

Key

Description OFF: No compositional tracking, just use the fluid table. ON: Enable compositional tracking. MEG/MEOH/ETOH: Use Inhibitor tracking with the given component. BLACKOIL: Use Black oil model. STEAMWATER-HC: Use steam model. SINGLE: Use single-component model Turn on or off printing of time step information to standard output. DEBUG = OFF reports only essential warnings. DEBUG = ON will report all informative messages and can slow down simulation significantly. DEBUG = LIMITED will be more silent about fluid table warnings and some informative messages, but otherwise report the same as DEBUG = ON. Set it to ON for simulation drilling process Mass transfer model. WATER: Mass transfer between gas-oil and gas-water. HYDROCARBON: Only mass transfer between gas-oil. This key (HYDSLUG) makes it possible to turn off the distributed flow regimes (hydrodynamic slug flow and dispersed bubble flow). HYDSLUG OFF will enforce stratified or annular flow (both including liquid droplets). Discretization scheme used for solving the mass equations. For further details, see User's manual. OFF: Slip between phases is calculated (recommended). ON: Should only be used for sensitivity simulations. The gas and liquid (oil and water) is treated as one single homogenized phase in the pressure drop and momentum calculations. The other calculations, mass conservation, mass transfer, etc, will be as for a normal simulation with slip. The no-slip option is implemented in both the steady state pre-

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PHASE

Symbol

[THREE]

SLUGVOID

Symbol

AIR | [SINTEF]

STEADYSTATE

Symbol

OFF | NOTEMP | [ON]

TABLETOLERANCE Symbol

ON | [OFF]

TEMPERATURE

ADIABATIC | UGIVEN | OFF | FASTWALL | [WALL]

Symbol

TRACERTRACKING Symbol WAXDEPOSITION Symbol

ON | [OFF] ON | [OFF]

WRITEPVTFILES

YES | [NO]

Symbol

implemented in both the steady state preprocessor and the dynamic code. Define the number of phases to be simulated. In OLGA 6 the only option is THREE. Select correlations for determining gas volume fraction in liquid slugs. Turns off the initial value (steady state) preprocessor or only turn off the temperature calculation in the pre-processor. Define the upper and lower limits of pressure and temperature allowed in the simulation. OFF: The limits will be the ones specified in the fluid tables (recommended). ON: This option should only be used when old PVT files with too narrow pressure/temperature ranges cannot be reproduced and improved. See User's manual for further information. Specify the desired temperature calculation option. OFF: No temperature calculation, initial values are used. ADIABATIC: No energy exchange with the walls. Adiabatic flow is assumed. UGIVEN: Total heat transfer coefficient for the pipe-wall is given. No wall temperatures are calculated. WALL: Heat transfer on wall inside and outside, wall heat conduction and heat storage is accounted for. FASTWALL: Same as option WALL except that heat storage is neglected. This option is used for a fast approach to steady state thermal conditions. Switch for using tracertracking Switch wax deposition model on or off. For STEAMWATER-HC and SINGLE only. YES: PVT table file(s) and saturation line file are written for steam and single component properties.

Link to: OPTIONS (on CASELevel) Description Keys

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OLGA 7

RESTART (on CASELevel) Description ( See also: Keys) The restart statement defines a restart of the program from a previous run. The restart file contains data necessary to restore the state of the simulation engine from a previous run. Unlike earlier versions of OLGA, OLGA 6 will not contain a complete snapshot of the in-memory data structures. This means in particular that the original input file has to be read to get information about e.g. the pipe line, sources, walls, time integration, and output information. The content of the restart file can be thought of as specialized initial conditions, but with more information than the standard user specified initial conditions. Please note that it is not allowed to change any geometry data in a restart run. E.g all pipes must have the same number of sections, section lengths, elevations and diameters. Nodes must have the same connections. Walls and materials must be the same. The setting for component tracking (keyword OPTIONS, key COMPOSITIONAL) cannot be changed. By default, without using the RESTART keyword, a restart file is written at the end of the simulation. To save restart files generated at other times, either of the keys DTWRITE or WRITETIME can be used. Several actions, such as activate/deactivate SLUGTRACKING, change valve openings, modify controller settings etc. may be performed in a restart. Discrepancies between the original and the restart case will be reported as info messages when the restart case is started. Watch out for these to catch any unintended effects in the restart run (e.g. a missing source or something else that will influence results).

RESTART (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

DTWRITE

Real (s)

FILE

String

READFILE

Symbol

READTIME

Real (s)

WRITE

Symbol

WRITETIME

RealList (s)

Description

ON | [OFF]

APPEND | OFF | [OVERWRITE]

Define the time interval at which to write restart data to file. The name of the restart file from which to restart the simulation. ON: Enable reading of the restart file. OFF: Restart is disabled. Time in previous simulation at which the state is read in order to restart this simulation (only one time point is allowed). OVERWRITE: Replace any existing restart file with the current data. APPEND: Add data to an existing restart file. OFF: No restart data is written to file. A specific time or time series when restart data is written to the restart file.

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OLGA 7

BLACKOILCOMPONENT (on CASELevel) Description ( See also: Keys) This statement defines a component (gas, oil or water) for the black oil options.

BLACKOILCOMPONENT (on CASELevel) Keys ( See also: Description ) Key

Type Unit:( )

APIGRAVITY

Real

CO2MOLEFRACTION

Real

GASSPECIFICGRAVITY

Real

H2SMOLEFRACTION

Real

LABEL

String

N2MOLEFRACTION

Real

OILSPECIFICGRAVITY

Real

TYPE

Symbol

WATERSPECIFICGRAVITY Real

Parameter set

Description

Default:[ ] API gravity. API = 141.5/(oil specific gravity) –131.5. Cannot be given if OILSPECIFICGRAVITY is given. Mole fraction of CO2 in gas at standard [0.0] conditions. CO2MOLEFRACTION has to be less than 10%. Gas specific gravity (gas density/air [0.64] density). GASSPECIFICGRAVITY has to be larger than 0.5 (0.55 is pure methane). Mole fraction of H2S in gas at standard [0.0] conditions. H2SMOLEFRACTION has to be less than 10%. [BOCOMP-1] Name of the blackoil component. Mole fraction of N2 in gas at standard [0.0] conditions. N2MOLEFRACTION has to be less than 10%. Oil specific gravity (oil density/water [0.876] density). Cannot be given if APIGRAVITY is given. OIL | GAS | Define if the component is an oil, Gas or WATER water component. Water specific gravity (water density/fresh water density). Used in order to include [1.0] density effect on water due to components other than salt, e.g. MEG. [30]

Link to: BLACKOILCOMPONENT (on CASELevel) Description Keys

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OLGA 7

BLACKOILFEED (on CASELevel) Description ( See also: Keys) This statement defines a black oil feed.

BLACKOILFEED (on CASELevel) Keys ( See also: Description ) Key

GASCOMPONENT GLR GOR LABEL LGR OGR OILCOMPONENT

Type Unit:( ) Symbol Real (Sm3/Sm3) Real (Sm3/Sm3) String Real (Sm3/Sm3) Real (Sm3/Sm3) Symbol

WATERCOMPONENT Symbol WATERCUT

Real

Parameter set

Description

Default:[ ] Ref. to blackoil component label of type gas. Gas/liquid ratio. Alternative to GOR. Gas/oil ratio. Alternative to GLR. [BOFEED-1] Blackoil feed label. Liquid/gas ratio. Alternative to GLR (to be used for gas feeds). Oil/gas ratio. Alternative to GOR (to be used for gas feeds). Ref. to blackoil component label of type oil. Ref. to blackoil component label of type water. [0.0] Watercut.

Link to: BLACKOILFEED (on CASELevel) Description Keys

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BLACKOILOPTIONS (on CASELevel) Description ( See also: Keys) This statement defines the black oil options.

BLACKOILOPTIONS (on CASELevel) Keys ( See also: Description ) Key

Type Unit:( )

APIGRAVITY

Real

BUBBLEPRESS

Real (Pa)

BUBBLETEMP

Real (C)

GASSPECIFICGRAVITY Real GOR

Real (Sm3/Sm3)

GORMODEL

Symbol

OILSPECIFICGRAVITY

Real

OILVISC-TUNING

Real (Ns/m2) Symbol

RSGO_BP-TUNING

Symbol

VISCPRESS

Real (Pa)

VISCTEMP

Real (C)

OILVISC

Parameter set

Description

Default:[ ] API gravity. API = 141.5/(oil specific gravity) –131.5. Cannot be given if OILSPECIFICGRAVITY is given. Bubble pressure at a given temperature. The temperature corresponding to the bubble pressure. Gas specific gravity (gas density/air density). GASSPECIFICGRAVITY has to be larger than 0.5 (0.55 is pure methane). Gas/oil ratio. The GOR should not be larger than 1000 Sm3/Sm3. STANDING | BEGGS | Correlation used to calculate the gas/oil GLASO | ratio. [LASATER] Oil specific gravity (oil density/water density). Cannot be given if APIGRAVITY is given. Measured oil viscosity at a given pressure and temperature. ON | [OFF] Enable tuning of oil viscosity. Enable tuning of RSGO (gas dissolved in ON | [OFF] oil) and Bubble point. The pressure at which the viscosity is measured. The temperature at which the viscosity is measured.

Link to: BLACKOILOPTIONS (on CASELevel) Description Keys

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OLGA 7

COMPOPTIONS (on CASELevel) Description ( See also: Keys) This statement specifies the different options used in the PVT routines for calculating material properties and flashing terms in the Compositional Tracking model. If VISCOSITYCORR is specified the chosen model is used for viscosity calculations for the gas and oil phases. An error is given if the feed has been tuned to another viscosity correlation in PVTsim, in which case this is the only allowed option. The FLASHTYPE key specifies the type of flash calculations to use. TWOPHASE is the simplest one and is default if no aqueous components (H2O, MEG, etc) are part of the feed. SIMPLETHREEPHASE is the default if there are at least one aqueous component. FULLTHREEPHASE is the most time-consuming option, but provides full mixing in all phases. This option must be used if any salt components are defined in the feed. The TCONDENSATION/TVAPORIZATION keys are non-equilibrium delay constants for the mass transfer from liquid phase to gas phase and vice versa. The keys can be introduced for each component specified with the COMPONENT key. The equilibrium state reached in the flash calculations will then be delayed for the specified components. The default is no delay. The DENSITYLIMIT key can be used to specify the limit for the dense phase region density. In the dense phase region, where there are no good criteria to distinguish gas from oil, a fluid with higher density than the given value is defined as liquid and a fluid with lower density is defined as gas.

COMPOPTIONS (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

COMPONENT

SymbolList

DENSITYLIMIT

Real

FLASHTYPE

Symbol

TBOILING

RealList (s)

Description

Components to specify delay constants for (defined in feed file). Used in the dense phase region. A fluid with a density higher than this limit is defined as a liquid and a fluid with lower density is identified as gas. If used, it should preferably be set equal to the fluid density at the critical point. If not used, internal routines will decide the phase (may cause instabilities when crossing bubble/dew point). Algorithm used in flash calculations. TWOPHASE is default if no aqueous TWOPHASE | components are part of the feed. SIMPLETHREEPHASE SIMPLETHREEPHASE is default if | FULLTHREEPHASE there is at least one aqueous component in the feed. Time constant for mass transfer from liquid phase to gas phase due to boiling [1.0] for components in COMPONENT. (Non-equilibrium delay constant). Only 445 / 769

OLGA 7

(s)

TCONDENSATION

RealList (s)

TIME

RealList (s)

TVAPORIZATION

RealList (s)

VISCOSITYCORR

Symbol

[0.0]

LBC | [CORRSTATE]

(Non-equilibrium delay constant). Only for STEAMWATER-HC. Time constant for mass transfer from gas phase to liquid phase (Nonequilibrium delay constant). When COMPOSITIONAL=ON, the default value is no delay and each value must have a corresponding component in COMPONENT. When COMPOSITIONAL=STEAMWATERHC, TCONDENSATION may be defined as a time series and the default value is 1 s. Time points for which TBOILING, TVAPORIZATION and TCONDENSATION changes. Only for STEAMWATER-HC. Time constant for mass transfer from liquid phase to gas phase (Nonequilibrium delay constant). When COMPOSITIONAL=ON, the default value is no delay and each value must have a corresponding component in COMPONENT. When COMPOSITIONAL=STEAMWATER-HC TVAPORIZATION may be defined as a time series and the default value is 1 s. Whether to use Corresponding state or Lohrenz-Bray-Clark correlation for viscosity correlation.

Link to: COMPOPTIONS (on CASELevel) Description Keys

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OLGA 7

FEED (on CASELevel) Description ( See also: Keys) This statement defines a feed (fluid composition used in a source or at a boundary) and its components with belonging mole fractions. The components in the feed must be defined in the feed file, and the properties for each component will be taken from the feed file. Feeds can also be defined directly in the feed file. The feed file is generated in PVTsim.

FEED (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

COMPONENT

SymbolList

LABEL

String

[FEED-1]

MASSFRACTION RealList MOLEFRACTION RealList

Description Components in feed. For COMOSITIONAL=ON the components are defined in the feed file. For DRILLING=ON available components are HC, H2O, MEG/MEOH/ETOH, CUTTING and MUD components. Name of feed. Mass fractions of the components of the feed. Mole fractions of the components of the feed. Can not be used with Drilling.

Link to: FEED (on CASELevel) Description Keys

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ALGEBRAICCONTROLLER Description ( See also: Keys) The controller type ALGEBRAIC can combine signals from other controllers using a defined set of operators, see below. The controller loops over all operators given in VARIABLEFUNCTION key. The number of operands is defined by the operation. The operators are applied to the current result (result from previous operation) as the first operand and additional operands in terms of input signals terminals (INPSIG_i). The initial current result (result from previous operation) is input signal one (INPSIG_1). The following unary operator has been implemented: ABS – Take the absolute value of the current result The following binary operators have been implemented: ADD – Add next input signal (INPSIG_i) to the current result SUB – Subtract next input signal (INPSIG_i) from the current result MUL – Multiply the current result with the next input signal (INPSIG_i) DIV – Divide the current result with the next input signal (INPSIG_i) GT – Compare current result with the next input signal (INPSIG_i), return value one if current result is greater than next input signal, value zero otherwise LT – Compare current result with the next input signal (INPSIG_i), return value one if current result is less than next input signal, value zero otherwise GE – Compare current result with the next input signal (INPSIG_i), return value one if current result is greater than or equal to the next input signal, value zero otherwise LE – Compare current result with the next input signal (INPSIG_i), return value one if current result is less than or equal to the next input signal, value zero otherwise EQ – Compare current result with the next input signal (INPSIG_i), return value one if current result is equal to the next input signal, value zero otherwise NEQ – Compare current result with the next input signal (INPSIG_i), return value one if current result is not equal to the next input signal, value zero otherwise Controller type Algebraic makes use of the following signal terminals: INPSIG_1..N

(Required input)

MODE

(Optional input)

SIGNAL

(Optional input)

ACTIVATE

(Optional input)

OUTSIG_1..N

(Optional output)

ALGEBRAICCONTROLLER Keys ( See also: Description ) Key BIAS

Type

Parameter set

Unit:( )

Default:[ ]

Real

[0.0]

Description Initial output signal. Time required to change valve settings or compressor speed from

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CLOSINGTIME

Real (s)

[0]

compressor speed from maximum to minimum value. Time from when the measured value is read to DELAY Real (s) [0.0] when it is used by the controller. Identification label for this LABEL String [ALGEBRAICCONTROLLER_tag] controller. MANUALOUTPUT RealList Manual output. MAXSIGNAL Real [1.0e10] Maximum output signal. MINSIGNAL Real [-1.0e10] Minimum output signal. AUTOMATIC: The setpoint is defined on the controller. MANUAL: The controller output is given by key MANUALOUTPUT. EXTERNALSIGNAL: The controller output is given by the controller MANUAL | EXTERNALSIGNAL | MODE SymbolList connected to the SIGNAL FREEZE | [AUTOMATIC] terminal. EXTERNALSETPOINT the setpoint is given by the controller connected to the SETPOINT terminal. FREEZE the controller output is frozen (kept constant). Time required to change valve settings or OPENINGTIME Real (s) [0] compressor speed from minimum to maximum value. Stroke or actuator time. Time required to change valve settings or STROKETIME Real (s) [0] compressor speed from minimum to maximum value or vice versa. RealList Time series for the TIME (s) SETPOINT key. For use when one or more variables are specified. The values of the variables will be subject to the operator specified. The first operator vill be ADD | SUB | MUL | DIV | GT | LT used on the first VARIABLEFUNCTION SymbolList | GE | LE | EQ | NEQ | ABS operand(s)=INPSIG terminal(s). The second operator will be used on the result ffor the first operation and possibley

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operation and possibley any additional INPSIG terminal. Link to: ALGEBRAICCONTROLLER Description Keys

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ASCCONTROLLER Description ( See also: Keys) The main purpose of the Anti Surge Controller (ASC) is to prevent a compressor from operating to the left of the Surge Line in a compressor performance map.

The controller uses a non-symmetrical PID algorithm. Two amplification constants must therefore be given. One amplification for positive and one for negative controller error.

The ASC controller has the following signal terminals:

MEASRD

(Required input)

MODE

(Optional input)

SIGNAL

(Optional input)

SETPOINT

(Optional input)

ACTIVATE

(Optional input)

OUTSIG_1..N

(Optional output)

ASCCONTROLLER Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

AMP1

Real

AMP2

Real

BIAS

Real

CLOSINGTIME

Real (s)

[10.0]

DELAY

Real (s)

[0.0]

DERIVATIVECONST

Real (s)

[0.0]

INTEGRALCONST

Real (s)

[1.0E+10]

Description Anti Surge Controller amplification (proportional term). Used for negative deviation from setpoint. Anti Surge Controller amplification (proportional term). Used for positive deviation from setpoint. Initial output signal. Time required to change valve settings or compressor speed from maximum to minimum value. Time from when the measured value is read to when it is used by the controller. Coefficient in front of the derivative term of a PID controller. Coefficient in front of the integral of PID controllers. It represents a characteristic time. N.b., it is the inverse of the coefficient which appears in the expression for the output signal. If the non-linear 451 / 769

OLGA 7

LABEL MANUALOUTPUT

MAXCHANGE

MAXSIGNAL MINSIGNAL

MODE

NORMRANGE

OPENINGTIME

SAMPLETIME SETPOINT

STROKETIME

output signal. If the non-linear option is chosen, this is an array as a function of the ERROR array. Identification label for this String [ASCCONTROLLER_tag] controller. RealList Manual output. Analog controller: Maximum allowed change in controller output signal from one time-step to the next. This restriction is used by the time-step control. If the change in output exceeds this value, OLGA will go back to the previous point in time and integrate with a shorter time-step. Real [0.2] Digital controller: Maximum discrepancy between the instance a sample should be taken and the actual time in the simulation in terms of a fraction of the sample time interval. (E.g., with SAMPLETIME=2.0s and MAXCHANGE=0.2, the maximum discrepancy will be ±0.4s.) Real [1.0] Maximum output signal. Real [0.0] Minimum output signal. AUTOMATIC: The setpoint is defined on the controller. MANUAL: The controller output is given by key MANUALOUTPUT. EXTERNALSIGNAL: The MANUAL | controller output is given by the EXTERNALSIGNAL | SymbolList controller connected to the EXTERNALSETPOINT | SIGNAL terminal. FREEZE | [AUTOMATIC] EXTERNALSETPOINT the setpoint is given by the controller connected to the SETPOINT terminal. FREEZE the controller output is frozen (kept constant). For normalized controllers (used together with AMPLIFICATION). Real Indicates measuring range for input to controller. Time required to change valve Real (s) [10.0] settings or compressor speed from minimum to maximum value. Time interval between each Real (s) sampling of input. Activates digital controller option. RealList Setpoint values. Stroke or actuator time. Time required to change valve settings Real (s) [10.0] or compressor speed from minimum to maximum value and 452 / 769

OLGA 7

TIME

RealList (s)

TIMESTEPCONTROL Symbol

OFF | [ON]

minimum to maximum value and vice versa. Time series for the SETPOINT key. If TIMESTEPCONTROL=OFF the time step control is bypassed. If STROKETIME is less than DTMIN the time step control is also bypassed.

Link to: ASCCONTROLLER Description Keys

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OLGA 7

CASCADECONTROLLER Description ( See also: Keys) A cascade controller (normal or extended) is a PID controller. The cascade controller is used in the inner loop of a cascade control. The output of the primary controller changes the setpoint of the secondary (cascade) controller. A cascade controller has the following terminals: MEASRD

(Required input)

MODE

(Optional input)

SIGNAL

(Optional input)

SETPOINT

(Optional input)

ACTIVATE

(Optional input)

OUTSIG_1..N

(Optional output)

CASCADECONTROLLER Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

AMPLIFICATION

RealList

AVERAGETIME

Real (s)

BIAS

Real

CLOSINGTIME

Real (s)

CONSTONE

Real (1/s)

CONSTSWITCH

Real

CONSTTWO

Real (1/s)

DEFAULTINPUT

Real

DELAY

Real (s)

RealList

[10.0]

[0.0]

Description PID amplification factor. If the nonlinear option is chosen, this is an array as a function of the ERROR array. For use with EXTENDED CASCADE controller. Average time for the moving averaging function of the primary controller variable. Initial output signal. Time required to change valve settings or compressor speed from maximum to minimum value. For use with EXTENDED CASCADE controller: Constant C1. For use with EXTENDED CASCADE controller: Switching value for using C1 and C2. For use with EXTENDED CASCADE controller: Constant C2. Setpoint for INACTIVEMODE=DEFAULTMODE. Time from when the measured value is read to when it is used by the controller. Coefficient in front of the derivative term of PID controllers. If the nonlinear option is chosen, this is an/ 769 454

OLGA 7

DERIVATIVECONST

RealList (s)

ERROR

RealList

EXTENDED

Symbol

INACTIVEMODE

Symbol

INITIALSETPOINT

Real

INTEGRALCONST

RealList (s)

LABEL

String

MANUALOUTPUT

RealList

MAXCHANGE

Real

[0.0]

linear option is chosen, this is an array as a function of the ERROR array. Activate the non-linear option for the PID. Coefficients are given as [0.0] an array of values representing each value in ERROR. Error is the deviation. Select ON to use the EXTENDED ON | [OFF] CASCADE controller. Specifies how the controller act when it is deactivated by a selector, override controller etc. ONHOLD: Restore old values, everything is on hold. INTERLOCK: The PID controller get feedback on the output signal used from the connected controller (Selector or ONHOLD | INTERLOCK | Override). If the PID controller DEFAULTINPUT | NORMAL becomes inactive it will back calculate its integral error to match the output signal of the connected controller. DEFAULTINPUT: Compute output signal based on default input, given in key DEFAULTINPUT. NORMAL: No action. Initial setpoint for extended cascade. Coefficient in front of the integral of PID controllers. It represents a characteristic time. N.b., it is the inverse of the coefficient which [1.0E+10] appears in the expression for the output signal. If the non-linear option is chosen, this is an array as a function of the ERROR array. Identification label for this [CASCADECONTROLLER_tag] controller. Manual output. Analog controller: Maximum allowed change in controller output signal from one time-step to the next. This restriction is used by the time-step control. If the change in output exceeds this value, OLGA will go back to the previous point in time and integrate with a shorter [0.2] time-step. Digital controller: Maximum discrepancy between the instance a sample should be taken and the actual time in the simulation in terms of a fraction of the sample time interval. (E.g., with SAMPLETIME=2.0s and MAXCHANGE=0.2, the maximum discrepancy will be ±0.4s.) 455 / 769

OLGA 7

discrepancy will be ±0.4s.) Maximum setpoint for secondary controller in cascade control loop. Maximum output signal. Minimum setpoint for secondary controller in cascade control loop. Minimum output signal. AUTOMATIC: The setpoint is defined on the controller. MANUAL: The controller output is given by key MANUALOUTPUT. EXTERNALSIGNAL: The controller output is given by the controller connected to the SIGNAL terminal. EXTERNALSETPOINT the setpoint is given by the controller connected to the SETPOINT terminal. FREEZE the controller output is frozen (kept constant). For normalized controllers (used together with AMPLIFICATION). Indicates measuring range for input to controller. Time required to change valve settings or compressor speed from minimum to maximum value. For use with EXTENDED CASCADE controller. Logging time interval for the primary controller variable. Time interval between each sampling of input. Activates digital controller option. Stroke or actuator time. Time required to change valve settings or compressor speed from minimum to maximum value or vice versa.

MAXSETPOINT

Real

MAXSIGNAL

Real

MINSETPOINT

Real

MINSIGNAL

Real

[0.0]

MODE

SymbolList

MANUAL | EXTERNALSIGNAL | FREEZE | [AUTOMATIC]

NORMRANGE

Real

OPENINGTIME

Real (s)

SAMPLEDT

Real (s)

SAMPLETIME

Real (s)

STROKETIME

Real (s)

TIME

RealList (s)

Time series for the SETPOINT key.

TIMESTEPCONTROL Symbol

If TIMESTEPCONTROL=OFF the time step control is bypassed. If STROKETIME is less than DTMIN the time step control is also bypassed.

[1.0]

[10.0]

[10.0]

OFF | [ON]

Link to: CASCADECONTROLLER Description Keys

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OLGA 7

ESDCONTROLLER Description ( See also: Keys) ESD - Emergency shutdown controller. The ESD controller will send a signal intended to close a valve when the measured variable is above or below (depending on the OPENMODE key) the setpoint value. The setpoint is given as a signal or a key. The valve is opened again if RESET is given, and if the measured variable is below or above (depending on the OPENMODE key) the setpoint value. The ESD controller has the following signal terminals: MEASRD_1..N

(Required input)

MODE

(Optional input)

SIGNAL

(Optional input)

SETPOINT

(Optional input)

ACTIVATE

(Optional input)

OUTSIG_1..N

(Optional output)

ESDCONTROLLER Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

CLOSINGTIME

Real (s)

DELAY

Real (s)

LABEL

String

MANUALOUTPUT

RealList

MAXCHANGE

Real

Description

Time required to change valve [10.0] settings or compressor speed from maximum to minimum value. Time from when the measured [0.0] value is read to when it is used by the controller. Identification label for this [ESDCONTROLLER_tag] controller. Manual output. Analog controller: Maximum allowed change in controller output signal from one time-step to the next. This restriction is used by the time-step control. If the change in output exceeds this value, OLGA will go back to the previous point in time and integrate with a shorter time-step. [0.2] Digital controller: Maximum discrepancy between the instance a sample should be taken and the actual time in the simulation in terms of a fraction of the sample time interval. (E.g., with 457 / 769

OLGA 7

time interval. (E.g., with SAMPLETIME=2.0s and MAXCHANGE=0.2, the maximum discrepancy will be ±0.4s.) MAXSIGNAL Real [1.0] Maximum output signal. MINSIGNAL Real [0.0] Minimum output signal. AUTOMATIC: The setpoint is defined on the controller. MANUAL: The controller output is given by key MANUALOUTPUT. EXTERNALSIGNAL: The MANUAL | controller output is given by the EXTERNALSIGNAL | MODE SymbolList controller connected to the EXTERNALSETPOINT | SIGNAL terminal. FREEZE | [AUTOMATIC] EXTERNALSETPOINT the setpoint is given by the controller connected to the SETPOINT terminal. FREEZE the controller output is frozen (kept constant). Time required to change valve OPENINGTIME Real (s) [10.0] settings or compressor speed from minimum to maximum value. For ESD. Either ABOVE or BELOW. Depending on whether OPENMODE Symbol BELOW | [ABOVE] the valve is to close when the signal goes above or below the setpoint. The valve closes if the input variable gets below or exceeds RESET RealList the reset value depending on OPENMODE. Time interval between each SAMPLETIME Real (s) sampling of input. Activates digital controller option. SETPOINT RealList Setpoint values. Stroke or actuator time. Time required to change valve settings STROKETIME Real (s) [10.0] or compressor speed from minimum to maximum value or vice versa. RealList Time series for the SETPOINT TIME (s) key. If TIMESTEPCONTROL=OFF the time step control is bypassed. If TIMESTEPCONTROL Symbol OFF | [ON] STROKETIME is less than DTMIN the time step control is also bypassed. Link to: ESDCONTROLLER Description Keys

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OLGA 7

MANUALCONTROLLER Description ( See also: Keys) The manual controller simulates an operator. It provides a valve opening directly from a user specified series, only dependent on time. The user specified series is given in the setpoint key, or as a setpoint signal. The manual controller limits the setpoint with STROKETIME or CLOSINGTIME/OPENINGTIME. A manual controller has the following signal terminals: MODE

(Optional input)

SIGNAL

(Optional input)

SETPOINT

(Optional input)

ACTIVATE

(Optional input)

OUTSIG_1..N

(Optional output)

MANUALCONTROLLER Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

CLOSINGTIME

Real (s)

LABEL

String

MANUALOUTPUT

RealList

MAXCHANGE

Real

Description

Time required to change valve settings or compressor [10.0] speed from maximum to minimum value. Identification label for this [MANUALCONTROLLER_tag] controller. Manual output. Analog controller: Maximum allowed change in controller output signal from one timestep to the next. This restriction is used by the time-step control. If the change in output exceeds this value, OLGA will go back to the previous point in time and integrate with a shorter time-step. Digital controller: [0.2] Maximum discrepancy between the instance a sample should be taken and the actual time in the simulation in terms of a fraction of the sample time interval. (E.g., with SAMPLETIME=2.0s and 459 / 769

OLGA 7

MAXSIGNAL MINSIGNAL

Real Real

MODE

MANUAL | EXTERNALSIGNAL | SymbolList EXTERNALSETPOINT | FREEZE | [AUTOMATIC]

OPENINGTIME

Real (s)

[10.0]

RANGECHECK

Symbol

ON | [OFF]

SAMPLETIME

Real (s)

SETPOINT

RealList

STROKETIME

Real (s)

TIME

RealList (s)

TIMESTEPCONTROL Symbol

[1.0] [0.0]

[10.0]

OFF | [ON]

SAMPLETIME=2.0s and MAXCHANGE=0.2, the maximum discrepancy will be ±0.4s.) Maximum output signal. Minimum output signal. AUTOMATIC: The setpoint is defined on the controller. MANUAL: The controller output is given by key MANUALOUTPUT. EXTERNALSIGNAL: The controller output is given by the controller connected to the SIGNAL terminal. EXTERNALSETPOINT the setpoint is given by the controller connected to the SETPOINT terminal. FREEZE the controller output is frozen (kept constant). Time required to change valve settings or compressor speed from minimum to maximum value. If RANGECHECK=ON MINSIGNAL and MAXSIGNAL will be used to limit the output signal. Time interval between each sampling of input. Activates digital controller option. Setpoint values. Stroke or actuator time. Time required to change valve settings or compressor speed from minimum to maximum value or vice versa. Time series for the SETPOINT key. If TIMESTEPCONTROL=OFF the time step control is bypassed. If STROKETIME is less than DTMIN the time step control is also bypassed.

Link to: MANUALCONTROLLER Description Keys

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OLGA 7

OVERRIDECONTROLLER Description ( See also: Keys) An override controller is a low select or high select operator. An override controller uses any number of input signals. The input signals are compared, and the minimum/maximum (depending on the SELECTIONMODE key) input signal is chosen as the output signal from the override controller. An override controller has the following signal terminals: MODE

(Optional input)

SIGNAL

(Optional input)

ACTIVATE

(Optional input)

INPSIG_1..N OUTSIG_1..N

(Required input) (Optional output)

OVERRIDECONTROLLER Keys ( See also: Description ) Key

CLOSINGTIME

LABEL MANUALOUTPUT MAXSIGNAL MINSIGNAL

MODE

Type

Parameter set

Unit:( )

Default:[ ]

Description

Time required to change valve settings or compressor speed Real (s) [10.0] from maximum to minimum value. Identification label for this String [OVERRIDECONTROLLER_tag] controller. RealList Manual output. Real [1.0] Maximum output signal. Real [0.0] Minimum output signal. AUTOMATIC: The setpoint is defined on the controller. MANUAL: The controller output is given by key MANUALOUTPUT. EXTERNALSIGNAL: The controller output is given by MANUAL | EXTERNALSIGNAL | SymbolList the controller connected to FREEZE | [AUTOMATIC] the SIGNAL terminal. EXTERNALSETPOINT the setpoint is given by the controller connected to the SETPOINT terminal. FREEZE the controller output is frozen (kept constant). Time required to change valve settings or compressor speed

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OPENINGTIME

Real (s)

SAMPLETIME

Real (s)

[10.0]

SELECTIONMODE Symbol

HIGH | [LOW]

STROKETIME

Real (s)

[10.0]

TIME

RealList (s)

settings or compressor speed from minimum to maximum value. Time interval between each sampling of input. Activates digital controller option. An override controller selects either minimum or maximum of the signals from all the subcontrollers. Key SELECTIONMODE determines the selection of minimum or maximum signal. Stroke or actuator time. Time required to change valve settings or compressor speed from minimum to maximum value or vice versa. Time series for the SETPOINT key.

Link to: OVERRIDECONTROLLER Description Keys

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OLGA 7

PIDCONTROLLER Description ( See also: Keys) PID (Proportional-Integral-Derivative) controllers are designed to maintain a specified value (given by a setpoint signal or key) for a measured flow variable (given as an input signal). The user can specify if the controller is linear or non-linear. If a controller is non-linear, the user has to give tables for specifying the amplification factors, integral time constants, and derivative time constants as functions of the error input. The PID controller has the following signal terminals: MEASRD

(Required input)

MODE

(Optional input)

SIGNAL

(Optional input)

SETPOINT

(Optional input)

ACTIVATE

(Optional input)

WINDUP

(Optional input)

OUTSIG_1..N

(Optional output)

PIDCONTROLLER Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

AMPLIFICATION

RealList

BIAS

Real

CLOSINGTIME

Real (s)

DEFAULTINPUT

Real

DELAY

Real (s)

[0.0]

DERIVATIVECONST

RealList (s)

[0.0]

[10.0]

Description PID amplification factor. If the nonlinear option is chosen, this is an array as a function of the ERROR array. Initial output signal. Time required to change valve settings or compressor speed from maximum to minimum value. Setpoint for INACTIVEMODE=DEFAULTMODE. Time from when the measured value is read to when it is used by the controller. Coefficient in front of the derivative term of PID controllers. If the nonlinear option is chosen, this is an array as a function of the ERROR array. 463 / 769

OLGA 7

ERROR

RealList

INACTIVEMODE

Symbol

INTEGRALCONST

RealList (s)

LABEL

String

MANUALOUTPUT

RealList

MAXCHANGE

Real

MAXSIGNAL MINSIGNAL

Real Real

array. Activate the non-linear option for the PID. Coefficients are given as [0.0] an array of values representing each value in ERROR. Error is the deviation. Specify how the controller acts when it is deactivated by a selector, override controller etc. ONHOLD: Restore old values, everything is on hold. INTERLOCK: The PID controller gets feedback on the output signal used from the ONHOLD | INTERLOCK connected controller (Selector or | DEFAULTINPUT | Override). If the PID controller NORMAL becomes inactive it will back calculate its integral error to match the output signal of the connected controller. DEFAULTINPUT: Compute output signal based on default input, given in key DEFAULTINPUT. NORMAL: no action. Coefficient in front of the integral of PID controllers. It represents a characteristic time. N.b., it is the inverse of the coefficient which [1.0E+10] appears in the expression for the output signal. If the non-linear option is chosen, this is an array as a function of the ERROR array. Identification label for this [PIDCONTROLLER_tag] controller. Manual output. Analog controller: Maximum allowed change in controller output signal from one time-step to the next. This restriction is used by the time-step control. If the change in output exceeds this value, OLGA will go back to the previous point in time and integrate with a shorter [0.2] time-step. Digital controller: Maximum discrepancy between the instance a sample should be taken and the actual time in the simulation in terms of a fraction of the sample time interval. (E.g., with SAMPLETIME=2.0s and MAXCHANGE=0.2, the maximum discrepancy will be ±0.4s.) [1.0] Maximum output signal. [0.0] Minimum output signal. 464 / 769

OLGA 7

AUTOMATIC: The setpoint is defined on the controller. MANUAL: The controller output is given by key MANUALOUTPUT. MANUAL | EXTERNALSIGNAL: The controller EXTERNALSIGNAL | output is given by the controller MODE SymbolList EXTERNALSETPOINT | connected to the SIGNAL terminal. FREEZE | EXTERNALSETPOINT the setpoint [AUTOMATIC] is given by the controller connected to the SETPOINT terminal. FREEZE the controller output is frozen (kept constant). For normalized controllers (used together with AMPLIFICATION). NORMRANGE Real Indicates measuring range for input to controller. Time required to change valve OPENINGTIME Real (s) [10.0] settings or compressor speed from minimum to maximum value. Time interval between each SAMPLETIME Real (s) sampling of input. Activates digital controller option. SETPOINT RealList Setpoint values. Stroke or actuator time. Time required to change valve settings STROKETIME Real (s) [10.0] or compressor speed from minimum to maximum value or vice versa. RealList TIME Time series for the SETPOINT key. (s) If TIMESTEPCONTROL=OFF the time step control is bypassed. If TIMESTEPCONTROL Symbol OFF | [ON] STROKETIME is less than DTMIN the time step control is also bypassed. Link to: PIDCONTROLLER Description Keys

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OLGA 7

PSVCONTROLLER Description ( See also: Keys) A Pressure Safety Valve controller (PSV) opens a valve when the pressure at a specified position (given by a measured signal) is above or below (depending on SETPOINTMODE) the setpoint value. The setpoint can be given as a key or as an input signal. The PSV controller closes the valve when the pressure is below or above (depending on SETPOINTMODE) a specified RESET value. The PSV controller has the following signal terminals: MEASRD_1..N

(Required input)

MODE

(Optional input)

SIGNAL

(Optional input)

SETPOINT

(Optional input)

ACTIVATE

(Optional input)

OUTSIG_1..N

(Optional output)

PSVCONTROLLER Keys ( See also: Description ) Type

Parameter set

Unit:( )

Default:[ ]

CLOSINGTIME

Real (s)

[10.0]

DELAY

Real (s)

LABEL

String

MANUALOUTPUT

RealList

MAXCHANGE

Real

Key

Description

Time required to change valve settings or compressor speed from maximum to minimum value. Time from when the measured [0.0] value is read to when it is used by the controller. Identification label for this [PSVCONTROLLER_tag] controller. Manual output. Analog controller: Maximum allowed change in controller output signal from one time-step to the next. This restriction is used by the time-step control. If the change in output exceeds this value, OLGA will go back to the previous point in time and integrate with a shorter time-step. [0.2] Digital controller: Maximum discrepancy between the instance a sample should be taken and the actual time in the simulation in466 / 769

OLGA 7

actual time in the simulation in terms of a fraction of the sample time interval. (E.g., with SAMPLETIME=2.0s and MAXCHANGE=0.2, the maximum discrepancy will be ±0.4s.) MAXSIGNAL Real [1.0] Maximum output signal. MINSIGNAL Real [0.0] Minimum output signal. AUTOMATIC: The setpoint is defined on the controller. MANUAL: The controller output is given by key MANUALOUTPUT. EXTERNALSIGNAL: The MANUAL | controller output is given by the EXTERNALSIGNAL | MODE SymbolList controller connected to the EXTERNALSETPOINT | SIGNAL terminal. FREEZE | [AUTOMATIC] EXTERNALSETPOINT the setpoint is given by the controller connected to the SETPOINT terminal. FREEZE the controller output is frozen (kept constant). Time required to change valve OPENINGTIME Real (s) [10.0] settings or compressor speed from minimum to maximum value. Either ABOVE or BELOW. Depending on whether the valve OPENMODE Symbol BELOW | [ABOVE] is to close when the signal goes above or below the setpoint. The valve closes if the input variable gets below or exceeds RESET RealList the reset value depending on OPENMODE. Time interval between each SAMPLETIME Real (s) sampling of input. Activates digital controller option. SETPOINT RealList Setpoint values. Stroke or actuator time. Time required to change valve settings STROKETIME Real (s) [10.0] or compressor speed from minimum to maximum value or vice versa. RealList Time series for the SETPOINT TIME (s) key. If TIMESTEPCONTROL=OFF the time step control is bypassed. If TIMESTEPCONTROL Symbol OFF | [ON] STROKETIME is less than DTMIN the time step control is also bypassed. Link to: PSVCONTROLLER Description Keys

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OLGA 7

SCALERCONTROLLER Description ( See also: Keys) The main purpose of a SCALER controller is to scale the measured signal from range LOWLIMIT..HIGHLIMIT to range MINSIGNAL..MAXSIGNAL. Output U is set: U = (Y -LOWLIMIT)/(HIGHLIMIT - LOWLIMIT)*(MAXSIGNAL-MINSIGNAL) + MINSIGNAL where Y is the measured signal, value at the MEASRD terminal. A scaler controller has the following terminals: MEASRD

(Required input)

OUTSIG_1..N

(Optional output)

SCALERCONTROLLER Keys ( See also: Description ) Type Key BIAS CLOSINGTIME

DELAY HIGHLIMIT LABEL LOWLIMIT MAXSIGNAL MINSIGNAL OPENINGTIME

STROKETIME

Parameter set Unit:( Default:[ ] ) Real

Description

[0.0]

Initial output signal. Time required to change valve settings Real [10.0] or compressor speed from maximum to (s) minimum value. Time from when the measured value is Real [0.0] read to when it is used by the (s) controller. Real High limit for measured signal. String [SCALERCONTROLLER_tag] Identification label for this controller. Real Low limit for measured signal. Real [1.0] Maximum output signal. Real [0.0] Minimum output signal. Time required to change valve settings Real [10.0] or compressor speed from minimum to (s) maximum value. Stroke or actuator time. Time required Real to change valve settings or compressor [10.0] (s) speed from minimum to maximum value or vice versa.

Link to: SCALERCONTROLLER Description Keys

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OLGA 7

SELECTORCONTROLLER Description ( See also: Keys) The selector controller has two sub controllers, SUBCONLOW and SUBCONHIGH. The selector controller switches between these sub-controllers depending of the low and high limits given as input through the HIGHLIMITSIG and LOWLIMITSIG signal terminals. A sub-controller that is active due to a limit being reached stays active until another limit is reached. Then another sub-controller takes over, and stays active until yet another limit is reached. Any number of limits (HIGHLIMITSIG/LOWLIMITSIG) can be given. A selector controller has the following signal terminals: SUBCONLOW

(Required input)

SUBCONHIGH

(Required input)

HIGHLIMITSIG_1..N

(Required input)

LOWLIMITSIG_1..N

(Required input)

MODE

(Optional input)

SIGNAL

(Optional input)

ACTIVATE

(Optional input)

OUTSIG_1..N

(Optional output)

SELECTORCONTROLLER Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

CLOSINGTIME

Real (s)

[10.0]

DELAY

Real (s)

[0.0]

Description Time required to change valve settings or compressor speed from maximum to minimum value. Time from when the measured value is read to when it is used by the controller. HIGHLIMIT is compared with the HIGHLIMITSIG signal input. If the signal from SUBCONLOW is used, the controller will switch to the SUBCONHIGH signal if

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SUBCONHIGH signal if HIGHLIMITSIG > HIGHLIMIT. If multiple HIGHLIMIT/HIGHLIMITSIG is given, the controller will loop all connections and test if HIGHLIMITSIG_i > HIGHLIMIT[i] Active sub-controller at the start of the simulation. Has INITIALCONTROLLER Symbol SUBCONHIGH | SUBCONLOW to refer to a SUBCON terminal. Identification label for this LABEL String [SELECTORCONTROLLER_tag] controller. LOWLIMIT is compared with the LOWLIMITSIG signal input. If the signal from SUBCONHIGH is used, the controller will switch to the SUBCONLOW signal if LOWLIMIT RealList LOWLIMITSIG < LOWLIMIT. If multiple LOWLIMIT/LOWLIMITSIG is given, the controller will loop all connections and test if LOWLIMITSIG_i < LOWLIMIT[i]. MANUALOUTPUT RealList Manual output. MAXSIGNAL Real [1.0] Maximum output signal. MINSIGNAL Real [0.0] Minimum output signal. AUTOMATIC: The setpoint is defined on the controller. MANUAL: The controller output is given by key MANUALOUTPUT. EXTERNALSIGNAL: The controller output is given by the controller MANUAL | EXTERNALSIGNAL | MODE SymbolList connected to the SIGNAL FREEZE | [AUTOMATIC] terminal. EXTERNALSETPOINT the setpoint is given by the controller connected to the SETPOINT terminal. FREEZE the controller output is frozen (kept constant). Time required to change valve settings or OPENINGTIME Real (s) [10.0] compressor speed from minimum to maximum value. HIGHLIMIT

RealList

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SAMPLETIME

Real (s)

STROKETIME

Real (s)

TIME

RealList (s)

[10.0]

Time interval between each sampling of input. Activates digital controller option. Stroke or actuator time. Time required to change valve settings or compressor speed from minimum to maximum value or vice versa. Time series for the SETPOINT key.

Link to: SELECTORCONTROLLER Description Keys

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STDCONTROLLER Description ( See also: Keys) The STDController converts mass flow rate to volumetric flow rate at standard conditions. Set correct phase in PHASE key. Specify the fluid in the FLUID or FEEDNAME keys. Specify the wanted GOR/CGR/WGR/WATERCUT/MOLWEIGHT, and the overall mass flow rate will be calculated. Connect the STDController output terminal OUTSIG to an PID controller MEASRD terminal.

STDCONTROLLER Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

Description

Condensate-gas ratio. The default value is the equilibrium value from PVT data. FEEDMASSFRACTION RealList Mass fraction of each feed. FEEDMOLEFRACTION RealList Mole fraction of each feed. Label of feeds feeding to terminal nodes. Requires FEEDNAME SymbolList FEED-1 | BOFEED-1 COMPOSITIONAL=ON or BLACKOIL under the OPTIONS keyword. Volume fraction of each feed FEEDVOLFRACTION RealList given in FEEDNAME for choke model (only for Blackoil model). Label or number of fluid table to apply for the specific branch. If a keyword based pvt-file is used, FLUID Symbol FLUID must be the same as the LABEL given in the pvt-file, i.e., numbering is not valid for this format. Real Gas/liquid volumetric flow ratio GLR (Sm3/Sm3) at standard conditions. Gas/oil volumetric flow ratio at Real standard conditions. By default, GOR [-1.0] (Sm3/Sm3) the GOR from the PVT table is used. Identification label for this LABEL String [STDCONTROLLER_tag] controller. Molecular weight of equivalent gas (total flow). By default, the Real gas density at standard MOLWEIGHT (kg/kmol) conditions from the PVT table is used to determine the molecular weight. Sm3/h | Sm3/d | scf/d | MMscf/d | STB/d | CGR

Real (Sm3/Sm3)

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OLGA 7

MMscf/d | STB/d | STB/M | scf/s | scf/h | MSm3/d | Mscf/d | [Sm3/s] GAS | OIL | WATER | LIQUID | ALL

OUTPUTUNIT

Symbol

PHASE

Symbol

WATERCUT

Real

WGR

Real [-1.0] (Sm3/Sm3)

[-1.0]

Unit of controller output.

The phase for which the volumetric flow rate is specified. Water volume fraction in oil/water mixture. With a value of -1.0 the total water fraction is taken from the fluid table. Water-gas ratio.

Link to: STDCONTROLLER Description Keys

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OLGA 7

SWITCHCONTROLLER Description ( See also: Keys) The main purpose of the switch controller is to switch between alternative inputs values. The output of the controller is selected based on the setpoint in MODE = AUTOMATIC or SETPOINT terminal if MODE = EXTERNALSETPOINT. SP < 1.5

unconstrained output A is set equal to controller at terminal INPSIG_1

1.5 <= SP < 2.5

unconstrained output A is set equal to controller at terminal INPSIG_2

2.5 <= SP < 3.5

unconstrained output A is set equal to controller at terminal INPSIG_3

…. (Ni-0.5) <= SP

unconstrained output A is set equal to controller at terminal INPSIG_N

Where Ni is the number of connected input terminals INPSIG A switch controller has the following terminals: INPSIG_1..Ni

(Required input)

MODE

(Optional input)

SIGNAL

(Optional input)

SETPOINT

(Optional input)

ACTIVATE

(Optional input)

OUTSIG_1..N

(Optional output)

SWITCHCONTROLLER Keys ( See also: Description ) Type

Parameter set

Unit:( )

Default:[ ]

BIAS

Real

[0.0]

CLOSINGTIME

Real (s)

DELAY

Real (s)

LABEL

String

Key

MANUALOUTPUT RealList MAXSIGNAL Real MINSIGNAL Real

Description

Initial output signal. Time required to change valve [10.0] settings or compressor speed from maximum to minimum value. Time from when the measured [0.0] value is read to when it is used by the controller. Identification label for this [SWITCHCONTROLLER_tag] controller. Manual output. [1.0] Maximum output signal. [0.0] Minimum output signal. 474 / 769

OLGA 7

MODE

MANUAL | EXTERNALSIGNAL | SymbolList EXTERNALSETPOINT | FREEZE | [AUTOMATIC]

OPENINGTIME

Real (s)

SETPOINT

RealList

STROKETIME

Real (s)

TIME

RealList (s)

[10.0]

[10.0]

AUTOMATIC: The setpoint is defined on the controller. MANUAL: The controller output is given by key MANUALOUTPUT. EXTERNALSIGNAL: The controller output is given by the controller connected to the SIGNAL terminal. EXTERNALSETPOINT the setpoint is given by the controller connected to the SETPOINT terminal. FREEZE the controller output is frozen (kept constant). Time required to change valve settings or compressor speed from minimum to maximum value. Setpoint values. Stroke or actuator time. Time required to change valve settings or compressor speed from minimum to maximum value or vice versa. Time series for the SETPOINT key.

Link to: SWITCHCONTROLLER Description Keys

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OLGA 7

TABLECONTROLLER Description ( See also: Keys) A table controller uses the input signal (terminal INPSIG) as lookup variable, x, in a table. The controller output is y = f(x). The look-up function is linear interpolation. The table controller has the following terminals: INPSIG

(Required input)

OUTSIG_1..N

(Optional output)

TABLECONTROLLER Keys ( See also: Description ) Key BIAS CLOSINGTIME DELAY LABEL MAXSIGNAL MINSIGNAL OPENINGTIME

STROKETIME

TABLE

Type

Parameter set

Unit:( ) Default:[ ] Real

Description

[0.0]

Initial output signal. Time required to change valve settings Real [10] or compressor speed from maximum to (s) minimum value. Real Time from when the measured value is [0.0] (s) read to when it is used by the controller. String [TABLECONTROLLER_tag] Identification label for this controller. Real [1.0] Maximum output signal. Real [0.0] Minimum output signal. Time required to change valve settings Real [10] or compressor speed from minimum to (s) maximum value. Stroke or actuator time. Time required Real to change valve settings or compressor [10] (s) speed from minimum to maximum value or vice versa. Label of the table. The table consist of x Symbol and y. Input signal x1 gives output signal y1 by table interpolation.

Link to: TABLECONTROLLER Description Keys

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OLGA 7

OUTPUTDATA (on ASCCONTROLLER) Description ( See also: Keys) This statement defines the controller variables to be printed to the output file (*.out). See Controller Output Variables for available variables.

OUTPUTDATA (on ASCCONTROLLER) Keys ( See also: Description ) Key

VARIABLE

Type Unit:( ) SymbolList (ValueUnitPair)

Parameter set

Description

Default:[ ] List of variables to be printed. Units may be specified.

Link to: OUTPUTDATA (on ASCCONTROLLER) Description Keys

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OLGA 7

TRENDDATA (on ASCCONTROLLER) Description ( See also: Keys) This statement defines the trend data to be plotted for controllers. A trend plot is a time series plot for a specified variable. For available variables see Controller Output Variables.

TRENDDATA (on ASCCONTROLLER) Keys ( See also: Description ) Key

VARIABLE

Type Unit:( ) SymbolList (ValueUnitPair)

Parameter set

Description

Default:[ ] List of variables to be plotted. Units may be specified.

Link to: TRENDDATA (on ASCCONTROLLER) Description Keys

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OLGA 7

FLUID (on CASELevel) Description ( See also: Keys) This statement enables the use of the complex viscosity model and the complex fluid model for simulation of non-Newtonian flows and high viscosity liquids. The complex fluid model The Complex Fluid module requires a separate license. The module utilizes either the Bingham, the power law or a Newtonian model. As opposed to the complex viscosity model, the complex fluid model includes numerous modifications to the physical models for both separated and distributed flow taking into account the non-Newtonian behavior of the fluids. As soon as TYPE is set to COMPLEXFLUID the modified physical models are used, even if CFLUML or CFLUMW are set to NEWTONIAN. Due to limited testing against Newtonian data, the complex fluid model is not recommended used on gas-condensate and oil-gas systems with oil viscosity less than 50 cp. For the complex fluid model, the fluid properties can be given in two ways, simple or full (FULL = YES). In the simple mode the power law exponent or yield stress is given in the main input file. In the full mode, the power law exponent or the yield stress is given as a function of pressure and temperature in the fluid property table file specified in PVTFILE in FILES. This implies that the FLUID keyword must be given above the FILES keyword in the OLGA input file since the fluid property files are read as soon as OLGA reads the FILES keyword. In all cases the hydrocarbon liquid and/or the water viscosity part of the usual PVT file is used. In the power law formulation it is used as the consistency factor K, and in the Bingham formulation it is used as the coefficient of rigidity. Therefore, setting CFLUML = NEWTONIAN is equivalent to CFLUML = BINGHAM with YIELDSTRL = 0, and CFLUML = POWERLAW with POWEXPL = 1.

FLUID (on CASELevel) Keys ( See also: Description ) Key

CFLUML

CFLUMW

Type

Unit:( ) Default:[ ] BINGHAM | Symbol POWERLAW | [NEWTONIAN] BINGHAM | Symbol POWERLAW | [NEWTONIAN]

CONSFL

Real

CONSFW

Real

CVISL

Parameter set

Description Type of complex fluid model of the liquid hydrocarbon phase. Type of complex fluid model of the water phase. Consistency factor for hydrocarbon liquid in the complex viscosity model. Consistency factor for water phase in the complex viscosity model.

BINGHAM | POWERLAW | Type of complex viscosity model of the Symbol HERSCHELBUCKLEY liquid hydrocarbon phase. 479 / 769

OLGA 7

CVISL

CVISW

FULL

PLASTL

PLASTW

POWEXPL

POWEXPW

TYPE

YIELDSTRL YIELDSTRW

Symbol

HERSCHELBUCKLEY liquid hydrocarbon phase. | [NEWTONIAN] BINGHAM | POWERLAW | Type of complex viscosity model of the Symbol HERSCHELBUCKLEY water phase. | [NEWTONIAN] Whether or not to use power exponent/yield Symbol YES | [NO] stress as function of P and T from the fluid property file in a complex fluid model. Real Hydrocarbon liquid plastic viscosity, used in (Nthe complex viscosity model. s/m2) Real Water plastic viscosity used in the complex (Nviscosity model. s/m2) Exponent for hydrocarbon liquid phase Real model, used in both the complex viscosity and complex fluid model. Exponent for water phase model, used in Real both the complex viscosity and complex fluid model. COMPLEXFLUID | Symbol COMPLEXVISCOSITY Fluid model type. | [NEWTONIAN] Yield stress for hydrocarbon liquid phase in Real the complex viscosity and complex fluid (Pa) models. Real Yield stress for water phase in the complex (Pa) viscosity and complex fluid models.

Link to: FLUID (on CASELevel) Description Keys

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OLGA 7

SINGLEOPTIONS (on CASELevel) Description ( See also: Keys) This statement defines options for simulation of single component systems in OLGA, turned on by specifying COMPOSITIONAL=SINGLE in keyword OPTIONS. There are three single component systems that can be specified. These are H2O, CO2 and OTHER, and is specified by key COMPONENT in SINGLEOPTIONS . For COMPONENT equal H2O and CO2 most physical parameters are implemented in OLGA, while for COMPONENT=OTHER the user needs to specify these parameters in SINGLEOPTIONS. Note: The availability of the single component module depends on the User's licensing agreement with SPT Group.

SINGLEOPTIONS (on CASELevel) Keys ( See also: Description ) Type

Parameter set

Unit:( )

Default:[ ]

COMPONENT

Symbol

H2O | CO2 | OTHER

CPIC

RealList

MAXPRESSURE

Real (Pa)

Key

MAXTEMPERATURE Real (C) MINPRESSURE

Real (Pa)

MINTEMPERATURE Real (C) MW

Real (g/mol)

OMEGA

Real

PC

Real (Pa)

TBOILING

RealList (s) [1.0]

TC

Real (C)

TCONDENSATION

RealList (s) [1.0]

TIME

RealList (s) [0.0]

VISX

Real

[1.0]

Description Name of single-component. Coefficients in equation for specific heat. Only for SINGLECOMPONENT=OTHER. Maximum pressure for PVT table generated. Maximum temperature for PVT table generated. Minimum pressure for PVT table generated. Minimum temperature for PVT table generated. Molecular weight. Only for SINGLECOMPONENT=OTHER. Accentric factor. Only for SINGLECOMPONENT=OTHER. Critical pressure. Only for SINGLECOMPONENT=OTHER. Time constant for mass transfer from liquid phase to gas phase due to boiling for component. (Non-equilibrium delay constant). Critical temperature. Only for SINGLECOMPONENT=OTHER. Time constant for mass transfer from gas phase to liquid phase for the component. (Non-equilibrium delay constant). Time points for which TBOILING and TCONDENSATION changes. Viscosity tuning factor. Only for SINGLECOMPONENT=OTHER. Volume tuning factor. Only for 481 / 769

OLGA 7

VOLX

RealList

[0.0]

Volume tuning factor. Only for SINGLECOMPONENT=OTHER.

Link to: SINGLEOPTIONS (on CASELevel) Description Keys

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OLGA 7

SLUGTRACKING (on CASELevel) Description ( See also: Keys) This statement defines the slug tracking option. This statement has two main sub-options for initiation of liquid slugs: the level slug option (LEVEL) and the hydrodynamic slug option (HYDRODYNAMIC). These two options may be used together or separately. Terrain slugging will be detected in ordinary simulations without the slug tracking module, and the interactions between terrain and hydrodynamic slugging can be investigated using the key HYDRODYNAMIC. The level slug option is mostly used for startup-slugs. If HYDRODYNAMIC = ON, the code will set up a new slug in a section whenever the set-up criteria are fulfilled. These are: (1) Flow regime at the section boundary changes from separated to slug flow. (2) Other slug fronts are the required distance away. (3) The time elapsed since the previous slug was generated in or passed this section is higher than a specified minimum time. If HYDRODYNAMIC = MANUAL, the user can specify a fixed number of slugs to be set up at predefined positions and times. Using this option, liquid will be injected into the pipeline to generate slugs of required size. Slugs are not allowed to be generated at the inlet and outlet sections by default. That is, the boundary sections are automatically set to illegal for slugs by the program itself. However, the slug front is allowed to move into the outlet section, and the slug tail into the inlet section. Users can specify the sections where slugs are not allowed to be generated by using SLUGILLEGAL keyword. The slug tracking option offers full temperature calculation capabilities. Remark: The availability of the slug tracking option depends on the user’s licensing agreement with SPT Group. To turn off slug-tracking in a restart there are two possibilities: (1) Set both LEVEL and HYDRODYNAMIC to OFF. Then the only slugs in the system will be the ones read from restart. (2) Remove SLUGTRACKING keyword. Average values will be used in the sections. No slugs in the simulation. More details can be found in the description of the slug tracking module.

SLUGTRACKING (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

BUBBLEVOID

Real

DELAYCONSTANT

Real

[150]

Description Minimum void required behind a level tail and ahead of a level front at initiation time Number of pipe diameters a slug needs to propagate before the next hydrodynamic slug is initiated. 483 / 769

OLGA 7

ENDTIME

Real (s)

GASENTRAINMENT Symbol

NYDAL | [VOIDINSLUG]

End time for level slug initiation. If not given no end time restriction is enforced. Gas entrainment into slug from bubble for breaking/level front in slug tracking. NYDAL: Nydal correlation for entrainment. VOIDINSLUG: Entrainment based on correlation for void in slug.

ON | MANUAL | Option for initiating hydrodynamic slugs. [OFF] INITBUBBLEVOIDS RealList [1] Void fractions in the slug bubbles. INITENDTIMES RealList (s) End times for slug generation. The minimum distance between two INITFREQUENCY Real (1/s) consecutive slugs is defined as (bubble vel./INITFREQUENCY). Maximum initial length of hydrodynamic INITLENGTH Real slugs in number of pipe diameters. Time interval between initiations of INITPERIODS RealList (s) consecutive slugs. Labels of section boundaries where slug INITPOSITIONS SymbolList generation zones are located. INITSLUGVOIDS RealList [0.0] Void fraction in the liquid slug. INITSTARTTIMES RealList (s) Start times for slug generation. RealList The length of zones where slugs are to be INITZONELENGTHS (m) generated. Option for detecting and initiating level LEVEL Symbol ON | [OFF] slugs. Max number of slugs allowed in the system, MAXNOSLUGS Integer if not given there are no restrictions. The maximum void allowed in a level slug at SLUGVOID Real initiation time. Start time for level slug initiation. If not STARTTIME Real (s) given, level detection is on from simulation start. HYDRODYNAMIC

Symbol

Link to: SLUGTRACKING (on CASELevel) Description Keys

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OLGA 7

SLUGTUNING (on CASELevel) Description ( See also: Keys) This statement defines the slug tuning option, witch makes it possible to tune certain parameters in the slug model. The parameters available for tuning are at the moment very limited. Remark: The availability of the slug tuning option depends on the user’s licensing agreement with SPT Group. The SLUGTUNING keyword may be used for adjusting the OLGA model to specific sets of measured data or for sensitivity studies. This keyword is available both in batch and server mode. SLUGTUNING should be applied with great care, as the validation and verification of the OLGA model may not be valid for such cases.

SLUGTUNING (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

DPFACT

Real

[1.0]

DPONSET

Real

[1.0]

SLUGLENGTH

Real

[1e+09]

UBCOEFF1

Real

[1.0]

UBCOEFF2

Real

[1.0]

VOIDINSLUG

Real

[1.0]

VOIDINVERTSLUG Real

[1.0]

Description Tuning coefficient for slug front pressure drop (with and without SLUGTRACKING). Has no effect for a large value of SLUGLENGTH when not SLUGTRACKING. Tuning coefficient for onset of slug front pressure drop (with and without SLUGTRACKING). The slug front pressure drop is set to 0 when the film velocity in the slug bubble region is larger than a certain critical velocity which can be tuned. Slug length (number of diameters) in slug front pressure drop correlation for unit cell model (ignored for SLUGTRACKING).dP/dz is inversly proporsional to SLUGLENGHT. Tuning coefficient 1 in Taylor bubble velocity calculation (with and without SLUGTRACKING). Tuning coefficient 2 in Taylor bubble velocity calculation (with and without SLUGTRACKING). Tuning coefficient for void in horizontal slug (with and without SLUGTRACKING). Tuning coefficient for void in vertical slug (with and without SLUGTRACKING).

Link to: SLUGTUNING (on CASELevel) Description Keys

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OLGA 7

WATEROPTIONS (on CASELevel) Description ( See also: Keys) In WATEROPTIONS several options are available for modeling the dispersion viscosity (DISPERSIONVISC) and the slip between the water and oil phases (WATERSLIP). If WATERSLIP = CONSTANT, the slip between the oil and water phases must be specified with VELOCITYDIFFERENCE. If WATERSLIP = ON, the velocities of liquid hydrocarbon and water is calculated by separate momentum balance equations. DISPERSIONVISC specifies which model is used to calculate the dispersion phase viscosity. If DISPERSIONVISC= OFF, a continuous phase is assumed (no dispersion). If DISPERSIONVISC = PALRHODES, PHI100 - value of the dispersed phase volume fraction when the relative viscosity = 100% - must be specified. The relative viscosity is the viscosity of the dispersed phase divided by the viscosity of the continuous phase. If DISPERSIONVISC = EXPERIMENT, values for the dispersed phase volume fraction (PHIREL) for each given value of the relative viscosity (VISCREL) must be specified. If DISPERSIONVISC = VOLUMEAVERAGE, the user may specify values for the viscosity tuning factor (VISCMOD) corresponding to given WATERCUT (volume fraction of water in the liquid phase) values. The flowing water volume fraction inversion point (INVERSIONWATERFRAC) can be specified for any Dispersion Viscosity model.

WATEROPTIONS (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( ) Default:[ ]

AWOELFLIN BWOELFLIN

Real Real

[4.2] [2.5]

DISPERSIONVISC

Symbol OFF | [ON]

DISPMODEL

RONNINGSEN | EXPERIMENT Symbol | WOELFLIN | BARNEA | INPUTVISC | [PALRHODES]

Description Constant A in Woelflin viscosity correlation Constant B in Woelflin viscosity correlation ON: Dispersion viscosity calculated according to DISPMODEL settings. OFF: Viscosity volume weighting if WATERSLIP = OFF or CONSTANT. Viscosity from tables for continuous phase is used if WATERSLIP = ON. Specify which model to be used to calculate the dispersion viscosity (DISPERSIONVISC=ON). For further details see User's manual. 486 / 769

OLGA 7

EMAX

Real

[1.0]

ENTRAINMENTFACTOR Real

[1.0]

FWLOW

Real

[0.0]

INVERSIONWATERFRAC Real

[0.5]

PHI100

Real

[0.765]

PHIREL

Real

[0.0]

VELOCITYDIFFERENCE

Real (m/s)

[0.0]

VISCMOD

RealList

VISCREL

Real

WATERCUT

RealList

WATERSLIP

OFF | Symbol CONSTANT | [ON]

[0.0]

Maximum fraction of water dispersed for FWLOW < WC < INVERSIONWATERFRAC Scaling factor for water entrainment rate from bulk to droplets Critical water fraction above which the fraction of the water dispersed into oil < EMAX Flowing water volume fraction at inversion point. Dispersed phase volume fraction when the relative viscosity (visc. of dispersed phase/ visc. of continuous phase) is 100%. Dispersed phase volume fraction given the relative viscosity (VISCREL). Used if DISPMODEL=EXPERIMENT. Define the velocity difference between the oil and water phases. Viscosity tuning factors corresponding to given WATERCUT values. Used if DISPERSIONVISC=OFF. Relative viscosity for a given dispersed phase volume fraction (PHIREL). Used if DISPMODEL=EXPERIMENT. Watercut values corresponding to a given viscosity tuning factor (VISCMOD). Used if DISPERSIONVISC=OFF. ON: Oil/water slip velocity is calculated within the flow model. OFF: No velocity difference. CONSTANT: A constant velocity difference between oil and water is specified. Should be used with great care.

Link to: WATEROPTIONS (on CASELevel) Description Keys

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OLGA 7

NODE Description ( See also: Keys) This statement defines the nodes in the flow network system. All nodes except CLOSED nodes need a fluid for fluid properties calculations. There are four types of nodes: CLOSED: The node represents a closed boundary (zero flow). This can be combined with a source or a well definition in the flow path. PRESSURE: The node represents a pressure boundary. Values for pressure, temperature and fluid must be given. INTERNAL: For definition of internal node. Fluid must be given. The model for internal nodes (merge/split nodes) uses more or less the same physics and the numerical methods as the sections in the pipes. Pressure, temperature and masses are calculated. Interphasial mass transfer is included in the node, but entrainment/deposition of liquid droplets are ignored. The current implementation of internal nodes require a finite volume in the node. If no volume is specified (or given as less than or equal to zero), a default volume is calculated by OLGA based on the sizes of incoming and outgoing sections:

where i is taken over all incoming/outgoing sections. It should be noted that the node does not account for heat lost to the surroundings. MASSFLOW: The node represents a mass flow boundary. Values for pressure, temperature, fluid and mass flow or standard mass flow must be given. The behaviour of the MASSFLOW node is very similar to a mass source. The main exception is that the MASSFLOW node has an internal pressure calculation for obtaining the correct pressure that will set up the user given mass flow rate into the connected pipe.

NODE Keys ( See also: Description ) Key

Type Unit:( )

CGR

RealList (Sm3/Sm3)

DENSITY

RealList (kg/m3)

Parameter set

Description

Default:[ ] Condensate-gas ratio. By default, CGR from the PVT table is used. Density of the drilling fluid for each time point. Must be within the min and max density as specified in the keyword DRILLINGFLUID Refer to the drilling fluid defined by the keyword DRILLINGFLUID. Requires 488 / 769

OLGA 7

DRILLINGFLUID

FEEDMASSFLOW FEEDMASSFRACTION FEEDMOLEFLOW FEEDMOLEFRACTION FEEDNAME

FEEDSTDFLOW

FEEDVOLFRACTION

FLUID

FLUIDTYPE

GASFRACEQ

GASFRACTION

GLR GOR INFO INHIBFRACTION LABEL LINE

Symbol

keyword DRILLINGFLUID. Requires access to the Wells module. Mass rate for each feed (used when RealList mass source is defined). One item per (kg/s) time and feed. RealList Mass fraction of each feed. Mole rate for each feed (used when mass RealList source is defined). One item per time and (kmol/s) feed. RealList Mole fraction of each feed. Label of feeds feeding to terminal nodes. FEED-1 | SymbolList Requires COMPOSITIONAL=ON or BOFEED-1 BLACKOIL under the OPTIONS keyword. Volumetric flow rate at standard RealList conditions of phase PHASE for each feed (Sm3/s) specified by FEEDNAME (only for Blackoil model). Volume fraction of each feed given in RealList FEEDNAME for choke model (only for Blackoil model). Label or number of fluid table to apply for the specific branch. If a keyword based Symbol pvt-file is used, FLUID must be the same as the LABEL given in the pvt-file, i.e., numbering is not valid for this format. GAS | OIL | The phase of a fluid from a single-phase Symbol WATER source. By default, the equilibrium gas fraction of the total flow is used for the gas flow in the compositional or the Blackoil model RealList [1.0] (GASFRACEQ=1). However, the user may specify a fraction of the gas equilibrium flow to be sent into the pipeline. Gas mass fraction of the inflow gas+oil mixture. Specify –1 for OLGA to use the RealList [-1.0] equilibrium values from the PVT table. A list of both positive and negative values is not allowed. RealList Gas/liquid volumetric flow ratio at (Sm3/Sm3) standard conditions. Gas/oil volumetric flow ratio at standard RealList [-1.0] conditions. By default, GOR from the (Sm3/Sm3) PVT table is used. General information about the node. For String information purposes only. Mass fraction of inhibitor in the water RealList [0.0] phase. Network component label (if nothing is String [NODE_tag] given the NC tag is used). YES | If connected to a single-phase flowpath Symbol CROSSOVER or not. CROSSOVER for a crossover | [NO] node. 489 / 769

OLGA 7

| [NO] MASSFLOW MAXPRESSUREBOOST

RealList (kg/s) RealList (Pa)

node. Total mass flow rate at different instants in time. Maximum pressure boost for a crossover node. Molecular weight of equivalent gas (total flow). By default, the gas density at standard conditions from the PVT table is used to determine the molecular weight. By default, the equilibrium oil fraction of the total flow is used for the oil flow in the compositional or the Black oil model (OILFRACEQ=1).

MOLWEIGHT

RealList (kg/kmol)

OILFRACEQ

RealList

[1.0]

Symbol

| LIQUID | GAS The phase for which the volumetric flow | OIL | rate is specified. WATER

PHASE

PRESSURE STDFLOWRATE

STEAMFRACTION

TEMPERATURE TIME TOTALINHIBFRACTION

RealList (Pa) RealList (Sm3/s)

RealList

RealList (C) RealList (s) RealList

TOTALWATERFRACTION RealList

TYPE

Symbol

Boundary pressure.

[-1.0]

Volumetric flow rate at standard conditions. Fraction of total mass of H2O component in the gas phase. By default (=-1), the mass of H2O component is in the gas phase if the temperature is greater than the saturation temperature, otherwise, the mass of H2O component is distributed between the gas phase and the water phase according to the vapor pressure of H2O in the gas phase. A list of both positive and negative values is not allowed. Temperature of the inflow mixture.

Instants in time for the specified values of the boundary conditions. Mass fraction of inhibitor in total water [0.0] (water phase+water vapor). Mass fraction of total water in the total boundary fluid mixture. Use –1 for the [-1.0] total water fraction to be taken from the PVT table. Either this key or WATERFRACTION can be specified. Boundary type. CLOSED: Closed inlet or outlet node. INTERNAL: Nodes or CLOSED | junctions that have one or more incoming PRESSURE | and one or more outgoing branches MASSFLOW | (covers both MERGE and SPLIT nodes). INTERNAL PRESSURE: Inlet or outlet node with a pressure condition. MASSFLOW: Inlet or outlet node with a massflow condition. Viscosity of the drilling fluids for each time point. Must be within the min and [0.0]

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OLGA 7

VISCOSITY

RealList (Ns/m2)

VOLUME

Real (m3)

[-1]

WATERCUT

RealList

[-1.0]

WATERFRACEQ

RealList

[1.0]

WATERFRACTION

RealList

WAXFRACTION

RealList

WGR

RealList [-1.0] (Sm3/Sm3)

X

Real (m)

[0]

Y

Real (m)

[0]

Z

Real (m)

[0]

[1.0]

time point. Must be within the min and max viscosity as specified in the keyword DRILLINGFLUID Volume of internal node. If specified volume is less than or equal to 0, OLGA will estimate the volume. Water volume fraction in oil/water mixture. With a value of -1.0 the total water fraction is taken from the PVT table. By default, the equilibrium water fraction of the total flow is used for the water flow in the compositional or the Black oil model (WATERFRACEQ=1). Mass fraction of free water in the total boundary fluid mixture. Either this key or TOTALWATERFRACTION can be specified. Scaling factor for determining the amount of wax forming components relative to HC mixture. The value must be in the range [0,1]. 1 means the amount of wax forming components is equal to values from the wax table. Requires WAXDEPOSITION=ON under OPTIONS and access to the waxdeposition module. Water-gas ratio. By default, WGR from the PVT table is used. x-coordinate of node in network. Used for 3D graphics only. y-coordinate (vertical axis) of node in network. Used for 3D graphics only. z-coordinate of node in network. Used for 3D graphics only.

Link to: NODE Description Keys

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OLGA 7

OUTPUTDATA (on NODE) Description ( See also: Keys) This statement defines the node variables to be printed to the output file (*.out). See Node Output Variables for available variables.

OUTPUTDATA (on NODE) Keys ( See also: Description ) Key

VARIABLE

Type Unit:( )

Parameter set

Description

Default:[ ]

SymbolList (ValueUnitPair)

List of variables to be printed. Units may be specified.

Link to: OUTPUTDATA (on NODE) Description Keys

492 / 769

OLGA 7

TRENDDATA (on NODE) Description ( See also: Keys) This statement defines the trend data to be plotted for nodes. A trend plot is a time series plot for a specified variable. For available variables see Node Output Variables.

TRENDDATA (on NODE) Keys ( See also: Description ) Key

VARIABLE

Type Unit:( )

Parameter set

Description

Default:[ ]

SymbolList (ValueUnitPair)

List of variables to be plotted. Units may be specified.

Link to: TRENDDATA (on NODE) Description Keys

493 / 769

OLGA 7

FLOWPATH Description ( See also: Keys) This statement defines the label of the flow path.

FLOWPATH Keys ( See also: Description ) Type

Parameter set

Unit:( )

Default:[ ]

FLUIDTYPE

Symbol

GAS | OIL | WATER

INFO

String

LABEL

String

[FLOWPATH_tag]

LINE

Symbol

YES | [NO]

Key

Description The phase of the fluid flowing in the singlephase line. General information about the flowpath. For information purposes only. Network component label (if nothing is given the NC tag is used). NO: Three-phase flow. YES: Use a singlephase fluid in the flowline.

Link to: FLOWPATH Description Keys

494 / 769

OLGA 7

BRANCH (on FLOWPATH) Description ( See also: Keys) This statements defines a grouping of pipes by reference to a GEOMETRY.

BRANCH (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

FLUID

Symbol

GEOMETRY

Symbol

INIFLOWDIR

Symbol

Description

NEGATIVE | [POSITIVE]

Label or number of the fluid table to apply for this branch. If a keyword based pvt-file is used, FLUID has to be the LABEL given in the pvt-file, i.e., numbering is not valid for this format. Label of GEOMETRY keyword. Only one geometry is allowed in each BRANCH statement. Preprocessor input. Defines whether the initial guess on the flow direction for a branch should be positive or negative. Changing the direction might avoid a crash in the preprocessor or result in a solution closer to the transient steady state solution.

Link to: BRANCH (on FLOWPATH) Description Keys

495 / 769

OLGA 7

GEOMETRY (on FLOWPATH) Description ( See also: Keys) This statement defines the geometry label and the co-ordinates of the starting point for a branch. The pipes belonging to this geometry must be defined sequentially after the geometry statement by use of the PIPE-keyword for each pipe.

GEOMETRY (on FLOWPATH) Keys ( See also: Description ) Type

Parameter set

Unit:( )

Default:[ ]

LABEL

String

[GEOMETRY-1]

XSTART

Real (m) [0]

YSTART

Real (m) [0]

ZSTART

Real (m) [0]

Key

Description Geometry label x-coordinate of the starting point of the geometry y-coordinate of the starting point of the geometry z-coordinate of the starting point of the geometry

Link to: GEOMETRY (on FLOWPATH) Description Keys

496 / 769

OLGA 7

PIPE (on FLOWPATH) Description ( See also: Keys) This statement defines the pipe elements in a geometry. A pipe is one straight part of a pipeline. Pipe data such as geometrical data: elevation, diameter, roughness, number and length of sections for discretization are specified. If the temperature option is WALL or FASTWALL in OPTIONS, a WALL for the pipe must be specified.

PIPE (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

AREA

Real (m2)

DIAMETER

Real (m)

ELEVATION

Real (m)

IDIAMETER

Real (m)

LABEL LENGTH LSEGMENT

String Real (m) RealList (m)

NEQUIPIPE

Real

NSEGMENT

Integer

ODIAMETER

Real (m)

ROUGHNESS WALL XEND YEND ZEND

Real (m) Symbol Real (m) Real (m) Real (m)

[PIPE-1]

[0]

Description Total cross-sectional flow area in case of equivalent pipes. Equivalent pipe means one single pipe representing a number of equal parallel pipes with a correct total flow area. Hydraulic diameter of the pipe. Equivalent to the pipe's inner diameter for normal pipe flow. End point elevation relative to starting point of the pipe. Inner diameter of external pipe for annulus flow. Pipe label. Length of the pipe. Section lengths. Total number of pipes represented in the equivalent pipe. The total flow area in the equivalent pipe will correspond to this number of original parallel pipes. Number of sections in the pipe. Outer diameter for internal pipe for annulus flow. Zero for internal flow. Absolute roughness of the pipe wall. Label of the wall used. x-coordinate of the pipe end. y-coordinate of the pipe end. z-coordinate of the pipe end.

Link to: PIPE (on FLOWPATH) Description Keys

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OLGA 7

POSITION (on FLOWPATH) Description ( See also: Keys) This statement specifies a position along the pipeline. It may either specify a distance from flow path inlet (ABSPOSITION), or a reference to a pipe and a section-volume/-boundary number.

POSITION (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

LABEL PIPE SECTION SECTIONBOUNDARY

String Symbol Integer Integer

[POS-1] 0 1

Description Absolute position. Distance from branch inlet. Position label. Pipe label. Section number of position. Section boundary number of position.

Link to: POSITION (on FLOWPATH) Description Keys

498 / 769

OLGA 7

CHECKVALVE (on FLOWPATH) Description ( See also: Keys) Defines a check valve in the pipeline. Allows flow only in the defined flow direction.

CHECKVALVE (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

DIRECTION

Symbol

LABEL

String

PIPE

Symbol

POSITION

Symbol

SECTIONBOUNDARY Integer

NEGATIVE | [POSITIVE] [CHECK-1]

1

Description Absolute position. Distance from branch inlet. Allowed direction. Positive direction refers to direction of increasing section number. Check valve label. Pipe number or pipe label where the check valve is located. Position label where the source is located. If this is defined, PIPE and SECTION should not be used. Section boundary number where the checkvalve is located.

Link to: CHECKVALVE (on FLOWPATH) Description Keys

499 / 769

OLGA 7

COMPRESSOR (on FLOWPATH) Description ( See also: Keys) Describes the configuration of a compressor in the system. The compressor is represented through its characteristics which give pressure increase and temperature as a function of flow and rotating speed (RPM). Note that the compressor characteristics are given in a separate file. It is possible to specify characteristics for more than one compressor. Each of the characteristics is assigned to a label, which is referred to in the COMPRESSOR statement. The compressor RPM is governed by the compressor speed controller: RPM = RPMmin + urpm × (RPMmax - RPMmin) where urpm = output signal from compressor speed controller The recirculation is governed by the anti surge controller (ASC). Note that a compressor cannot be defined at the first or last section boundary of a pipeline.

COMPRESSOR (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

CD

Real

COMPRDATA

Symbol

COOLCAPACITY

Real (W)

COOLER

Symbol

DIAMETER

Real (m)

LABEL MAXRPM MINRPM

String [COMPR-1] Real (rpm) Real (rpm)

PIPE

Symbol

POSITION

Symbol

SECTIONBOUNDARY Integer

[0.84]

ON | [OFF]

1

Description Absolute position. Distance from branch inlet. Discharge coefficient of valve/choke in recycle loop. Name of compressor data. This refers to a label in the compressor characteristics file. Maximum heat transfer rate from fluid flowing through the heat exchanger in the recycle loop. Switch for turning on or off heat exchanger in recycle loop. Orifice diameter of valve/choke in recycle loop. Label of the compressor. Maximum RPM. Minimum RPM. Number/name of pipe where compressor is located. Position of the compressor. If POSITION is defined, PIPE and SECTIONBOUNDARY should not be used. Section boundary number where compressor is located.

500 / 769

OLGA 7

SECTIONBOUNDARY Integer SECURITYFACTOR

Real

TEMPERATURE

RealList (C)

TIME

RealList (s)

1

compressor is located. Security factor (e.g. 1.2 implies that the min. flow is 120% of surge rate). Temperature values out of heat exchanger. Number of temperature values must correspond to the number of times given in the TIME-key. Time series for temperature out of heat exchanger.

Link to: COMPRESSOR (on FLOWPATH) Description Keys

501 / 769

OLGA 7

HEATEXCHANGER (on FLOWPATH) Description ( See also: Keys) This statement describes the effects of a heat exchanger. There are two types of heat exchangers; setpoint and controlled. The setpoint heat exchanger is represented as an ideal loss. The heat exchanged is equal to the enthalpy difference corresponding to the difference between the inlet temperature and a user specified outlet temperature of the heat exchanger. The controlled heat exchanger does not know the outlet temperature and does not calculate the heat exchanged. Instead it uses a controller to specify the effect to be used. The controller signal (which should be between 0 and 1) is the fraction of the heat exchangers maximum capacity. A controller signal of 1 implies that the heat exchanger uses its maximum capacity. Note that a heat exchanger cannot be defined at the first or last section boundary of the pipeline.

HEATEXCHANGER (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

CAPACITY

Real (W)

LABEL

String

PIPE

Symbol

POSITION

Symbol

SECTION

Integer

TEMPERATURE TIME TYPE

[HEATEX-1]

0

RealList (C) RealList (s) Symbol

Description Absolute position. Distance from branch inlet. Maximum heat exchanger capacity. Positive value is for heating and negative value for cooling. Heat exchanger label. Number/name of the pipe where heat exchanger is located. Position of the heat exchanger. If POSITION is defined, PIPE and SECTIONBOUNDARY should not be used. Section number where the heat exchanger is located. Heat exchanger outlet temperature set points. Time series in temperature set point table.

CONTROLLED | [SETPOINT]

Heat exchanger type.

Link to: HEATEXCHANGER (on FLOWPATH) Description Keys

502 / 769

OLGA 7

LEAK (on FLOWPATH) Description ( See also: Keys) This statement specifies a negative mass source (mass out of the pipe). The leak is positioned in the middle of the section that is specified. Both sub-critical and critical flow is modelled. It can be used to model a valve or rupture where the mass out of the pipe is removed from the simulated system, that is, the mass is lost to the surroundings. Backflow is not allowed for the LEAK, that is, there will be no backflow if section pressure is lower than the backpressure. The LEAK has one optional input terminal, INPSIG. INPSIG scales the LEAK flow area.

LEAK (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

ALFA

Real

BACKPRESSURE

RealList (Pa)

Description Absolute position. Distance from branch inlet. For TEMPDEPENDENCY=ON. Constant used for a temperature dependent GLV. 0 means that the bellows temperature equals the injection temperature, 1 means the production temperature, and interpolation for <0,1>. Leak back pressure

For TEMPDEPENDENCY=ON. Pressure in GLV bellows (dome) at BELLOWSPRESSURE Real (Pa) REFTEMPERATURE, used for a temperature dependent GLV. Leak discharge coefficient. Used only in CD Real [0.84] pressure driven source. Ratio between gas and liquid sizing CF Real coefficient. Choice of critical flow model to be used. HENRYFAUSKE | CRITFLOWMODEL Symbol Homogenous frozen critical flow model [FROZEN] or Henry-Fauske model. Maximum equivalent diameter of leak DIAMETER Real (m) area Names of tables (defined in keyword GASLIFTTABLES SymbolList TABLE) that define the curves of a GLV. For TEMPDEPENDENCY=ON. Specify PRODOPERATED whether a GLV is operated by injection GLVOPERATION Symbol | [INJOPERATED] pressure or production pressure. Used for a temperature dependent GLV. LABEL String [LEAK-1] Label of the leak. 503 / 769

OLGA 7

PHASE

Symbol

PIPE

Symbol

POSITION

Symbol

R

Real

REFTEMPERATURE

Real (C)

SECTION

Integer

TABLE

SymbolList

TEMPDEPENDENCY

Symbol

TIME

RealList (s)

TOPOSITION

Symbol

| GAS | LIQUID

0

ON | [OFF]

Predominant phase. Used with valve characteristics. Number/name of pipe where leak is located. Position of the leak. If POSITION or ABSPOSITION is defined, PIPE and SECTION should not be used. For TEMPDEPENDENCY=ON. Geometry factor used for a temperature dependent GLV. For TEMPDEPENDENCY=ON. The temperature for which the gas lift response curve is defined. Section number where the leak is located. Label of table containing valve characteristics. Specify the temperature dependency of a GLV. OFF: No temperature dependency. ON: Temperature dependency for a nitrogen charged bellow. Sub-keys ALFA, BELLOWPRESSURE, GLVOPERATION, R and REFTEMPERATURE must be specified. The time series for the leak back pressure Refer to position the leak is targeted to. When this key is used, the following sub-keys cannot be defined: TIME, BACKPRESSURE.

Link to: LEAK (on FLOWPATH) Description Keys

504 / 769

OLGA 7

LOSS (on FLOWPATH) Description ( See also: Keys) This statement defines pressure loss due to valves, bends, contractions, expansions or other obstructions in or between pipes. The expansion pressure recovery that is always included in OLGA is:

The contraction pressure loss that is always included in OLGA is:

The additional loss specified by the user for positive flow is:

The additional loss specified by the user for negative flow is:

Figure A

An illustration of the use of loss coefficients for contraction and expansion.

LOSS (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

LABEL

String

[LOSS-1]

Description Absolute position where the pressure loss is located. Distance from branch inlet. Loss label. Loss coefficient when the flow is in negative 505 / 769

OLGA 7

NEGCOEFF

Real

PIPE

Symbol

POSCOEFF

Real

POSITION

Symbol

SECTIONBOUNDARY Integer

1

Loss coefficient when the flow is in negative direction. Pipe label with pressure loss. Loss coefficient when the flow is in positive direction. Position where the pressure loss is located. Section boundary where pressure loss is located.

Link to: LOSS (on FLOWPATH) Description Keys

506 / 769

OLGA 7

PUMP (on FLOWPATH) Description ( See also: Keys) OLGA contains four pump models: the centrifugal pump, the displacement pump, the simplified centrifugal pump and the pump battery model. The desired pump model is selected by setting the PUMPTYPE subkey of the PUMP keyword.. Centrifugal pump For the centrifugal pump, the pressure increase over the pump, ∆P, is dependent on the flow rate Q, pump speed N, inlet gas volume fraction αI, and the pump inlet pressure PI. A valve can be located at the centrifugal pump section boundary for controlling flow through the pump. The transient pump characteristics for a centrifugal pump presented in the form of four quadrant curves. The four quadrant curves are converted to a simpler form by the development of homologous curves where the head and torque ratios (actual value to rated value) are functions of the pump speed and flow rate ratios. A complete default set of homologous curves is tabulated in the code. These are based on experimental data and are representative for centrifugal pumps. If other curves shall be used they must be given with the TABLE keyword. Displacement pump For the displacement pump, the pump flow rate can be expressed as the difference between the theoretical flow rate and the back flow rate. For a given pump the theoretical rate is proportional to pump speed. The back flow is tabulated as a function of pump speed, pressure increase across the pump, void fraction at pump inlet, liquid kinetic viscosity and pressure at pump inlet. A default table is included in the code. If other table values shall be used they must be given with the TABLE keyword. The following options are available for controlling the pump speed: (1). Controlled manually by specifying time and speed series in the controller definition. The setpoint specifies the required N (MAXSPEED > N > MINSPEED) (2). Regulated by a physical parameter. The speed is calculated by N = MINSPEED + u (MAXSPEED - MINSPEED) Here MAXSPEED is the maximum pump speed (defined by user), MINSPEED is the minimum pump speed (defined by user) and u the signal from the controller. Simplified centrifugal pump A simplified description of a centrifugal pump is used for modeling the behavior of a centrifugal pump around an operational point. Simple algebraic expressions are used to calculate pressure increase over the pump and pump efficiency. Pump battery The pump battery is used for pumping drilling fluid, e.g. muds in a drilling operation. The purpose is to get an overall estimate of pump power needed as well as the volume of mud pumped. The volume delivered iby the pump is proportional to the rate of pump strokes. (k) where QP

=

Volume delivered by the pump battery 507 / 769

OLGA 7

PFAC SPES

= =

Pumping factor Strokes per time unit

The pump rate is normally controlled by the following set of controllers: Controller on the maximum hydraulic horsepower allowed Controller on the maximum pump rate Controller on the minimum pump rate Controller on the maximum pump pressure allowed If either one of these controllers is set into action the pump rate is reduced automatically. The number of controllers can be extended above the number shown above and different variables (e.g. fluid rate, inflow rate) can be used to control the pumps. Note that a pump cannot be defined at the first or last section boundary of a pipeline. See also: Pump - Purpose

PUMP (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

ACCECOEFF

Real [0.0] (rad/s2)

ACOEFFICIENT

Real

[1.6]

BCOEFFICIENT

Real

[1.6]

BYDIAMETER

Real (m) [0.0]

DCOEFF1 DCOEFF2 DCOEFF3

Real [0.0] (1/rpm) Real [0.0] (1/m3/s) Real Real

[0.0]

Description Absolute position. Distance from branch inlet. Pump speed acceleration. When recycle flow is over or below the limits, this value will be used to increase or decrease the pump speed. For centrifugal and displacement pumps. Experimentally determined exponent for calculating the mechanical friction loss for a displacement pump. Experimentally determined exponent for calculating the viscous friction loss for a displacement pump. Diameter of the valve in the bypass flow line. For centrifugal and displacement pumps. Has to be 0.0 if PUMPTYPE=SIMPLIFIED. Relative change in pump pressure increase with pump speed for simplified pump. Relative change in pump pressure increase with flow rate for simplified pump. Relative reduction in pump pressure increase with gas volume fraction. Rated pump density. Used for centrifugal 508 / 769

OLGA 7

DENSITYR DPRATED ECOEFF1 ECOEFF2

Real [900] (kg/m3) Real (bar) Real [0.0] (1/rpm) Real [0.0] (1/m3/s)

ECOEFF3

Real

[0.0]

EFFIMECH

Real

[0.7]

EFFRATED

Real

[0.5]

FLOWRATED

Real (m3/s)

HEADRATED

Real (m)

HPMAX LABEL MAXCAPACITY MAXPRESSURE MAXRECYCLE MAXSPEED MDISSIPATION MINCAPACITY MINRECYCLE MINSPEED PIPE POSITION PREFSPEED

PUMPTYPE

RECDIAMETER

RECPHASE

Real (W) String Real (m3/s) Real (Pa) Real (kg/s) Real (rpm) Real (W) Real (m3/s) Real (kg/s) Real (rpm) Symbol Symbol Real (rpm)

[PUMP-1]

Rated pump density. Used for centrifugal and simplified pumps. Pump pressure increase at rated conditions for simplified pump. Relative change in pump efficiency with pump speed for simplified pump. Relative change in pump efficiency with pump speed for simplified pump. Relative reduction in pump efficiency with gas volume fraction. Mechanical efficiency of centrifugal and simplified pump. Adiabatic efficiency of simplified pump at rated conditions. Rated pump flow. Used for centrifugal and simplified pumps. Rated pump head. Used for centrifugal pumps. Maximum hydraulic horsepower for each single pump in the pump battery. Label of the pump. Maximum flow capacity for pump battery. Maximum downstream pressure for pump battery. Maximum recycle mass flow rate. Maximum pump speed.

[0.0]

Mechanical dissipation at nominal speed for a displacement pump. Minimum flow capacity for pump battery.

[0.0]

Minimum recycle mass flow rate.

[0.0]

Minimum pump speed.

[3000]

Pipe label for pump location. Position where pump is located. Pump reference speed. Used for displacement pumps.

DISPLACEMENT | SIMPLIFIED | Symbol PUMPBATTERY Pump model. | [CENTRIFUGAL] Choke diameter for recycle flow. For Real (m) centrifugal and displacement pumps. Has to be 0.0 if PUMPTYPE=SIMPLIFIED. | GAS | Phase of recycle flow. For centrifugal and Symbol LIQUID | WATER displacement pumps.

509 / 769

OLGA 7

RECPHASE

Symbol

SECTIONBOUNDARY Integer SPECAPACITY SPEEDR TABLE TORQMAX TORQR VDISSIPATION

LIQUID | WATER | [MIXTURE] 0

Real (m3/R) Real (rpm) Symbol Real (Nm) Real (Nm) Real (W)

[0.0]

displacement pumps. Section boundary number where the pump is located. Pump specific volumetric capacity, Qspc. Used for displacement pumps. Rated pump speed. Used for centrifugal and simplified pumps. Name of the tables of pump back flow data or pump characteristic data. For centrifugal and displacement pumps. Maximum motor torque allowed. Can only be used for centrifugal pumps. Rated pump hydraulic torque. Used for centrifugal pumps. Viscous dissipation at nominal speed for a displacement pump.

Link to: PUMP (on FLOWPATH) Description Keys

510 / 769

OLGA 7

TRANSMITTER (on FLOWPATH) Description ( See also: Keys) This keyword defines output-signals sent from the branch. The signals can be received by a signalcomponent (typicallly a controller). The signals can be measured values in the branch, e.g. pressure, massflow etc. Controllers that receive these measured values use them to calculate new signal which in turn is used to regulate e.g. a valve opening (see Controllers).

TRANSMITTER (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

LABEL PIPE

String Symbol

[TM-1]

SECTION

Integer

0

SECTIONBOUNDARY Integer

1

Description Absolute position. Distance from branch inlet. Transmitter Terminal label. Pipe number for the transmitter. Section number where the transmitter is located. Section boundary number where the transmitter is located.

Link to: TRANSMITTER (on FLOWPATH) Description Keys

511 / 769

OLGA 7

VALVE (on FLOWPATH) Description ( See also: Keys) Here data for valves and chokes are defined. The position of the valve can be specified in 3 ways: 1. 2. 3.

by referring to a pipe and a section boundary number by referring to a pre-define position by specifying the distance from the left end of the branch (absolute position)

The valve performance is either obtained from a discharge coefficient and the maximum choke diameter, or from a table with valve characteristics. The relative opening of the valve can be prescribed as a function of time, or it can be driven by a controller. There are two valve models (GASSIZING and HYDROVALVE). Model selection is done with the MODEL key. GASSIZING is a implementation of the gas sizing equation given in Valve - Methods and assumptions Valve - Methods and assumptions. The GASSIZING option requires gas valve characteristics given by the TABLE key. HYDROVALVE can be used to simulate chokes, liquid valves and gas valves.

VALVE (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

CD

Real

CF

Real

CRITFLOWMODEL

Symbol

DIAMETER LABEL

Real (m) String

MODEL

Symbol

OPENING

RealList

PHASE

Symbol

PIPE

Symbol

POSITION

Symbol

Description

Absolute position. Distance from branch inlet. [0.84] Discharge coefficient. Ratio between gas and liquid sizing coefficient. Choice of critical flow model to be used. HENRYFAUSKE Homogenous frozen critical flow model or | [FROZEN] Henry-Fauske model. In addition, a forced subcritical option is available. Maximum valve diameter. [VALVE-1] Valve label. Default is valve number. Valve model. HYDROMODEL is used for chokes and valves with liquid/gas GASSIZING | characteristics. GASSIZING can only be [HYDROVALVE] used to simulate valves with gas characteristics.' Relative openings in the valve opening [1.0] timetable. | GAS | The type of flow through the valve. For two LIQUID or three phase flow, use LIQUID. Pipe label where the valve is located. Position where the valve is located. If this value is defined PIPE and SECTIONBOUNDARY should not be used. 512 / 769

OLGA 7

SECTIONBOUNDARY Integer STROKETIME TABLE TIME

1

Real (s) [0.0] SymbolList RealList [0.0] (s)

Section boundary number where the valve is located. Stroke time of the valve. Label of table for valve characteristics. Time series for valve opening table.

Link to: VALVE (on FLOWPATH) Description Keys

513 / 769

OLGA 7

HEATTRANSFER (on FLOWPATH) Description ( See also: Keys) This statement specifies the heat transfer data for the pipe walls. The temperature of the surroundings must be given. In addition to this one of the following three options must be used: 1. Specify overall heat transfer coefficient: UVALUE (requires TEMPERATURE=UGIVEN in OPTIONS) 2. Specify ambient heat transfer coefficient: HAMBIENT (HOUTEROPTION=HGIVEN, requires TEMPERATURE=WALL in OPTIONS) 3. Specify properties of the ambient fluid (HOUTEROPTION=OTHER / WATER / AIR, requires TEMPERATURE=WALL in OPTIONS) For options 2 and 3, the overall heat transfer coefficient is calculated and the keyword WALL have to be specified. If option 3 is used, the ambient heat transfer coefficient is a function of the pipe diameter, the fluid velocity, and fluid properties such as density and viscosity. Velocity and fluid properties have to be given only if a user specified fluid is used (HOUTEROPTION=OTHER). The VELOCITY can be specified for HOUTEROPTION=AIR or WATER, otherwise the default values 4 m/s and 1 m/s, respectively, will be used. Default values are applied for all other properties when HOUTEROPTION=AIR or WATER. In order to simplify the input of the ambient temperature distribution along a predefined pipeline section, the user can specify start and end ambient temperature and OLGA will perform an interpolation along the pipeline. Four different interpolation options are available. For the default option, SECTIONWISE, the ambient temperature is given by the user for the midpoint of the first and last section. The interpolation is performed between these points using the distance between section midpoints to achieve a linear temperature profile with respect to the distance along the pipeline. For the options HORIZONTAL, LENGTH, and VERTICAL, the ambient temperature is specified at the inlet and outlet boundaries (INTAMBIENT and OUTTAMBIENT). The interpolation is then based on either horizontal length, actual length, or vertical depth.

HEATTRANSFER (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

CAPACITY

RealList (J/kg-C)

CONDUCTIVITY

RealList (W/m-C)

Description Heat capacity of ambient fluid. If HOUTEROPTION is AIR, 1000 J/KG-K is used. If HOUTEROPTION is WATER, 4186 J/KG-K is used. Input can either be a single value (constant along range of sections), two values (length-interpolated) or given explicitly for each section. Thermal conductivity of ambient fluid. If HOUTEROPTION is AIR, 0.023 W/mK is used. If HOUTEROPTION is WATER, 0.56 W/mK is used. Input can either be a single value (constant along range of sections), two values (length-interpolated) or given explicitly for each section. Density of ambient fluid. If HOUTEROPTION is AIR, 1.29 kg/m3 is

514 / 769

OLGA 7

DENSITY

RealList (kg/m3)

EXPANSION

RealList (1/C)

HAMBIENT

RealList (W/m2-C)

HMININNERWALL

RealList (W/m2-C)

[0.0]

HOUTEROPTION

Symbol

AIR | WATER | OTHER | [HGIVEN]

INHAMBIENT

Real (W/m2-C)

INTAMBIENT

INTERPOLATION

OUTHAMBIENT

OUTTAMBIENT

PIPE SECTION TAMBIENT

HOUTEROPTION is AIR, 1.29 kg/m3 is used. If HOUTEROPTION is WATER, 1000 kg/m3 is used. Input can either be a single value (constant along range of sections), two values (length-interpolated) or given explicitly for each section. Thermal expansion coefficient of ambient fluid. If HOUTEROPTION is AIR, 34E-4 1/C is used. If HOUTEROPTION is WATER, 21E-5 1/C is used. Input can either be a single value (constant along range of sections), two values (lengthinterpolated) or given explicitly for each section. Mean heat transfer coefficient on outer wall surface. Input can either be a single value (constant along range of sections) or given explicitly for each section. Minimum inner heat transfer coefficient on inner wall surface. Option for ambient heat transfer coefficient.

Overall heat transfer coefficient at the inlet of the first pipe in a pipeline section where interpolation is used for overall heat transfer coefficient. Ambient temperature at the inlet of the Real (C) first pipe in a branch where interpolation is used for ambient temperature. Type of interpolation used to calculate the | ambient temperature and outer heat LENGTH | transfer coefficient. Note that the outer Symbol HORIZONTAL | heat transfer coefficient is only affected by VERTICAL | the INTERPOLATION key when [SECTIONWISE] HOUTEROPTION = HGIVEN. Overall heat transfer coefficient at the Real outlet of the last pipe in a pipeline section (W/m2-C) where interpolation is used for overall heat transfer coefficient. Ambient temperature at the outlet of the last pipe in a pipeline section where Real (C) interpolation is used for ambient temperature. Pipe label or pipe number (single or SymbolList [ALL] continuous range in the form x-y). IntegerList 0 Section number. Ambient temperature. Input can either be RealList a single value (constant along range of (C) sections) or given explicitly for each section. List of reference to TIMESERIES keywords. The value of each time series 515 / 769

OLGA 7

TAMBIENTSERIES

SymbolList

TAMBSERIESFACTOR RealList

UVALUE

RealList (W/m2-C)

VELOCITY

RealList (m/s)

VISCOSITY

RealList (N-s/m2)

[1]

is scaled with a corresponding factor in TAMBSERIESFACTOR and added as an increment to the temperature defined in TAMBIENT or INTAMBIENT and OUTTAMBIENT. List of factors to be used to scale ambient temperature time series in TAMBIENTSERIES. Note that this key also introduces the unit of the function. Overall heat transfer coefficient given by user based on the inner pipe diameter. Speed of ambient fluid. If HOUTEROPTION is AIR, default is 4 m/s. If HOUTEROPTION is WATER, default is 1 m/s. Input can either be a single value (constant along range of sections), two values (length-interpolated) or given explicitly for each section. Viscosity of ambient fluid. If HOUTEROPTION is AIR, 1.8E-5 N-s/m2 is used. If HOUTEROPTION is WATER, 1E-3 N-s/m2 is used. Input can either be a single value (constant along range of sections), two values (length-interpolated) or given explicitly for each section.

Link to: HEATTRANSFER (on FLOWPATH) Description Keys

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INITIALCONDITIONS (on FLOWPATH) Description ( See also: Keys) This statement defines initial conditions for the dynamic calculation. The initial conditions are given flow path-, pipe- or section-wise. The total mass flow is defined at section boundaries while the remaining parameters are given for section volumes. There are several ways to define initial data, depending on the key STEADYSTATE in the OPTIONS statement: 1. STEADYSTATE=OFF (initial conditions not calculated by steady state pre-processor): User defines the pressure, temperature, gas volume fraction, mass flow, and water volume fraction in the liquid phase for all sections in each flow path. 2. STEADYSTATE=NOTEMP (initial temperature not calculated by steady state pre-processor): User defines the temperature for all sections in each flow path. The latter option can be useful if the pre-processor has problems finding a solution. This implies that the simulation must be run for some time in order to achieve a steady state solution. Compositional tracking input such as FEEDMOLEFRACTION can be given for all settings of STEADYSTATE (in OPTIONS). For STEADYSTATE=ON or NOTEMP, the given FEEDMOLEFRACTION will be an initial input to the steady state pre-processor. In order to simplify the input for certain initial condition variables, OLGA can perform interpolation along pre-defined flow path segments. Three different interpolation options are available; HORIZONTAL, LENGTH and VERTICAL. The variable is specified at the inlet and outlet of the pipeline segment, and the interpolation is performed based on horizontal length, actual length or vertical depth along the pipeline. LENGTH is the default option.

INITIALCONDITIONS (on FLOWPATH) Keys ( See also: Description ) Key

Type Unit:( )

Parameter set Default:[ ]

FEEDMASSFRACTION RealList FEEDMOLEFRACTION RealList

FEEDNAME

SymbolList

FEEDVOLFRACTION

RealList

INHIBFRACTION

RealList

Description

FEED-1 | BOFEED-1

[0.0]

Mass fraction of each feed given in FEEDNAME. Mole fraction of each feed given in FEEDNAME. Can not be used with Drilling. Label(s) of initial feed(s) to be used for calculating the local fluid compositions in the pipe(s)/section(s). A list means mixing of feeds. Requires COMPOSITIONAL=ON/BLACKOIL or DRILLING=ON under the OPTIONS keyword. Volume fraction of each feed given in FEEDNAME (only for blackoil model). Mass fraction of inhibitor in water phase in each section. 517 / 769

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ININHIBFRACTION

Real

INPRESSURE

Real (Pa)

INSTEAMFRACTION

Real

INTEMPERATURE

Real (C)

[0.0]

[-1.0]

| HORIZONTAL Type of interpolation used to calculate the | VERTICAL | initial conditions. [LENGTH] Void fraction at the inlet to the first pipe in a branch where interpolation is used. Watercut at the inlet to the first pipe in a branch where interpolation is used.

INTERPOLATION

Symbol

INVOIDFRACTION

Real

INWATERCUT

Real

MASSFLOW

RealList (kg/s)

[0.0]

OUTINHIBFRACTION

Real

[0.0]

OUTPRESSURE

Real (Pa)

OUTSTEAMFRACTION Real

OUTTEMPERATURE

Real (C)

OUTVOIDFRACTION

Real

OUTWATERCUT

Real

Mass fraction of inhibitor in water phase at the inlet to the first pipe in a pipeline section where interpolation is used. Pressure at the inlet to the first pipe in a branch where interpolation is used. Fraction of total mass of h2o component in the gas phase inlet to the first pipe in a pipeline section where interpolation is used. By default (=-1), the mass of h20 component is in the gas phase if the temperature is greater than the saturation temperature, otherwise, the mass of h2o component is distributed between the gas phase and the water phase according to the vapor pressure of h2o in the gas phase. A list of both positive and negative values is not allowed. Temperature at the inlet to the first pipe in a branch where interpolation is used.

[-1.0]

Total mass flow at each section boundaries. Mass fraction of inhibitor in water phase at the outlet of the last pipe in a pipeline section where interpolation is used. Pressure at the outlet of the last pipe in a branch where interpolation is used Fraction of total mass of h2o component in the gas phase outlet to the last pipe in a pipeline section where interpolation is used. By default (=-1), the mass of h20 component is in the gas phase if the temperature is greater than the saturation temperature, otherwise, the mass of h2o component is distributed between the gas phase and the water phase according to the vapor pressure of h2o in the gas phase. A list of both positive and negative values is not allowed. Temperature at the outlet of the last pipe in a branch where interpolation is used. Void fraction at the outlet of the last pipe in a branch section where interpolation is used. Watercut at the outlet of the last pipe in a branch section where interpolation is used. 518 / 769

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PIPE

SymbolList [ALL]

REFPIPE

RealList (Pa) Symbol

REFPRESSURE

Real (Pa)

REFSECTION SECTION

Integer IntegerList 0

STEAMFRACTION

RealList

PRESSURE

TEMPERATURE VOIDFRACTION WATERCUT

RealList (C) RealList RealList

Pipe label or pipe number (single or continuous range in the form x-y). Initial pressure in each section.

[-1.0]

Pipe label for REFPRESSURE. Reference pressure used if no pressure boundary condition is used. To be given for one section only. Section number for REFPRESSURE. Section number. Fraction of total mass of h2o component in the gas phase. By default (=-1), the mass of h20 component is in the gas phase if the temperature is greater than the saturation temperature, otherwise, the mass of h2o component is distributed between the gas phase and the water phase according to the vapor pressure of h2o in the gas phase. A list of both positive and negative values is not allowed. Initial temperature in each section.

[0.0]

Initial void fraction in each section. Initial watercut in each section.

Link to: INITIALCONDITIONS (on FLOWPATH) Description Keys

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NEARWELLSOURCE (on FLOWPATH) Description ( See also: Keys) This input definition specifies the data for a ”r;NEARWELLSOURCE” which links OLGA TO the near-wellbore reservoir simulator Rocx developed by IFE. OLGA delivers boundary conditions to Rocx, and the production from (or injection into) the reservoir is received by OLGA from Rocx as mass rate for each phase. Areas for use The link provides coupled transient simulation of near-wellbore reservoir flow and well flow. Dynamic phenomena not accurately predicted or even not seen with the steady-state inflow performance relationship model (WELL) may therefore be simulated in a more realistic way. Typical examples are well shut-in and start-up, dynamic gas and water coning, cross flow between layers, etc. Input The position of the NEARWELLSOURCE is given by referring to the distance from the inlet of the branch (ABSPOSITION), a pipe and a section number, or by reference to a defined POSITION. RESBOUNDNAME must refer to a boundary label defined in the Rocx input file. Each Rocx boundary label can only be refereed once, which means it is not allowed to split the flow from one Rocx boundary into two or more OLGA sections. But for one OLGA section, there can be several NEARWELLSOUCES. Rocx reads a separate input file describing the reservoir properties, boundary conditions and initial conditions. The file name should be given under the key ROCX under FILES. This input file is edited with the ROCX GUI. Rocx writes both formatted and binary industry standard Eclipse output files for post processing (3D visualization). Please refer to the ”r;Rocx User Manual” for how to define a proper input file for the Rocx simulator. There is no automatic check of the correspondence in positioning and size between numerical sections in OLGA and boundary grid blocks in Rocx. The user must therefore discretize both grids in such a way that this is satisfied. The flow area at the wellbore and near-wellbore interface is calculated based on the Rocx grid block rather than the corresponding OLGA numerical section. Rocx may be run with the RESTART option. Definition of the file with restart data for Rocx should be given in the Rocx input file. Rocx may be set up to read the same PVT data file as OLGA. Rocx can be run as a standalone tool. This is a useful way to obtain a suitable condition for the reservoir before initiating a coupled (and more time consuming) simulation. Limitations OLGA Rocx is not compatible with these fluid property models o Compositional option o Black oil module Other limitations on the Rocx reservoir simulator are given in the ”r;Rocx User Manual”.

NEARWELLSOURCE (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Description 520 / 769

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Key

Unit:( )

ABSPOSITION

Real (m)

LABEL PIPE POSITION RESBOUNDNAME

String Symbol Symbol String

ROCX

String

SECTION

Integer

Default:[ ]

[NWSOUR-1]

0

Description Absolute position. Distance from branch inlet. NearWellSOURCE label. Pipe number for well. Position label for where the well is located. Name of boundary in OLGA Rocx. Name of input filename for boundary in OLGA Rocx. Section number for well.

Link to: NEARWELLSOURCE (on FLOWPATH) Description Keys

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SOURCE (on FLOWPATH) Description ( See also: Keys) This statement specifies the input data needed for the simulation of sources. OLGA uses mass flow rate for internal calculations, but input flow rate may also be given as volumetric flow at standard conditions. Also, this statement may be used to specify the fraction of wax forming components in the inflow hydrocarbon mixture. A drilling fluid used with the Wells Module can be defined. There are two options to specify a mass source: 1.

The mass flow rate is given. For a positive mass source (flowing into the pipe), users can specify the upstream pressure as well as the upstream temperature. If the upstream pressure is given in the input, the expansion from the upstream pressure to the pressure inside the pipe section will be taken into account for the temperature calculations. If the upstream pressure is not given, the upstream pressure is set to the pressure inside the pipe section where the source is introduced. If a controller is used, the actual mass rate into/out of the section is a fraction of the mass rate given in the time series with the fraction regulated by the controller.

2.

The mass flow rate is to be calculated based on the opening of the choke through which a mass source is introduced into or taken out of the pipe section. The choke opening is regulated by a controller. Both critical and sub-critical flow through the choke are modelled.

When the mass flow rate is to be specified at the source temperature and pressure without compositional tracking, do the following:

Use key: MASSFLOW

Specify: Total mass flow rate (if option 1)

GASFRACTION

Gas mass fraction in gas and oil mixture at the source temperature and pressure. Free water is excluded. As default, the gas mass fraction is determined from the PVT table.

WATERFRACTION

Mass fraction of free water in the gas-oil-water mixture at the source temperature and pressure. Default value is zero, i.e. no free water.

TOTALWATERFRACTION

Mass fraction of total water in the gas-oil-water mixture at the source temperature and pressure. Default value is zero. Only one of WATERFRACTION or TOTALWATERFRACTION could be defined.

INHIBFRACTION

Mass fraction of inihibitor in water phase at source temperature and pressure. Only used 522 / 769

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source temperature and pressure. Only used together with inhibitor tracking, default value is zero for inhibitor tracking. TOTALINHIBFRACTION

Mass fraction of inhibitor in total water at source temperature and pressure. Only used together with inhibitor tracking, default value is zero for inhibitor tracking.

When the mass flow rate is to be specified at the source temperature and pressure with compositional tracking, do the following: Use key: Specify: FEEDMASSFLOW Total mass flow rate (if option 1) GASFRACEQ

OILFRACEQ

WATERFRACEQ

Fraction of gas mass flow relative to equilibrium flow at the source temperature and pressure. As default, the gas mass flow is equal to the equilibrium flow determined from the feed file (equilibrium gas mass fraction) and FEEDMASSFLOW: (GG = FEEDMASSFLOW * RSEQ * GASFRACEQ). Fraction of oil mass flow relative to equilibrium flow at the source temperature and pressure. Fraction of water mass flow relative to equilibrium flow at the source temperature and pressure.

Note: If GASFRACEQ, OILFRACEQ or WATERFRACEQ is lower than 1 (default value), the total flow will not add up to the specified FEEDMASSFLOW. When the volumetric flow rate at the standard conditions is given, do the following: Use key: STDFLOWRATE

Specify: Volumetric flow rate at standard conditions for the specified phase (if option 1)

PHASE

The phase for which the volumetric flow rate is specified. The allowed options are GAS, OIL, WATER, LIQUID. The total source flow is determined so that the specified flow is obtained, for the phase in question, at standard conditions. If the total volumetric flow is meant to represent equivalent gas flow instead of the single gas phase flow, the molweight of the total flow must be given.

GOR

Gas/oil ratio. By default, the GOR from PVT table is used.

GLR

Gas/liquid ratio. Note that GOR and GLR can not be used at the same time.

WATERCUT

Water cut, i.e. water volume fraction in water and oil mixture.

MOLWEIGHT

If the equivalent gas volumetric flow rate is specified, the molecular weight of the total flow should be given in order

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molecular weight of the total flow should be given in order to account for the density of the equivalent gas. By default, the gas density at the standard condition from the PVT table is used. Available units for standard volumetric flow rate, STDFLOWRATE, are listed in Conversion Factors. Default is (Sm3/s). When volumetric flow rate at standard conditions is used, the table for PVT-data must cover the standard conditions for pressure and temperature. Internal dependencies of keys: either BRANCH = 1 PIPE = 1 SECTION = [1] or POSITION = SOURCE-1 end TIME = (0, 100 ) If the mass flow rate is given, then CONTROLLER = C-101 ! Controls fraction of given mass flow either MASSFLOW = (0.0, 10.0) [kg/s] GASFRACTION = [(-1,-1)] PRESSURE = [Section pressure] either WATERFRACTION = [(0.0, 0.0)] INHIBFRACTION = [(0.0, 0.0)] ! only for inhibitor tracking or TOTALWATERFRACTION = [(0.0, 0.0)] either INHIBFRACTION = [(0.0, 0.0)] ! only for inhibitor tracking or TOTALINHIBFRACTION = [(0.0, 0.0)] ! only for inhibitor tracking end end if WAXDEPOSITION=ON in OPTIONS WAXFRACTION = [2:1.0] end if or STDFLOWRATE = (0.0, 1000) STB/D WATERCUT = (0.1, 0.1) PRESSURE = [Section pressure] PHASE = LIQUID If PHASE = GAS MOLWEIGHT = (20.5) ! If equivalent gas stdflowrate (gas+liquid) end if either GLR = (100, 100) or GOR = (120, 120) 524 / 769

OLGA 7

end if WAXDEPOSITION=ON in OPTIONS WAXFRACTION = [2:1.0] end if or if COMPOSITIONAL=ON in OPTIONS, then FEEDNAME = (FEED-1, FEED-3) either FEEDMASSFLOW = (20, 35.3, 20, 35.3) [kg/s] or FEEDMOLEFLOW = (50, 30.5, 50, 30.5) [kmol/s] end PRESSURE = [section pressure] GASFRACEQ = (0.5,0.5) ! override equilibrium phase fractions OILFRACEQ = (0,0) ! override equilibrium phase fractions WATERFRACEQ = (0,0) ! override equilibrium phase fractions or if the COMPOSITIONAL = BLACKOIL, then FEEDNAME = (BO-1, BO-3) STDFLOWRATE = (0.0, 0.0, 1000, 1000) STB/D PHASE = GAS || OIL or if DRILLING = ON, then MASSFLOW = (0.0, 10.0) [kg/s] PRESSURE = [Section pressure] DRILLINGFLUID = DRILLINGFLUID-1 if drillingfluid properties are NOT given in a separate file, then DENSITY = (1000, 1000) VISCOSITY = (1, 1) cP end end end if If the mass flow is to be calculated based on the opening of the choke, then (standard conditions not allowed) CD = [0.84] DIAMETER = 0.45 CONTROLLER = C-101 PRESSURE = 2:40 bara either GASFRACTION = 2:-1 either WATERFRACTION = 2:0 INHIBFRACTION = [(0.0, 0.0)] ! only for inhibitor tracking or TOTALWATERFRACTION = 2:0 TOTALINHIBFRACTION = [(0.0, 0.0)] ! only for inhibitor tracking end or if COMPOSITIONAL = ON, (multiple time and feeds, see note below) FEEDNAME = (FEED-1, FEED-3) either FEEDMASSFRACTION = (0.7, 0.3, 0.7, 0.3) or FEEDMOLEFRACTION = (0.6, 0.4, 0.5, 0.5) 525 / 769

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end WATERFRACEQ = (0,0) ! override equilibrium phase fractions or if COMPOSITIONAL = BLACKOIL then FEEDNAME = (BO-1, BO-3) FEEDVOLFRACTION = ( 0.7, 0.3, 0.7, 0.3 ) or if DRILLING = ON then DRILLINGFLUID = DRILLINGFLUID-1 DENSITY = 2:1000 VISCOSITY = 2:1 cP end end if Note: For the subkeys FEEDMASSFLOW, FEEDMOLEFLOW, FEEDMASSFRACTION and FEEDMOLEFRACTION, the array is a function of both feed and time as shown below. FEEDMASSFRACTION = FEED-1 (T1), FEED-2(T1), FEED1(T2), FEED-2(T2))

SOURCE (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

CD

Real

CF

Real

CGR

RealList (Sm3/Sm3)

COMPONENT

Symbol

PRODUCTION | DRILLINGFLUID | [ALL]

CRITFLOWMODEL

Symbol

HENRYFAUSKE | [FROZEN]

DENSITY

RealList (kg/m3)

[0.84]

Description Absolute position. Distance from branch inlet. Discharge coefficient. Used for pressure driven source. Ratio between gas and liquid sizing coefficient. Condensate-gas ratio. By default, CGR from the PVT table is used. Component specify the fluid that is going to be exstracted by a negative source. ALL defines that both types shall be exstracted, production fluid and drillingfluids. If only one of more drilling fluids are to be extracted, DRILLINGFLUID = must be specified instead. Choice of critical flow model to be used. Homogenous frozen critical flow model or Henry-Fauske model. The density of the drilling fluid injected at a given time point. The density must be at standard conditions and within the min and max density as specified in the keyword DRILLINGFLUID 526 / 769

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DIAMETER

DRILLINGFLUID

FEEDMASSFLOW

FEEDMASSFRACTION

FEEDMOLEFLOW

FEEDMOLEFRACTION

FEEDNAME

FEEDSTDFLOW

FEEDVOLFRACTION

GASFRACEQ

GASFRACTION

Maximum orifice diameter in pressure driven source. Refer to the drilling fluid defined by the keyword DRILLINGFLUID. Symbol Requires access to the Wells module. Mass rate for each feed (used RealList when mass source is defined). (kg/s) One item per time and feed. Mass fraction of each feed (used when pressure driven source is RealList defined). One item per time and feed. Mole rate for each feed (used RealList when mass source is defined). (kmol/s) One item per time and feed. Mole fraction of each feed (used when pressure driven source is RealList defined). One item per time and feed. Labels of feeds in the mass source defining the fluid FEED-1 | BOFEED- composition. Requires SymbolList 1 COMPOSITIONAL=ON or BLACKOIL under the OPTIONS keyword. Volumetric flow rate at standard condition of phase PHASE for RealList each feed specified by (Sm3/s) FEEDNAME (only for Blackoil model). Volume fraction of each feed RealList given in FEEDNAME for choke model (only for Blackoil model). By default, the equilibrium gas fraction of the total flow is used for the gas flow in the compositional or the Black oil RealList [1.0] model (GASFRACEQ=1), however the user may specify a fraction of the gas equilibrium flow to be sent into the pipeline. Gas mass fraction in gas and oil mixture. By default, the gas mass fraction from the PVT table is used for inflow (GASFRACTION<0). A list of both RealList [-1.0] positive and negative values is not allowed. For outflow, the gas mass fraction can be specified as equal to the gas mass fraction in the source section by setting GASFRACTION<0. Real (m)

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GLR GOR INHIBFRACTION LABEL MASSFLOW

MOLWEIGHT

OILFRACEQ

PHASE PIPE POSITION

PRESSURE

SECTION SOURCETYPE SOVAPHASE STDFLOWRATE

RealList (Sm3/Sm3)

Gas/liquid volumetric flow ratio at standard conditions. Gas/oil volumetric flow ratio at RealList [-1.0] standard conditions. By default, (Sm3/Sm3) GOR from the PVT table is used. Mass fraction of inhibitor in the RealList [0.0] water phase. Source label. Default is source String [SOUR-1] number. RealList Total mass flow rate for the time (kg/s) series. Molecular weight of equivalent gas (total flow). By default, the RealList gas density at standard (kg/kmol) conditions from the PVT table is used to determine the molecular weight. By default, the equilibrium oil fraction of the total flow is used for the oil flow in the compositional or the Black oil RealList [1.0] model (OILFRACEQ=1), however the user may specify a fraction of the oil equilibrium flow to be sent into the pipeline. | LIQUID | The phase for which the Symbol GAS | OIL | WATER volumetric flow rate is specified. Symbol Pipe label. Position label where the source is located. If this is defined, PIPE Symbol and SECTION should not be used. Upstream pressure for a positive source (flow into pipeline). RealList Downstream pressure for a (Pa) negative source. Required key if pressure driven source. Section number where the source Integer 0 is located. PRESSUREDRIVEN Symbol Type of source. | TRACER | [MASS] The type of the flow through the | GAS | Symbol pressure driven source. For two LIQUID or three phase flow, use LIQUID. RealList Volumetric flow rate at standard (Sm3/s) conditions. Fraction of total mass of H2O component in the gas phase. By default (=-1), the mass of H2O component is in the gas phase if the temperature is greater than the saturation temperature, otherwise, the mass of H2O

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STEAMFRACTION

RealList

[-1.0]

STROKETIME

Real (s)

[0.0]

TABLE

SymbolList

TEMPERATURE

RealList (C)

TIME

RealList (s)

TOTALINHIBFRACTION

RealList

[0.0]

TOTALWATERFRACTION

RealList

[-1.0]

TRACERAGE TRACERFEED TRACERMASSFLOW

RealList [0.0] (s) SymbolList RealList (kg/s)

TRACERRESIDENCETIME

RealList (s)

[0.0]

VALVEMODEL

Symbol

GASSIZING | [HYDROVALVE]

VISCOSITY

RealList (N-s/m2)

WATERCUT

RealList

[-1.0]

otherwise, the mass of H2O component is distributed between the gas phase and the water phase according to the vapor pressure of H2O in the gas phase. A list of both positive and negative values is not allowed. Stroke time of valve. Label of table for valve characteristics. Mixture temperature of the mass flow rate at all points in time specified. Points in time when the flow is to be changed. Note that the value used by the program is interpolated between the values specified by the given timetable. Mass fraction of inhibitor in total water (water phase+water vapor). Mass fraction of total water in the total source flow mixture. With a value of -1.0 the total water fraction is taken from the fluid table. Either this key or WATERFRACTION can be specified. For outflow, this key is ignored if GASFRACTION<0 (the water fraction in the source section is used). Age of tracer feed in source.One item per time and feed. Tracer feed name Mass rate for each tracer feed. One item per time and feed. Residence time of tracer feed in source. One item per time and feed. Valve model. The viscosity of the drilling fluid injected at a given time point. The viscosity must be at standard conditions and within the min and max viscosity as specified in the keyword DRILLINGFLUID Water volume fraction in oil/water mixture. With a value of -1.0 the total water fraction is taken from the fluid table. By default, the equilibrium water fraction of the total flow is used for the water flow in the

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WATERFRACEQ

RealList

[1.0]

WATERFRACTION

RealList

WAXFRACTION

RealList

WGR

RealList [-1.0] (Sm3/Sm3)

[1.0]

for the water flow in the compositional or the Black oil model (WATERFRACEQ=1), however the user may specify a fraction of the water equilibrium to be sent into the pipeline. Mass fraction of free water in the total source flow mixture. Either this key or TOTALWATERFRACTION can be specified. For outflow, this key is ignored if GASFRACTION<0 (the water fraction in the source section is used). Scaling factor for determining the amount of wax forming components relative to HC mixture. The value must be in the range [0,1]. 1 means that the amount of wax forming components is equal to the values from the wax table. Requires WAXDEPOSITION=ON under the OPTIONS keyword and access to the wax deposition module. Water-gas ratio. By default, WGR from the PVT table is used.

Link to: SOURCE (on FLOWPATH) Description Keys

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OLGA 7

WELL (on FLOWPATH) Description ( See also: Keys) The well statement is used to define required data for calculating the flow performance of wells. There are two ways of specifying the data for flow between the reservoir and the well. You may either specify the coefficients used in the inflow correlations directly, or you may specify traditional well/reservoir variables like permeability and net pay. When you use the latter, the well/reservoir variables are translated into the coefficients used in the inflow correlations. This option is only available with the Wells Module. Observe that the linear coefficient BPROD can not be zero if the well is located in the first (inlet) section of a flow path. Internal dependencies of keys:

! Alphanumeric values are only ! given as samples

either BRANCH = 1 PIPE = 1 SECTION = 1 or POSITION = POSITION-1 end If you want to use the coefficients directly for standard inflow types: either WATERFRACTION = [0.0] or TOTALWATERFRACTION = [0.0] end end if GASFRACTION = -1 If INJOPTION = LINEAR, then AINJ = 0.0 [kg/s] BINJ = 0.1E-5 [kg/s/Pa] else if INJOPTION = QUADRATIC, then AINJ = 0.0 [Pa2] BINJ = 0.0 [Pa2-s/kg] CINJ = 0.3354E08 [Pa2-s2/kg2] else if INJOPTION = TABULAR, then INJTABLE = TABLE-1 end if If PRODOPTION = LINEAR, then APROD = 0.0 [kg/s] BPROD = 0.1E-5 [kg/s/Pa] else if PRODOPTION = QUADRATIC, then APROD = 0.0 [Pa2] BPROD = 0.0 [Pa2-s/kg] CPROD = 0.3354E08 [Pa2-s2/kg2] else if PRODOPTION = TABULAR, then 531 / 769

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PRODTABLE = TABLE-2 If phase front transient is to be simulated, then GASDIS = [0.0] [m] GASPLIMIT = [RESPRESSURE] [Pa] GFRTC = [0.0] [s] OILDIS = [0.0] [m] OILPLIMIT = [RESPRESSURE] [Pa] OFRTC = [0.0] [s] WATDIS = [0.0] [m] WATPLIMIT = [RESPRESSURE] [Pa] WFRTC = [0.0] [s] end if end if If you want to use the coefficients directly for Advanced Well inflow types: WATERCUT = [0.0] [-] ROGST = [from PVT tables] [kg/Sm3] ROLST = [from PVT tables] [kg/Sm3] GORST = [from PVT tables] [kg/Sm3] if INJOPTION = FORCHHEIMER, then BINJ = 0.6 [psi2-d/scf] CINJ = 1.E-9 [psi2-d2/scf2] else if INJOPTION = SINGLEFORCHHEIMER, then BINJ = 1.E-4 [psi-d/scf] CINJ = 1.E-9 [psi-d2/scf2] else if INJOPTION = BACKPRESSURE, then EXPONENTN = 1 CINJ = 1 [scf/d/psi2] end if if PRODOPTION = FORCHHEIMER, then BPROD = 0.6 [psi2-d/scf] CPROD = 1.E-9 [psi2-d2/scf2] else if PRODOPTION = SINGLEFORCHHEIMER, then BPROD = 1.E-4 [psi-d/scf] CPROD = 1.E-9 [psi-d2/scf2] else if PRODOPTION = BACKPRESSURE, then EXPONENTN = 1 CPROD = 1 [scf/d/psi2] end if If you want to use well/reservoir variables: WATERCUT = [0.0] [-] If INJOPTION = LINEAR, then either INJECTIVITY = 240 stb/d/Psi FRACPR = 1000 bar ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] 532 / 769

OLGA 7

PHASE = [OIL] or FRACPR = 1000 bar ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] VISLRES = 0.2 cP BOOIL = 1.4 KPERM = 20 mD HPAY = 20 [m] RESEXT = 1000 [m] HOLES = 8.5 in SKINS = 3 end else if INJOPTION = FORCHHEIMER, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] VISGRES = 0.03 cP ZFACT = 1 KPERM = 20 mD HPAY = 20 [m] RESEXT = 1000 [m] HOLES = 8.5 in SKINS = 3 SKIND = 0.01 else if INJOPTION = SINGLEFORCHHEIMER, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] VISGRES = 0.03 cP ZFACT = 1 KPERM = 20 mD HPAY = 20 [m] RESEXT = 1000 [m] HOLES = 8.5 in SKINS = 3 SKIND = 0.01 else if INJOPTION = VOGELS, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] QMAX = 10 000 Sm3/d else if INJOPTION = BACKPRESSURE, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] VISGRES = 0.03 cP ZFACT = 1 KPERM = 20 mD HPAY = 20 [m] 533 / 769

OLGA 7

RESEXT = 1000 [m] HOLES = 8.5 in SKINS = 3 SKIND = 0.01 EXPONENTN = 1 else if INJOPTION = NORMALIZEDBACKPR, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] QMAX = 10 000 Sm3/d EXPONENTN = 1 PHASE = [OIL] else if INJOPTION = UNDERSATURATED, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] VISLRES = 0.2 cP BOOIL = 1.4 KPERM = 20 mD HPAY = 20 [m] RESEXT = 1000 [m] HOLES = 8.5 in SKINS = 3 BPPRESSURE = 600 bar end if If the user wants to define a specific linear injectivity index for one or more of the phases GASINJ = 100 stb/d/Psi OILINJ = 100 stb/d/Psi WATINJ = 180 stb/d/Psi end if If PRODOPTION = LINEAR, then either PRODI = 240 stb/d/Psi FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] PHASE = [OIL] or FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] VISLRES = 0.2 cP BOOIL = 1.4 KPERM = 20 mD HPAY = 20 [m] RESEXT = 1000 [m] HOLES = 8.5 in SKINS = 3 end 534 / 769

OLGA 7

else if PRODOPTION = FORCHHEIMER, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] VISGRES = 0.03 cP ZFACT = 1 KPERM = 20 mD HPAY = 20 [m] RESEXT = 1000 [m] HOLES = 8.5 in SKINS = 3 SKIND = 0.01 else if PRODOPTION = SINGLEFORCHHEIMER, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] VISGRES = 0.03 cP ZFACT = 1 KPERM = 20 mD HPAY = 20 [m] RESEXT = 1000 [m] HOLES = 8.5 in SKINS = 3 SKIND = 0.01 else if PRODOPTION = VOGELS, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] QMAX = 10 000 Sm3/d else if PRODOPTION = BACKPRESSURE, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] VISGRES = 0.03 cP ZFACT = 1 KPERM = 20 mD HPAY = 20 [m] RESEXT = 1000 [m] HOLES = 8.5 in SKINS = 3 SKIND = 0.01 EXPONENTN = 1 else if PRODOPTION = NORMALIZEDBACKPR, then FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] QMAX = 10 000 Sm3/d EXPONENTN = 1 PHASE = [OIL] else if PRODOPTION = UNDERSATURATED, then 535 / 769

OLGA 7

FRACPR = 1000 bara ROGST = 0.8 [kg/Sm3] ROLST = 700 [kg/Sm3] GORST = 1000 [Sm3/Sm3] VISLRES = 0.2 cP BOOIL = 1.4 KPERM = 20 mD HPAY = 20 [m] RESEXT = 1000 [m] HOLES = 8.5 in SKINS = 3 BPPRESSURE = 600 bar end if If COMPOSITIONAL = ON in OPTION, then (multiple time and feeds, see note below) TIME = (0, 5) h FEEDNAME = (FEED-1, FEED-3) either FEEDMASSFRACTION = (0.7, 0.3, 0.7, 0.3) or FEEDMOLEFRACTION = (0.6, 0.4, 0.5, 0.5) end or if COMPOSITIONAL = BLACKOIL in OPTIONS, then TIME = (0, 5) h FEEDNAME = (BO-1, BO-2) FEEDVOLFRACTION = [1.0, 0.0, 0.5, 0.5] endif Note: For the subkeys FEEDMASSFRACTION, FEEDMOLEFRACTION and FEEDVOLFRACTION, the array is a function of both feed and time as shown below. FEEDMASSFRACTION = FEED-1 (T1), FEED-2(T1), FEED1(T2), FEED-2(T2))

WELL (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

Real (m)

AINJ

RealList

Description Absolute position. Distance from branch inlet. Negative coefficient A in well flow equation. Less than zero if a minimum pressure difference is required for fluid flow from well into reservoir. Unit: kg/s for the linear formula, Pa2 for the nonlinear formula. Given at in situ conditions - uses gas mass fraction from the PVT table to calculate the split between the phases. 536 / 769

OLGA 7

APROD

RealList

BINJ

RealList

BOOIL

Real

BPPRESSURE

RealList (Pa)

BPROD

RealList

CGR

RealList [-1.0] (Sm3/Sm3)

CINJ

RealList

Positive coefficient A in well flow equation. Less than zero if a minimum pressure difference is required for fluid flow from reservoir into well. Unit: kg/s for the linear formula, Pa2 for the nonlinear formula. Given at in situ conditions - uses gas mass fraction from the PVT table to calculate the split between the phases. Negative coefficient B in well flow equation. Injectivity index for linear inflow equation. Unit: kg/s/Pa for the linear formula, Pa2-s/kg for the non-linear formula, psi2-d/scf for Forchheimer, psi-d/scf for Single Forchheimer. Given at in situ conditions - uses gas mass fraction from the PVT table to calculate the split between the phases. Oil formation volume factor Bubble point pressure at reservoir temperature for Undersaturated oil wells. Positive coefficient B in well flow equation. Productivity index for linear inflow equation. Unit: kg/s/Pa for the linear formula, Pa2-s/kg for the non-linear formula, psi2-d/scf for Forchheimer, psi-d/scf for Single Forchheimer. Given at in situ conditions - uses gas mass fraction from the PVT table to calculate the split between the phases. Condensate-gas ratio. By default, CGR from the PVT table is used. Negative coefficient C in well flow equation. Unit: Pa2s2/kg2 for the non-linear formula, psi2-d2/scf2 for Forchheimer, psi2-d2/scf2 for Single Forchheimer, scf/d/psi2n for Backpressure. Positive coefficient C in well flow equation. Unit: Pa2s2/kg2 for the non-linear 537 / 769

OLGA 7

CPROD

RealList

EXPONENTN

RealList

FEEDMASSFRACTION FEEDMOLEFRACTION

RealList RealList

FEEDNAME

SymbolList FEED-1 | BOFEED-1

FEEDVOLFRACTION

RealList

FRACPR

RealList (Pa)

[1.0]

Fracture pressure.

GASDIS

Real (m)

[0.0]

GASFRACTION

RealList

[-1.0]

GASINJ

RealList (Sm3/s/Pa)

GASPLIMIT

Real (Pa)

GFRTC

Real (s)

GORST

RealList [-1.0] (Sm3/Sm3) RealList

s2/kg2 for the non-linear formula, psi2-d2/scf2 for Forchheimer, psi2-d2/scf2 for Single Forchheimer, scf/d/psi2n for Backpressure. Constant in Backpressure inflow equation. It normally varies between 0.5 and 1.0. Mass fraction of each feed. Mole fraction of each feed. Label of initial feed to be used for calculating local fluid compositions in the branch (from feed file and FEED keyword). A list means mixing of feeds for each section in the branch. Note that this key can only be specified branchwise. Requires COMPOSITIONAL=ON or BLACKOIL under the OPTIONS keyword. Volume fraction of each feed given in FEEDNAME (only for blackoil model).

Distance gas front has to travel before it reaches the well bore. Requires PRODOPTION=TABULAR. Gas mass fraction in the gas+oil mixture for positive flow. -1 indicates equilibrium. A list of both positive and negative values is not allowed. Linear injectivity index for gas entering the well section. Normally given in (Sm3/d/bar). Pressure at which the gas front will be at the well bore at steady-state conditions. Requires PRODOPTION=TABULAR. Time constant for the gas front movement. Requires PRODOPTION=TABULAR. Gas/oil volumetric ratio. By default, GOR from the PVT table is used. Hole size (diameter). 538 / 769

OLGA 7

HOLES HPAY

INJECTIVITY

RealList (m) RealList (m)

Symbol

INJPOSTFRACFACTOR

Real

INJPREFRACFACTOR

Real

INJTABLE

Symbol

INJTHRESHOLD

RealList (Pa)

LABEL

Symbol RealList (mD) String

LOCATION

Symbol

KPERM

Net pay from inflow zone. Injectivity. Given at std conditions - uses GOR from the PVT table (or the specified GORST) and the PHASE to calculate the split between the phases.

RealList (Sm3/s/Pa)

INJOPTION

ISOTHERMAL

Hole size (diameter). Normally given in inches (in).

LINEAR | QUADRATIC | SINGLEFORCHHEIMER | FORCHHEIMER | Negative well flow equation BACKPRESSURE | type. UNDERSATURATED | VOGELS | TABULAR | NORMALIZEDBACKPR Multiplier for injection rate when BH pressure is above fracture pressure. If BH pressure has been above [1.0] fracture pressure this is a multiplier when BH pressure is above INJTHRESHOLD as well. Multiplier for injection rate when BH pressure is below fracture pressure. If the BH [1.0] pressure has been above fracture pressure this is a multiplier only below INJTHRESHOLD. Table reference for negative well flow performance. Option for supporting coning. The table variables must be given at reservoir conditions. Pressure. If BH pressure has been above fracture pressure the injection rate multiplied by the INJPOSTFRACFACTOR will be used when the BH pressure is above INJTHRESHOLD. NO | [YES] Turn on or off isothermal. Effective permeability. [WELL-1]

BOTTOM | [MIDDLE]

Well label. Well location in the well section. MIDDLE if the reservoir pressure at the middle of the zone is specified. BOTTOM if the 539 / 769

OLGA 7

specified. BOTTOM if the reservoir pressure given is at the bottom of the zone. Time constant for the oil front OFRTC Real (s) movement. Requires PRODOPTION=TABULAR. Distance oil front has to travel before it reaches the OILDIS Real (m) well bore. Requires PRODOPTION=TABULAR. Linear injectivity index for oil RealList entering the well section. OILINJ (Sm3/s/Pa) Normally given in (Sm3/d/bar). Pressure at which the oil front will be at the well bore OILPLIMIT Real (Pa) at steady-state conditions. Requires PRODOPTION=TABULAR. The phase for which | GAS | WATER PHASE Symbol productivity index or absolute | LIQUID | [OIL] open flow rate is given. PIPE Symbol Pipe number for well. Position where the well is located. If POSITION is POSITION Symbol defined, BRANCH, PIPE, and SECTION should not be used. Productivity index for linear inflow equation. Normally given in (Sm3/d/bar). Given RealList at std conditions - uses GOR PRODI (Sm3/s/Pa) from the PVT table (or the specified GORST) and the PHASE to calculate the split between the phases. LINEAR | QUADRATIC | SINGLEFORCHHEIMER | FORCHHEIMER | Positive well flow equation PRODOPTION Symbol BACKPRESSURE | type. UNDERSATURATED | VOGELS | TABULAR | NORMALIZEDBACKPR Multiplier for production rate after the reservoir is fractured. Use when the well PRODPOSTFRACFACTOR Real [1.0] parameters are given for conditions before the reservoir is fractured. Multiplier for production rate before the reservoir is fractured. Used when the PRODPREFRACFACTOR Real [1.0] well parameters are given for conditions after the reservoir 540 / 769

OLGA 7

PRODTABLE

Symbol

QMAX

RealList (Sm3/s)

RESEXT RESPRESSURE RESTEMPERATURE

conditions after the reservoir is fractured. Table reference for positive flow performance. Option for supporting coning. The table variables must be given at reservoir conditions. Maximum flow in Vogels and Normalized Backpressure inflow equation.

RealList (m) RealList (Pa) RealList (C)

Reservoir extension. Reservoir pressure. Reservoir temperature.

ROGST

Real (kg/Sm3)

[-1.0]

ROLST

Real (kg/Sm3)

[-1.0]

SECTION

Integer

0

SKIND

RealList (1/Sm3/s)

SKINS

RealList

STEAMFRACTION

RealList

[-1.0]

TIME

RealList (s)

[0.0]

Gas density at standard conditions. By default value from PVT table is used. Oil density at standard conditions. By default value from PVT table is used. Section number for well. Turbulent non-darcy skin. Normally given in (1/MMSCF/d). Mechanical damage skin. Fraction of total mass of H2O component in the gas phase. By default (=-1), the mass of H2O component is in the gas phase if the temperature is greater than the saturation temperature, otherwise, the mass of H2O component is distributed between the gas phase and the water phase according to the vapor pressure of H2O in the gas phase. A list of both positive and negative values is not allowed. Time series when the reservoir conditions are to be changed. Note that the value actually used by the program is interpolated between the values specified by the time table. Mass fraction of total water in the in the total fluid mixture of the reservoir. With a value of –1, the total water fraction is 541 / 769

OLGA 7

TOTALWATERFRACTION

RealList

[-1.0]

VISGRES

Real (Ns/m2)

[-1]

VISLRES

Real (Ns/m2)

[-1]

WATDIS

Real (m)

WATERCUT

RealList

WATERFRACTION

RealList

WATINJ

RealList (Sm3/s/Pa)

WATPLIMIT

Real (Pa)

WAXFRACTION

RealList

[-1.0]

[1.0]

–1, the total water fraction is taken from the fluid table. Either this key or WATERFRACTION can be specified. Viscosity of gas reservoir conditions. By default value from PVT table is used. Viscosity of oil reservoir conditions. By default value from PVT table is used. Distance water front has to travel before it reaches the well bore. This key can only be used if water option is available. Non-zero values are ignored for two-phase simulations, even if the water option is available. Requires PRODOPTION=TABULAR. Watercut at standard conditions. With a value of 1.0 the total water fraction is taken from the fluid table. Mass fraction of free water in the total flow mixture of the reservoir. Either this key or TOTALWATERFRACTION can be specified. For outflow, this key is ignored if GASFRACTION<0 (the water fraction in the source section is used). Linear injectivity index for water entering the well section. Normally given in (Sm3/d/bar). Pressure at which the water front will be at the well bore at steady-state conditions. This key can only be used if water option is available. Requires PRODOPTION=TABULAR. Scaling factor for determining the amount of wax forming components relative to HC mixture. The value must be in the range [0,1]. 1 means that the amount of wax forming components is equal to the values from the wax table. Requires WAXDEPOSITION=ON under the OPTIONS keyword

542 / 769

OLGA 7

WFRTC

Real (s)

WGR

RealList [-1.0] (Sm3/Sm3)

ZFACT

Real

[1]

under the OPTIONS keyword and access to the wax deposition module. Time constant for the water front movement. This key can only be used if water option is available. Requires PRODOPTION=TABULAR. Water-gas ratio. By default, WGR from the PVT table is used. Gas compressibility factor.

Link to: WELL (on FLOWPATH) Description Keys

543 / 769

OLGA 7

PROFILEDATA (on FLOWPATH) Description ( See also: Keys) This statement defines profile plot variables along the pipeline at specified time points. For available profile variables see Output Variables.

PROFILEDATA (on FLOWPATH) Keys ( See also: Description ) Key

Type Unit:( )

AGEGROUPID

IntegerList

COMPONENT

SymbolList

HYKPID

IntegerList

LAYER

IntegerList

TRACERFEED

SymbolList

VARIABLE

SymbolList (ValueUnitPair)

Parameter set

Description

Default:[ ]

BOCOMP-1

Age group for plotting inhibitors variables with aging effect, e.g. Kinetic hydrate inhibitor (KHI). Component names. Using the Inhibitor tracking module, available components are HC, H2O and MEG/MEOH/ETOH. Using DRILLING=ON under OPTIONS, available components are HC, H2O, MEG/MEOH/ETOH, CUTTING and MUD components. For compositional models the names of the available components are given in the feed file. Array element index of HYKPLIST. Wall layer number for plotting of wall temperatures. Layer no. 1 is the innermost one. Tracer label that the tracer type variables are plotted for. Variables to be written to the profile plot file. Units should not be used.

Link to: PROFILEDATA (on FLOWPATH) Description Keys

544 / 769

OLGA 7

OUTPUTDATA (on FLOWPATH) Description ( See also: Keys) This statement defines the variables to be printed to the output file (*.out). Global variables are not available on this level.

OUTPUTDATA (on FLOWPATH) Keys ( See also: Description ) Key

Type Unit:( )

AGEGROUPID

IntegerList

COMPONENT

SymbolList

LAYER

IntegerList

PIPE

SymbolList

SECTION

IntegerList

TRACERFEED

SymbolList

VARIABLE

SymbolList (ValueUnitPair)

Parameter set

Description

Default:[ ]

BOCOMP-1

0

Age group for plotting inhibitors variables with aging effect, e.g. Kinetic hydrate inhibitor (KHI). Component names. Using the Inhibitor tracking module, available components are HC, H2O and MEG/MEOH/ETOH. Using DRILLING=ON under OPTIONS, available components are HC, H2O, MEG/MEOH/ETOH, CUTTING and MUD components. For compositional models the names of the available components are given in the feed file. Wall layer numbers for plotting of wall temperatures. Layer no. 1 is the innermost one. Pipe numbers or labels where the variables will be plotted. Section numbers where the variables will be plotted. Tracer label that the tracer type variables are plotted for. List of variables to be printed. Units may be specified.

Link to: OUTPUTDATA (on FLOWPATH) Description Keys

545 / 769

OLGA 7

TRENDDATA (on FLOWPATH) Description ( See also: Keys) This statement defines the trend data to be plotted. A trend plot is a time series plot for a specified variable. Global and branch variables are not available on this level. For available variables see Output Variables.

TRENDDATA (on FLOWPATH) Keys ( See also: Description ) Key

Type Unit:( )

ABSPOSITION

RealList (m)

AGEGROUPID

IntegerList

CHECKVALVE

SymbolList

COMPONENT

SymbolList

COMPRESSOR

SymbolList

HEATEXCHANGER

SymbolList

HYKPID

IntegerList

LAYER

IntegerList

LEAK

SymbolList

NEARWELLSOURCE SymbolList PIG

SymbolList

PIPE

SymbolList

POSITION

SymbolList

PUMP

SymbolList

Parameter set Description Default:[ ] Pipeline position where the variable will be plotted. Absolute position. Distance from branch inlet. Age group for plotting inhibitors variables with aging effect, e.g. Kinetic hydrate inhibitor (KHI). Checkvalve for which the variable is to be plotted. Component names. Using the Inhibitor tracking module, available components are HC, H2O and MEG/MEOH/ETOH. Using DRILLING=ON under OPTIONS, available BOCOMPcomponents are HC, H2O, 1 MEG/MEOH/ETOH, CUTTING and MUD components. For compositional models the names of the available components are given in the feed file. Compressor for which the variable is to be plotted. HeatExchanger for which the variable is to be plotted. Array element index of HYKPLIST. Wall layer number for plotting of wall temperatures. Layer no. 1 is the innermost one. Leak for which the variable is to be plotted. NearWellSource for which the variable is to be plotted. Pig for which the variable is to be plotted. Pipe numbers or labels where the variables will be plotted. Labels of specified positions where the variables will be plotted. Pump for which the variable is to be plotted. 546 / 769

OLGA 7

SECTION

IntegerList

0

SLUGID

IntegerList

[0]

SOURCE

SymbolList

TRACERFEED

SymbolList

VALVE

SymbolList SymbolList (ValueUnitPair) SymbolList

VARIABLE WELL

Section numbers where the variables will be plotted. Unique identity defining a slug or a pig. Source for which the variable is to be plotted. Tracer label that the tracer type variables are plotted for. Valve for which the variable is to be plotted. List of variables to be plotted. Units should not be used. Well for which the variable is to be plotted.

Link to: TRENDDATA (on FLOWPATH) Description Keys

547 / 769

OLGA 7

CORROSION (on FLOWPATH) Description ( See also: Keys) This statement is used to define corrosion module input parameters. Requires access to the corrosion module. If the corrosion rate in single phase liquid flow is to be calculated correctly, PTMAX must be set equal to the pressure in the pipeline where gas is formed (bubble point pressure). That is, if a simulation shows single phase liquid flow, a new simulation should be performed with the correct PTMAX set to the pressure in the section where gas is formed. Alternatively, the output variable PCO2 can be read and PCO2MAX can be set to the PCO2 value in the section where gas is formed. The corrosion module cannot be applied together with the wax deposition module.

CORROSION (on FLOWPATH) Keys ( See also: Description ) Key

Type Unit:( )

Parameter set Description Default:[ ]

BICARBONATE

Real

[0.0]

CO2FRACTION

Real

GLYCOLFRACTION

Real

[0.0]

INHIBITOREFFICIENCY Real

[0.0]

IONICSTRENGTH

Real

MODEL

SymbolList

[0.0] MODEL1 | MODEL2 | MODEL3 | [ALL]

PCO2MAX

Real (Pa)

[1000000]

PHSAT

Symbol

ON | [OFF]

Bicarbonate (HCO3-) concentration in water given in Molar (M=mol/l). Mole percentage of CO2 in gas phase (ratio of CO2 partial pressure to total pressure in %). Glycol concentration in weight-% in a glycol/water mixture. Only used if Inhibitor tracking is not used. If Inhibitor tracking is used, the glycol fraction will be calculated. Inhibitor (not glycol) efficiency in %. The effect of glycol and an additional inhibitor (through INHIBITOREFFICIENCY) depends on the model used. For the NORSOK model, the larger of the two resulting reduction factors is used, while for the de Waard models the product of the two factors is used. INHIBITOREFFICIENCY=100% means no corrosion. Total ionic strength in Molar (M=mol/l). Which model to use. MODEL1: NORSOK. MODEL2: Top of Line corrosion model. MODEL3: de Waard 95. Maximum CO2 partial pressure in single phase liquid flow. Whether or not to calculate the pH for condensed water saturated with ion carbonate. 548 / 769

OLGA 7

PTMAX

Real (Pa)

WCWET

Real

[30.0]

Bubble point pressure from which the CO2 partial pressure for a single phase liquid flow will be calculated. Water droplet wall wetting limit. Has to be given as watercut in %. If the liquid film watercut is higher than this value, the water droplets will wet the wall, even if no continuous water film is present. It is only used in the corrosion module to detect if water droplets are wetting the wall. It has no influence on the flow conditions. If a continuous water film is predicted by the flow model, water wetting is detected by the corrosion module regardless of the water cut set as the wetting limit. See the corrosion module description in ch. 2 for further information.

Link to: CORROSION (on FLOWPATH) Description Keys

549 / 769

OLGA 7

DTCONTROL (on FLOWPATH) Description ( See also: Keys) This statement defines a switch for stability control. See restrictions and limitations for more information.

DTCONTROL (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ABSPOSITION

RealList (m)

CFL

Symbol

OFF | [ON]

CFLFACTOR

Real

[0.8]

GRADPRESSURE Symbol

ON | [OFF]

PIPE

SymbolList

POSITION

SymbolList

PREFACTOR

Real

[0.8]

PRESSURE

Symbol

ON | [OFF]

SECTION

IntegerList

0

SOUND_CFL

Symbol

ON | [OFF]

Description Pipeline position where the variable will be plotted. Absolute position. Distance from branch inlet. The Courant-Friedrichs-Lewy (CFL) criterion based on the flow velocity. Adjust the CFL time-step. Time-step control based on the first-order derivative of pressure w.r.t. time. Pipe numbers or labels where the variables will be plotted. Labels of specified positions where the variables will be plotted. Tuning factor for pressure criterion. Time-step control based on the secondorder derivative of pressure w.r.t. time. Section numbers where the variables will be plotted. Time-step control based on the speed of pressure waves.

Link to: DTCONTROL (on FLOWPATH) Description Keys

550 / 769

OLGA 7

HYDRATECHECK (on FLOWPATH) Description ( See also: Keys) This keyword can be used to specify a set of hydrate formation curves and how these should be treated in the flowpath. See also: HYDRATECHECK

HYDRATECHECK (on FLOWPATH) Keys ( See also: Description ) Key

HAMCONST

Type Unit:( ) Real (C)

HAMMERSCHMIDT Symbol

Parameter set

Description

Default:[ ] [1297]

ON | [OFF]

HYDRATECURVE

SymbolList

PRESSOVERRIDE

Real (Pa)

[-5000000]

TEMPOVERRIDE

Real (C)

[-50]

WATERLIMIT

Real

[0]

Constant in Hammerschmidt equation. Note that unit is delta temperature. Switch for activating the Hammerschmidt formula for computing hydrate temperature curves for different inhibitor concentrations. Can only be used with a single hydrate curve without any specified inhibitor concentration (i.e. INHIBITORCONC=0). Labels of the HYDRATECURVEs (from Library) that shall be used in this flowpath. With PRESSOVERRIDE the limit for the difference between hydrate and section pressure, DPHYD (default -50 bar), can be changed. Such sections are not used when calculating the maximum DPHYD in a branch. With TEMPOVERRIDE the limit for the difference between hydrate and section temperature, DTHYD (default -50 C), can be changed. Such sections are not used when calculating the maximum DTHYD in a branch. Hydrates will not form in sections with less water than the waterlimit (default = 0).

Link to: HYDRATECHECK (on FLOWPATH) Description Keys

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OLGA 7

HYDRATEKINETICS (on FLOWPATH) Description ( See also: Keys) The hydrate kinetics module combines the hydrate kinetics and rheological model developed by Colorado School of Mines with the flow equations of the OLGA model. The hydrate kinetics model determines the amount of gas and water consumed by hydrate formation and the effective viscosity of the hydrate particle laden oil phase. The flow model integrates the mass consumption rate to obtain the amount of hydrate phase and uses the effective viscosity for the flow calculations. The model is still in the research phase, and the initial emphasis has been on flowing liquid dominated systems with excess of water and gas for hydrate formation. Future versions will likely also address gas dominated systems and include deposition mechanisms. Special care should be taken when using the model since the model has only been validated against limited data sets. Further, it is not designed for shut-in and depressurization studies.

HYDRATEKINETICS (on FLOWPATH) Keys ( See also: Description ) Key

Type Unit:( )

Parameter set Default:[ ]

COIL

Real

[1.0]

CWATER

Real

[0.0]

DIFFUSIVITY DRIFTFLUX

Real (m2/s) Symbol

Description Weighting factor for hydrate velocity related to oil velocity Weighting factor for hydrate velocity related to water velocity

[1.0e-16]

Diffusivity

YES | [NO]

Force slip between phases by users. Drift velocity of gas. Used when DRIFTFLUX = YES. gas velocity = VELOCITYRATIO times (liquid velocity +'DRIFTVELOCITY') Scaling factor for gas-liquid interface friction. (Use of KEY will alter how the oil/water momentum equations are solved. Oil/water will be solved with a drift-flux approach.) Hydrate equilibrium temperature and pressure is from hydrate check keyword. Force all of oil or water to be dispersed in water or oil. Mass fraction of hydrate guest molecules in gas phase Name of the hydrate curve used to calculate the hydrate equilibrium temperature. Scaling factor for the first reaction coefficient Scaling factor for the second reaction coefficient.

DRIFTVELOCITY

Real (m/s)

[0]

FOGEXPONENT

Real

[0]

FROMHYDRATECHECK Symbol

YES | [NO]

FULLDISPERSION

Symbol

YES | [NO]

GASGUESTFRACTION

Real

[1]

HYDRATECURVE

Symbol

K1SCALINGFACTOR

Real

[1.0]

K2SCALINGFACTOR

Real

[1.0]

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OLGA 7

MEANDIAMETER

Real (m)

[4.0e-5]

OILGUESTFRACTION

Real

[0]

SIZESCALINGFACTOR

Real

[1.0]

SUBCOOLING

Real (C)

[3.611111]

USEDLL

Symbol

YES | [NO]

VELOCITYRATIO

Real

[1]

Mean droplet diameter Mass fraction of hydrate guest molecules in oil phase Monomer size Subcooling from hydrate equilibrium before nucleation. Default 6.5 F. NO: The routines embedded in the olga executable are used. YES: csmhyddll.dll is used. Distribution coefficient for gas velocity. Used when DRIFTFLUX = YES

Link to: HYDRATEKINETICS (on FLOWPATH) Description Keys

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OLGA 7

PIG (on FLOWPATH) Description ( See also: Keys) This statement defines the pig option. The pig keyword should be used when the user wants to simulate a pig or plug in the pipeline. The pig is inserted at LAUNCHPOSITION and taken out when it reaches either the TRAPPOSITION or a boundary NODE. TRAPPOSITION can be in the same flowpath as LAUNCHPOSITION or in a different flowpath. When the pig comes to an internal NODE or SEPARATOR it will take the path with the highest volume flow. The path the pig takes in a network can be overridden by the ROUTING key. If the TRAPPOSITION is specified in a different flowpath than LAUNCHPOSITION and the pig does not reach the TRAPPOSITION (because highest volume flow or ROUTING does not take it there) the pig is taken out when it reaches a boundary node. The keys LINEARFRIC, QUADRATICFRIC and STATICFORCE are the usual way to define the friction of the pig. The keys LEAKAGEFACTOR, LEAKDPCOEF or LEAKOPENING are used to specify the leakage in the propagation direction of the pig. The key DIAMETER is used to calculate the liquid backflow around the pig.

PIG (on FLOWPATH) Keys ( See also: Description ) Key

Type Unit:( )

DIAMETER

Real (m)

INSERTTIME LABEL

Real (s) String

Parameter set

Description

Default:[ ]

[PIG-1]

LAUNCHPOSITION Symbol

LEAKAGEFACTOR Real

LEAKDPCOEF

Real

[1E199]

LEAKOPENING

Real

[0.0]

Pig diameter NOTE! If no diameter is given, the diameter of the pig is set to the inner pipe diameter minus 4 times the wall roughness. This implies that leakage between the pig and the wall will occur Pig launch time. Pig label, default is pig number. Position for pig launch. The pig is launched downstream of the section boundary closest to the launch position. Pig leakage factor. Leakage factor at 0 corresponds to no fluid leaking past pig, and 1.0 corresponds to all fluid leaking past pig. When not given for the hydrate model, the program will calculate the leakage factor from the cross sectional area. Pressure loss coefficient measured by letting the fluid flow past a pig that is fixed to the pipe wall. Described in section 2.2.6 Leakage opening relative to pipe cross section area.

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OLGA 7

LEAKOPENING

Real

[0.0]

LINEARFRIC

Real (Ns/m)

[10]

MASS

Real (kg)

[140]

PGWXFORMFAC

Real

[0.0]

QUADRATICFRIC

Real (Ns2/m2) [0.0]

ROUTING

SymbolList

STATICFORCE

Real (N)

[1000.0]

TRACKSLUG

Symbol

ON | [OFF]

TRAPPOSITION

Symbol

WALLFRICTION

Real (Ns/m)

WPPLASTVISC

Real (N-s/m2) [-1]

WPPOROSITY

Real

[1000.0]

[-1]

WPYIELDSTRESS Real (Pa)

[-1]

WXBRFCOEF

Real

[0.0]

WXRMEFF

Real

[1.0]

section area. Linear friction factor coefficient for fluid friction of fluid film between pig and pipe wall. Pig mass. Wax cutting efficiency, see eq. for breaking force in sec. 2.2.6. Only available with the wax module. Quadratic friction factor coefficient for fluid friction of fluid film between pig and pipe wall. Name of branches a pig passes from the launch position to trap position. This key is optional. If not given, a pig goes to the branch that has the highest volumetric flowrate out of the node the pig enters. When given, the launch branch name must be the first in the list. Force necessary to tear pig loose from the wall. When turned on the slug in front of the pig is generated and tracked, else no slug is set up in front of the pig. Activating this key requires access to the slugtracking module. Position for pig trap. The pig is trapped at the boundary closest to the trap position. Trap position is optional and if not given, the pig is removed when it exits through a terminal node. Factor for wall friction between pig and pipe. Plastic viscosity of wax plug in front of pig. The wax plug is assumed to exhibit Bingham fluid behavior. –1 implies using internal model for estimating the plastic viscosity. See 2.2.6 for further details. Only available with the wax module. Porosity of wax plug in front of pig. Used for wax plug friction calculation. Default value –1 implies that no special friction calculation for the wax plug is performed. Only available with the wax module. Yield stress of wax plug in front of pig. The wax plug is assumed to exhibit Bingham fluid behavior. –1 implies using internal model for estimating the yield stress. See 2.2.6 for further details. Only available with the wax module. Coefficient C in wax breaking force equation, see eq. in sec. 2.2.6. Only available with the wax module. Wax removal efficiency. Only available with the wax module.

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OLGA 7

WXRMEFF

Real

[1.0]

WXYIELDSTR

Real (Pa)

[-1]

the wax module. Yield stress of wax layer on the wall. –1 imples that the internal yieldstress correlation is used, see sec. 2.2.6. Only available with the wax module.

Link to: PIG (on FLOWPATH) Description Keys

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OLGA 7

SLUGILLEGAL (on FLOWPATH) Description ( See also: Keys) SLUGILLEGAL is part of the SLUGTRACKING keyword. Slugs are not allowed to be generated at illegal sections. A slug front or tail may propagate into an illegal section, but it will not propagate through it. The first and the last section in a pipeline are by definition illegal sections. This means that slugs do not propagate through a network. The user may add extra illegal section by using the SLUGILLEGAL keyword. This may speed up the simulation or make the simulation more robust. More info on when to use illegal sections can be found under SLUGTRACKING MODULE.

SLUGILLEGAL (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ILLEGALSECTION Symbol

PIPE

Symbol

POSITION

SymbolList

SECTION

IntegerList

OFF | [ON]

0

Description Specify whether or not slugs are allowed in sections defined by PIPE and SECTION. OFF: Slugs are allowed. Used for sections where illegal sections previously have been switched on. ON: Slugs are not allowed to be generated. Slugs generated elsewhere may move into the section, but are not allowed to pass through this section. The slugs will be destroyed when both the front and tail are within the section. Pipe numbers/pipe labels for illegal sections. Define the positions of illegal sections. If this option is used, sub-keys PIPE and SECTION should not be used. Section numbers for illegal sections.

Link to: SLUGILLEGAL (on FLOWPATH) Description Keys

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OLGA 7

SLUGTRACKING (on FLOWPATH) Description ( See also: Keys) This statement defines the slug tracking option. This statement has two main sub-options for initiation of liquid slugs: the level slug option (LEVEL) and the hydrodynamic slug option (HYDRODYNAMIC). These two options may be used together or separately. Terrain slugging will be detected in ordinary simulations without the slug tracking module, and the interactions between terrain and hydrodynamic slugging can be investigated using the key HYDRODYNAMIC. The level slug option is mostly used for startup-slugs. If HYDRODYNAMIC = ON, the code will set up a new slug in a section whenever the set-up criteria are fulfilled. These are: (1) Flow regime at the section boundary changes from separated to slug flow. (2) Other slug fronts are the required distance away. (3) The time elapsed since the previous slug was generated in or passed this section is higher than a specified minimum time. If HYDRODYNAMIC = MANUAL, the user can specify a fixed number of slugs to be set up at predefined positions and times. Using this option, liquid will be injected into the pipeline to generate slugs of required size. Slugs are not allowed to be generated at the inlet and outlet sections by default. That is, the boundary sections are automatically set to illegal for slugs by the program itself. However, the slug front is allowed to move into the outlet section, and the slug tail into the inlet section. Users can specify the sections where slugs are not allowed to be generated by using SLUGILLEGAL keyword. The slug tracking option offers full temperature calculation capabilities. Remark: The availability of the slug tracking option depends on the user’s licensing agreement with SPT Group. To turn off slug-tracking in a restart there are two possibilities: (1) Set both LEVEL and HYDRODYNAMIC to OFF. Then the only slugs in the system will be the ones read from restart. (2) Remove SLUGTRACKING keyword. Average values will be used in the sections. No slugs in the simulation. More details can be found in the description of the slug tracking module.

SLUGTRACKING (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

BUBBLEVOID

Real

DELAYCONSTANT

Real

[150]

Description Minimum void required behind a level tail and ahead of a level front at initiation time Number of pipe diameters a slug needs to propagate before the next hydrodynamic slug is initiated. 558 / 769

OLGA 7

ENDTIME

Real (s)

GASENTRAINMENT Symbol

NYDAL | [VOIDINSLUG]

End time for level slug initiation. If not given no end time restriction is enforced. Gas entrainment into slug from bubble for breaking/level front in slug tracking. NYDAL: Nydal correlation for entrainment. VOIDINSLUG: Entrainment based on correlation for void in slug.

ON | MANUAL | Option for initiating hydrodynamic slugs. [OFF] INITBUBBLEVOIDS RealList [1] Void fractions in the slug bubbles. INITENDTIMES RealList (s) End times for slug generation. The minimum distance between two INITFREQUENCY Real (1/s) consecutive slugs is defined as (bubble vel./INITFREQUENCY). Maximum initial length of hydrodynamic INITLENGTH Real slugs in number of pipe diameters. Time interval between initiations of INITPERIODS RealList (s) consecutive slugs. Labels of section boundaries where slug INITPOSITIONS SymbolList generation zones are located. INITSLUGVOIDS RealList [0.0] Void fraction in the liquid slug. INITSTARTTIMES RealList (s) Start times for slug generation. RealList The length of zones where slugs are to be INITZONELENGTHS (m) generated. Option for detecting and initiating level LEVEL Symbol ON | [OFF] slugs. Max number of slugs allowed in the system, MAXNOSLUGS Integer if not given there are no restrictions. The maximum void allowed in a level slug at SLUGVOID Real initiation time. Start time for level slug initiation. If not STARTTIME Real (s) given, level detection is on from simulation start. HYDRODYNAMIC

Symbol

Link to: SLUGTRACKING (on FLOWPATH) Description Keys

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OLGA 7

TUNING (on FLOWPATH) Description ( See also: Keys) This statement defines the tuning option, witch makes it possible to tune certain parameters in the model. The parameters available for tuning are at the moment very limited. Remark: The availability of the tuning option depends on the user’s licensing agreement with SPT Group. The TUNING keyword may be used for adjusting the OLGA model to specific sets of measured data or for sensitivity studies. TUNING should be applied with great care, as the validation and verification of the OLGA model may not be valid for such cases.

TUNING (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

AREA

RealList

[1.0]

DIAMETER

RealList

[1.0]

ENTRAINMENT

RealList

[1.0]

GROUGHNESS

Real

[1.0]

LAM_LGI

RealList

[1.0]

LAM_WOI

RealList

[1.0]

MASSTRANSFER RealList

[1.0]

OILDENSITY OILVISC

RealList RealList

[1.0] [1.0]

PIPE

SymbolList

[ALL]

POSITION

SymbolList

REHIGH

RealList

[3000]

Description Tuning coefficient for AREA in PIPE (used for equivalent pipes). NOTE: Cannot be applied on individual sections. Pipe level and higher is allowed. Tuning coefficient for diameter. NOTE: Cannot be applied on individual sections. Pipe level and higher is allowed. Tuning coefficient for entrainment rate of liquid droplets in gas Tuning coefficient for roughness from droplets. Tuning coefficient for interfacial friction factor between liquid and gas Tuning coefficient for interfacial friction factor between oil and water Tuning coefficient for mass transfer between gas and oil. Tuning coefficient for oil density Tuning coefficient for oil viscosity Pipe numbers or labels where the tuning parameters will be applied. Positions where the tuning parameters will be applied. If this key is defined, PIPE and SECTION can not be used in the same keyword statement. Maximum of laminar and turbulent friction factor will be used for Reynold's number higher than REHIGH, and an interpolated value will be used for Re between RELOW and REHIGH. Can be applied on individual sections, pipes and branches. 560 / 769

OLGA 7

RELOW

RealList

[2300]

ROUGHNESS

RealList

[1.0]

SECTION

RealList

TAMBIENT RealList WATERDENSITY RealList WATERVISC RealList

[1.0] [1.0] [1.0]

Laminar friction factor will be used for Reynold's number lower than RELOW, and an interpolated value will be used for Re between RELOW and REHIGH. Can be applied on individual sections, pipes and branches. Tuning coefficient for inner wall roughness. NOTE: Cannot be applied on individual sections. Pipe level and higher is allowed. Section or section boundary numbers where the tuning parameters will be applied. Tuning coefficient for ambient temperature. Tuning coefficient for water density Tuning coefficient for water viscosity

Link to: TUNING (on FLOWPATH) Description Keys

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OLGA 7

WAXDEPOSITION (on FLOWPATH) Description ( See also: Keys) This group is used to define input parameters for the wax deposition module. Wax deposition is defined for all flow paths, that is, all flow paths must have assigned a wax table. If multiple wax tables are used in a network, the fluid properties must be generated in a specific manner. The derivative of wax porosity (if POROSITYOPTION=AGEING) is defined in this manner: (INITPOROSITY-HARDPOROSITY)/AGEINGTIME Full temperature calculation (OPTIONS TEMPERATURE = WALL) is necessary when simulating wax deposition. Remarks:The availability of the wax deposition option depends on the user's licensing agreement with SPT Group. The wax deposition module cannot be applied together with the slug tracking or corrosion modules. The wax file is generated in PVTsim.

WAXDEPOSITION (on FLOWPATH) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

AGEINGOPT

Symbol

AGEING | [CONSTANT]

AGEINGTIME

RealList (d)

[7]

COEFSHEAR

RealList (kg/m2)

[0.0]

Description Options for treatment of porosity of deposited wax as function of time. If CONSTANT, no aging mechanism is activated. The porosity will either be directly given by WAXPOROSITY or an average value calculated by OLGA . If AGEING, INITPOROSITY, HARDPOROSITY and AGEINGTIME will be used to find change in porosity with time. New deposits will still have the porosity according to WAXPOROSITY settings. If INITPOROSITY is to be used as porosity values of new deposits, WAXPOROSITY must be set to the same values. Time for reduction of porosity from INITPOROSITY to HARDPOROSITY. Used to describe change in porosity with time due to aging. Branch-wise input. Shear deposition rate constant for deposition of precipitated wax. Branch-wise input. 562 / 769

OLGA 7

CONDUCTIVITY

RealList (W/m-K)

[0.242]

CONDUCTOPT

Symbol

TABLE | [MANUAL]

DIFFCOEFFMULT

RealList

[1.0]

DISSOLPRESS

RealList (Pa)

DISSOLRATE

RealList (kg/s-m2)

[1.e+12]

DISSOLTDIFF

RealList (C)

[0.0]

DISSOLUTION

Symbol

ON | [OFF]

HARDPOROSITY

RealList

[0.2]

INITPOROSITY

RealList

[0.8]

Pure paraffin wax thermal conductivity. Branch-wise input. Options for pure wax thermal conductivity. TABLE: The wax conductivity is taken from the wax tables. MANUAL: The conductivity is given through the key CONDUCTIVITY. Branch-wise input. Linear multiplier for modification of the component specific diffusion coefficients given in the wax-table. Branch-wise input. Pressures at which the values of DISSOLTDIFF apply. The melting/dissolve table (defined by DISSOLRATE, DISSOLTDIFF and DISSOLPRESS) will apply to all branches referred to in the BRANCH list. If different tables are wanted, separate WAXDEPOSITON statements must be given for each branch. Linear interpolation between table values. NOTE! Works only for MODEL=RRR. Maximum melting/diffusion rate. Applied for all branches given in keyword. Works only for MODEL=RRR. Difference between dissolution temperature and wax appearance temperature as function of pressure. The melting/dissolve table (defined by DISSOLRATE, DISSOLTDIFF and DISSOLPRESS) will apply to all branches referred to in the BRANCH list. If different tables are wanted, separate WAXDEPOSITON statements must be given for each branch. Linear interpolation between table values. Works only for MODEL=RRR. Switch for turning on/off dissolution. Only applicable with RRR model. Lower value of porosity after the given ageing period through AGEINGTIME. Has the following purposes: 1. To calculate change in porosity with time due to ageing. 2. Giving lower limit for porosity in the case of ageing when INSTPOROSITYOPT = MANUAL. When INSTPOROSITYOPT = AUTOMATIC, the lower limit for the porosity is given by MINPOROSITY, and HARDPOROSITY is only used for calculating the porosity change rate. HARDPOROSITY must be equal to or larger than MINPOROSITY. Branch-wise input. Initial porosity of deposited wax, used only for describing change in porosity with time due to ageing. Branch-wise input. 563 / 769

OLGA 7

INSTPOROSITYOPT Symbol

MANUAL | [AUTOMATIC]

MAXPOROSITY

RealList

[0.8]

MAXROUGHNESS

RealList (m)

[1.0E6]

MINPOROSITY

RealList

[0.2]

MODEL

Symbol

SHEARMULTC2

Real

SHEARMULTC3

Real

VISCMULTD

Real

VISCMULTE

Real

VISCMULTF

Real

Options for calculating instantaneous porosity of deposited wax. MANUAL: A constant value is used, given by WAXPOROSITY. AUTOMATIC: The porosity will be calculated by the internal flow dependent model. The keys MINPOROSITY and MAXPOROSITY are used to determine the minimum and maximum limits for the porosity. The wax porosity may be changing with changing flow conditions, and the average porosity seen at a given point may be different from the instantaneous porosity given by the internal porosity model. Branch-wise input. The maximum limit for the calculated porosity is given by this key. Used when INSTPOROSITYOPT=AUTOMATIC. The porosity of new deposits is calculated by OLGA and an volume averaging of the porosity of new and old layers will be performed. Branch-wise input. Maximum wax layer roughness allowed. Branch-wise input. The minimum limit for the calculated porosity is given by this key. Used when INSTPOROSITYOPT=AUTOMATIC. The porosity of new deposits is calculated by OLGA and an volume averaging of the porosity of new and old layers will be performed. Branch-wise input.

MATZAIN | HEATANALOGY Wax deposition model. | [RRR] Tuning multiplier for empirical constant C2 [1.0] in MATZAIN wax deposition model. Branchwise input. Tuning multiplier for empirical constant C3 [1.0] in MATZAIN wax deposition model. Branchwise input. Tuning multiplier for the “D” parameter in the internal non-Newtonian viscosity [1.0] correlation. Only used when VISCOPTION=CALSEP. Branch-wise input. Tuning multiplier for the “E” parameter in the internal non-Newtonian viscosity [1.0] correlation. Only used when VISCOPTION=CALSEP. Branch-wise input. Tuning multiplier for the “F” parameter in the internal non-Newtonian viscosity [1.0] correlation. Only used when VISCOPTION=CALSEP. Branch-wise input. Option for calculating the wax/oil dispersion viscosity TABULAR: Viscosity multiplier given as function of volume fraction of wax.

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OLGA 7

TABULAR | [CALSEP]

VISCOPTION

Symbol

VISMULTIPLIER

RealList

WAXPOROSITY

RealList

[0.6]

WAXROUGHNESS

RealList

[0.0]

WAXTABLE

SymbolList

WAXVOLFRACTION

RealList

given as function of volume fraction of wax. CALSEP: Use internal model. VISCOPTION must be selected for the whole system of branches. Ratio of viscosity of wax/oil dispersion to oil viscosity. Corresponding to the wax volume fractions given in WAXVOLFRACTION. The viscosity multiplier table (defined by VISMULTIPLIER and WAXVOLFRACTION) will apply to all branches referred to in the BRANCH list. If different tables are wanted, separate WAXDEPOSITON statements must be given for each branch. Linear interpolation between table values. Porosity of new deposits in wax layer. Used when INSTPOROSITYOPT=MANUAL. Branch-wise input. Fraction of wax layer thickness that is interpreted as wax layer roughness (i.e. wall roughness). Limited by MAXROUGHNESS. Branch-wise input. Name of wax table. Branch-wise input. Volume fractions of precipitated wax dispersed in oil corresponding to the viscosity multiplier values given in VISMULTIPLIER. The viscosity multiplier table (defined by VISMULTIPLIER and WAXVOLFRACTION) will apply to all branches referred to in the BRANCH list. If different tables are wanted, separate WAXDEPOSITON statements must be given for each branch. Linear interpolation between table values.

Link to: WAXDEPOSITION (on FLOWPATH) Description Keys

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OLGA 7

DRILLINGFLUID (on LibraryLevel) Description ( See also: Keys) This statement enables the use of drilling fluids. They are treated as extra fluids and are tracked through the pipeline. They do not replace any of the phases. The fluid properties of a drilling fluid can be given in two different ways: 1. Define the range of density and viscosity at standard conditions for a drilling fluid. The density and viscosity used at the inlet is given in SOURCE or NODE. 2. Get the fluid properties for the drilling fluid from a separate fluid property file. The fluid property file must then have an appropriate string in the header of the file: string "GASMUD" if gas phase is used as drilling fluid string "OILMUD” if oil phase is used as drilling fluid string "WATERMUD" if water phase is used as drilling fluid Non-Newtonian rheology is applied if the PVT table contains the rheology parameters yield stress or power law exponent. The non-Newtonian models Bingham and Power law are used to modify the viscosity of the drilling fluid as for the complex viscosity option, see (Complex Fluid Module). For oil-based mud, the power law exponent or yield stress is read when the heading contains the strings "POWEXPL" or "YIELDSTRL" respectively. For water-based mud, the power law exponent or yield stress is read when the heading contains the strings "POWEXPW" or "YIELDSTRW" respectively. For both types of mud the power law exponent and/or the yield stress should then be given in the file as a function of pressure and temperature. A combination of 1) and 2) can not be used in the same case. This keyword requires access to the Wells Module.

DRILLINGFLUID (on LibraryLevel) Keys ( See also: Description ) Key CUTDENSITY FLUIDTABLE LABEL

Type

Parameter set

Unit:( ) Default:[ ] Real [2100.0] (kg/m3) Symbol [DRILLINGFLUIDString 1]

MAXDENSITY

Real (kg/m3)

MAXVISCOSITY

Real (Ns/m2)

MINDENSITY

Real (kg/m3)

Description Density of cutting particles. Global value that only should be set once. Label or number of fluid table in PVT file. Name of definition. The maximum density of the drilling fluid to be used in the entire drilling process. The densisty must be given at standard conditions. The maximum viscosity of the drilling fluid to be used in the entire drilling process. The viscosity must be given at standard conditions. The minimum density of the drilling fluid to be used in the entire drilling process. The density must be given at standard 566 / 769

OLGA 7

MINDENSITY

(kg/m3)

MINVISCOSITY

Real (Ns/m2)

TYPE

WATERMUD | Symbol OILMUD | GASMUD

VISCOSITYBCONST Real

VISCOSITYCCONST Real

density must be given at standard conditions. The minimum viscosity of the drilling fluid to be used in the entire drilling process. The viscosity must be given at standard conditions. Type of drilling fluid. The following types are allowed: WATER, OIL, and GAS. B constant in the Vogel viscosity model for water based muds. visc = visc0*exp(B/(T+C)) where visc0 is given in SOURCE and/or NODE. C constant in the Vogel viscosity model for water based muds. visc = visc0*exp(B/(T+C)) where visc0 is given in SOURCE and/or NODE.

Link to: DRILLINGFLUID (on LibraryLevel) Description Keys

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OLGA 7

HYDRATECURVE (on LibraryLevel) Description ( See also: Keys) This keyword defines a hydrate formation curve to be used with the HYDRATECHECK keyword. See also: HYDRATECHECK

HYDRATECURVE (on LibraryLevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

Description

Units and orders of columns of the temperature and pressure in the SymbolList TEMPERATURE COLUMNHEADER HYDRATEFILE. By default the first (ValueUnitPair) | PRESSURE column is for temperature and the second for pressures. YES: The hydrate dissociation curve is to be read from a data file. NO: The hydrate FROMFILE Symbol YES | [NO] curve is specified using the keys PRESSURE and TEMPERATURE. The name of the file containing hydrate temperature as a function of pressure or HYDRATEFILE String vice versa. Must be specified when FROMFILE=YES. Inhibitor concentration (in weight percent) INHIBCONC Real [0] for a hydrate curve (default = 0). The inhibitor component to use with the hydrate curve. For Compositional Tracking only. The inhibitor component INHIBITOR Symbol must be defined in the feed file, possible selections are: EtOH, MeOH, MEG, DEG and TEG. LABEL String [HYD-1] The label of this hydrate curve. Hydrate formation pressure for each given temperature point. The pressure points PRESSURE RealList (Pa) have be unique and entered in increasing order. Temperature points defining the hydrate TEMPERATURE RealList (C) curve. The temperature points have to be unique and entered in increasing order. Link to: HYDRATECURVE (on LibraryLevel) Description Keys

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OLGA 7

MATERIAL (on LibraryLevel) Description ( See also: Keys) This statement specifies physical properties of the materials associated with the pipe wall, pipeline coating, insulation and soil. If a fluid is enclosed between two concentric cylinders, natural convection will be significant for the heat transfer rate. By choosing TYPE = FLUID, OLGA will calculate the natural convection. The viscosity and expansion coefficient of the fluid must then be given. If the fluid is a gas at low pressure (< 100 bar) natural convection will have less influence on the heat transfer rate and radiation will become important as well. Radiation is included in heat transfer calculation by setting RADIATION = YES. INNEREMISSIVITY and OUTEREMISSIVITY must then be specified. (High emissivity means low reflectivity.) Stefan-Boltzmann's law for long concentric cylinders is used to calculate the heat transfer rate. The heat transfer rate due to radiation is negligible if one or both of the emissivities are small.

MATERIAL (on LibraryLevel) Keys ( See also: Description ) Key CAPACITY

CONDMULT

Type

Parameter set

Unit:( )

Default:[ ]

Real (J/kgC)

Thermal capacity of the material.

Real

Conductivity multiplier below PHCHMIN. Between PHCMIN and PHCMAX, the multiplier is linearly interpolated from CONDMULT to 1.

EXPANSION

Real (W/mC) Real (kg/m3) Real (1/C)

FUSIONMULT

Real

HCAPMULT INNEREMISSIVITY LABEL OUTEREMISSIVITY

Real Real String Real

PHCHMAX

Real (C)

PHCHMIN

Real (C)

RADIATION

Symbol

CONDUCTIVITY DENSITY

Description

Thermal conductivity of the material. Material density.

[0] [MAT-1] [0]

YES | [NO]

Expansion coefficient of fluid layer. Heat capacity multiplier between PHCHMIN and PHCHMAX used to model latent heat of fusion. If FUSIONMULT is 0, the heat capacity multiplier is linearly interpolated from HCAPMULT to 1 between PHCMIN and PHCMAX. Heat capacity multiplier below PHCHMIN Emissivity of inner surface of fluid layer. Material label. Emissivity of outer surface of fluid layer. Upper temperature limit for phase change region Lower temperature limit for phase change region NO: No radiation across fluid layer. Yes: Radiation across fluid layer. 569 / 769

OLGA 7

RADIATION

Symbol

YES | [NO]

TYPE

Symbol

FLUID | PCM | [SOLID]

VISCOSITY

Real (Ns/m2)

Radiation across fluid layer. Type of wall material. SOLID: Normal wall layer material. FLUID: Stagnant fluid material. PCM: Phase changing material Dynamic viscosity of fluid material

Link to: MATERIAL (on LibraryLevel) Description Keys

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OLGA 7

SHAPE (on LibraryLevel) Description ( See also: Keys) This keyword describes the external contour of a material. The type of the shape can be one of the following: CIRCLE, ELLIPSE, RECTANGLE, POLYGON. The material inside the shape is being described with the MATERIAL keyword. The shape keyword is being used for solid bundles.

SHAPE (on LibraryLevel) Keys ( See also: Description ) Key LABEL MATERIAL RADIUS

Type

Parameter set

Unit:( )

Default:[ ]

String Symbol Real (m)

[SHAPE-1]

TYPE

Symbol

X_LOWER_LEFT

Real (m)

X_UPPER_RIGHT Real (m) XPOINTS

RealList (m)

Y_LOWER_LEFT

Real (m)

Y_UPPER_RIGHT Real (m) YPOINTS

RealList (m)

Description Name of shape. Name/label of solid inside the shape. Radius of the circle.

| CIRCLE Type of shape. CIRCLEs are automatically | RECTANGLE | placed in the origin. POLYGON x-coordinate of the lower left corner of the rectangle. x-coordinate of the upper right corner of the rectangle. x-coordinates of the polygon. Polygon points have to be specified counter clockwise. y-coordinate of the lower left corner of the rectangle. y-coordinate of the upper right corner of the rectangle. y-coordinates of the polygon points. Polygon points have to be specified counter clockwise.

Link to: SHAPE (on LibraryLevel) Description Keys

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OLGA 7

TABLE (on LibraryLevel) Description ( See also: Keys) This statement defines a function in tabular form either valve sizing coefficient or well flow parameters.

TABLE (on LibraryLevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

INJECTIONPRESSURE Real (Pa) LABEL LOOKUP

String Symbol

OPENING

Real

POINT

RealList

TABLE

Symbol

XLOOKUPVARIABLE

Symbol

XVARIABLE

YVARIABLE

[TABLE-1] ON | [OFF]

Description Injection pressure at which the GLV curve is defined. Table label. Turn on look-up function. Define the opening for which DELTAP-CV relationship is valid. Instead of defining one OPEN-CV table for a valve, one can instead define a list of DELTAPCV tables, and the CV for the valve is found by interpolating w.r.t. both DELTAP and OPENING. This functionality is only valid for valves with PHASE=LIQUID. Define the list of values of both independent and dependent variables in the table (x1, y1, x2, y2, ...). Table where XLOOKUPVARIABLE input is sampled. Name of x variable

XVAR | [YVAR] NOTGIVEN | OPEN | SymbolList Independent variable DELTAP | LEVEL | (ValueUnitPair) name PRODUCTIONPRESSURE NOTGIVEN | CV | FLOW | GASFL | LIQFL | PILIQ | SymbolList WATFR | OILTC | GASTC | Dependent variable name (ValueUnitPair) WATTC | STDGASFLOW | VOLUME

Link to: TABLE (on LibraryLevel) Description Keys

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OLGA 7

TIMESERIES (on LibraryLevel) Description ( See also: Keys) The TIMESERIES keyword is a generic function of time. This means that it can be used for different physical properties. There is a built in sine function, normal point series can be used, and in addition a combination of these are possible. The time series functionality is implemented for ambient temperature, soil temperature and radiation.

TIMESERIES (on LibraryLevel) Keys ( See also: Description ) Type

Parameter set

Unit:( )

Default:[ ]

AMPLITUDE

Real

COMBINETYPE

Symbol

FACTOR

RealList

INTERPOLATION

Symbol

LABEL

String

PERIOD

Real (s)

PERIODIC

Symbol

SERIES

RealList

SERIESREF

SymbolList

TIME

RealList (s)

TIME0

Real (s)

TRANSITION

Symbol

Amplitude of the sine function This key determines how the time series in SERIESREF are combined. When using SEQUENTIAL, the time series are | combined in sequence according to the SEQUENTIAL | order in which they are defined. The [ADDITIVE] transition from one to the next is defined in the keys TRANSITIONTIME and TRANSITION. If ADDITIVE is used, the values are simply added. Scaling factor for each time series in [1] SERIESREF. If this key is not given, a factor of 1 is used. | STEP | Type of interpolation between each point in [LINEAR] time. [TIMESERIES-1] Label of timeseries The time it takes for the sine function to start repeating itself. If this key is set to ON, the function will be repeated. If the first and last value of the function are equal, the function will be | ON | smooth. If PERIODIC = OFF, the last value [OFF] will be used for the remainder of the simulation when the time exceeds the defined range. Series of function values at corresponding times defined in key TIME List of TIMESERIES labels to be used. Note that circular references are not allowed. Points in time for every given value in the key SERIES This key is used to define the phase shift of [0] the sine function. If it is set to a quarter period, a cosine function is created. | STEP | Type of transition from one time series in [LINEAR] SERIESREF to the next.

Key

Description

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OLGA 7

This key is used to determine the points in time when the transition from one time series in SERIESREF to the next occur. If PERIODIC = ON, the difference between the first and last point is used to determine the period of the function.

TRANSITIONTIME RealList (s)

TYPE

Symbol

| POINTS | COMBINE | [SINE]

Option for type of time series.

Link to: TIMESERIES (on LibraryLevel) Description Keys

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OLGA 7

TRACERFEED (on LibraryLevel) Description ( See also: Keys) This statement defines a feed of tracer, for instance a feed of kinetic hydrate inhibitor or corrosion inhibitor. When used for tracking a tracer with aging effect, a distribution in age groups may be chosen, otherwise the key AGING should be set to OFF. The tracer mass, residence time and age are tracked through the pipeline system. Tracers are, however, assumed to be present in such small concentrations that they do not influence the hydraulics. TRACERFEEDs may be referenced in a SOURCE or MASSFLOW node. To use TRACERFEED, the key TRACERTRACKING must be set to ON under the OPTIONS keyword.

TRACERFEED (on LibraryLevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

AGEBOUNDARIES RealList (s)

AGING

Symbol

ON | [OFF]

CARRIERPHASE

Symbol

GAS | OIL | [WATER]

HIGHLOWBOUND Real

[0.0]

LABEL

[TFEED-1]

String

LOWLOWBOUND Real

[0.0]

Description Boundaries of age groups [s]. N AGEBOUNDARIES give N+1 age groups, one below the lowest boundary, one above the highest boundary, and N-1 groups bounded by the N boundaries. Switch for activating aging effect on. Carrying phase of the inhibitor. KHI will not follow any vaporization to the gas phase. Gas/liquid phase transfer will not affect the KHI amounts in the carrying phase, only the concentrations. Age output variables are set to zero if (tracer mass)/(tracer mass + carrier phase mass) of the requested feed/age group is lower than this value and the ratio hasn't been above HIGHLOWBOUND since it was lower than LOWLOWBOUND. Tracer feed label. Age output variables are set to zero if (tracer mass)/(tracer mass + carrier phase mass) of the requested feed/age group is lower than this value.

Link to: TRACERFEED (on LibraryLevel) Description Keys

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OLGA 7

WALL (on LibraryLevel) Description ( See also: Keys) This statement specifies the wall data for pipes. In the wall statement the user specifies the wall layer geometry and the name of the wall. These data are required if the TEMPERATURE option is "WALL" or "FASTWALL" in OPTIONS. The user also specifies the required data if the walls are to be heated. Heated walls can only be used together with TEMPERATURE = WALL. The pipe wall may consist of different material layers, specified by the keys "MATERIAL" and "THICKNESS". Each material layer can be divided into sub layers either by specifying each sub layer as a new material layer or by automatic discretization of the material layers by the use of the key "DISCRETIZATION". Heat can be provided to a user specified wall layer in each wall. Constant heat or heat varying with time. Each wall in OLGA may contain only one heat source, i.e. the heat per unit length supplied to the wall is constant along the pipe having this specific wall. The heat sources may vary along the pipelines by specifying different walls along the line. A combination of walls having constant power supply and no power supplied at all can be specified in the same OLGA case.

WALL (on LibraryLevel) Keys ( See also: Description ) Key

Type Unit:( )

CONTROLLERLABEL Symbol DISCRETIZATION

SymbolList

ELECTRICHEAT INNERDIAMETER LABEL

Symbol Real (m) String

MATERIAL

SymbolList

MAXNOLAYERS

IntegerList

MAXRATIO

RealList

POWERCONTROL

RealList (W/m) Symbol

POWERMAX

Real (W/m)

THICKNESS

RealList (m)

TIME

RealList (s)

WALLAYER

Integer

POWER

Parameter set

Description

Default:[ ] Name of controller for electric heating | ON Switch on or off auto-discretization for each | [OFF] wall material layer. ON | [OFF] Switch electric heating on or off. Pipe's inner diameter. [WALL-1] Label of the wall. Names of materials that are used in the wall layers. Maximum number of sub-layers allowed for each of the layers. Maximum ratio of outer to inner radius of [2] sub-layers. Power per unit length for the electric heating time series. ON | [OFF] Switch power control on or off. Max. power per unit length for electric heating if it is restricted by a control system. Thickness of each wall layer. Time series when POWER is to be [0.0] modified. Wall layer for electric heating.

Link to: WALL (on LibraryLevel) Description Keys 576 / 769

OLGA 7

Output Variables The variables belonging to a section in the pipeline are divided between boundary variables and volume variables. This is due to the staggered mesh used in the numeric solution of the problem, where some variables are computed at the section boundaries (boundary variables) while others are computed in the middle of the section (volume variables). Branch variables will give quantities, relating to the branch, such as, for instance, liquid content. Global variables will give quantities relating to the total system, such as total mass in the system, or relating to the integration, such as the time step. In addition to the variables describing the pipeline, we have variables describing the process equipment, such as compressors, sources etc. All variables listed can be written to the trend plot data file. Variables defined as boundary or volume variables can also be written to the profile plot data file. The abbreviations for the use of the variables (in the «Use as» column in the listing) are as follows: O: TP: PP: C: S:

Printed output variable (to be specified with keyword OUTPUT). Trend plot variable (to be specified with keyword TREND). Profile plot variable (to be specified with keyword PROFILE). Controller signal input variable (to be specified as the controlled variable for a controller, input group CONTROLLER). Only for server output

Variables belonging to different groups cannot be specified together in the input for trend plotting (except the boundary and volume variable groups). A new TRENDDATA entry has to be specified for each variable group.

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OLGA 7

OUTPUT (on CASELevel) Description ( See also: Keys) This statement defines the time intervals for when the variables defined in OUTPUTDATA is reported. The information is saved as an output file (*.out) which can be opened in a text editor. It is possible to specify either time points for output (TIME) or a time interval for output (DTOUT). It is also possible to specify different time intervals for output using a combination of TIME and DTOUT.

OUTPUT (on CASELevel) Keys ( See also: Description ) Type

Parameter set

Unit:( )

Default:[ ]

COLUMNS

Integer

[4]

DTOUT

RealList (s)

TIME

RealList (s)

Key

[0.0]

Description Number of variable columns per page. Must not be greater than 6. Time interval(s) between subsequent printings of output. The time interval is changed at the times specified in TIME. If TIME is not specified or only contains one value, only one value must be given for DTOUT. This value is used throughout the entire simulation. Instants in time when the plot interval is changed.

Link to: OUTPUT (on CASELevel) Description Keys

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OLGA 7

OUTPUTDATA (on CASELevel) Description ( See also: Keys) This statement defines the variables to be printed to the output file (*.out). Only the global variables are

available on this level.

OUTPUTDATA (on CASELevel) Keys ( See also: Description ) Key

VARIABLE

Type Unit:( ) SymbolList (ValueUnitPair)

Parameter set

Description

Default:[ ] List of variable names to be printed. Units may be specified.

Link to: OUTPUTDATA (on CASELevel) Description Keys

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OLGA 7

PLOT (on CASELevel) Description ( See also: Keys) This statement defines the time interval (DTPLOT) for the plot variables. Plot files: The graphical presentation of results should be considered the primary source to an understanding of the calculated state in the pipeline. A graphical package is supplied as part of the OLGA GUI. The trend plot file and the profile plot file are in ASCII format. The ASCII format files can be used to interface the results from OLGA with any graphical package the user might have access to. Both the trend plot file and the profile plot file consist of a heading and the time and variables specified with the keyword statement TREND and PROFILE in the input file (extension inp). In addition to the OLGA GUI graphical package, the stand-alone tools OLGA Viewer (.plt files) and FEMTherm Viewer (.osi) are available for visualisation of results. The .plt and .osi files are in binary format. Also, the stand-alone tool FEMThermTool can be used for both 2D thermal computation in a cross section and visualisation of the triangular grid generated when using the FEMTherm module.

PLOT (on CASELevel) Keys ( See also: Description ) Key

Type Unit:( )

DTPLOT

RealList (s)

TIME

RealList (s)

VARIABLE

SymbolList (ValueUnitPair)

Parameter set

Description

Default:[ ]

[0.0]

Time interval between subsequent printouts of the plot variables. Instants in time when the plot interval is changed. List of variable names to be plotted. Units may be included in the list. N.b., variables from different groups can be defined on the same line.

Link to: PLOT (on CASELevel) Description Keys

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OLGA 7

PROFILE (on CASELevel) Description ( See also: Keys) This statement defines either time points (TIME) or a time interval (DTPLOT) for the profile plot variables.

PROFILE (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

DTPLOT

RealList (s)

DTTIME

RealList (s)

TIME

RealList (s)

Description

[0.0]

Time interval between subsequent printouts to the profile plot file. Points in time when the plot interval is changed. Instants in time when data is written to the profile plot file.

Link to: PROFILE (on CASELevel) Description Keys

581 / 769

OLGA 7

PROFILEDATA (on CASELevel) Description ( See also: Keys) This statement defines profile plot variables along the pipeline at specified time points. Flow path variables defined on this level will be reported for all flow paths. For available profile variables see Output Variables.

PROFILEDATA (on CASELevel) Keys ( See also: Description ) Key

Type Unit:( )

AGEGROUPID

IntegerList

COMPONENT

SymbolList

HYKPID

IntegerList

LAYER

IntegerList

TRACERFEED

SymbolList

VARIABLE

SymbolList (ValueUnitPair)

Parameter set

Description

Default:[ ]

BOCOMP-1

Age group for plotting inhibitors variables with aging effect, e.g. Kinetic hydrate inhibitor (KHI). Component names. Using the Inhibitor tracking module, available components are HC, H2O and MEG/MEOH/ETOH. Using DRILLING=ON under OPTIONS, available components are HC, H2O, MEG/MEOH/ETOH, CUTTING and MUD components. For compositional models the names of the available components are given in the feed file. Array element index of HYKPLIST. Wall layer numbers for plotting of wall temperatures. Layer no. 1 is the innermost one. Tracer label that the tracer type variables are plotted for. List of variable names to be plotted. Units may be specified.

Link to: PROFILEDATA (on CASELevel) Description Keys

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OLGA 7

TREND (on CASELevel) Description ( See also: Keys) This statement defines the time interval for trend plotting. The time intervals may be given as single time interval (DTPLOT), directly as a set of time points (TIME) or as a set of time intervals changing at specified time points (combination of DTPLOT and TIME).

TREND (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

DTPLOT

RealList (s)

NPLOT

IntegerList

TIME

RealList (s)

[0.0]

Description Time interval between subsequent trend variable printouts. DTPLOT should only be given once in the input file, if given more than once, OLGA will use the last value given. Number of data points. A list of NPLOT values refers to the time points given in TIME, i.e., the sample period will be DTIME/NPLOT. Instants in time when the plot interval is changed.

Link to: TREND (on CASELevel) Description Keys

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OLGA 7

TRENDDATA (on CASELevel) Description ( See also: Keys) This statement defines the trend data to be plotted. A trend plot is a time series plot for a specified variable. Only global and branch variables are available on this level.

TRENDDATA (on CASELevel) Keys ( See also: Description ) Key HYKPID VARIABLE

Type Unit:( ) Integer SymbolList (ValueUnitPair)

Parameter set

Description

Default:[ ] Array element index of HYKPLIST. List of variable names to be plotted. Units may be specified.

Link to: TRENDDATA (on CASELevel) Description Keys

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OLGA 7

PHASESPLITNODE Description ( See also: Keys) The phase split node behaves as something in-between the internal network node and the network separator. There are no level controls and separator efficiencies included, but the phase distributions for the outgoing branches can be specified. The phase split node has an arbitrary number of inlets/outlets. It has six different types of terminals: GAS, OIL, WATER, LIQUID, DRYGAS and MIXTURE. Terminal = GAS Terminal = OIL Terminal = WATER Terminal = LIQUID Terminal = DRYGAS Terminal = MIXTURE

- gas +droplets - oil bulk - water bulk - oil and water bulk - gas only - all phases within the node itself(default)

The following connections are defined:

· · · · · ·

MIXTURE_1, … MIXTURE _N inlets and outlets GAS_1, … GAS_N outlets OIL_1, …OIL_N outlets WATER_1, …WATER_N outlets LIQUID_1, ... LIQUID_N outlets DRYGAS _1, … DRYGAS _N outlets

PHASESPLITNODE Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

FEEDMASSFRACTION RealList FEEDMOLEFRACTION RealList

FEEDNAME

SymbolList FEED-1 | BOFEED-1

FEEDVOLFRACTION

RealList

FLUID

Symbol

Description Mass fraction of each feed. Mole fraction of each feed. Label of feeds feeding to terminal nodes. Requires COMPOSITIONAL=ON or BLACKOIL under the OPTIONS keyword. Volume fraction of each feed given in FEEDNAME for choke model (only for Blackoil model). Label or number of PVT table to apply for the specific branch. If a keyword based pvt-file is used, FLUID must be the same as the LABEL given in the pvt-file, i.e., numbering is not valid for this format. 585 / 769

OLGA 7

INFO

String

INHIBFRACTION

Real

LABEL

String

PRESSURE

Real (Pa)

STEAMFRACTION

Real

TEMPERATURE

Real (C)

VOIDFRACTION

Real

VOLUME

Real (m3)

WATERCUT

Real

X

Real (m)

Y

Real (m)

Z

Real (m)

General information about the PhaseSplitNode. For information purposes only. Mass fraction of inhibitor in the [0.0] water phase. Network component label (if [PHASESPLITNODE_tag] nothing is given the NC tag is used). Initial pressure when using INITIALCONDITIONS. Fraction of total mass of H2O component in the gas phase. By default (=-1), the mass of H2O component is in the gas phase if the temperature is greater than the saturation temperature, otherwise, the mass of H2O [-1.0] component is distributed between the gas phase and the water phase according to the vapor pressure of H2O in the gas phase. A list of both positive and negative values is not allowed. Initial temperature when using INITIALCONDITIONS. Gas volume fraction when using INITIALCONDITIONS.. Specify –1 for OLGA to use the equilibrium values from the fluid property tables. Volume of PhaseSplitNode. If specified volume is less than or [-1] equal to 0, OLGA will estimate the volume (see User's manual). Initial watercut when using [0.0] INITIALCONDITIONS. x-coordinate of node in network. [0] Used for 3D graphics only. y-coordinate (vertical axis) of [0] node in network. Used for 3D graphics only. z-coordinate of node in network. [0] Used for 3D graphics only.

Link to: PHASESPLITNODE Description Keys

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OLGA 7

SEPARATOR Description ( See also: Keys) The network separator model in OLGA is not intended to accurately model separation phenomena, but is meant to include the influence of a separator on transient pipeline dynamics. The network separators have arbitrary number of outlets. Two phase separators must have connected at least one gas-outlet and one oil-outlet to pipes. Three phase separators must have connected at least one gas-outlet, one oil-outlet and one water-outlet to pipes. The user can define the separation efficiency (gas/liquid and oil/water), and set critical levels for oil and water drainage. Model description and user guidelines: 1. Separator type: The separator may be horizontal or vertical, two-phase of three-phase. 2. Pipelines downstream of network separators. For a two phase separator, the following outlets are defined: GAS_1, .., GAS_N outlets (Use Gas_2 to model flare outlet) OIL_1, .., OIL_N outlets (Use OIL_2 to model emergency outlet) For a three-phase separator, the following outlets are defined: GAS_1, .., GAS_N outlets OIL_1, .., OIL_N outlets WATER_1, .., WATER_N outlets 3. Valves. The network separators have no internal valves. All valves must be defined on the outgoing branches, using the VALVE keyword. 4. Levels used by a network separator. The separator levels are controlled by the valves and controllers in the outlet branches. Moreover, the water level limit for when the water will be drained together with the oil can be specified by the keys: HHWATHOLDUP or HHWATLEVEL

SEPARATOR Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

DIAMETER

Real (m)

EFFHIGH

Real

[0.995]

EFFICIENCY

Real

[1.0]

EFFLOW

Real

[0.995]

FEEDMASSFRACTION RealList FEEDMOLEFRACTION RealList FEEDNAME

SymbolList

FEED-1 | BOFEED-1

Description Separator diameter. Liquid volume fraction when the efficiency goes toward zero and the separator is treated as a normal section. Gas/liquid separation efficiency. (One minus the volume fraction of liquid droplets in the gas outlet stream.) Liquid volume fraction when the efficiency is reduced. Mass fraction of each feed. Mole fraction of each feed. Label of feeds used to initialize separator. Requires COMPOSITIONAL=ON or BLACKOIL under the OPTIONS keyword.

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OLGA 7

FEEDVOLFRACTION

RealList

FLUID

Symbol

HHWATHOLDUP

Real

HHWATLEVEL

Real (m)

INITOILLEVEL INITPRESSURE INITTEMPERATURE INITWATLEVEL

Real (m) Real (Pa) Real (C) Real (m)

LABEL

String

LENGTH

Real (m)

LEVELTABLE

Symbol

OILTCONST

Real (s)

ORIENTATION

Symbol

PHASE

Symbol

SURFACEAREA

Real (m2) RealList (C) RealList (s) Real (W/m2-C)

TAMBIENT TIME UVALUE

under the OPTIONS keyword. Volume fraction of each feed given in FEEDNAME for choke model (only for Blackoil model). Label or number of fluid table to apply for the specific branch. If a keyword based pvt-file is used, FLUID must be the same as the LABEL given in the pvt-file, i.e., numbering is not valid for this format. Water hold-up upper limit. If the water hold-up exceeds this value water will be drained together with oil through the oil drain. Water level upper limit. If the water level exceeds this value water will be drained together with oil through the oil drain. The initial oil level. Initial pressure. Initial temperature. [0.0] The initial water level. Network component label (if nothing is [SEPARATOR_tag] given the NC tag is used). Separator length. Label of the table where the relation between level (height) in the separator and volume of the separator is given. Time constant for separation of oil from [0.0] water. | VERTICAL | Orientation of the separator.. HORIZONTAL Number of phases separated in the TWO | THREE separator. Surface area of the separator. Ambient temperature. [0.0] [0.0]

WATTCONST

Real (s)

[0.0]

X

Real (m)

[0]

Y

Real (m)

[0]

Z

Real (m)

[0]

Time series for specified boundary values. Overall heat transfer coefficient given by user based on inner pipe diameter. Time constant for separation of water from oil. x-coordinate of separator in network. Used for 3D graphics only y-coordinate (vertical axis) of separator in network. Used for 3D graphics only z-coordinate of separator in network. Used for 3D graphics only 588 / 769

OLGA 7

Link to: SEPARATOR Description Keys

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OLGA 7

OUTPUTDATA (on SEPARATOR) Description ( See also: Keys) This statement defines the separator variables to be printed to the output file (*.out). See Separator Output Variables for available variables.

OUTPUTDATA (on SEPARATOR) Keys ( See also: Description ) Key

VARIABLE

Type Unit:( ) SymbolList (ValueUnitPair)

Parameter set

Description

Default:[ ] List of variables to be printed. Units may be specified.

Link to: OUTPUTDATA (on SEPARATOR) Description Keys

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OLGA 7

TRENDDATA (on SEPARATOR) Description ( See also: Keys) This statement defines the trend data to be plotted for separators. A trend plot is a time series plot for a specified variable. For available variables see Separator Output Variables.

TRENDDATA (on SEPARATOR) Keys ( See also: Description ) Key

VARIABLE

Type Unit:( ) SymbolList (ValueUnitPair)

Parameter set

Description

Default:[ ] List of variables to be plotted. Units may be specified.

Link to: TRENDDATA (on SEPARATOR) Description Keys

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OLGA 7

ANNULUS Description ( See also: Keys) Annulus is a network component. See ANNULUS COMPONENT for more description. See also ANNULUS COMPONENT Keys

ANNULUS Keys ( See also: Description ) Key LABEL

Type

Parameter set

Unit:( )

Default:[ ]

String

[ANNULUS_tag]

Description Network component label (if nothing is given the NC tag is used).

Link to: ANNULUS Description Keys

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OLGA 7

COMPONENT (on ANNULUS) Description ( See also: Keys) This statement defines the configuration of pipes which are bundled together and have thermal interaction. Gas-lifted wells are typical examples, where gas is injected in the annulus between the casing and tubing while the production fluid together with the injected gas is produced in the tubing.

COMPONENT (on ANNULUS) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

FLOWPATH

Symbol

FROM

Symbol

OUTERHVALUE

Real (W/m2C)

TO

Symbol

XOFFSET

Real (m)

[0.0]

YOFFSET

Real (m)

[0.0]

Description Label of a FLOWPATH that resides inside the BUNDLE. Label of the POSITION on the FLOWPATH where it enters the BUNDLE. Heat transfer coefficient at the wall surface of a branch to the bulk fluid in the carrier line. Forced/free convection will be applied if this key is not defined. Label of the POSITION on the FLOWPATH where it exits the BUNDLE. The component's displacement along the xaxis relative to the center of the bundle. The component's displacement along the yaxis relative to the center of the bundle.

Link to: COMPONENT (on ANNULUS) Description Keys

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OLGA 7

FLUIDBUNDLE Description ( See also: Keys) FLUIDBUNDLE is a network component. See FLUIDBUNDLE COMPONENT for details. See also FLUIDBUNDLE COMPONENT Keys

FLUIDBUNDLE Keys ( See also: Description ) Type Key

LABEL

Parameter set Unit:( Default:[ ] ) String [FLUIDBUNDLE_tag]

Description Network component label (if nothing is given the NC tag is used).

Link to: FLUIDBUNDLE Description Keys

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OLGA 7

COMPONENT (on FLUIDBUNDLE) Description ( See also: Keys) This keyword defines a carrier line that encloses one or several FLOWPATHS, LINES and/or FLUIDBUNDLES. The carrier line itself must be specified as either a FLOWPATH or a LINE. The length and elevation of each pipe section contained in the bundle must be maintained. Pipe diameters must be constant in the axial direction. The effects of heat transfer between all the pipelines will be accounted for. A LINE is a FLOWPATH for which simplified one-phase calculations are performed. It is activated by choosing LINE=YES as a parameter for a FLOWPATH. FLOWPATHS must be connected to nodes when the sub key LINE=YES. The CROSSOVER functionality must be set up explicitly with nodes of type CROSSOVER with a specified reference pressure and boost pressure. The outer heat transfer coefficients and the ambient temperatures used by the Fluid Bundle are the values given for the outermost pipeline. The outer surface heat transfer coefficient for each OLGA FLOWPATH can be calculated by the code or specified by the user. If calculated by the code the forced/free convection on the outer surface will be taken into account. The user can specify the outer surface heat transfer coefficient by the sub key OUTERHVALUE. See also FLUIDBUNDLE COMPONENT Keys

COMPONENT (on FLUIDBUNDLE) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

FLOWPATH

Symbol

FLUIDBUNDLE

Symbol

FROM

Symbol

LINE

Symbol

OUTERHVALUE

Real (W/m2C)

TO

Symbol

XOFFSET

Real (m)

[0.0]

YOFFSET

Real (m)

[0.0]

Description Label of a FLOWPATH that resides inside the BUNDLE. Label of a bundle that resides inside the BUNDLE. Label of the POSITION on the FLOWPATH where it enters the BUNDLE. Label of a line (FLOWPATH) that resides inside the BUNDLE. Heat transfer coefficient at the wall surface of a branch to the bulk fluid in the carrier line. Forced/free convection will be applied if this key is not defined. Label of the POSITION on the FLOWPATH where it exits the BUNDLE. The component's displacement along the xaxis relative to the center of the bundle. The component's displacement along the yaxis relative to the center of the bundle.

Link to: COMPONENT (on FLUIDBUNDLE) Description Keys 595 / 769

OLGA 7

SOLIDBUNDLE Description ( See also: Keys) This network component stores all information that is required to configure a solid bundle. This may be done by either editing the keywords and keys directly, or through the Bundle Editor in the GUI. Associated keywords: COMPONENT AMBIENTDATA TRENDDATA PROFILEDATA

Example - Buried pipeline In the following example, a (partially) buried pipeline is modelled. The pipe is assumed to have a centre line, yc, located 25 cm below the soil surface. The air temperature is measured to be 25 ° C and the soil temperature 1 m under the ground is 20 ° C. The soil temperature reading is assumed to be uninfluenced by the presence of the pipe.

1. 2.

3.

Start by adding a COMPONENT and associate the flowpath to this. A natural choice for the soil surface is y = 0, so the pipe must be moved down 25 cm. This is done by setting YOFFSET = -25 cm for this COMPONENT. The soil is modelled by using a rectangular SHAPE with an associated soil MATERIAL. We assume that the effect of the pipe on the soil temperature is negligible at a distance of approximately 1.5 m to each side and 2 m down. The parameters for the shape then becomes: X_LOWER_LEFT = -1.5 m, Y_LOWER_LEFT = -2 m, X_UPPER_RIGHT = 1.5 m, Y_UPPER_RIGHT = 0 m. Finally, the ambient conditions must be specified. In this case we can use a single AMBIENTDATA with TYPE = SIMPLEBURIED. Above ground we have air at 25 ° C, thus HOUTEROPTION = AIR and TAMBIENT = 25 C. We have positioned the soil surface at y = 0 m, so SOILSURFACELEVEL = 0 m. The soil temperature is set by specifying SOILTEMPERATURE = 20 C and SOILTEMPLEVEL = -1 m.

COMMENTS: In this example, the OLGA WALL is in contact with both air and the solid SHAPE. Due to the potentially large temperature difference between the top and botom of the pipe, it may be advisable 596 / 769

OLGA 7

potentially large temperature difference between the top and botom of the pipe, it may be advisable to remove some of the outer wall layers from the OLGA WALL and use one or more SHAPES to model the wall layers. This is done by simply creating a circular SHAPE with the outer radius of the wall layer. Please note that the order of the SHAPE COMPONENTS are important and that the wall layer COMPONENT must be defined after the rectangular soil COMPONENT. Otherwise, the wall layer COMPONENT will be hidden by the soil COMPONENT. The vertical boundaries of the soil above SOILTEMPLEVEL was modelled using the default NOFLUX option for SOILVERTBOUND. This option assumes that there naturally is no heat flux across these boundaries. However, if the boundaries are too close to the pipe, the temperature in the soil may be overestimated. A better choice may then be to use the FIXEDTEMP option. This will force the temperature to be equal to the SOILTEMPERATURE on these boundaries

SOLIDBUNDLE Keys ( See also: Description ) Key

Type

Unit:( ) Default:[ ]

DELTAT DTPLOT

Real (s) Real (s)

LABEL

String

MESHFINENESS Integer

PLOTTING

Parameter set

[SOLIDBUNDLE_tag]

[32]

Symbol OFF | [ON]

Description Time-step in thermal calculations. Time-step for saving thermal data. Network component label (if nothing is given the NC tag is used). The number of nodes on the largest SHAPE in the SOLIDBUNDLE. The higher the number the finer the mesh. Minimum value is 32 and it will always be rounded down to nearest multiple of 32. Key for turning ON/OFF detailed plot of Finite Element results in .osi file

Link to: SOLIDBUNDLE Description Keys

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OLGA 7

COMPONENT (on SOLIDBUNDLE) Description ( See also: Keys) The COMPONENT keyword is used to define the geometric layout of the SOLIDBUNDLE cross section. The keyword has a reference to a geometric object and an offset from the origin (XOFFSET and YOFFSET). The following objects may be placed within a solid bundle:

· SHAPE · Line · FLUIDBUNDLE · BRANCH When using FLUIDBUNDLE or BRANCH (flow components), the POSITION keyword must be used in order to define the start and end pipe between which the solid bundle applies. Please note a pipe wall is not allowed to intersect another pipe wall. However, a SHAPE may intersect another SHAPE or a pipe wall, unless it has already been placed in the interior of another shape. The cross section of the bundle is the union of all SHAPES and flow components. When two objects intersect, the following rules are used: Intersecting SHAPES: If the first SHAPE is defined in COMPONENT[i] and the second in COMPONENT[j] (i < j), the SHAPE in COMPONENT[j] will have the highest rank and it will remain unchanged. For the SHAPE in COMPONENT[i], the intersecting area will be removed. Intersecting SHAPE and flow components: Flow components always has infinite rank

COMPONENT (on SOLIDBUNDLE) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

ANNULUS

Symbol

FLOWPATH

Symbol

FLUIDBUNDLE

Symbol

FROM

Symbol

LINE

Symbol

OUTERHVALUE

Real (W/m2C)

SHAPE

Symbol

Description Label of an annulus that reside inside the BUNDLE. Label of a FLOWPATH that resides inside the BUNDLE. Label of a bundle that resides inside the BUNDLE. Label of the POSITION on the FLOWPATH where it enters the BUNDLE. Label of a line (FLOWPATH) that resides inside the BUNDLE. Heat transfer coefficient at the wall surface of a branch to the bulk fluid in the carrier line. Forced/free convection will be applied if this key is not defined. Label of a shape that reside inside the BUNDLE. The SHAPE with the largest circumference is automatically the outer surface of BUNDLE. 598 / 769

OLGA 7

TO

Symbol

XOFFSET

Real (m)

[0.0]

YOFFSET

Real (m)

[0.0]

Label of the POSITION on the FLOWPATH where it exits the BUNDLE. The component's displacement along the xaxis relative to the center of the bundle. The component's displacement along the yaxis relative to the center of the bundle.

Link to: COMPONENT (on SOLIDBUNDLE) Description Keys

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OLGA 7

TOOLJOINT (on CASELevel) Description ( See also: Keys) This statement defines the geometrical data for internal and external pipe upsets in the flow path. The purpose is to calculate a correction factor for the pipe wall roughness due to the pipe upsets. The TOOLJOINT keyword is part of the Wells Module.

Figure A Side view and cross section of flow path with upsets

TOOLJOINT (on CASELevel) Keys ( See also: Description ) Key

Type

Parameter set

Unit:( )

Default:[ ]

D1EXUP D2INUP DD1 DD2

Real (m) Real (m) Real (m) Real (m)

GEOMETRY

Symbol

LABEL LJOINT LUPSET

String Real (m) Real (m)

PIPE

SymbolList

[TOOLJ-1]

Description External upset of pipe/tubing. Internal upset in annulus/tubing. Inner diameter of annulus. Outer diameter of annulus. Geometry label to where the tool-joint is located. Tool-joint label, default is tool-joint number. Distance between upsets. Length of upset. Label of pipe(s) for which the wall roughness shall be adjusted.

Link to: TOOLJOINT (on CASELevel) Description Keys

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OLGA 7

Boundary Variables Description ( See also: Variables) WCST, GORST, QGST, QLST, QOST and QWST are given at standard conditions (60 oF, 1 atm). A single stage flash from in-situ to standard conditions has been performed, that is, mass transfer between the phases from in-situ to standard conditions is taken into account. The gas is not dehydrated unless WATERFLASH = OFF. For table-based simulations, OLGA uses the gas mass fractions and densities from the fluid property file to perform the conversion. Note: These variables are CPU demanding for Compositional Tracking simulations since a flash must be performed for each section and time they are plotted, and should be used with care. Erosional velocity ratio (EVR) EVR = Vactual / Vmax Vactual = Usg + Usl + Usd Vmax = C / (Rons)1/2 Rons = [ g Usg + l(Usl + Usd)]/(Usg+ Usl + Usd) C = 100 for U in ft/s and in Lb/ft3 C = 121.99 for U in m/s and in kg/m3

Boundary Variables ( See also: Description) Use as Name Units

Definition

Boundary Variables TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

ACCGAG ACCGAQ ACCGT ACCLIG ACCLIQ ACCOIG ACCOIQ ACCWAG ACCWAQ CFLFACT DPZA DPZF DPZG DS DUG DUL EVR FRRG

KG M3 KG KG M3 KG M3 KG M3 PA/M PA/M PA/M M/S2 M/S2 KG/M3-S

Accumulated gas mass flow Accumulated gas volume flow Accumulated total mass flow Accumulated liquid mass flow Accumulated liquid volume flow Accumulated oil mass flow Accumulated oil volume flow Accumulated water mass flow Accumulated water volume flow Local CFL factor Additional pressure drop gradient Frictional pressure drop gradient Gravitational pressure drop gradient Distribution slip ratio Time derivative of gas velocity Time derivative of liquid velocity Erosional velocity ratio Gas wall drift friction factor 601 / 769

OLGA 7

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

FRRH FRRW GASMFRBOUN GD GDHL GDWT GG GL GLHL GLRST GLT GLTHL GLTWT GLWT GLWV

KG/M3-S KG/M3-S KG/S KG/S KG/S KG/S KG/S KG/S SM3/SM3 KG/S KG/S KG/S KG/S KG/S

TP/PP/C

GLWVT

KG/S

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

GORST GT HOLHLNS HOLNS HOLWTNS HTOT

SM3/SM3 KG/S W

TP/PP/C

ID

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

INHIBMFRBOUN MDHLCONV MDHLSLOPE MDWTCONV MDWTSLOPE MGCONV MGSLOPE MLHLCONV MLHLSLOPE MLWTCONV MLWTSLOPE PSID PSIE QD QDHL QDWT QG QGST QL QLHL QLST

KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3-S KG/M3-S M3/S M3/S M3/S M3/S SM3/S M3/S M3/S SM3/S

Oil wall drift friction factor Water wall drift friction factor Gas mass fraction at boundary Droplet mass flow Mass flow rate of oil in droplet field Mass flow rate of water in droplet field Gas mass flow Liquid bulk mass flow Mass flow rate of oil in film Gas/liquid ratio at standard conditions Total liquid mass flow Mass flow rate of oil Mass flow rate of water excluding vapour Mass flow rate of water in film Mass flow rate of water vapour Total mass flow rate of water including Vapour Gas/oil ratio at standard conditions Total mass flow No-slip oil volume fraction No-slip liquid volume fraction No-slip water volume fraction Total Enthalpy flow rate Flow regime: 1=Stratified, 2=Annular, 3=Slug, 4=Bubble. Inhibitor mass fraction in water at boundary Specific convective mass of oil droplets Specific mass adjustment of oil droplets Specific convective mass of water droplets Specific mass adjustment of water droplets Specific convective mass of gas Specific mass adjustment of gas Specific convective mass of oil in film Specific mass adjustment of oil in film Specific convective mass of water in film Specific mass adjustment of water in film Deposition rate Entrainment rate Droplet volume flow Volumetric flow rate oil droplets Volumetric flow rate water droplets Gas volume flow Gas volume flow at standard conditions Liquid bulk volume flow Volumetric flow rate oil film Liquid volume flow at standard conditions 602 / 769

OLGA 7

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

QLT QLTHL QLTWT QLWT QOST QT QWST

M3/S M3/S M3/S M3/S SM3/S M3/S SM3/S

TP/PP/C

REGIMETYPE

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

SHRHL SHRWT SLAG SLAI SLAIGHL SLAIHLWT SLAIWTG SLAL SLALHL SLALWT SLGH SLGW SLHG SLWG STDROG STDROHL STDROWT TAUWG TAUWHL TAUWWT

1/s 1/s KG/M3-S KG/M3-S KG/M3-S KG/M3-S KG/M3-S KG/M3-S KG/M3-S KG/M3-S KG/M3-S KG/M3-S KG/M3-S KG/M3-S KG/M3 KG/M3 KG/M3 PA PA PA

TP/PP/C

TINHIBMFRBOUN

-

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

TWATMFRBOUN UD UDHL UDO UDWT UG UHLCONT UL ULHL ULWT UO USD USDHL USDWT USG

M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S

Total liquid volume flow Volumetric flow rate oil Volumetric flow rate water Volumetric flow rate water film Oil volume flow at standard conditions Total volume flow Water volume flow at standard conditions Slug-trac regime: 0=Free, 1=LiquidSlug, 2=SlugBubble Oil film - shear strain rate Water film - shear strain rate Gas friction coefficient Interfacial friction coefficient Gas/oil film interfacial friction factor Oil film/water film interfacial friction factor Water film/gas interfacial friction factor Liquid friction coefficient Oil film wall friction factor Water film wall friction factor Oil wall friction due to gas Water wall friction due to gas Gas wall friction due to oil Gas wall friction due to water Standard gas density Standard oil density Standard water density Gas - max. wall shear stress Oil film - max. wall shear stress Water film - max. wall shear stress Inhibitor mass fraction in water+vapour at boundary Total water mass fraction at boundary Droplet velocity Oil droplet velocity Relative velocity droplets Water droplet velocity Gas velocity Oil continuous velocity Liquid velocity Oil film velocity Water film velocity Relative velocity Superficial velocity droplets Superficial oil droplet velocity Superficial water droplet velocity Superficial velocity gas 603 / 769

OLGA 7

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

USL USLHL USLT USLTHL USLTWT USLWT USTOT UWTCONT WATMFRBOUN WCST WD WDHL WDWT WG WL WLHL WLWT WTOT

M/S M/S M/S M/S M/S M/S M/S M/S KG/S-M2 KG/S-M2 KG/S-M2 KG/S-M2 KG/S-M2 KG/S-M2 KG/S-M2 KG/S-M2

Superficial velocity film Superficial oil film velocity Superficial velocity liquid Superficial velocity oil Superficial velocity water Superficial water film velocity Total volume flux Water continuous velocity Water mass fraction at boundary Water cut at standard conditions Droplet mass flux Mass flux of oil in droplet field Mass flux of water in droplet field Gas mass flux Liquid mass flux Mass flux of oil in film Mass flux of water in film Total mass flux

Link to: Boundary Variables Description Variables

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OLGA 7

Branch Variables Description ( See also: Variables)

Branch Variables ( See also: Description) Use as Name Units

Definition

Branch Variables TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

DPABR DPBR DPFBR DPGBR

PA PA PA PA

TP/C/GTP

DTBR

C

TP/C/GTP TP/C/GTP

GASC GASCFR

M3 -

TP/C/GTP

GASCST

M3

TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

GASIN GASMASS GASOUT LIQBC LIQC LIQCFR LIQDC LIQIN LIQMASS LIQOUT MASOUT MASSIN MAXPTBR MAXPTBRCT

KG KG KG M3 M3 M3 KG KG KG KG KG PA PA

TP/C/GTP

MAXPTPOS

M

TP/C/GTP

MAXTMBR

C

TP/C/GTP

MAXTMBRCT

C

TP/C/GTP

MAXTMPOS

M

TP/C/GTP

MDPHYD

PA

TP/C/GTP

MDPPOS

M

Additional pressure drop Total pressure drop Frictional pressure drop Gravitational pressure drop Total temperature drop (inlet minus outlet) in branch Gas content in branch Gas volume fraction in branch Gas content in branch converted to standard conditions Accumulated gas flow inlet boundary Gas mass in branch Accumulated gas flow outlet boundary Liquid bulk content in branch Total liquid content in branch Liquid volume fraction in branch Liquid droplet content in branch Accumulated liquid flow inlet boundary Total liquid mass in branch Accumulated liquid flow outlet boundary Accumulated mass flow outlet boundary Accumulated mass flow inlet boundary Maximum pressure in branch since start Maximum pressure in branch at current time Distance from branch inlet where maximum pressure since start occurs Maximum temperature in branch since start Maximum temperature in branch at current time Distance from branch inlet where maximum temperature since start occurs Maximum difference between section and hydrate pressure since last write Distance where section and hydrate pressure differs most since last write 605 / 769

OLGA 7

TP/C/GTP

MDTHYD

C

TP/C/GTP

MDTPOS

M

TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

MEANPTBRCT MEANTMBRCT MINPTBR MINPTBRCT

PA C PA PA

TP/C/GTP

MINPTPOS

M

TP/C/GTP

MINTMBR

C

TP/C/GTP

MINTMBRCT

C

TP/C/GTP

MINTMPOS

M

TP/C/GTP TP/C/GTP TP/C/GTP

OILBC OILC OILCFR

M3 M3 -

TP/C/GTP

OILCST

M3

TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

OILDC OILIN OILMASS OILOUT

M3 KG KG KG

TP/C/GTP

RGASIN

KG

TP/C/GTP

RGASOUT

KG

TP/C/GTP

RLIQIN

KG

TP/C/GTP

RLIQOUT

KG

TP/C/GTP

RMASIN

KG

TP/C/GTP

RMASOUT

KG

TP/C/GTP

ROILIN

KG

TP/C/GTP

ROILOUT

KG

TP/C/GTP

RWATIN

KG

TP/C/GTP

RWATOUT

KG

TP/C/GTP

RWINHIBTOT

-

TP/C/GTP TP/C/GTP TP/C/GTP

WATBC WATC WATCFR

M3 M3 -

Maximum difference between hydrate and section temp since last write Distance where section and hydrate temperature differs most since last write Mean pressure in branch at current time Mean temperature in branch at current time Minimum pressure in branch since start Minimum pressure in branch at current time Distance from branch inlet where minimum pressure since start occurs Minimum temperature in branch since start Minimum temperature in branch at current time Distance from branch inlet where minimum temperature since start occurs Oil film content in branch Total oil content in branch Oil volume fraction in branch Total oil content in branch converted to standard conditions Oil droplet content in branch Accumulated oil flow inlet boundary Total oil mass in branch Accumulated oil flow outlet boundary Accumulated gas flow after restart at inlet boundary Accumulated gas flow after restart at outlet boundary Accumulated liquid flow after restart at inlet boundary Accumulated liquid flow after restart at outlet boundary Accumulated mass flow after restart at inlet boundary Accumulated mass flow after restart at outlet boundary Accumulated oil flow after restart at inlet boundary Accumulated oil flow after restart at outlet boundary Accumulated water flow after restart at inlet boundary Accumulated water flow after restart at outlet boundary Total mass fraction in water phase in branch for inhibitor Water film content in branch Total water content in branch Water volume fraction in branch 606 / 769

OLGA 7

TP/C/GTP

WATCST

M3

TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

WATDC WATIN WATMASS WATOUT

M3 KG KG KG

Total water content in branch converted to standard conditions Water droplet content in branch Accumulated water flow inlet boundary Total water mass in branch Accumulated water flow outlet boundary

Link to: Branch Variables Description Variables

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OLGA 7

Bundle Variables Description ( See also: Variables) Bundle variables can only be used when a SOLIDBUNDLE, a FLUIDBUNDLE or an ANNULUS is given

Bundle Variables ( See also: Description) Use as Name Units

Definition

Boundary Variables TP/PP/C

LINEGT

KG/S

TP/PP/C

HHIN

W/M2-C

TP/PP/C

HHOUT

W/M2-C

TP/PP/C TP/PP/C TP/PP/C

QMO TBUN ULINE

W/M C M/S

TP/PP/C

UVALUE

W/M2-C

Total mass flow of line

Volume Variables Bundles: line inner wall heat transfer coefficient Bundles: line outer wall heat transfer coefficient Bundles: line heat flux Bundles: line temperature Line fluid velocity Bundles: line overall heat transfer coefficient

Link to: Bundle Variables Description Variables

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OLGA 7

Check valve Variables Description ( See also: Variables)

Check valve Variables ( See also: Description) Use as Name Units

Definition

Check valve Variables TP/C/GTP

CHECK

Check valve position: 0=open 1=closed

Link to: Check valve Variables Description Variables

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OLGA 7

Compositional Variables Description ( See also: Variables) Compositional variables can only be used when compositional mass equations are used. This means when the COMPOSITIONAL key in the OPTIONS keyword is either ON, MEG, MEOH, ETOH, BLACKOIL or STEAMWATER-HC When compositional variables can be used are: 1. GLTWTLEAK is the same variable as CGWLEAK 2. GLTWTSOUR is the same variable as CGWSOUR 3. GLTWTWELL is the same variable as CGWWELL GLTWTLEAK, GLTWTSOUR, GLTWTWELL is only available when using inhibitor tracking (MEG, MEOH or ETOH)

Compositional Variables ( See also: Description) Use as Name Units

Definition

Branch Variables TP/GTP

CMTOT

KG

Total mass in branch

CGDH CGDW CGG CGHT CGLH CGLW CGWT PTG

KG/S KG/S KG/S KG/S KG/S KG/S KG/S Pa

Component mass rate in oil droplets Component mass rate in water droplets Component mass rate in gas phase Component mass rate in oil phase Component mass rate in oil film Component mass rate in water film Component mass rate in water phase Partial pressure in gas phase

CGPSI CHPSI CMG CMHD CMHL CMWD CMWL CWPSI DMGE DMHE

KG/M3-S KG/M3-S KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3-S KG/M3 KG/M3

Mass rate of flashing to gas phase Mass rate of flashing to oil phase Mass in gas phase Mass in oil droplets Mass in oil film Mass in water droplets Mass in water film Mass rate of flashing to water phase (Equilibrium mass - mass) in gas phase (Equilibrium mass - mass) in oil phase

Boundary Variables TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP Volume Variables TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP

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OLGA 7

TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP TP/PP

DMWE MWGAS MWOIL MWWAT XG XGE XGM XGME XH XHE XHM XHME XW XWE XWM XWME Z ZM

KG/M3 KG/KMOL KG/KMOL KG/KMOL -

(Equilibrium mass - mass) in water phase Mole weight of gas phase Mole weight of oil phase Mole weight of water phase Mole fraction of gas phase Equilibrium mole weight in gas phase Mass fraction in gas phase Equilibrium mole weight of gas phase Mole fraction of oil phase Equilibrium mole weight of gas phase Mass fraction in oil phase Equilibrium mass fraction in oil phase Mole fraction in water phase Equilibrium mole fraction in water phase Mass fraction in water phase Equilibrium mass fraction in water phase Total molar composition Total mass composition

CGGLEAK CGHLEAK CGTLEAK CGWLEAK GLTWTLEAK XGLEAK XGMLEAK XHLEAK XHMLEAK XWLEAK XWMLEAK ZLEAK ZMLEAK

KG/S KG/S KG/S KG/S KG/S -

Leak mass rate in gas phase Leak mass rate in oil phase Leak mass rate in all phases Leak mass rate in water phase Leak mass rate in water phase Leak mole fraction in gas phase Leak mass fraction in gas phase Leak mole fraction in oil phase Leak mass fraction in oil phase Leak mole fraction in water phase Leak mass fraction in water phase Leak mole fraction in all phases Leak mass fraction in all phases

Leak Variables TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP

Separator Variables SEP

CAEDLM

KG

SEP

CAEDOM

KG

SEP

CAEDWM

KG

SEP

CAGOGM

KG

SEP

CAGOLM

KG

SEP

CAGOOM

KG

ACCUMULATED EMERGENCY DRAIN LIQUID MASS FLOW ACCUMULATED EMERGENCY DRAIN OIL MASS FLOW ACCUMULATED EMERGENCY DRAIN WATER MASS FLOW ACCUMULATED GAS OUTLET GAS MASS FLOW ACCUMULATED GAS OUTLET LIQUID MASS FLOW ACCUMULATED GAS OUTLET OIL MASS FLOW

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OLGA 7

SEP

CAGOOM

KG

SEP

CAGOTM

KG

SEP

CAGOWM

KG

SEP

CAODLM

KG

SEP

CAODOM

KG

SEP

CAODWM

KG

SEP

CATDGM

KG

SEP

CATDLM

KG

SEP

CATDOM

KG

SEP

CATDTM

KG

SEP

CATDWM

KG

SEP

CAWDLM

KG

SEP

CAWDOM

KG

SEP

CAWDWM

KG

SEP SEP

CEDLMF CEDOMF

KG/S KG/S

SEP

CEDWMF

KG/S

SEP

CGOGMF

KG/S

SEP

CGOLMF

KG/S

SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP

CGOOMF CGOTMF CGOWMF CODLMF CODOMF CODWMF CTDGMF CTDLMF CTDOMF CTDTMF CTDWMF CWDLMF CWDOMF CWDWMF

KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S

FLOW ACCUMULATED GAS OUTLET TOTAL MASS FLOW ACCUMULATED GAS OUTLET WATER MASS FLOW ACCUMULATED OIL DRAIN LIQUID MASS FLOW ACCUMULATED OIL DRAIN OIL MASS FLOW ACCUMULATED OIL DRAIN WATER MASS FLOW ACCUMULATED TOTAL DRAIN GAS MASS FLOW ACCUMULATED TOTAL DRAIN LIQUID MASS FLOW ACCUMULATED TOTAL DRAIN OIL MASS FLOW ACCUMULATED TOTAL DRAIN TOTAL MASS FLOW ACCUMULATED TOTAL DRAIN WATER MASS FLOW ACCUMULATED WATER DRAIN LIQUID MASS FLOW ACCUMULATED WATER DRAIN OIL MASS FLOW ACCUMULATED WATER DRAIN WATER MASS FLOW EMERGENCY DRAIN LIQUID MASS FLOW EMERGENCY DRAIN OIL MASS FLOW EMERGENCY DRAIN WATER MASS FLOW GAS OUTLET GAS MASS FLOW GAS OUTLET TOTAL LIQUID MASS FLOW GAS OUTLET OIL MASS FLOW GAS OUTLET TOTAL MASS FLOW GAS OUTLET WATER MASS FLOW OIL DRAIN LIQUID MASS FLOW OIL DRAIN OIL MASS FLOW OIL DRAIN WATER MASS FLOW TOTAL DRAIN GAS MASS FLOW TOTAL DRAIN LIQUID MASS FLOW TOTAL DRAIN OIL MASS FLOW TOTAL DRAIN TOTAL MASS FLOW TOTAL DRAIN WATER MASS FLOW WATER DRAIN LIQUID MASS FLOW WATER DRAIN OIL MASS FLOW WATER DRAIN WATER MASS FLOW 612 / 769

OLGA 7

Well Variables TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP

CGGWELL CGHWELL CGTWELL CGWWELL GLTWTWELL XGMWELL XGWELL XHMWELL XHWELL XWMWELL XWWELL ZMWELL ZWELL

KG/S KG/S KG/S KG/S KG/S -

Well mass rate in gas phase Well mass rate in oil phase Well mass rate in all phases Well mass rate in water phase Well mass rate in water phase Well mass fraction in gas phase Well mole fraction in gas phase Well mass fraction in oil phase Well mole fraction in oil phase Well mass fraction in water phase Well mole fraction in water phase Well mass fraction in all phases Well mole fraction in all phases

CGGSOUR CGHSOUR CGTSOUR CGWSOUR GLTWTSOUR XGMSOUR XGSOUR XHMSOUR XHSOUR XWMSOUR XWSOUR ZMSOUR ZSOUR

KG/S KG/S KG/S KG/S

Source mass rate in gas phase Source mass rate in oil phase Source mass rate in all phases Source mass rate in water phase Source mass rate in water phase Source mass fraction in gas phase Source mole fraction in gas phase Source mass fraction in oil phase Source mole fraction in oil phase Source mass fraction in water phase Source mole fraction in water phase Source mass fraction in all phases Source mole fraction in all phases

Source Variables TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP TP/GTP

-

Link to: Compositional Variables Description Variables

613 / 769

OLGA 7

Compositional slugtracking Variables Description ( See also: Variables) Compositional Slugtracking variables can only be used when compositional mass equations are used. This means when the COMPOSITIONAL key in the OPTIONS keyword is either ON, MEG, MEOH, ETOH, BLACKOIL or STEAMWATER-HC. In addition to this the SLUIGTRACKING keyword has to have been given.

Compositional slugtracking Variables ( See also: Description) Use as Name Units Definition Slug Variables TP

CMGFSB

KG/M3

TP

CMGFSL

KG/M3

TP

CMGTSB

KG/M3

TP

CMGTSL

KG/M3

TP

CMHDFSB

KG/M3

TP

CMHDFSL

KG/M3

TP

CMHDTSB

KG/M3

TP

CMHDTSL

KG/M3

TP

CMHLFSB

KG/M3

TP TP

CMHLFSL CMHLTSB

KG/M3 KG/M3

TP

CMHLTSL

KG/M3

TP

CMWDFSB

KG/M3

TP

CMWDFSL

KG/M3

TP

CMWDTSB

KG/M3

TP

CMWDTSL

KG/M3

TP

CMWLFSB

KG/M3

Component mass in gas phase ahead of slug front Component mass in gas phase behind slug front Component mass in gas phase behind slug tail Component mass in gas phase ahead of slug tail Component mass in oil droplets ahead of slug front Component mass in oil droplets behind slug front Component mass in oil droplets behind slug tail Component mass in oil droplets ahead of slug tail Component mass in oil film ahead of slug front Component mass in oil film behind slug front Component mass in oil film behind slug tail Component mass in oil film ahead of slug tail Component mass in water droplets ahead of slug front Component mass in water droplets behind slug front Component mass in water droplets behind slug tail Component mass in water droplets ahead of slug tail Component mass in water film ahead of slug front 614 / 769

OLGA 7

TP

CMWLFSL

KG/M3

TP

CMWLTSB

KG/M3

TP

CMWLTSL

KG/M3

Component mass in water film behind slug front Component mass in water film behind slug tail Component mass in water film ahead of slug tail

Link to: Compositional slugtracking Variables Description Variables

615 / 769

OLGA 7

Compressor Variables Description ( See also: Variables)

Compressor Variables ( See also: Description) Use as Name Units

Definition

Compressor Variables TP/C/GTP

DHRCOO

W

TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

GCOMP GREC HCOMP HREC QGSURGE RPM

KG/S KG/S W W M3/S RPM

Compressor recycle heat exchanger Enthalpy Compressor mass flow rate Compressor recycle mass flow rate Compressor enthalpy Compressor recycle enthalpy Corrected compressor surge flow Compressor speed

Link to: Compressor Variables Description Variables

616 / 769

OLGA 7

Controller Variables Description ( See also: Variables)

Controller Variables ( See also: Description) Use as Name Units

Definition

Controller Variables GTP/C GTP/C GTP/C GTP/C GTP/C

ACTIVATED CONTR ERRVAR INTGVAR MEASVAR

GTP/C

MODE

GTP/C

PMCAS

GTP/C GTP/C GTP/C GTP/C

RATELIMITED SATURATED SETPOINT SETPVAR

Controller activate signal Controller output Controller error signal Controller integral signal Controller measured variable Controller mode: 1=Automatic, 2=Manual, 3=External signal, 4=External setpoint, 5=Freeze Moving averaged of primary controller variable Controller rate limited signal Controller saturated signal Setpoint of extended cascade controller Controller setpoint variable

Link to: Controller Variables Description Variables

617 / 769

OLGA 7

List of Units and Conversion Factors Quantity

1/ANGULAR_VELOCITY

Unit name 1/rpm s M h d

Conversion to the first unit, multiply by 0.016667 60 1440

1/FLOWRATE

1/m3/s 1/ft3/s 1/m3/h 1/ft3/h 1/bbl/d 1/m3/d 1/bbl/M

35.3107 3600 127119 543396 86400 377.358

1/LENGTH

1/m 1/ft 1/cm 1/in 1/MILES 1/km 1/mm

3.28084 100 39.3701 0.000621371 0.001 1000

1/STDFLOWRATE

1/Sm3/s 1/MSm3/s 1/Sm3/d 1/MSm3/d 1/scf/d 1/MMscf/d 1/scf/s

1e-06 86400 0.0864 3.05e+06 3.05 0.0283

ACCELERATION

m/s2 ft/s2 cm/s2 in/s2

0.3048 0.01 0.0254

ANGLE

DEGREE rad

57.2958

ANGULAR_ACCELERATION

rad/s2 R/s2

6.2832

ANGULAR_VELOCITY

rpm rad/s 1/s

9.549 60

m2 ft2 cm2

0.0929 0.0001

AREA

618 / 769

OLGA 7

in2

CGR

Sm3/Sm3 STB/SCF m3/m3 SCF/SCF STB/MMSCF

0.0006451 5.61458

5.61458e-06

CORROSION_RATE

mm/y

DENSITY

kg/m3 lb/ft3 g/cm3 lb/in3

DENSITY/PRESSURE

kg/m-N s2/m2

DENSITY/TEMPERATURE

kg/m3-K kg/m3-C

DENSITY/TIME

kg/m3-s

DIFFUSION_COEFFICIENT

m2/s cm2/s

0.0001

DYNAMIC_VISCOSITY

N-s/m2 lb/ft-h CP kg/m-h

0.0004134 0.001 0.0002778

ENTHALPY

J Btu cal

1055 4.187

ENTHALPY/MASS

J/kg Btu/lb cal/kg

2326 4.187

ENTHALPY/MOL

J/mol Btu/lbmol cal/mol

2.326 4.187

ENTHALPY/MOL-TEMP

J/mol-K Btu/lbmol-R

4.187

ENTHALPY/VOLUME

J/m3 Btu/ft3 cal/m3

37260 4.187

ENTROPY

J/K Btu/R cal/K

1899 4.187

ENTROPY/MASS

J/kg-K Btu/lb-R cal/kg-K J/kg-C

16.02 1000 27680

4187 4.187 619 / 769

OLGA 7

ENTROPY/MOL

J/mol-K Btu/lbmol-R cal/mol-K

4187 4.187

ENTROPY/VOLUME

J/m3-K Btu/ft3-R cal/m3-K

37260 4.187

FORCE

N dyn kgf lbf

1e-05 9.819 4.4482

FRACTION

%

0.01

FREQUENCY

1/s 1/M 1/h Hz

FRICTION_FACTOR

Ns/m

GAS_STDFLOWRATE

Sm3/s Sm3/h Sm3/d scf/d MMscf/d STB/d STB/M scf/s scf/h MSm3/d Mscf/d

0.00027778 1.1574e-05 3.2774e-07 0.32774 1.8401e-06 0.002651 0.0283169 7.8667e-06 11.574 0.000327778

GAS_VOLUME

m3 ft3 cm3 L USgal bbl

0.02832 1e-06 0.001 0.003786 0.158987

GAS_VOLUME/TIME

m3/s ft3/s m3/h ft3/h bbl/d m3/d bbl/m

0.02832 0.00027778 7.8667e-06 1.841e-06 1.1574e-05 0.002651

GOR

Sm3/Sm3 SCF/STB m3/m3 SCF/SCF

0.016667 0.000277778

0.17811

620 / 769

OLGA 7

MMSCF/STB

178110

HEAT_TRANS./LENGTH

W/m Btu/s-ft kW/m

3461 1000

HEATFLUX

W/m2 kW/m2 W/cm2 Btu/ft2-s Btu/in2-s

1000 10000 11360 1.635e+06

KINEMATIC_VISCOSITY

m2/s CST FT2/HR in2/s

1e-06 2.5806e-05 0.00064516

LENGTH

m ft cm in MILES km mm

0.3048 0.01 0.0254 1609 1000 0.001

LIQ_STDFLOWRATE

Sm3/s Sm3/h Sm3/d scf/d MMscf/d STB/d STB/M scf/s scf/h MSm3/d Mscf/d

0.00027778 1.1574e-05 3.2774e-07 0.32774 1.8401e-06 0.002651 0.0283169 7.8667e-06 11.574 0.000327778

LIQ_VOLUME

m3 ft3 cm3 L USgal bbl

0.02832 1e-06 0.001 0.003786 0.158987

LIQ_VOLUME/TIME

m3/s ft3/s m3/h ft3/h bbl/d m3/d bbl/m

0.02832 0.00027778 7.8667e-06 1.841e-06 1.1574e-05 0.002651

LOGARITHMIC_FRICTION_FACTOR N/m2 621 / 769

OLGA 7

MASS

kg lb g oz t

0.4536 0.001 0.02835 1000

MASS/AREA

kg/m2 g/m2 g/cm2 kg/ft2 g/ft2 g/in2

0.001 10 10.7639 0.010764 1.55

MASS/TIME

kg/s lb/s kg/h lb/h

0.4536 0.00027778 0.000126

MASS/TIME-AREA

kg/s-m2 kg/s-cm2 lb/s-m2 kg/h-m2 lb/h-m2

10000 0.4536 0.00027778 0.000126

MASS/TIME-PRESSURE

kg/s-Pa lb/s-psi

6.5788e-05

MOL

mol lbmol kmol

453.6 1000

MOL/MASS

mol/kg lbmol/lb mol/g

1000 1000

MOL/VOLUME

mol/m3 lbmol/ft3 mol/cm3 mol/L

16020 1e+06 1000

MOLAR_RATE

kmol/s lbmol/s mol/s

0.4536 0.001

MOLCONC/METER

mol/m4 lbmol/ft4 mol/cm4

52550 1e+08

MOLDEN/TEMPERATURE

mol/m3-K

MOLECULAR_WEIGHT

kg/kmol lb/lbmol kg/mol g/mol

PERMEABILITY

1000

mD 622 / 769

OLGA 7

PERMEABILITY

D

1000

POWER

W hp Btu/h kW

745.7 0.2931 1000

POWER/LENGHT

W/m hp/m Btu/h*m kW/m

745.7 0.2931 1000

POWERS_OF_TEN

k M G T

1000 1e+06 1e+09 1e+12

PRESSURE

Pa bara psia atm bar KP/cm2 kPa psig barg kgf/cm2

100000 6895 101300 100000 98066.5 1000 6895 100000 98066.5

PRESSURE/DISTANCE

Pa/m psi/ft

22621

PRESSURE/TIME

Pa/s bar/s psi/s atm/s

100000 6895 101300

PRESSURE_DIFFERENCE

Pa bara psia atm bar KP/cm2 kPa psig barg kgf/cm2

100000 6895 101300 100000 98066.5 1000 6895 100000 98066.5

PRESSURE-TIME/MASS

Pa-s/kg psi-s/lb

15200.3

QUADRATIC_FRICTION_FACTOR

Ns2/m2

RATE_PER_UNIT_TIME

s M h

0.01667 0.0002778 623 / 769

OLGA 7

d

1.157e-05

RELATIVE_DENSITY

SPGR API

131.5

RESVOLUME/STDVOLUME

Rm3/Sm3

SPECIFIC_CAPACITY

m3/R ft3/R

0.02832

SPECIFIC_HEAT

J/kg-C J/kg-K Btu/lbm-R Btu/lbm-F

4186.8 4186.8

STANDARD_VOLUME

Sm3 SCF Scm3 SL Sgal MMscf Mscf Sbbl

0.02832 1e-06 0.001 0.003786 28316.8 28.3168 0.158987

STD_DENSITY

kg/Sm3

STDFLOWRATE/PRESSURE

Sm3/s/Pa Sm3/d/bar scf/d/psi STB/d/psi

1.1574e-10 4.7533e-11 2.6687e-10

SURFACE_TENSION

N/m DYNE/cm

0.001

TEMPERATURE

C R K F

TEMPERATURE/TIME

C/s R/s K/s

TEMPERATURE_DIFFERENCE

C R K F

0.555556 0.555556 0.5556

0.555556 0.555556

THERMAL_CONDUCTANCE

W/m2-C W/m2-K Btu/ft2-h-F cal/m2-h-C

5.678 0.001163

THERMAL_CONDUCTIVITY

W/m-K W/m-C Btu/ft-h-R cal/m-h-K

1.731 0.001163 624 / 769

OLGA 7

THERMAL_EXPANSION

1/C 1/R 1/K 1/F

1.8 1.8

TIME

s M h d 1/rpm

60 3600 86400 60

TORQUE

Nm ft-lb

1.35582

VELOCITY

m/s ft/s m/h ft/h MILES/h

0.3048 0.0002778 8.467e-05 0.447

VOLUME/MASS

m3/kg ft3/lb cm3/g in3/lb

0.06243 0.001 3.613e-05

VOLUME/MOL

m3/mol ft3/lbmol cm3/mol L/mol

6.243e-05 1e-06 0.001

VOLUME/REVOLUTION

m3/R ft3/R

0.02832

WAX_VOLUME

m3 ft3 cm3 L USgal bbl

0.02832 1e-06 0.001 0.003786 0.158987

625 / 769

OLGA 7

Corrosion Variables Description ( See also: Variables) Corrosion variables can only be used when the CORROSION keyword is given.

Corrosion Variables ( See also: Description) Use as Name Units

Definition

Volume Variables TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

COBICARB CONDRATE CORR1 CORR2 CORR3 CORRW1 CORRW2 CORRW3 GLYCOL INHIB IONIC PCO2 PH1 PH2 PH3 SOLFE

KG/S-M2 MM/Y MM/Y MM/Y MM/Y MM/Y MM/Y

PA

Bicarbonate concentration (Molar) Conden.rate in pipe upper half Corrosion rate Corrosion rate Corrosion rate Corr. rate, full water wet. Corr. rate, full water wet. Corr. rate, full water wet. Glycol concentration Inhibitor efficiency Ionic strength concentration (Molar) Partial pressure of CO2 pH for model 1 pH for model 2 pH for model 3 Saturated iron concentration in PPM

Link to: Corrosion Variables Description Variables

626 / 769

OLGA 7

Drilling Variables Description ( See also: Variables) Drilling variables can only be used when DRILLING=ON in the OPTIONS keyword.

Drilling Variables ( See also: Description) Use as Name Units

Definition

Boundary Variables TP/PP/C TP/PP/C TP/PP/C TP/PP/C

DRLFROGSTD GDOMUD GDPH2O GDPHC

KG/M3 KG/S KG/S KG/S

TP/PP/C

GDWMUD

KG/S

TP/PP/C

GGGMUD

KG/S

TP/PP/C

GGOMUD

KG/S

TP/PP/C

GGPH2O

KG/S

TP/PP/C

GGPHC

KG/S

TP/PP/C

GGWMUD

KG/S

TP/PP/C TP/PP/C TP/PP/C

GLOMUD GLPH2O GLPHC

KG/S KG/S KG/S

TP/PP/C

GLTPH2O

KG/S

TP/PP/C

GLTPHC

KG/S

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

GLWMUD GTOMUD GTPH2O GTPHC GTWMUD

KG/S KG/S KG/S KG/S KG/S

TP/PP/C TP/PP/C TP/PP/C

MDOMUD MDPH2O MDPHC

KG/M3 KG/M3 KG/M3

TP/PP/C

MDWMUD

KG/M3

TP/PP/C

MFAMUD

-

Flowing standard gas density Mass flow rate of oil-based mud in droplet Mass flow rate of produced water in droplet Mass flow rate of produced hc in droplet Mass flow rate of water-based mud in droplet Mass flow rate of gas-based mud Mass flow rate of oil-based mud in gas phase Mass flow rate of produced water in gas phase Mass flow rate of produced hc in gas phase Mass flow rate of water-based mud in gas phase Mass flow rate of oil-based mud in film Mass flow rate of produced water in film Mass flow rate of produced hc in film Mass flow rate of produced water in film and droplets Mass flow rate of produced hydrocarbons in film and droplets Mass flow rate of water-based mud in film Total mass flow rate of oil-based mud Total mass flow rate of produced water Total mass flow rate of produced hc Total mass flow rate of water-based mud

Volume Variables Specific mass of oil-based mud in droplet Specific mass of produced water in droplet Specific mass of produced hc in droplet Specific mass of water-based mud in droplet Mass fraction of all muds in total mass 627 / 769

OLGA 7

TP/PP/C

MFGMUD

-

TP/PP/C

MFOMUD

-

TP/PP/C

MFPH2O

-

TP/PP/C

MFPHC

KG/M3

TP/PP/C

MFWMUD

-

TP/PP/C

MGGMUD

KG/M3

TP/PP/C

MGOMUD

KG/M3

TP/PP/C

MGPH2O

KG/M3

TP/PP/C

MGPHC

KG/M3

TP/PP/C

MGWMUD

KG/M3

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

MLOMUD MLPH2O MLPHC MLWMUD MTAMUD MTOMUD MTPH2O MTPHC MTWMUD

KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3

Mass fraction of gas-based mud in total mass Mass fraction of oil-based mud in total mass Mass fraction of produced water in total mass Mass fraction of produced hc in total mass Mass fraction of water-based mud in total mass Specific mass of gas-based mud Specific mass of oil-based mud in gas phase Specific mass of produced water in gas phase Specific mass of produced hc in gas phase Specific mass of water-based mud in gas phase Specific mass of oil-based mud in film Specific mass of produced water in film Specific mass of produced hc in film Specific mass of water-based mud in film Specific mass of all muds Specific mass of oil-based mud Specific mass of produced water Specific mass of produced hc Specific mass of water-based mud

Link to: Drilling Variables Description Variables

628 / 769

OLGA 7

Global Variables Description ( See also: Variables)

Global Variables ( See also: Description) Use as Name Units

Definition

Global Variables TP/C/GTP GTP/GO

ABSMASSERR HT

GTP/GO

HTCRIT

TP/C/GTP GTP/GO GTP/GO GTP/GO GTP/GO TP/C/GTP GTP/GO GTP/GO GTP/GO GTP/GO GTP/GO GTP/GO GTP/GO GTP/GO GTP/GO

HTCRITSEC NINTGR REDEL REERR RELGT RELMASSERR RETOT RETOT0 RMDEL RMERR RMLGT RMOUT RMTOT RMTOT0 VOLGBL

KG S

J J J KG KG KG KG -

Absolute mass error Time step The current criterion used to limit the time step Section causing time step limitation Number of time steps Relative changes of energy from start Accumulated energy balance error Total amount of energy Relative mass error Total amount of energy time integrated Initial total amount of energy Relative changes of mass from start Accumulated mass balance error Total amount of mass Cumulative mass release pipeline exit Total amount of mass time integrated Initial total amount of mass Global max volume error since last write

Link to: Global Variables Description Variables

629 / 769

OLGA 7

Heat exchanger Variables Description ( See also: Variables)

Heat exchanger Variables ( See also: Description) Use as Name Units Definition Heat exchanger Variables TP/C/GTP

DHCOOL

W

Heat exchanger enthalpy

Link to: Heat exchanger Variables Description Variables

630 / 769

OLGA 7

Hydrate kinetics Variables Description ( See also: Variables) Hydrate Kinetics variables can only be used when the HYDRATEKINETICS keyword is given.

Hydrate kinetics Variables ( See also: Description) Use as Name Units Definition Volume Variables TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

BEHYD CPHYD GASRATE HHYD HYDFRAC HYDMASS HYDPT HYDTM HYKPLIST NPARTICLE PSIHYD SAREA VISRATIO

J/KG-C KG/M3-S J/KG KG/M3 PA C

KG/M3-S 1/M -

Hydrate volume fraction Specific heat of hydrate phase Hydrate gas consumption rate Hydrate enthalpy Hydrate volume fraction in slurry Specific hydrate mass Hydrate formation pressure Hydrate formation temperature CSMHYK parameter Number of hydrate monomer particles Hydrate formation rate per unit volume Hydrate formation area per per unit volume Hydrate slurry viscosity ratio

GLHYD SRATEHYD UHYD WLHYD

KG/S 1/S M/S KG/S-M2

Hydrate mass flow Shear rate used for hydrate kinetic model Hydrate slurry velocity Hydrate mass flux

TP/C/GTP

MASSHYD

KG

TP/C/GTP

MDPHYDC

PA

TP/C/GTP

MDPPOSC

M

TP/C/GTP

MDTHYDC

C

TP/C/GTP

MDTPOSC

M

TP/C/GTP

VOLHYD

M3

Hydrate mass in branch Current maximum difference between section and hydrate pressure Current distance where section and hydrate pressure differs most Current maximum difference between hydrate and section temperature Current distance where section and hydrate temperature differs most Hydrate volume in branch

Boundary Variables TP/PP/C TP/PP/C TP/PP/C TP/PP/C Branch Variables

Link to: Hydrate kinetics Variables Description Variables 631 / 769

OLGA 7

632 / 769

OLGA 7

Inhibitor Variables Description ( See also: Variables) Inhibitor variables can only be used when COMPOSITIONAL key in the OPTIONS keyword is MEG, MEOH or ETOH.

Inhibitor Variables ( See also: Description) Use as Name Units

Definition

Branch Variables TP/C/GTP

INHIBMASS

KG

Total mass of inhibitor in branch

Link to: Inhibitor Variables Description Variables

633 / 769

OLGA 7

Leak Variables Description ( See also: Variables) QGSTLK, QLSTLK, QOSTLK and QWSTLK are given at standard conditions (60 oF, 1 atm). A single stage flash from in-situ to standard conditions has been performed, that is, mass transfer between the phases from in-situ to standard conditions is taken into account. The gas is not dehydrated unless WATERFLASH = OFF. For table-based simulations, OLGA uses the gas mass fractions and densities from the fluid property file to perform the conversion. Note: These variables are CPU demanding for Compositional Tracking simulations since a flash must be performed for each section and time they are plotted, and should be used with care.

Leak Variables ( See also: Description) Use as Name Units

Definition

Leak Variables TP/C/GTP

ACGLK

KG

TP/C/GTP

ACGLKEX

KG

TP/C/GTP

ACHLLK

KG

TP/C/GTP

ACHLLKEX

KG

TP/C/GTP

ACMLK

KG

TP/C/GTP

ACQGLKEX

M3

TP/C/GTP

ACQOLKEX

M3

TP/C/GTP

ACQWLKEX

M3

TP/C/GTP

ACWTLK

KG

TP/C/GTP

ACWTLKEX

KG

TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

DPPROD GGLEAK GGLKEX GLHLLK GLLEAK GLLKEX GLVTEMP GLWTLK GOLKEX

PA KG/S KG/S KG/S KG/S KG/S C KG/S KG/S

Leakage accumulated released gas mass upstream Leakage accumulated released gas mass downstream Leakage accumulated released oil mass upstream Leakage accumulated released oil mass downstream Leakage accumulated released mass Accumulated gas volume downstream of leakage Accumulated oil volume downstream of leakage Accumulated water volume downstream of leakage Leakage accumulated released water mass upstream Leakage accumulated released water mass downstream GLV change in opening production pressure Gas mass flow upstream of leakage Gas mass flow downstream of leakage Oil mass flow upstream of leakage Liquid mass flow upstream of leakage Liquid mass flow downstream of leakage GLV bellows temperature Water mass flow upstream of leakage Oil mass flow downstream of leakage 634 / 769

OLGA 7

TP/C/GTP TP/C/GTP TP/C/GTP

GTLEAK GWLKEX HLEAK

KG/S KG/S W

TP/C/GTP

LMLEAK

KG

TP/C/GTP TP/C/GTP

PTLEAK PTLKUP

PA PA

TP/C/GTP

QGLKEX

M3/S

TP/C/GTP

QGSTLK

SM3/S

TP/C/GTP

QLSTLK

SM3/S

TP/C/GTP TP/C/GTP

QOLKEX QOSTLK

M3/S SM3/S

TP/C/GTP

QTLKEX

M3/S

TP/C/GTP

QWLKEX

M3/S

TP/C/GTP

QWSTLK

SM3/S

TP/C/GTP TP/C/GTP TP/C/GTP

TLEAEX TLEAK WLLEAK

C C KG/S-M2

Leakage total mass flow rate Water mass flow downstream of leakage Leakage enthalpy Leakage accumulated released liquid mass upstream Leakage downstream pressure Leak upstream pressure Gas volume flow rate downstream of leakage Leak gas volume flow at standard conditions Leak liquid volume flow at standard conditions Oil volume flow rate downstream of leakage Leak oil volume flow at standard conditions Total volume flow rate downstream of leakage Water volume flow rate downstream of leakage Leak water volume flow at standard conditions Fluid temperature downstream of leakage Fluid temperature upstream of leakage Leakage liquid mass flux

Link to: Leak Variables Description Variables

635 / 769

OLGA 7

Node Variables Description ( See also: Variables) In addition to the NODE variables are many VOLUME variables available for the node

Node Variables ( See also: Description) Use as Name

Units

Definition

Node Variables N N N N N N

DGGDPB DGLTHLDPB DGLTWTDPB DPBDGG DPBDGLTHL DPBDGLTWT

kg/s-Pa kg/s-Pa kg/s-Pa Pa-s/kg Pa-s/kg Pa-s/kg

Gas mass flow derivative w.r.t. pressure Oil mass flow derivative w.r.t. pressure Water mass flow derivative w.r.t. pressure Pressure derivative w.r.t. gas mass flow Pressure derivative w.r.t. oil mass flow Pressure derivative w.r.t. water mass flow

Link to: Node Variables Description Variables

636 / 769

OLGA 7

Pig Variables Description ( See also: Variables) All the variables that are available for Slug tracking can be used with Pig. However, not all of the variables are relevant. The pig variables with their equivalent slugtracking variables are listed below. Pig variable ALGL ALGR HOLHLL HOLHLR HOLWTL HOLWTR UPIG ZPIG

Equivalent slugtracking variable ALTSB ALTSL BEHLTSB + GAHLTSB BEHLTSL BEWTTSB + GAWTTSB BEWTTSL UST ZTSL

When the key TRACKSLUG=ON, the PIG may be without slug, be a slug tail (pig to the left of the slug) or be a slug front (pig to the right of the slug) TRENDDATA PIG=PIG-1, VARIABLE=UST (same as UPIG) TRENDATA PIG=PIG-1, VARIABLE= BEHLTSB This should be used with caution. If the pig is a slug tail, BEHLTSB represents the holdup to the left of the pig. If the pig is a slug front, BEHLTSB represents the holdup to the right of the pig. TRENDDATA PIPE=PIPE-1, SECTION=5, VARIABLE=HOLEXP This works the same way as for slugtracking.

Pig Variables ( See also: Description) Use as Name

Units

Definition

Pig Variables TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

ALGL ALGR GAL GAR HOLHLL HOLHLR HOLWTL HOLWTR

-

TP/C/GTP

IDL

-

TP/C/GTP

IDR

-

Void behind pig Void ahead pig Droplet fraction behind pig Droplet fraction ahead pig Oil holdup behind pig Oil holdup ahead pig Water holdup behind pig Water holdup ahead pig Flow regime behind pig (only valid without TRACKSLUG) Flow regime ahead pig (only valid without TRACKSLUG) 637 / 769

OLGA 7

TP/C/GTP

LIQCDOWN

M3

TP/C/GTP

LIQCUP

M3

TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

PIGM PIGSTA REMDIST REMTIME_AVRG RPIG UPIG UPIG_AVRG ZPIG ZZPIG

KG M S M/S M/S M M

Liquid content between plug and trap position Liquid content between launch position and plug Pig mass Pig status: 0=Not pigging, 2=Pigging Remaining distance for pig Averaged remaining travel time for pig Pig leakage factor Pig velocity Averaged velocity for pig Pig position in branch Pig total distance travelled

Link to: Pig Variables Description Variables

638 / 769

OLGA 7

Pump Variables Description ( See also: Variables)

Pump Variables ( See also: Description) Use as Name Units

Definition

Pump Variables TP/C/GTP TP/C/GTP TP/C/GTP

PUBYGG PUBYGL PUBYGT

KG/S KG/S KG/S

TP/C/GTP

PUMPDP

PA

TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

PUMPGG PUMPGL PUMPGT PUMPHEAT PUMPHP PUMPQB PUMPQG PUMPQL PUMPQT PUMPSPEED PUMPTH PUMPTT PUREGG PUREGL PUREGT PUREGW

KG/S KG/S KG/S W W M3/S M3/S M3/S M3/S RPM NM W KG/S KG/S KG/S KG/S

Gas mass flow through bypass line Liquid mass flow through bypass line Total mass flow through bypass line Pressure difference between pump outlet and inlet Gas mass flow through the pump Liquid mass flow through the pump Total mass flow through the pump Heat added to fluid in pump Hydraulic horsepower Pump back flow (volume) Gas volume flow through the pump Liquid volume flow through the pump Total volume flow through the pump Pump speed Pump hydraulic torque Total pump power Recycle gas mass flow Recycle liquid mass flow Total recycle mass flow Recycle water mass flow

Link to: Pump Variables Description Variables

639 / 769

OLGA 7

Separator Variables Description ( See also: Variables) QGSTxD, QLSTxD, QOSTxD and QWSTxD (x = E, D, O and W) are given at standard conditions (60 oF, 1 atm). A single stage flash from in-situ to standard conditions has been performed, that is, mass transfer between the phases from in-situ to standard conditions is taken into account. The gas is not dehydrated unless WATERFLASH = OFF. For table-based simulations, OLGA uses the gas mass fractions and densities from the fluid property file to perform the conversion. It should be noted that for simulations using PVT tables (not CompTrack), the variables for each drain is not accurate since the flashing is performed using the PVT tables for the total composition. Note: These variables are CPU demanding for Compositional Tracking simulations since a flash must be performed for each section and time they are plotted, and should be used with care. In addition to the SEPARATOR variables are many VOLUME variables available for the separator

Separator Variables ( See also: Description) Use as Name Units

Definition

Separator Variables SEP

ACMDGS

KG

SEP

ACMDHL

KG

SEP

ACMDWT

KG

SEP

ACMGDGS

KG

SEP

ACMODHL

KG

SEP

ACMODWT

KG

SEP

ACMWDHL

KG

SEP

ACMWDWT

KG

SEP

ACVDGS

M3

SEP

ACVDHL

M3

SEP

ACVDWT

M3

SEP

ACVGDGS

M3

SEP

ACVODHL

M3

Separator: accumulated gas mass flow gas outlet Separator: accumulated total oil mass drain Separator: accumulated total water mass drain Separator: accumulated gas mass flow gas outlet Separator: accumulated oil mass flow oil drain Separator: accumulated water mass flow oil drain Separator: accumulated oil mass flow water drain Separator: accumulated water mass flow water drain Separator: accumulated gas volume flow gas outlet Separator: accumulated total oil volume drain Separator: accumulated total water volume drain Separator: accumulated gas volume flow gas outlet Separator: accumulated oil volume flow oil drain 640 / 769

OLGA 7

SEP

ACVODHL

M3

SEP

ACVODWT

M3

SEP

ACVWDHL

M3

SEP

ACVWDWT

M3

SEP

GGGDCONVST

SM3/S

SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP SEP

GNGDGS GNGDHL GNGDWT GNINDHL GNINDWT GNINGS GNINLHL GNINLWT GNODHL GNODWT GNWDHL GNWDWT GTDGS GTDHL GTDWT LIQLV OILLV PTBOTTUMN PTSEP

KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S KG/S M M PA PA

SEP

QGSTGD

SM3/S

SEP

QGSTOD

SM3/S

SEP

QGSTWD

SM3/S

SEP

QLSTGD

SM3/S

SEP

QLSTOD

SM3/S

SEP

QLSTWD

SM3/S

SEP SEP SEP

QNGD QNOD QNWD

M3/S M3/S M3/S

SEP

QOSTGD

SM3/S

SEP

QOSTOD

SM3/S

SEP

QOSTWD

SM3/S

drain Separator: accumulated water volume flow oil drain Separator: accumulated oil volume flow water drain Separator: accumulated water volume flow water drain Separator gas train gas mass rate divided by standard conditions density Separator: gas mass flow rate gas outlet Separator: oil mass flow rate gas outlet Separator: water mass flow rate gas outlet Separator: oil droplet mass flow rate inlet Separator: water droplet mass flow rate inlet Separator: gas mass flow rate inlet Separator: oil film mass flow rate inlet Separator: water film mass flow rate inlet Separator: oil mass flow rate oil drain Separator: water mass flow rate oil drain Separator: oil mass flow rate water drain Separator: water mass flow rate water drain Separator: total gas mass flow gas outlet Separator: total oil mass drain rate Separator: total water mass drain rate Separator liquid level Separator oil level Pressure at liquid outlets Separator pressure Separator gas train gas volume flow at standard conditions Separator oil train gas volume flow at standard conditions Separator water train gas volume flow at standard conditions Separator gas train liquid volume flow at standard conditions Separator oil train liquid volume flow at standard conditions Separator water train liquid volume flow at standard conditions Separator: flow rate at gas outlet Separator: oil drain flow rate Separator: water drain flow rate Separator gas train oil volume flow at standard conditions Separator oil train oil volume flow at standard conditions Separator water train oil volume flow at standard conditions 641 / 769

OLGA 7

SEP

QOSTWD

SM3/S

SEP SEP SEP

QTDGS QTDHL QTDWT

M3/S M3/S M3/S

SEP

QWSTGD

SM3/S

SEP

QWSTOD

SM3/S

SEP

QWSTWD

SM3/S

SEP SEP SEP

SEPEFF TMSEP WATLV

C M

standard conditions Separator: total gas volume flow gas outlet Separator: total oil volume drain rate Separator: total water volume drain rate Separator gas train water volume flow at standard conditions Separator oil train water volume flow at standard conditions Separator water train water volume flow at standard conditions Separator efficiency Separator temperature Separator water level

Link to: Separator Variables Description Variables

642 / 769

OLGA 7

SlugTracking Variables Description ( See also: Variables) There are four main groups of slug tracking variables: 1. Global variables: NSLUG, SLUPRO 2. Variables for plotting properties of a specific unique slug: ALFSB, ALFSL, ALTSB, ALTSL, BEFSB, BEFSL, BETSB, BETSL, BEHLFSB, BEHLFSL, BEHLTSB, BEHLTSL, BEWTFSB, BEWTFSL, BEWTTSB, BEWTTSL, GAFSB, GAFSL, GATSB, GATSL, GAHLFSB, GAHLFSL, GAHLTSB, GAHLTSL, GAWTFSB, GAWTFSL, GAWTTSB, GAWTTSL, DPSB, DPSBF, DPSL, DPSLF, DPSLG, JSLT, JSLF, LSL, LSB, PTJF, PTJT, SLUQT, SLUQF, SLTYPT, SLTYPF, UGFSB, UGFSL, UGTSB, UGTSL, ULFSB, ULFSL, ULTSB, ULTSL, USF, UST, ZTSL, ZFSL, ULHLFSB, ULHLFSL, ULHLTSB, ULHLTSL, ULWTFSB, ULWTFSL, ULWTTSB, ULWTTSL These variables show the development of unique slugs as they pass through the pipeline. 3. Variables for plotting properties of slugs passing at a specified section boundary: SIDEXP, USTEXP, USFEXP, LSLEXP, LSBEXP, QTEXP, QFEXP, ZSTEXP, ZSFEXP These variables are nonzero only when the specified integer pipeline position is within a liquid slug. Note: A table containing slug statistics will be written to the .out file for positions where LSLEXP has been defined in TREND, see Chapter 2.3.1.1. 4. Modified "standard" OLGA variables accounting for the effects of the slug tracking option at a specified section boundary: ALEXP, BEEXP, BEHLEXP, BEWTEXP, GAEXP, GAHLEXP, GAWTEXP, HOLEXP, HOLHLEXP, HOLWTEXP, UGEXP, ULEXP, ULHLEXP, ULWTEXP, UDEXP, UDHLEXP, UDWTEXP

643 / 769

OLGA 7

Fig. 1

Definition sketch of position and length plot variables for the slug tracking option

Fig. 2

Definition sketch of void plot variables for the slug tracking option

Fig. 3

Definition sketch of velocity plot variables for the slug tracking option

SlugTracking Variables ( See also: Description) Use as Name Units

Definition

Boundary Variables TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

ALEXP BEEXP BEHLEXP BEWTEXP GAEXP GAHLEXP

-

TP/PP/C

GAWTEXP

-

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

HOLEXP HOLHLEXP HOLWTEXP LSBEXP LSLEXP QFEXP QTEXP SIDEXP SLTYPFEXP SLTYPTEXP UDEXP UDHLEXP

M M M/S M/S

M/S M/S

Void fraction in slug (no slug: AL) Liquid film fraction in slug (no slug: BE) Oil film fraction in slug (no slug: BEHL) Water film fraction in slug (no slug: BEWT) Liquid droplet fraction in slug (no slug: GA) Oil droplet fraction in slug (no slug: GAHL) Water droplet fraction in slug (no slug: GAWT) Liquid holdup in slug (no slug: HOL) Oil holdup in slug (no slug: HOLHL) Water holdup in slug (no slug: HOLWT) Bubble length (no slug: 0) Slug length (no slug: 0) Volume flux through slug front (no slug: 0) Volume flux through slug tail (no slug: 0) Slug identification (no slug: 0) Type of slug front Type of slug tail Droplet velocity in slug (no slug: UD) Oil droplet velocity in slug (no slug: UDHL) 644 / 769

OLGA 7

TP/PP/C

UDWTEXP

M/S

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

UGEXP ULEXP ULHLEXP ULWTEXP USFEXP USTEXP ZSFEXP ZSTEXP

M/S M/S M/S M/S M/S M/S M M

Water droplet velocity in slug (no slug: UDWT) Gas velocity in slug (no slug: UG) Liquid velocity in slug (no slug: UL) Oil film velocity in slug (no slug: ULHL) Water film velocity in slug (no slug: ULWT) Slug front velocity (no slug: 0) Slug tail velocity (no slug: 0) Slug front position (no slug: 0) Slug tail position (no slug: 0)

ALFSB ALFSL ALTSB ALTSL BEFSB BEFSL BEHLFSB BEHLFSL BEHLTSB BEHLTSL BETSB BETSL BEWTFSB BEWTFSL BEWTTSB BEWTTSL DPSB DPSBF DPSL DPSLF DPSLG GAFSB GAFSL GAHLFSB GAHLFSL GAHLTSB GAHLTSL GATSB GATSL GAWTFSB GAWTFSL GAWTTSB GAWTTSL HOLFSB

PA/M PA/M PA/M PA/M PA/M -

Void fraction ahead of slug front Void fraction behind slug front Void fraction behind slug tail Void fraction ahead of slug tail Liquid film fraction ahead of slug front Liquid film fraction behind slug front Oil film fraction ahead of slug front Oil film fraction behind slug front Oil film fraction behind slug tail Oil film fraction ahead of slug tail Liquid film fraction behind slug tail Liquid film fraction ahead of slug tail Water film fraction ahead of slug front Water film fraction behind slug front Water film fraction behind slug tail Water film fraction ahead of slug tail Total pressure gradient in slug bubble Frictional pressure gradient in slug bubble Total pressure gradient in liquid slug Frictional pressure gradient in liquid slug Gravitational pressure gradient in liquid slug Droplet fraction ahead of slug front Droplet fraction behind of slug front Oil droplet fraction ahead of slug front Oil droplet fraction behind of slug front Oil droplet fraction behind slug tail Oil droplet fraction ahead slug tail Droplet fraction behind slug tail Droplet fraction ahead slug tail Water droplet fraction ahead of slug front Water droplet fraction behind of slug front Water droplet fraction behind slug tail Water droplet fraction ahead slug tail Liquid holdup ahead of slug front

Slug Variables TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP

645 / 769

OLGA 7

TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP TP

HOLFSL HOLHLFSB HOLHLFSL HOLHLTSB HOlHLTSL HOLTSB HOlTSL HOLWTFSB HOLWTFSL HOLWTTSB HOlWTTSL JSLF JSLT LSB LSL PTJF PTJT SID SLTYPF SLTYPT SLUQF SLUQT UDFSB UDFSL UDHLFSB UDHLFSL UDHLTSB UDHLTSL UDTSB UDTSL UDWTFSB UDWTFSL UDWTTSB UDWTTSL UGFSB UGFSL UGTSB UGTSL ULFSB ULFSL ULHLFSB ULHLFSL ULHLTSB ULHLTSL ULTSB

-

M M PA PA

M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S M/S

Liquid holdup behind slug front Oil holdup ahead of slug front Oil holdup behind slug front Oil holdup behind slug tail Oil holdup ahead of slug tail Liquid holdup behind slug tail Liquid holdup ahead of slug tail Water holdup ahead of slug front Water holdup behind slug front Water holdup behind slug tail Water holdup ahead of slug tail Section number of slug front Section number of slug tail Slug bubble length Slug length Pressure at slug front Pressure at slug tail Slug id Type of slug front Type of slug tail Volume flux throgh slug front Volume flux throgh slug tail Droplet velocity ahead of slug front Droplet velocity behind slug front Oil droplet velocity ahead of slug front Oil droplet velocity behind slug front Oil droplet velocity behind slug tail Oil droplet velocity ahead of slug tail Droplet velocity behind slug tail Droplet velocity ahead of slug tail Water droplet velocity ahead of slug front Water droplet velocity behind slug front Water droplet velocity behind slug tail Water droplet velocity ahead of slug tail Gas velocity ahead of slug front Gas velocity behind slug front Gas velocity behind slug tail Gas velocity ahead of slug tail Liquid velocity ahead of slug front Liquid velocity behind slug front Oil velocity ahead of slug front Oil velocity behind slug front Oil velocity behind slug tail Oil velocity ahead of slug tail Liquid velocity behind slug tail 646 / 769

OLGA 7

TP TP TP TP TP TP TP TP TP

ULTSL ULWTFSB ULWTFSL ULWTTSB ULWTTSL USF UST ZFSL ZTSL

M/S M/S M/S M/S M/S M/S M/S M M

Liquid velocity ahead of slug tail Water velocity ahead of slug front Water velocity behind slug front Water velocity behind slug tail Water velocity ahead of slug tail Slug front velocity Slug tail velocity Slug front position Slug tail position

Global Variables GTP/GO GTP/GO

NSLUG SLUPRO

Total number of slugs in the pipeline Number of slugs initiated

Link to: SlugTracking Variables Description Variables

647 / 769

OLGA 7

Source Variables Description ( See also: Variables) QGSTSOUR, QLSTSOUR, QOSTSOUR and QWSTSOUR are given at standard conditions (60 oF, 1 atm). A single stage flash from in-situ to standard conditions has been performed, that is, mass transfer between the phases from in-situ to standard conditions is taken into account. The gas is not dehydrated unless WATERFLASH = OFF. For table-based simulations, OLGA uses the gas mass fractions and densities from the fluid property file to perform the conversion. Note: These variables are CPU demanding for Compositional Tracking simulations since a flash must be performed for each section and time they are plotted, and should be used with care. PTSOUR is the pressure specified in a pressure driven source. If the pressure is not given as input to the source this variable will return the pressure of the section where the source is located.

Source Variables ( See also: Description) Use as Name Units

Definition

Source Variables TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

DGGSDP DGLTHLSDP DGLTWTSDP DPDGGS DPDGLTHLS DPDGLTWTS GGSOUR GLHLMA GLSOUR GLWTMA GTSOUR HSOURC PTSOUR

kg/s-Pa kg/s-Pa kg/s-Pa Pa-s/kg Pa-s/kg Pa-s/kg KG/S KG/S KG/S KG/S KG/S W PA

TP/C/GTP

QGSTSOUR

SM3/S

TP/C/GTP

QLSTSOUR

SM3/S

TP/C/GTP

QOSTSOUR

SM3/S

TP/C/GTP

QWSTSOUR

SM3/S

TP/C/GTP TP/C/GTP TP/C/GTP

TMSOUR TSOUR USGSOU

C C M/S

Gas mass flow derivative w.r.t. pressure Oil mass flow derivative w.r.t. pressure Water mass flow derivative w.r.t. pressure Pressure derivative w.r.t. gas mass flow Pressure derivative w.r.t. oil mass flow Pressure derivative w.r.t. water mass flow Source gas mass rate Source oil mass rate Source liquid mass rate Source water mass rate Source mass rate Source enthalpy Valve-source pressure Source gas volume flow at standard conditions Source liquid volume flow at standard conditions Source oil volume flow at standard conditions Source water volume flow at standard conditions Valve-source temperature Source temperature Source superf. gas velocity 648 / 769

OLGA 7

Link to: Source Variables Description Variables

649 / 769

OLGA 7

SteamAndSingle Variables Description ( See also: Variables) Steam and single component variables can only be used when COMPOSITIONAL=STEAMWATERHC or COMPOSITIONAL=SINGLE in the OPTIONS keyword.

SteamAndSingle Variables ( See also: Description) Use as Name Units Definition Volume Variables TP/PP/C TP/PP/C TP/PP/C TP/PP/C

PSAT PVAP TSAT TSV

PA PA C C

Saturation pressure at fluid temperature Partial pressure of vapor Saturation temperature at system pressure Vapor temperature

Link to: SteamAndSingle Variables Description Variables

650 / 769

OLGA 7

TracerTracking Variables Description ( See also: Variables) Tracer tracking variables can only be used when TRACERTRACKING=ON in the OPTIONS keyword.

TracerTracking Variables ( See also: Description) Use as Name Units

Definition

TracerFeed Variables TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

Conc. wrt. oil carrier phase of tracer feed Conc. wrt. water carrier phase of tracer CONCTOTTRACERWATER feed GTOTTRACER KG/S Total mass flow rate of tracer feed MTOTTRACER KG Mass of tracer feed RESTIMED S Droplet residence time of tracer feed RESTIMEL S Film residence time of tracer feed RESTIMET S Residence time of tracer feed SMDTOTTRACER KG/M3 Specific droplet mass of tracer feed SMLTOTTRACER KG/M3 Specific film mass of tracer feed SMTOTTRACER KG/M3 Specific mass of tracer feed TOTAGETRACER S Average age of tracer feed Mass fraction wrt. oil carrier phase of XTOTTRACEROIL tracer feed Mass fraction wrt. water carrier phase of XTOTTRACERWATER tracer feed CONCTOTTRACEROIL

-

FeedAge Variables TP/PP/C TP/PP/C TP/PP/C

AGEDTRACER AGEFTRACER AGETRACER

S S S

TP/PP/C

CONCTRACEROIL

-

TP/PP/C

CONCTRACERWATER

-

TP/PP/C

GDHLTRACER

KG/S

TP/PP/C

GDTRACER

KG/S

TP/PP/C

GDWTTRACER

KG/S

TP/PP/C

GGTRACER

KG/S

TP/PP/C

GLHLTRACER

KG/S

Droplet age of tracer age group Film age of tracer age group Age of tracer age group Conc.wrt. oil carrier phase of tracer age group Conc. wrt. water carrier phase of tracer age group Mass flow rate of oil in droplet field of tracer age group Droplet mass flow of tracer age group Mass flow rate of water in droplet field of tracer age group Gas mass flow of tracer age group Mass flow rate of oil in film of tracer age group 651 / 769

OLGA 7

TP/PP/C

GLHLTRACER

KG/S

TP/PP/C

GLTHLTRACER

KG/S

TP/PP/C

GLTRACER

KG/S

TP/PP/C

GLTTRACER

KG/S

TP/PP/C

GLTWTTRACER

KG/S

TP/PP/C

GLWTTRACER

KG/S

TP/PP/C

GTTRACER

KG/S

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

MDTRACER MGTRACER MLHLTRACER MLTHLTRACER MLTRACER MLTTRACER MLTWTTRACER

KG KG KG KG KG KG KG

TP/PP/C

MLWTTRACER

KG

TP/PP/C

MTRACER

KG

TP/PP/C

SMDTRACER

KG/M3

TP/PP/C

SMGTRACER

KG/M3

TP/PP/C

SMLHLTRACER

KG/M3

TP/PP/C TP/PP/C

SMLTHLTRACER SMLTRACER

KG/M3 KG/M3

TP/PP/C

SMLTTRACER

KG/M3

TP/PP/C

SMLTWTTRACER

KG/M3

TP/PP/C

SMLWTTRACER

KG/M3

TP/PP/C

SMTRACER

KG/M3

TP/PP/C

XTRACEROIL

-

TP/PP/C

XTRACERWATER

-

GSTRACER

KG/S

group Mass flow rate of oil of tracer age group Liquid bulk mass flow of tracer age group Total liquid mass flow of tracer age group Mass flow rate of water excluding vapour of tracer age group Mass flow rate of water in film of tracer age group Total mass flow rate of tracer for tracer age group Droplet mass of tracer age group Mass of gas of tracer age group Mass of oil in film of tracer age group Mass of oil of tracer age group Film mass of tracer age group Total liquid mass of tracer age group Mass of water in film of tracer age group Mass of water excluding vapour of tracer age group Mass of tracer age group Specific droplet mass of tracer age group Specific mass of gas of tracer age group Specific mass of oil in film of tracer age group Specific mass oil of of tracer age group Specific film mass of tracer age group Specific total liquid mass of tracer age group Specific mass of water in film of tracer age group Specific mass of water excluding vapour of tracer age group Specific mass of tracer age group Mass fraction wrt. oil carrier phase of tracer age group Mass fraction wrt. water carrier phase of tracer age group

Source Variables TP/GTP

Tracer source mass flow rate

Link to: TracerTracking Variables Description Variables

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OLGA 7

Valve Variables Description ( See also: Variables)

Valve Variables ( See also: Description) Use as Name Units

Definition

Valve Variables TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

ARCH CV GCRIT GVALVE ICRIT PVALVE TTHRC TVALVE UCRIT UVALVE VALSCC VALVAR VALVDP VALVOP WCRIT

M2 KG/S KG/S PA C C M/S M/S M2 PA KG/S-M2

Choke area Valve CV (0 for chokes) Critical mass flow rate Valve mass flow Valve critical flow: 0=subcrit, 1=crit Valve pressure Critical temperature at throat Valve temperature Critical velocity at throat Valve velocity Valve sub-critical coefficient Valve flow area Subcritical pressure drop across valve Relative valve opening Critical mass flux at throat

Link to: Valve Variables Description Variables

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OLGA 7

Volume Variables Description ( See also: Variables) SSP gives an average speed of sound in fluid. However, it is only calculated if SOUND_CFL = ON in keyword DTCONTROL. Else, the value is 0.

Volume Variables ( See also: Description) Use as Name Units

Definition

Volume Variables TP/PP/C

ACCDPZA

PA

TP/PP/C

ACCDPZF

PA

TP/PP/C

ACCDPZG

PA

TP/PP/C TP/PP/C TP/PP/C TP/PP/C/N/SEP TP/PP/C TP/PP/C/N/SEP TP/PP/C/N/SEP TP/PP/C TP/PP/C TP/PP/C/N/SEP TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

ACCLIQBR ACCOILBR ACCWATBR AL ANGLE BE BEHL BEHLCONT BEHLDISP BEWT BEWTCONT BEWTDISP CPG CPHL CPWT CVOL DIAM

M3 M3 M3 -

TP/PP/C

DPHYD

PA

TP/PP/C TP/PP/C TP/PP/C TP/PP/C

DPZ DRGP DRHLDP DRWTDP

PA/M KG/M-N S2/M2 S2/M2

TP/PP/C

DTHYD

C

TP/PP/C TP/PP/C/N/SEP

DTM GA

C/S -

-

-

J/KG-C J/KG-C J/KG-C M

Integrated additional pressure drop along branch Integrated frictional pressure drop along branch Integrated gravitational pressure drop along branch Accumulated liquid volume along branch Accumulated oil volume along branch Accumulated water volume along branch Void (gas volume fraction) Pipe angle Liquid film volume fraction Oil film volume fraction Oil continuous fraction Oil dispersed in water fraction Water film volume fraction Water continuous fraction Water dispersed in oil fraction Specific heat of gas phase Specific heat of oil phase Specific heat of water phase volume error control factor Pipe diameter Difference between section and hydrate pressure Space derivative of pressure Pressure derivative of gas density Pressure derivative of oil density Pressure derivative of water density Difference between hydrate and section temperature Time derivative of temperature Liquid droplet volume fraction 654 / 769

OLGA 7

TP/PP/C/N/SEP

GAHL

-

TP/PP/C

GASMFR

-

TP/PP/C/N/SEP TP/PP/C TP/PP/C TP/PP/C TP/PP/C/N/SEP TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C/N/SEP TP/PP/C/N/SEP TP/PP/C/N/SEP TP/PP/C/N/SEP TP/PP/C TP/PP/C TP/PP/C/N/SEP TP/PP/C/N/SEP TP/PP/C TP/PP/C TP/PP/C TP/PP/C/N/SEP TP/PP/C TP/PP/C

GAWT HDIAM HG HL HOL HOLHL HOLWT HTK HTKO IDIAM INCL INHIBMFR MACH MD MDHL MDWT MG MHLCONT MHLDISP ML MLHL MLT MLTHL MLTWT MLWT MWTCONT MWTDISP

M J/KG J/KG W/M2-C W/M2-C M DEGREE KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3 KG/M3

TP/PP/C

OILMFR

-

TP/PP/C TP/PP/C TP/PP/C TP/PP/C/N/SEP TP/PP/C TP/PP/C TP/PP/C

PSI PSIHL PSIWT PT PTMAX PTMIN Q2

KG/M3-S KG/M3-S KG/M3-S PA PA PA W/M2-C

TP/PP/C

QM

W/M

TP/PP/C TP/PP/C TP/PP/C TP/PP/C

ROG ROHL ROL ROWT

KG/M3 KG/M3 KG/M3 KG/M3

Oil droplet volume fraction Gas mass fraction relative to the mass from all phases Water droplet volume fraction Hydraulic diameter Enthalpy gas Enthalpy liquid Holdup (liquid volume fraction) Oil volume fraction Water volume fraction Heat transfer coefficient of inner wall Ambient heat transfer coefficient Inner diameter Inclination from horizontal Inhibitor mass fraction in water Mach number Specific mass droplet Specific mass of oil droplets Specific mass of water droplets Specific mass gas Specific oil continuous mass Specific oil dispersed in water mass Specific mass liquid Specific mass of oil in film Total liquid mass Specific mass oil Specific mass water Specific mass of water in film Specific water continuous mass Specific water dispersed in oil mass Oil mass fraction relative to the mass from all phases Mass rate of flashing to gas phase Mass rate of flashing to oil phase Mass rate of flashing to water phase Pressure Maximum pressure Minimum pressure Overall heat transfer coefficient Heat loss per unit length from pipe wall to fluid Density of gas Oil density Density of liquid Water density Gas mass fraction relative to hydrocarbon liquid and gas mass;

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OLGA 7

TP/PP/C

RS

-

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C/N/SEP TP/PP/C TP/PP/C TP/PP/C

RSW SECLENGTH SEG SEL SIG SSP TCONG TCONHL TCONWT TINHIBMFR TM TMMAX TMMIN TU

M J/KG-K J/KG-K N/M M/S W/M-K W/M-K W/M-K C C C C

TP/PP/C

TW

C

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

TWATMFR TWS TWSO UHLDISP UWTDISP VISG VISHL

C C M/S M/S N-S/M2 N-S/M2

TP/PP/C

VISHLEFF

N-S/M2

TP/PP/C TP/PP/C

VISHLTAB VISL

N-S/M2 N-S/M2

TP/PP/C

VISWT

N-S/M2

TP/PP/C

VISWTEFF

N-S/M2

TP/PP/C TP/PP/C/N/SEP

VISWTTAB VOL

N-S/M2 -

TP/PP/C

WACBEWA

-

TP/PP/C

WACWA

-

TP/PP/C

WALLROUGH

TP/PP/C

WATMFR

-

TP/PP/C

WC

-

liquid and gas mass; (MG/(MG+MLTHL))from PVT table Mass fraction of water vapour in gas Section Length Gas entropy Liquid entropy Surface tension Speed of sound in fluid Thermal conductivity of gas phase Thermal conductivity of oil phase Thermal conductivity of water phase Total inhibitor mass fraction in water+ vapor Fluid temperature Maximum Fluid temperature Minimum Fluid temperature Ambient temperature Temperature in center of gravity of wall (100 C for non-existing layers) Total water mass fraction Inner wall surface temperature Outer wall surface temperature Oil dispersed in water velocity Water dispersed in oil velocity Gas viscosity Oil viscosity including wax/meg/mud effects Effective oil viscosity including dispersion effects Oil viscosity from fluid tables Liquid viscosity (no water-slip) Water viscosity including wax/meg/mud effects Effective water viscosity including dispersion effects Water viscosity from fluid tables Volume error Volume fraction of free water to total liquid film Volume fraction of free water to total water in film Pipe wall roughness Water mass fraction relative to the mass from all phases Water cut (In-situ)

Link to: Volume Variables Description Variables

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OLGA 7

Waxdeposition Variables Description ( See also: Variables) Wax deposition variables can only be used when WAXDEPOSITION=ON in the OPTIONS keyword.

Waxdeposition Variables ( See also: Description) Use as Name Units Definition Branch Variables TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

MLTWLBR MLTWSBR MTWXBR WAXMASBR WAXVOLBR

KG KG KG KG M3

Mass of dissolved wax in branch Mass of suspended wax in branch Total mass of wax in branch Wax deposit mass in branch Wax deposit volume in branch

ACCGLTWL ACCGLTWS GWXDIP GWXDIS

KG KG KG/S KG/S

Accumulated dissolved wax mass flow Accumulated suspended wax mass flow Mass flow rate of wax dispersed in oil Mass flow rate of wax dissolved in oil

TP/PP/C TP/PP/C

BEWX DXWX

M

TP/PP/C

GAWX

-

TP/PP/C TP/PP/C TP/PP/C TP/PP/C TP/PP/C

LEWIS MWXDIP MWXDIS MWXWAL SCHMIDT

KG/M3 KG/M3 KG/M3

TP/PP/C

TWSWX

C

TP/PP/C

WAX_TCOND

W/M-K

TP/PP/C TP/PP/C TP/PP/C

WAXAP WAXPOROSITY WXAVDC

C M2/S

TP/PP/C

WXCDCDR

1/M

TP/PP/C

WXCDIFFC

M2/S

TP/PP/C

WXCMCDB

Volume fraction of wax dispersed in oil film Thickness of wax layer deposited at wall Volume fraction of wax dispersed in oil droplet field Lewis number Mass of wax dispersed in oil Mass of wax dissolved in oil Specific wax mass at wall Schmidt number Inner wall surface temperature adjusted for wax layer Thermal conductivity of wax film, porosity included Wax appearance temperature Wax porosity (oil volume fraction in wax film) Molar average wax diffusion coefficient Concentration gradient of dissolved wax near wall Wax component diffusion coefficient Molar concentration of dissolved wax components in bulk 657 / 769

Boundary Variables TP/PP/C TP/PP/C TP/PP/C TP/PP/C Volume Variables

OLGA 7

TP/PP/C

WXCMCDB

TP/PP/C

WXCMCDW

TP/PP/C TP/PP/C TP/PP/C

WXDIFFC WXDR WXMPREC

M2/S M KG/S

TP/PP/C

WXMTRW

KG/S

TP/PP/C

WXMTRWD

KG/S

TP/PP/C

WXMTRWS

KG/S

components in bulk Molar concentration of dissolved wax near wall Apparent wax diffusion coefficient Laminar boundary layer thickness Wax mass precipitation rate Net wax mass transport rate to wall (diffusi+ shear) Wax mass transport rate to wall due to diffusion Wax mass transport rate to wall due to shear

Link to: Waxdeposition Variables Description Variables

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OLGA 7

Well Variables Description ( See also: Variables) QGSTWELL, QLSTWELL, QOSTWELL and QWSTWELL are given at standard conditions. A single stage flash from in-situ to standard conditions has been performed. For table-based simulations, OLGA uses the gas mass fractions and densities from the fluid property file to perform the conversion. The gas is not dehydrated unless WATERFLASH = OFF. Note: The standard gas density can be given in the well input as ROGST, but this is not used when calculating QGSTWELL. This means that there will be a difference between the given QGSTWELL and the standard gas flowrate given by the well equations, since ROGST is used to convert to gas mass rate and the value in the fluid property file is used to convert back to QGSTWELL (correspondingly for ROLST and QOSTWELL/QLSTWELL). Note: These variables are CPU demanding for Compositional Tracking simulations since a flash must be performed for each section and time they are plotted, and should be used with care.

Well Variables ( See also: Description) Use as Name Units

Definition

Well Variables TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP TP/C/GTP

GASFRT GGSWST GGWELL GHLWST GLHLWE

M KG/S KG/S KG/S KG/S

TP/C/GTP

GLTWST

KG/S

TP/C/GTP TP/C/GTP TP/C/GTP

GLWELL GLWTWE GTWELL

KG/S KG/S KG/S

TP/C/GTP

GWTWST

KG/S

TP/C/GTP TP/C/GTP TP/C/GTP

HWELL OILFRT QGSTWELL

W M SM3/S

TP/C/GTP

QLSTWELL

SM3/S

TP/C/GTP

QOSTWELL

SM3/S

TP/C/GTP

QWSTWELL

SM3/S

TP/C/GTP

WATFRT

M

Well source gas cone front Well source steady-state gas mass flow rate Well source gas mass flow rate Well source steady-state oil mass flow rate Well source oil mass flow rate Well source steady-state liquid mass flow rate Well source liquid mass flow rate Well source water mass flow rate Well source mass flow rate Well source steady-state water mass flow rate Well source enthalpy Well source oil cone front Well gas volume flow at standard conditions Well liquid volume flow at standard conditions Well oil volume flow at standard conditions Well water volume flow at standard conditions Well source water cone front

Link to: Well Variables Description Variables

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OLGA 7

FLUID PROPERTIES AND other DATA FILES In addition to the main file describing the simulation model, OLGA also requires a description of the fluid properties as a unique function of temperature and pressure. These can be given either as a fluid file, through specific component data given in a feed file (Compositional Tracking) or defined in the main file (Blackoil), or computed internally (STEAMWATER-HC) A previous simulation run can be continued through the use of a restart file, as described with the RESTART keyword. If a compressor is present in the pipeline, a file specifying the compressor characteristics is also required. If pumps are used in the simulation, the pump characteristics are specified through a pump file. A complete set of pump characteristics is given in the code. This set can be used if no pump characteristics are available. If wax deposition is simulated, the wax data are specified through a wax file. If the possible formation of hydrate is simulated, a hydrate curve file might be required. If the OLGA Rocx module is used for simulating near wellbore, a Rocx input file is required. These files have to be written in certain formats that are described in the following sections.

See also Fluid properties file Compressor data file Pump data Files Wax table file Hydrate curve definition file OLGA Rocx input file

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OLGA 7

Compressor data file This file contains tables of the compressor characteristics, defined below, as functions of reduced RPM and reduced inlet mass flow. The reason for giving the characteristics as functions of reduced RPM and reduced inlet mass flow, is to obtain one table for several inlet conditions (pressure, temperature), instead of having one table for each inlet condition. Variables The definitions of reduced mass flows and reduced RPM are as follows: Reduced inlet mass flow : MASSRE = Reduced surge mass flow : MREDSU = Reduced RPM

: RPMRED =

G = inlet mass flow (kg/s) GSURGE = surge mass flow (kg/s) RPM = rotational speed (r/min) = normalized inlet temp = inlet temp / 288 K ( ) = normalized inlet pressure = inlet pressure / (1.013*105 Pa) ( ) The table values can be equidistant or non-equidistant. Variables: Name IDENTF NCOMTA COMPID(I)

Unit

Definition

File identification (40 characters) ( ) Number of compressors Compressor identification, compressor(I) (40 characters) Note! All characters after a blank in a character string are

omitted. (I = 1, NCOMTA) NTABWG(I) ( ) Number of reduced mass flow points, compressor(I) NTABOM(I) ( ) Number of reduced RPM points, compressor(I) RPMRED(K,I) (r/min) Reduced RPM, compressor(I) K=1,NTABOM(I) MASSRE(J,I) (kg/s) Reduced inlet mass flow, compressor(I) J=1,NTABWG(I) COTEXT(1,I) Heading, pressure ratio table, compressor(I) (40 characters) PRATIO(J,K,I)( ) Pressure ratio, d . compressor(I) K=1,NTABOM J=1,NTABWG(I) COTEXT(2,I) Heading, temperature ratio table, compressor(I) (40 characters) TRATIO(J,K,I) ( ) Temperature ratio, Q. Compressor(I) K=1,NTABOM(I), J=1,NTABWG(I) COTEXT(3,I) Heading, reduced surge mass-flow table, compressor(I) (40 characters) MREDSU(K,I) (kg/s) Reduced surge mass flow, compressor(I) K=1,NTABOM(I) Data file structure: 661 / 769

OLGA 7

IDENTF NCOMTA The following data is repeated for each compressor : COMPID(I) NTABWG(I) NTABOM(I) RPMRED(1,I). . . . . . . RPMRED(NTABOM(I),I) MASSRE(1,I). . . . . . . MASSRE(NTABWG(I),I) COTEXT(1,I) PRATIO(1,1,I). . . . . . PRATIO(1,NTABOM(I),I) . . . . . PRATIO(NTABWG(I),1,I). . PRATIO(NTABWG(I),NTABOM(I),I) COTEXT(2,I) TRATIO(1,1,I). . . . . . TRATIO(1,NTABOM(I),I) . . . . . TRATIO(NTABWG(I),1,I). . TRATIO(NTABWG(I),NTABOM(I),I) COTEXT(3,I) MREDSU(1,I). . . . . . . MREDSU(NTABOM(I),I) Note that the number of compressor tables must equal the number of compressors. The tables must be given in increasing order; the first table is for compressor number one etc.

662 / 769

OLGA 7

Wax table file This file can contain tables with the properties of the wax forming components for multiple fluids. The table for each fluid should have the following format: 1. 2.

4. 5. 6. 7. 8. 9. 10. 11. 12.

13. 14. 15

Name of table. No more than 20 characters and no blanks. Number of wax components. 3. Names of wax components. Each name may take up max. 20 characters. No blanks. Component names encircled by apostrophes and separated by commas. Example: 'C10-C20','C35','C40-C50' Molecular weights (g/mol) of wax components. Liquid densities of wax components (kg/m3). Heat of melting (J/kg) of wax components. Concentration (mol/mol) of wax components in HC mixture. Number of pressure points, number of temperature points. Pressure points (Pa). Cloud point temperatures (C) for each pressure point. First pressure point. Columns with Temperature (C) Solubility of wax component 1 (mol/mol) in oil including wax forming components Solubility of wax component 2 (mol/mol) in oil including wax forming components etc. Wax phase density (kg/m3) Gas phase molecular weight (g/mol) Liquid phase molecular weight (g/mol) Wax phase molecular weight (g/mol) Enthalpy of wax (J/kg) Heat capacity of wax (J/kg K) Thermal conductivity of wax (W/m K) Second pressure point etc. Repeat 1-14 for next fluid

Comment lines start with an !. If the temperature is above the cloud point temperature, oil properties should be used. The wax file is generated in PVTSim. NOTE! The following requirements need to be fulfilled when using multiple fluids in networks:

· Same pseudo-components (number of components and lumping) for all fluids. · All fluids in one wax data file. Procedure for generating PVT tables in PVTSIM: 1. Add the inlet fluids as separate fluids. 2. Use Fluids-> Same pseudos (Select the resulting fluids for inlets. Resulting fluids with same pseudos available at bottom of fluid table from database) 3. Use Mix to mix ”r;same pseudos” inlet fluids in proper ratios 4. Generate OLGA and wax tables for each fluid made by ”r;same pseudos” and mix.

663 / 769

OLGA 7

[1] Subkey not used by OLGA. [2] Only if PHASE = THREE. Ignored if PHASE = TWO.

664 / 769

OLGA 7

Hydrate curve definition file A hydrate curve must be defined as pairs of corresponding temperature and pressure points, which must be unique and in increasing order. A header line must include the temperature and pressure units. An example hydrate definition file is shown below:

TEMPERATURE (C) PRESSURE (BAR) 0.4853 32.4656 1.9738 36.7623 3.4717 41.6277 4.9768 47.1369 6.4870 53.3754 7.9997 60.4394 9.5125 68.4384 11.0227 77.4959

665 / 769

OLGA 7

OLGA Rocx Rocx reads a separate input file describing the reservoir properties, boundary conditions and initial conditions. The file name should be given in the NEARWELLSOURCE keyword. This input file is edited with the Rocx GUI. Please refer to the OLGA Rocx User Manual for how to define a proper input file for use with OLGA Rocx.

666 / 769

OLGA 7

Fluid properties file The file that contains the fluid data, is either a feed file with data for each component used in compositional tracking, or a file that have fluid properties as a function of temperature and pressure. There are two valid formats of the latter file, either the standard format or a keyword based format. When more than one fluid properties file is used, they all have to have the same format. Note that the fluid label cannot start with a number. This is a general limitation for labels.

667 / 769

OLGA 7

Feed file for compositional tracking This file is generated in PVTSim, and contains data for each fluid component as well as the fluid composition (component mole fractions) for one or more feeds. The syntax of the file is complex, and is not explained here. There should be no need to view the contents of the file, as the feed and component names can be chosen directly from the OLGA GUI when a feed file has been specified.

668 / 769

OLGA 7

PVT properties for non-existing phase When generating an OLGA fluid properties file (TAB file) all properties need to be given at all pressure and temperature points in the file. That applies also if the phase the property belongs to does not exist at the pressure and temperature in question. OLGA does in certain cases use the numbers in the TAB file for the non-existent phase, so these should generally be sensible numbers rather than for instance a zero. How this can be done is briefly described below. Some examples of when the non-existent phase is used are: 1. The user specifies a well or source with non-equilibrium inflow. That is, the user can for instance specify that there is gas present at conditions where according to the fluid file there is single phase liquid. This is typically done to adjust the GOR of the fluid or for simulation of gas lift. 2. During a shut-in the liquid in the pipeline redistributes. The gas and liquid volumes in a section are then no longer well represented by the TAB file. Subsequent pressure and temperature changes can result in a phase being present outside the region where it should be according to the TAB file. 3. During the numerical solving process OLGA may stray outside of the 2-phase region as part of its iteration sequence before converging to a point which is inside the 2-phase region. There are no specific requirements on how the properties of the non-existent phase should be generated. However, the numbers should be reasonable, since they in many cases in reality are used to represent fluids with slightly different composition than what the TAB file was made with. However, two main approaches have been used: Extrapolation: The value and its derivative with respect to pressure at the phase boundary are used to extrapolate into the region where the property does not exist. Compositional: By addition of gas or condensate the phase envelope is expanded so that it passes through the P and T for which a property is to be calculated. The experience is that the extrapolation method is preferable, but unreasonable values are often seen when extrapolation is performed far into the non-existing region. It is further important that the there are no abrupt changes in property values with changing pressure and temperature. Step changes in property values will generally create numerical instabilities when a simulation is performed in that pressure and temperature region. The extrapolation of enthalpy and entropy should be consistent with thermal capacity. Extrapolation of density should be consistent with the derivative of density with regard to pressure. Note that going vertically up from the critical point, OLGA considers the phase to the left (lower T) to be dense oil, and the phase to the right to be dense gas. The properties set for the non-existing phase must ensure that properties are continuous at the critical line so that this is a virtual transition with no actual effect.

669 / 769

OLGA 7

Keyword based format for fluid properties This format has all the possibilities as the standard format, and some additional ones. The intension of introducing a table based format is to: 1. 2.

Improve the readability of PVT table Be able to give bubble points and dew points curve to improve the accuracy close to the saturation line 3. Use different units for the various PVT parameters 4. Facilitate conversion between mass flow rate and volumetric flow rate at standard conditions (Not implemented yet) 5. Be able to adapt more easily the temperature and pressure mesh to the phase envelope 6. Make a format that is easily extendable for new parameters 7. Provide composition information to help custom support for PVT related problems 8. Easily export PVT data to spreadsheets

See also The syntax of the keyword Table Structure Keyword PVTTABLE Examples

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OLGA 7

The syntax of the keyword The syntax of OLGA input applies to the new table format. Specifically, an input statement has the general form: KEYWORD KEY = Parameter list, ... where the ellipses (...) indicate that the statement may contain more than one "KEY = Parameter list" combinations. Commas separate such combinations. The KEYWORD identifies the input statement. Each keyword has a set of variables, each identified by a KEY (e.g. SETPOINT). Separators: Items are separated by commas (,). Tabulation is treated as one single space. Line continuation: An input statement can be written on several lines by ending each line with the continuation character: \ (backslash) Comments: Comments are indicated with the comments mark: ! (exclamation mark) Any information on a line after a comment mark is ignored. The comment mark can be put anywhere on the line. String protector: A string that contains spaces or commas should be protected with double quotes: " (double quote) List protector: Any list should be put inside a parenthesis: ( ... )

671 / 769

OLGA 7

Table Structure A table is defined through the keyword: PVTTABLE The structure of the fluid property table is as follows: For each of the tables PVTTABLE LABEL = fluid-1, etc For each of the pressure and temperature points PVTTABLE POINT = (…) End of pressure and temperature points End of tables The values of all parameters except POINT must be written in a single line. Fluid properties for each pressure/temperature point must subsequently be specified through the PVTTABLE POINT structure, repeated for each pressure/temperature point. See also Keyword PVTTABLE

672 / 769

OLGA 7

Keyword PVTTABLE Key

Type Parameter Unit: ( ) set Default: [ ]

LABEL PHASE

str. sym

EOS[1]

str.

MESHTYPE

sym.

COMPONENTS1

str.l.

MOLES1

r.l.

DENSITY1

r.l. (kg/m3)

[TWO] | THREE

Description

Name of the table. Two or three phase table

Equation of state used in generating the pvt table. Optional. [STANDARD] STANDARD: Both | temperature and pressure FREEPRES points are fixed independently | FREETEMP FREEPRES: Temperature points are fixed first and the pressure points are specified for each of the individual temperature points. FREETEMP: Pressure points are fixed first and the temperature points are specified for each of the individual pressure points. List of names of the components in the composition. Optional. Mole fraction for each of the components in the composition. Optional.

MOLWEIGHT1

r.l. (g/mol)

STDPRESSURE1

r. (Pa)

[ 1 ATM]

STDTEMPERATURE1

r. (°C)

[15.5 °C]

GOR1

r. (Sm3/Sm3)

Density for each of the components in the composition. Set to –999 if not available. Optional. Molecular weight for each of the components in the composition. Optional. Pressure at standard conditions (1 atm) . Optional Temperature at standard conditions (15.5 oC). Optional. Gas/oil ratio at standard conditions. For two-phase flow, GOR is interpreted as gas/liquid ratio, i.e. it is ratio of gas volume fraction 673 / 769

OLGA 7

GLR1

r. (Sm3/Sm3)

WC1,2

r. (-)

STDGASDENSITY1

r. (kg/m3)

STDOILDENSITY1

r. (kg/m3)

STDWATDENSITY1,[2]

r. (kg/m3)

TOTWATERFRACTION2 r. (-) DEWPRESSURES

r.l. (Pa)

DEWTEMPERATURES

r.l. (°C)

BUBBLEPRESSURES

r.l. (Pa)

BUBBLETEMPERATURESr.l. (°C)

CRITICALPRESSURE

r. (Pa)

CRITICALTEMPERATURE r. (°C)

ratio of gas volume fraction to the liquid volume fraction at standard conditions. For cases where there is no oil/liquid, set GOR = -999. Gas/liquid ratio at standard conditions. For cases where there is no liquid, set GLR = -999. Water cut standard conditions, for three-phase table only. Gas density at standard conditions. Oil density at standard conditions. Water density at standard conditions. Mass fraction of water component in the composition. Dewpoint pressures. The subkeys DEWPRESSURES and DEWTEMPERATURES are optional. Leave out these two subkeys if no dew point curve is found Dewpoint temperatures cor-responding to the dewpoint pressure given in keyword DEWPRESSURES. Bubble point pressures Bubble point temperatures corresponding to the bubble point pressures given in keyword BUBBLEPRESSURES The subkeys BUBBLEPRESSURE and BUBBLETEMPERATURE are optional. Leave out these two subkeys if no bubble point curve is found. Pressure at the critical point Temperature at the critical point. The subkeys CRITICALPRESSURE and

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OLGA 7

NOPRES

i.l.

TEMPERATURE

r.l. (°C)

NOTEMP

i.l.

PRESSURE

r.l. (pa)

COLUMNS

sym.l.

The default unit is given in parenthesis TM (°C) PT (Pa) RS (-)

CRITICALPRESSURE and CRITICALTEMPERATURE are optional. If the critical point is not found, either set the values of critical pressure and temperature to –999, or leave out these two subkeys. Number of pressure points for each of temperature points given in subkey TEMPERATURE. Only if MESHTYPE = FREEPRES Temperature points if MESHTYPE = FREEPRES or STANDARD Number of temperature points for each of pressure points given in subkey PRESSURE. Only if MESHTYPE = FREETEMP Pressure points if MESHTYPE = FREETEMP or STANDARD Specify orders and units of parameters for a table point.

Temperature Pressure Gas mass fraction in gas/oil mixture RSW (-) Water vapour mass fraction in gas phase2 ROG (kg/m3) Gas density DROGDP Derivative of gas density (s2/m2) w.r.t pressure DROGDT Derivative of gas density (kg/m3°C) w.r.t temperature ROHL Oil density (kg/m3)

Key

Type Parameter Unit: ( ) set Default: []

Description

DROHLDP Derivative of oil density (s2/m2) w.r.t pressure 675 / 769

OLGA 7

DROHLDT (kg/m3°C) ROWT (kg/m3) DROWTDP (s2/m2) DROWTDT (kg/m3°C) TCG (W/m°C) TCHL (W/m°C) TCWT (W/m°C) CPG (J/kg°C) CPHL (J/kg°C) CPWT (J/kg°C) HG (J/kg) HHL (J/kg) HWT (J/kg) VISG (Ns/m2) VISHL (Ns/m2) VISWT (Ns/m2) SEG (J/kg°C) SEHL (J/kg°C) SEWT (J/kg°C) SIGGHL (N/m) SIGGWT (N/m) SIGHLWT (N/m) POINT

r.l.

Derivative of oil density w.r.t temperature Water density.2 Derivative of water density w.r.t pressure.2 Derivative of water density w.r.t temperature.2 Gas thermal conductivity. Oil thermal conductivity. Water thermal conductivity. Gas thermal capacity. Oil thermal capacity. Water thermal capacity.2 Gas enthalpy. Oil enthalpy. Water enthalpy.2 Gas viscosity. Oil viscosity. Water viscosity.2 Gas entropy. Oil entropy. Water entropy.2 Surface tension between gas and oil. Surface tension between gas and water. 2 Surface tension between oil and water.2 Values of parameters, see note 1 and 2 below.

Note 1: The pressure and temperature values must be the same as specified in the keys PRESSURE and TEMPERATURE for mesh type STANDARD. Pressure must be the same as specified in the keys PRESSURE for mesh type FREETEMP. Temperature must be the same as specified in the keys TEMPERATURE for mesh type FREEPRES. Note 2: The order and the units must be the same as specified in the key COLUMNS. Note 3: The use of pressure and temperature dependant values in the complex fluid module is not yet implemented.

676 / 769

OLGA 7

yet implemented.

677 / 769

OLGA 7

Examples Example 1: Two-phase, Standard mesh type Example 2: Two-phase, freepressure mesh type Example 3: Two-phase, freetemperature mesh type Example 4: Three-phase, Standard mesh type

Example 1: Two-phase, Standard mesh type PVTTABLE LABEL = FLUID-1, PHASE = TWO, \ COMPONENTS =(N2,CO2,C1,C2, C3, IC4, NC4, IC5,NC5, C6,C7) ,\ MOLES = ( 4.64,3.02,65.39,5.04,2.97,0.90,1.72,0.85,0.84,1.6,13.03),\ MOLWEIGHT = (28.0,44.01,16.04,30.1,44.1,58.1,58.1,72.1,72.1,86.2,154.3) DENSITY = (0,0,0,0,0,0,0,0,0,0,0.789) g/cm3 STDPRESSURE = 1 ATM, \ STDTEMPERATURE = 15.5 C, \ GLR = 768 SM3/SM3, \ STDGASDENSITY = 1.0 KG/M3, \ STDOILDENSITY = 787.7 KG/M3, \ DEWTEMPERATURE = ( 281.27,285.66,291.15,296.62,302.03,\ 307.32,312.44,317.28,321.74,325.65,\ 328.81,330.91,331.56,331.54,330.50,\ 327.48,321.73,312.37,298.41,278.85,\ 261.62,247.00,228.69,213.56,194.95,\ 179.74,170.39,160.41,156.59) C, \ DEWPRESSURE = ( 5.00, 5.99, 7.50, 9.39, 11.74 ,\ 14.67, 18.32, 22.87, 28.55, 35.65, \ 44.57, 55.79, 67.71, 70.01, 84.78, \ 102.96,125.37,152.53,184.55,220.92, \ 247.76,267.66,289.40,304.96,321.31, \ 332.46,338.34,343.81,345.68) BARA, \ BUBBLETEMPERATURE=( 139.72,125.96,112.46,103.52,92.67,\ 73.39, 54.56, 36.12, 26.85,22.85, \ 18.85, 18.00, 14.85, 10.85, 6.85,\ 2.85, 0.09, -1.15,- 5.15,-9.15,\ -13.15,-17.78,-32.86) C, \ BUBBLEPRESSURE=( 352.44,356.11,358.07,358.44,357.88, \ 354.02,346.52,335.35,328.21,324.81, \ 321.20,320.41,317.39,313.36,309.13, \ 304.68,301.49,300.01,295.12,290.00, \ 284.65,278.16,254.79) BARA, \ CRITICALPRESSURE (345.68) BARA, \ CRITICALTEMPERATURE = 156.59 C, \ MESHTYPE = STANDARD, \ ! !both temperature points and pressure points are fixed ! TEMPERATURE =(1,2,3,4,5) C,\ PRESSURE = (1,2,3,4,5) BARA, \ COLUMNS =(PT BARA, TM C, ROG KG/M3, ROHL KG/M3, DROGDP, DROHLDP, DROGDT, \ DROHLDT,RS,VISG,VISHL,CPG,CPHL,HG, HHL,TCG,TCHL,SIGGHL,SEG,SEHL) PVTTABLE POINT = (1,1, 9.628E-01, 7.919E+02, 9.666E-06, 8.513E-07, -3.557E-03, \ -5.931E-01, 4.617E-01, 1.054E-05, 1.299E-03, 1.805E+03, 1.963E+03, \ 678 / 769

OLGA 7

4.841E+02, -3.884E+05, 2.738E-02, 1.379E-01, 2.284E-02, 3.816E+02, \ -7.810E+02) PVTTABLE POINT = (1,2,…) … PVTTABLE POINT = (1,5,..) … ) PVTTABLE POINT = (5,1,..) … ) PVTTABLE POINT = (5,5,…)

Example 2: Two-phase, freepressure mesh type PVTTABLE LABEL = FLUID-1, PHASE = TWO, \ COMPONENTS =(N2,CO2,C1,C2, C3, IC4, NC4, IC5,NC5, C6,C7) ,\ MOLES = ( 4.64,3.02,65.39,5.04,2.97,0.90,1.72,0.85,0.84,1.6,13.03) ,\ MOLWEIGHT = (28.0,44.01,16.04,30.1,44.1,58.1,58.1,72.1,72.1,86.2,154.3) ,\ DENSITY = (0,0,0,0,0,0,0,0,0,0,0.789) g/cm3 ,\ STDPRESSURE = 1 ATM, \ STDTEMPERATURE = 15.5 C, \ GLR = 768 SM3/SM3, \ STDGASDENSITY = 1.0 KG/M3, \ STDOILDENSITY = 787.7 KG/M3 ,\ DEWTEMPERATURE = ( 281.27,285.66,291.15,296.62,302.03, \ 307.32,312.44,317.28,321.74,325.65, \ 328.81,330.91,331.56,331.54,330.50, \ 327.48,321.73,312.37,298.41,278.85, \ 261.62,247.00,228.69,213.56,194.95, \ 179.74,170.39,160.41,156.59) C, \ DEWPRESSURE = (5.00,5.99,7.50,9.39,11.74,14.67,18.32,22.87, \ 28.55,35.65,44.57,55.79,67.71,70.01,84.78, \ 102.96,125.37,152.53,184.55,220.92, \ 247.76,267.66,289.40,304.96,321.31, \ 332.46,338.34,343.81,345.68) BARA, \ BUBBLETEMPERATURE=( 139.72,125.96,112.46,103.52,92.67, \ 73.39, 54.56, 36.12, 26.85,22.85, \ 18.85, 18.00, 14.85, 10.85, 6.85,\ 2.85, 0.09, -1.15,- 5.15,-9.15,\ -13.15,-17.78,-32.86) C, \ BUBBLEPRESSURE=( 352.44,356.11,358.07,358.44,357.88, \ 354.02,346.52,335.35,328.21,324.81, \ 321.20,320.41,317.39,313.36,309.13, \ 304.68,301.49,300.01,295.12,290.00. \ 284.65,278.16,254.79) BARA, \ CRITICALPESSURE (345.68) BARA, \ CRITICALTEMPERATURE = 156.59 C, \ MESHTYPE = FREEPRES, \ ! ! temperature points are specified here. ! number of pressure points and pressure values can be different for ! (be dependent on) different temperature points. ! number of pressure points for each of the temperature points are given here !..the pressure values are given in subkey POINT 679 / 769

OLGA 7

TEMPERATURE =(1.0,2.0,3.0,4.0,5.0) C,\ NOPRES =(5,5,5,5,6),\ COLUMNS =(PT BARA, TM C,ROG KG/M3, ROHL KG/M3, DROGDP, DROHLDP, \ DROGDT,DROHLDT,RS,VISG,VISHL,CPG,CPHL,HG,HHL,TCG, \ TCHL,SIGGHL,SEG,SEHL) ! first temp. point contains five pressure points ranging from 1 to 10 bara PVTTABLE POINT = (1.0,1.0, 9.628E-01, 7.919E+02, 9.666E-06, 8.513E-07, \ -3.557E-03,-5.931E-01,4.617E-01, 1.054E-05, 1.299E-03, \ 1.805E+03, 1.963E+03, 4.841E+02, -3.884E+05, 2.738E-02, \ 1.379E-01, 2.284E-02, 3.816E+02, -7.810E+02) PVTTABLE POINT = (2.0,1.0,…) PVTTABLE POINT = (3.0,1.0,…) PVTTABLE POINT = (5.0,1.0,…) PVTTABLE POINT = (10.0,1.0,…) ! ! more temperature points. Each has five pressure points. ! … ! !last temperature point contains six pressure points ! PVTTABLE POINT = (1.0,5.0,..) PVTTABLE POINT = (5.0,5.0,..) PVTTABLE POINT = (6.0,5.0,..) PVTTABLE POINT = (7.0,5.0,..) PVTTABLE POINT = (8.0,5.0,..) PVTTABLE POINT = (9.0,5.0,..)

Example 3: Two-phase, freetemperature mesh type PVTTABLE LABEL = FLUID-1, PHASE = TWO, \ COMPONENTS =(N2,CO2,C1,C2, C3, IC4, NC4, IC5,NC5, C6,C7) ,\ MOLES = ( 4.64,3.02,65.39,5.04,2.97,0.90,1.72,0.85,0.84,1.6,13.03),\ MOLWEIGHT = (28.0,44.01,16.04,30.1,44.1,58.1,58.1,72.1,72.1,86.2,154.3),\ DENSITY = (0,0,0,0,0,0,0,0,0,0,0.789) g/cm3, \ STDPRESSURE = 1 ATM, \ STDTEMPERATURE = 15.5 C, \ GLR = 768 SM3/SM3, \ STDGASDENSITY = 1.0 KG/M3, \ STDOILDENSITY = 787.7 KG/M3, \ DEWTEMPERATURE = ( 281.27,285.66,291.15,296.62,302.03,\ 307.32,312.44,317.28,321.74,325.65,\ 328.81,330.91,331.56,331.54,330.50,\ 327.48,321.73,312.37,298.41,278.85,\ 261.62,247.00,228.69,213.56,194.95,\ 179.74,170.39,160.41,156.59) C, \ DEWPRESSURE = (5.00,5.99,7.50,9.39,11.74,14.67,18.32,\ 22.87,28.55,35.65,44.57,55.79,67.71,70.01, \ 84.78,102.96,125.37,152.53,184.55,220.92, \ 247.76,267.66,289.40,304.96,321.31, \ 332.46,338.34,343.81,345.68) BARA, \ BUBBLETEMPERATURE=(139.72,125.96,112.46,103.52,92.67,\ 73.39,54.56, 36.12, 26.85,22.85, \ 680 / 769

OLGA 7

18.85,18.00, 14.85, 10.85, 6.85,\ 2.85,0.09, -1.15,- 5.15,-9.15,\ -13.15,-17.78,-32.86) C, \ BUBBLEPRESSURE=( 352.44,356.11,358.07,358.44,357.88, \ 354.02,346.52,335.35,328.21,324.81, \ 321.20,320.41,317.39,313.36,309.13, \ 304.68,301.49,300.01,295.12,290.00, \ 284.65,278.16,254.79) BARA, \ CRITICALPRESSURE (345.68) BARA, \ CRITICALTEMPERATURE = 156.59 C, \ ! ! Pressure points are specified here. ! Number of temperature points and temperature values can change for ! (be dependent on) different pressure points. ! Number of temperature points for each of the pressure points are given here !..The temperature values are given in subkey POINT MESHTYP = FREETEMP, \ PRESSURE =(1.0,2.0,3.0,4.0,5.0) BARA,\ NOTEMP =(5,5,5,5,6),\ COLUMNS =(PT BARA, TM C, ROG KG/M3, ROHL KG/M3, DROGDP, \ DROHLDP,DROGDT,DROHLDT,RS,VISG,VISHL,CPG,CPHL,HG, \ HHL,TCG,TCHL,SIGGHL,SEG,SEHL) ! First pressure point contains five temperature points ! Temperature ranging from 1 to 20 C PVTTABLE POINT = (1.0, 1.0, 9.628E-01, 7.919E+02, 9.666E-06, 8.513E-07, \ -3.557E-03,-5.931E-01, 4.617E-01, 1.054E-05, 1.299E-03, \ 1.805E+03, 1.963E+03, 4.841E+02,-3.884E+05, 2.738E-02, \ 1.379E-01, 2.284E-02, 3.816E+02, -7.810E+02) PVTTABLE POINT = (1.0, 2.0,…) PVTTABLE POINT = (1.0, 4.0,…) PVTTABLE POINT = (1.0,10.0,…) PVTTABLE POINT = (1.0,20.0,…) ! ! more pressure points. Each has five temperature points. ! … ! !last pressure point contains six temperature points ! PVTTABLE POINT = (5.0, 1.0,..) PVTTABLE POINT = (5.0, 5.0,..) PVTTABLE POINT = (5.0,13.0,..) PVTTABLE POINT = (5.0,14.0,..) PVTTABLE POINT = (5.0,15.0,..) PVTTABLE POINT = (5.0,20.0,..) Example 4: Three-phase, Standard mesh type PVTTABLE LABEL = FLUID-1, PHASE = THREE, \ COMPONENTS =(N2,CO2,C1,C2, C3, IC4, NC4, IC5,NC5, C6,C7) ,\ MOLES = ( 4.64,3.02,65.39,5.04,2.97,0.90,1.72,0.85,0.84,1.6,13.03),\ MOLWEIGHT = (28.0,44.01,16.04,30.1,44.1,58.1,58.1,72.1,72.1,86.2,154.3) DENSITY = (0,0,0,0,0,0,0,0,0,0,0.789) g/cm3 681 / 769

OLGA 7

STDPRESSURE = 1 ATM, \ STDTEMPERATURE = 15.5 C, \ GLR = 768 SM3/SM3, \ STDGASDENSITY = 1.0 KG/M3, \ STDOILDENSITY = 787.7 KG/M3, \ STDWATDENSITY = 998. KG/M3, \ DEWTEMPERATURE = ( 281.27,285.66,291.15,296.62,302.03,\ 307.32,312.44,317.28,321.74,325.65,\ 328.81,330.91,331.56,331.54,330.50,\ 327.48,321.73,312.37,298.41,278.85,\ 261.62,247.00,228.69,213.56,194.95,\ 179.74,170.39,160.41,156.59) C, \ DEWPRESSURE = ( 5.00, 5.99, 7.50, 9.39, 11.74 ,\ 14.67, 18.32, 22.87, 28.55, 35.65, \ 44.57, 55.79, 67.71, 70.01, 84.78, \ 102.96,125.37,152.53,184.55,220.92, \ 247.76,267.66,289.40,304.96,321.31, \ 332.46,338.34,343.81,345.68) BARA, \ BUBBLETEMPERATURE=( 139.72,125.96,112.46,103.52,92.67,\ 73.39, 54.56, 36.12, 26.85,22.85, \ 18.85, 18.00, 14.85, 10.85, 6.85,\ 2.85, 0.09, -1.15,- 5.15,-9.15,\ -13.15,-17.78,-32.86) C, \ BUBBLEPRESSURE=( 352.44,356.11,358.07,358.44,357.88, \ 354.02,346.52,335.35,328.21,324.81, \ 321.20,320.41,317.39,313.36,309.13, \ 304.68,301.49,300.01,295.12,290.00, \ 284.65,278.16,254.79) BARA, \ CRITICALPRESSURE (345.68) BARA, \ CRITICALTEMPERATURE = 156.59 C, \ MESHTYPE = STANDARD, \ ! !both temperature points and pressure points are fixed ! TOTWATERFRACTION = 0.112, \ WC=.489380E-02,\ TEMPERATURE =(1,2,3,4,5) C,\ PRESSURE = (1,2,3,4,5) BARA, \ COLUMNS = (PT,TM,ROG,ROHL,ROWT,DROGDP,DROHLDP,DROWTDP,DROGDT,DROHLDT, \ DROWTDT,RS,RSW,VISG,VISHL,VISWT,CPG,CPHL,CPWT,HG,HHL,HWT,TCG, \ TCHL,TCWT,SIGGHL,SIGGWT,SIGHLWT,SEG,SEHL,SEWT) ! PVTTABLE POINT = (1,1,.112510E+01,.708593E+03,.677649E+03,.113188E-04, \ .520848E-06,.156303E-06,-.418187E-02,-.332632E+00,.535346E+00, \ .372160E-01,.182867E-02,.979882E-05,.591224E-02,.263150E-02, \ .176425E+04,.202253E+04,.449390E+04,.731026E+02,-.345943E+06, \ -.196628E+07,.248102E-01,.148744E+00,.570657E+00,.118942E-01, \ .755188E-01,.544038E-01,.435748E+03,-.631419E+03,-.537537E+04) PVTTABLE POINT = (1,2,…) … PVTTABLE POINT = (1,5,..) … ) PVTTABLE POINT = (5,1,..) … 682 / 769

OLGA 7

) PVTTABLE POINT = (5,5,…)

683 / 769

OLGA 7

Standard conditions for keyword based PVT file STDPRESSURE and STDTEMPERATURE in the PVT table file (keyword format) are the standard pressure and temperature given in PVTsim when creating the file, while GOR, GLR, STDGASDENSITY, STDOILDENSITY, STDWATDENSITY and WC (the two latter only for 3 phase table files) are the properties at this standard condition. These values have not been used in previous OLGA versions, but are used in Olga 6.2 and Olga 5.3.4 for input (e.g. GORST in WELL) and output (e.g. QGST - Gas volume flow at standard conditions). This will give more precise results in simulations where e.g. GORST in WELL is used and the table is coarse around the standard conditions (e.g. if the two lowest pressure is 0.1 and 10 bara) since the gas mass fraction is not linear with pressure for such low pressures. A new key STDLIQDENSITY will be introduced in the next PVTsim version. This gives the standard density of liquid water and hydrocarbons (HC) in the case where a two phase PVT file is generated from a composition with water. STDOILDENSITY is the density for HC only and thus does not contain the necessary information. If the keys are not present (removed manually since always written), linear interpolation between the pressure and temperature points will be used as before. Note that the given STDPRESSURE and STDTEMPERATURE will be used for both input and output instead of the default values of 1 atm and 15.56 °C/60 F.

684 / 769

OLGA 7

Standard format for fluid properties The fluid properties are given as functions of pressure and temperature. This table of properties can be equidistant or non-equidistant in pressure and temperature. A more refined interpolation in the fluid property tables close to the two-phase envelope is performed only for the gas mass fraction utilising the bubble point pressure given in the file. The dew point pressures are not used in the present OLGA version. Figure A shows the above mentioned two-phase envelope as a function of pressure and temperature. If OLGA is used with the water option, water properties are also needed. These properties may be given as tables in the fluid properties file, or may be calculated by the code itself. This is determined by the text, in the fluid identifier, FLUIDF, given in the fluid properties file. If the fluid contains water and it is decided to use the two phase option in OLGA, only two-phase tables for fluid properties must be used. Liquid properties must be for the mixture of oil and water. The partial derivatives of gas and liquid densities with respect to pressure and temperature are required as separate tables. The reason is that the partial derivatives should be those of the isolated phase, gas or liquid, at the actual thermodynamic conditions. These cannot be obtained from the densities by interpolation in the tables since the partial derivatives in that case would also include phase mass transfer/changes in phase compositions. Remarks: -The gas mass fraction may not be zero for pressures above the bubble point pressure due to linear interpolation in the tables. For pressures above the bubble point pressure, the gas mass fraction calculated from the tables will, however, always be set to zero. Indicators for the fluid file content: The interpretation of tables in the fluid properties file is determined from: 1.

Whether there is more than one fluid.

2.

The content of the fluid identifier, FLUIDF, as follows: If the sub-string "WATER-OPTION" is present, three phase tables are expected in the file. If the sub-string "NONEQ" is present, non-equidistant spacing in the tables are expected. If the sub-string "ENTROPY" is present, entropy tables for gas, oil and eventually water are expected.

The input variables FILEID, NCOMP and LC can be collectively omitted for single branch cases. Variables:

Name Unit Definition [FILEID] File identification (60 characters) [NCOMP] Number of fluids in this file. The following data are repeated for each fluid: FLUIDF (-) Fluid identifier enclosed in apostrophes. If FLUIDF contains the sub-string WATER-OPTION, NONEQ or ENTROPY the tables will be read as explained above. [LC] Fluid label The label must be unique and may be a number or a text string. (LAB_1,LAB_2, ... ,LAB_NCOMP) NTABP (-) Number of pressure points in the table NTABT (-) Number of temperature points in the table 685 / 769

OLGA 7

RSWTOTB

(kg/kg)

DP

(N/m2) (°C)

DT PP(I) TT(J) PBB(J) PDEW(J)

Total water mass fraction for the feed. Optionally, default value = 0 (Only used together with three-phase tables) Pressure step in the table Temperature step in the table

(N/m2) (°C)

Pressure values in the table, I=1,NTABP

(N/m2) (N/m2)

Bubble point pressures, J = 1, NTABT

(kg/m3) (kg/m3)

Oil densities

(s2/m2) (s2/m2)

Partial derivatives of gas densities with respect to pressure

Temperature values in the table, J = 1, NTABT

Dew point pressures, J = 1, NTABT For temperatures in the table which indicate single phase flow for the whole range of pressures (all points are outside the two phase envelope for a specific temperature, see Figure A), the corresponding bubble point pressures must be greater than the largest pressure point in the tables. The dew point pressures are not used in the present OLGA version TABTEX(L) (-) Text string to identify the different properties. NB! For all tables below, J = 1, NTABT and I = 1, NTABP ROGTB(J,I) Gas densities (kg/m3) ROOTB(J,I) ROWTB(J,I) DRGPTB(J,I) DROPTB(J,I)

Water densities Partial derivatives of oil densities with respect to pressure

DRWPTB(J,I)

Partial derivatives of water densities with respect to pressure. (s2/m2) DRGTTB(J,I) (kg/m3C) Partial derivatives of gas densities with respect to temperature

DROTTB(J,I) DRWTTB(J,I) RSGTB(J,I)

RSWTB(J,I) VSGTB(J,I)

(kg/m3C) Partial derivatives of oil densities with respect to temperature (kg/m3C) Partial derivatives of water densities with respect to temperature. (kg/kg) Gas mass fraction in gas and oil mixture; the gas mass divided by the gas and oil mass. All values in this table must be set to a constant (between 0 and 1) (for all points) in case of no interphase mass transfer. ( = 0 gives single phase liquid, =1 gives single phase gas). REMARK: The gas may also contain water vapour. (kg/kg) Water vapour mass fraction in the gas phase Dynamic viscosities for gas

VSOTB(J,I)

(Ns/m2) (Ns/m2)

VSWTB(J,I) CPGTB(J,I)

(Ns/m2) (J/kgC)

Dynamic viscosities for water Gas heat capacities at constant pressure

CPOTB(J,I) CPWTB(J,I) HGTB(J,I) HOTB(J,I) HWTB(J,I) TKGTB(J,I) TKOTB(J,I) TKWTB(J,I) SIGOGT(J,I)

(J/kgC) (J/kgC) (J/kg) (J/kg) (J/kg) (W/mC) () (W/mC) (N/m)

Oil heat capacities at constant pressure Water heat capacities at constant pressure Gas enthalpies Oil enthalpies Water enthalpies Gas thermal conductivities Oil thermal conductivities Water thermal conductivities Surface tension between gas and oil

Dynamic viscosities for oil

686 / 769

OLGA 7

SIGWGT(J,I) SIGWOT(J,I) SGTB(J,I) SOTB(J,I) SWTB(J,I)

(N/m) (N/m) (J/kgC) (J/kgC) (J/kgC)

Surface tension between gas and water Surface tension between water and oil Gas specific entropy Oil specific entropy Water specific entropy.

Figure A Example of the use of the bubble and dew point pressures in relation to the two-phase envelope and the fluid property table points (NTABT=6 and NTABP=5). The figure does not correspond to the tables of fluid properties used in the sample case. Data file structure: The data enclosed in brackets can collectively be omitted for single branch cases. [FILEID] [NCOMP]

The following data are repeated for each fluid composition. The file heading for equidistant tables. Note that RSWTOTB is set to zero by OLGA if omitted: FLUIDF [LC] NTABP NTABT RSWTOTB DP DT PP(1) TT(1) The file heading for non-equidistant tables. Note that RSWTOTB is set to zero by OLGA if omitted: FLUIDF [LC] NTABP NTABT RSWTOTB 687 / 769

OLGA 7

PP(1) . . . . . . . . PP(NTABP) TT(1) . . . . . . . . TT(NTABT) The fluid property tables: PBB(1) . . . . . . . . PBB(NTABT) PDEW(1) . . . . . . . . PDEW(NTABT) TABTEX(1) ROGTB(1,1) . . . . . . . ROGTB(NTABT,1) . . ROGTB(1,NTABP) . . . . . ROGTB(NTABT,NTABP) TABTEX(2) ROOTB(1,1) . . . . . . . ROOTB(NTABT,1) . . ROOTB(1,NTABP) . . . . . ROOTB(NTABT,NTABP) if FLUIDF contains substring WATER-OPTION, then TABTEX(3) ROWTB(1,1) . . . . . ROWTB(NTABT,1) . . ROWTB(1,NTABP) . . . ROWTB(NTABT,NTABP) end WATER-OPTION TABTEX(4) DRGPTB(1,1). . . . . . . DRGPTB(NTABT,1) . . DRGPTB(1,NTABP). . . . . DRGPTB(NTABT,NTABP) TABTEX(5) DROPTB(1,1). . . . . . . DROPTB(NTABT,1) . . DROPTB(1,NTABP). . . . . DROPTB(NTABT,NTABP) if FLUIDF contains substring WATER-OPTION, then TABTEX(6) DRWPTB(1,1). . . . . . . DRWPTB(NTABT,1) . . DRWPTB(1,NTABP). . . . . DRWPTB(NTABT,NTABP) end WATER-OPTION TABTEX(7) DRGTTB(1,1). . . . . . . DRGTTB(NTABT,1) . . DRGTTB(1,NTABP). . . . . DRGTTB(NTABT,NTABP) TABTEX(8) DROTTB(1,1). . . . . . . DROTTB(NTABT,1) . . DROTTB(1,NTABP). . . . . DROTTB(NTABT,NTABP) 688 / 769

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if FLUIDF contains substring WATER-OPTION, then TABTEX(9) DRWTTB(1,1). . . . . . . DRWTTB(NTABT,1) . . DRWTTB(1,NTABP). . . . . DRWTTB(NTABT,NTABP) end WATER-OPTION TABTEX(10) RSGTB(1,1). . . . . . . RSGTB(NTABT,1) . . RSGTB(1,NTABP). . . . . RSGTB(NTABT,NTABP) if FLUIDF contains substring WATER-OPTION, then TABTEX(11) RSWTB(1,1) . . . . . . . RSWTB(NTABT,1) . . RSWTB(1,NTABP) . . . . . RSWTB(NTABT,NTABP) end WATER-OPTION TABTEX(12) VSGTB(1,1) . . . . . . . VSGTB(NTABT,1) . . VSGTB(1,NTABP) . . . . . VSGTB(NTABT,NTABP) TABTEX(13) VSOTB(1,1) . . . . . . . VSOTB(NTABT,1) . . VSOTB(1,NTABP) . . . . . VSOTB(NTABT,NTABP) if FLUIDF contains substring WATER-OPTION, then TABTEX(14) VSWTB(1,1) . . . . . . . VSWTB(NTABT,1) . . VSWTB(1,NTABP) . . . . . VSWTB(NTABT,NTABP) end WATER-OPTION TABTEX(15) CPGTB(1,1) . . . . . . . CPGTB(NTABT,1) . . CPGTB(1,NTABP) . . . . . CPGTB(NTABT,NTABP) TABTEX(16) CPOTB(1,1) . . . . . . . CPOTB(NTABT,1) . . CPOTB(1,NTABP) . . . . . CPOTB(NTABT,NTABP) if FLUIDF contains substring WATER-OPTION, then TABTEX(17) CPWTB(1,1) . . . . . . . CPWTB(NTABT,1) 689 / 769

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. . CPWTB(1,NTABP) . . . . . CPWTB(NTABT,NTABP) end WATER-OPTION TABTEX(18) HGTB(1,1) . . . . . . . HGTB(NTABT,1) . . HGTB(1,NTABP). . . . . . HGTB(NTABT,NTABP) TABTEX(19) HOTB(1,1) . . . . . . . HOTB(NTABT,1) . . HOTB(1,NTABP). . . . . . HOTB(NTABT,NTABP) if FLUIDF contains substring WATER-OPTION, then TABTEX(20) HWTB(1,1) . . . . . . . HWTB(NTABT,1) . . HWTB(1,NTABP). . . . . . HWTB(NTABT,NTABP) end WATER-OPTION TABTEX(21) TKGTB(1,1) . . . . . . . TKGTB(NTABT,1) . . TKGTB(1,NTABP) . . . . . TKGTB(NTABT,NTABP) TABTEX(22) TKOTB(1,1) . . . . . . . TKOTB(NTABT,1) . . TKOTB(1,NTABP) . . . . . TKOTB(NTABT,NTABP) if FLUIDF contains substring WATER-OPTION, then TABTEX(23) TKWTB(1,1) . . . . . . . TKWTB(NTABT,1) . . TKWTB(1,NTABP) . . . . . TKWTB(NTABT,NTABP) end WATER-OPTION TABTEX(24) SIGOGT(1,1). . . . . . . SIGOGT(NTABT,1) . . SIGOGT(1,NTABP). . . . . SIGOGT(NTABT,NTABP) if FLUIDF contains substring WATER-OPTION, then TABTEX(25) SIGWGT(1,1) . . . . . . . SIGWGT(NTABT,1) . . 690 / 769

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SIGWGT(1,NTABP) . . . . . SIGWGT(NTABT,NTABP) TABTEX(26) SIGWOT(1,1) . . . . . . . SIGWOT(NTABT,1) . . SIGWOT(1,NTABP) . . . . . SIGWOT(NTABT,NTABP) end WATER-OPTION if FLUIDF contains substring ENTROPY, then TABTEX(27) SGTB(1,1) . . . . . . . SGTB(NTABT,1) . . SGTB(1,NTABP). . . . . . SGTB(NTABT,NTABP) TABTEX(28) SOTB(1,1) . . . . . . . SOTB(NTABT,1) . . SOTB(1,NTABP). . . . . . SOTB(NTABT,NTABP) if FLUIDF also contains substring WATER-OPTION, then TABTEX(29) SWTB(1,1) . . . . . . . SWTB(NTABT,1) . . SWTB(1,NTABP) . . . . . SWTB(NTABT,NTABP) end WATER-OPTION end if The entropy data will be used if a Henry-Fauske type critical flow model is chosen for the flow through a valve. If the entropy is not given, the entropy data will be computed by the code. The tables for heat capacity, enthalpy and thermal conductivity are used only for temperature calculations. The water tables are used only if the water option is used. Examples of fluid property tables are given electronically with the OLGA software package.

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Complex fluid module The liquid viscosity table in the fluid properties file plays different, but related, roles in the three different rheology models in the complex fluid module. 1. The Newtonian option (TYPE=COMPLEXFLUID and CFLUML=NEWTONIAN in the FLUID keyword) yields the original interpretation. 2. The power law model (TYPE=COMPLEXFLUID and CFLUML=POWERLAW in the FLUID keyword) yields the consistency factor, K. 3. The Bingham fluid model (TYPE=COMPLEXFLUID and CFLUML=BINGHAM in the FLUID keyword) yields the coefficient of rigidity. If simplified input is used (FULL=NO in the FLUID keyword), the non-Newtonian parameters are used at the in situ shear stress to calculate the effective viscosity of the fluid at standard conditions. In order to obtain the effective viscosity of the fluid at pipeline conditions, the effective viscosity at standard conditions have to be multiplied by the ratio of the viscosity (as given in the viscosity table in the fluid data file) at pipeline conditions and standard conditions. The fluid identifier FLUIDF, see Standard format for fluid properties, have to include certain text strings in order to enable OLGA to interpret the fluid property file correctly. The strings required are explained below. POWEXPL: The fluid property file contains a table of the power law exponent for the oil phase. POWEXPW: The fluid property file contains a table of the power law exponent for the water phase. YIELDSTRL: The fluid property file contains a table of yield stress for the oil phase. YIELDSTRW: The fluid property file contains a table of yield stress for the water phase. The text string that identifies the different properties TABTEX(), see Standard format for fluid properties, also have to include the same text strings as described above. Example: TABTEX(:) VSOTB(1,1) : VSOTB(1,NTABP)

... ...

VSOTB(NTABT,1) : VSOTB(NTABT,NTABP)

if FLUIDF contains substring WATER-OPTION, then TABTEX(:) VSWTB(1,1) . . . VSWTB(NTABT,1) : : VSWTB(1,NTABP) . . . VSWTB(NTABT,NTABP) end WATER-OPTION if FLUIDF contains substring POWEXPL, then TABTEX(:) POWNTB(1,1) . . . POWNTB(NTABT,1) : : POWNTB(1,NTABP) . . . POWNTB(NTABT,NTABP) end if FLUIDF contains substring YIELDSTRL, then TABTEX(:) 692 / 769

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TAUITB(1,1) : TAUITB(1,NTABP) end

... ...

TAUITB(NTABT,1) : TAUITB(NTABT,NTABP)

if FLUIDF contains substring POWEXPW, then TABTEX(:) POWNWTB(1,1) . . . POWNWTB(NTABT,1) : : POWNWTB(1,NTABP) . . . POWNWTB(NTABT,NTABP) end if FLUIDF contains substring YIELDSTRW, then TABTEX(:) TAUIWTB(1,1) . . . TAUIWTB(NTABT,1) : : TAUIWTB(1,NTABP) . . . TAUIWTB(NTABT,NTABP) end TABTEX(:) CPGTB(1,1) : CPGTB(1,NTABP)

... ...

CPGTB(NTABT,1) : CPGTB(NTABT,NTABP)

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Pump Data Files Pump Data Table for Centrifugal Pumps Pump Data Table for Displacement Pumps

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Pump Data Table for Centrifugal Pumps The pump characteristics for the centrifugal pump are presented in the form of four quadrant curves. These curves are empirically developed by the pump manufacturer. The four quadrant curves must be converted to a dimensionless form by the development of homologous curves where the head and torque ratios (actual value to rated value) are functions of the pump speed and flow rate ratios. In order to interpret the homologous curves, the following variables are defined: - head ratio

- flow ratio

- speed ratio - torque ratio where subscript R means rated value. Four sets of homologous curves are tabulated: 1. 2. 3. 4.

Single phase head HS Two phase head HT Single phase torque THS Two phase torque THT

Each set of homologous curves consists of four curves, comprised of two dependent variables each as function of two independent variables. A more detailed description is given under Pumps . The transfer from single phase to fully degraded two phase conditions is described by the two phase head and two phase torque multipliers. A complete default set of homologous curves is tabulated in the code. These are based on experimental data and are representative for centrifugal pumps. However, the users can change these data easily by specifying their own experimental or model-specific data through the pump data table. The structure of the table is as shown in the example below. The reading of the input is based on keywords, but the sequence of the keywords must be as shown in the example. For the independent variables, the keyword QOMEG is used for q/ and the keyword OMEGQ is used for /q. For each table, the number of dependent and independent variable entries must be the same. !************************************************************************************************* ! Pump type and label !************************************************************************************************* TYPE = CENTRIFUGAL, LABEL = Label of the table ! !************************************************************************************************* ! Table for single phase head HS !************************************************************************************************* ! HS1 QOMEG = (x1, x2, … , xHS1) HEADS1 = (y1, y2, … , YHS1) ! HS2 OMEGQ = (x1, x2, … , xHS2) HEADS2 = (y1, y2, … , YHS2) ! HS3 OMEGQ = (x1, x2, … , xHS3) HEADS3 = (y1, y2, … , YHS3) ! HS4 QOMEG = (x1, x2, … , xHS4) 695 / 769

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HEADS4 = (y1, y2, … , YHS4) ! !************************************************************************************************* ! Table for two phase head HT !************************************************************************************************* ! HT1 QOMEG = (x1, x2, … , xHT1) HEADT1 = (y1, y2, … , YHT1) ! HT2 OMEGQ = (x1, x2, … , xHT2) HEADT2 = (y1, y2, … , YHT2) ! HT3 OMEGQ = (x1, x2, … , xHT3) HEADT3 = (y1, y2, … , YHT3) ! HT4 QOMEG = (x1, x2, … , xHT4) HEADT4 = (y1, y2, … , YHT4) ! !************************************************************************************************* ! Table for single phase torque THS !************************************************************************************************* ! THS1 QOMEG = (x1, x2, … , xTHS1) TORQS1 = (y1, y2, … , YTHS1) ! THS2 OMEGQ = (x1, x2, … , xTHS2) TORQS2 = (y1, y2, … , YTHS2) ! THS3 OMEGQ = (x1, x2, … , xTHS3) TORQS3 = (y1, y2, … , YTHS3) ! THS4 QOMEG = (x1, x2, … , xTHS4) TORQS4 = (y1, y2, … , YTHS4) ! !************************************************************************************************* ! Table for two phase torque THT !************************************************************************************************* ! THT1 QOMEG = (x1, x2, … , xTHT1) TORQS1 = (y1, y2, … , YTHT1) ! THT2 OMEGQ = (x1, x2, … , xTHT2) TORQS2 = (y1, y2, … , YTHT2) ! THT3 OMEGQ = (x1, x2, … , xTHT3) TORQS3 = (y1, y2, … , YTHT3) ! THT4 QOMEG = (x1, x2, … , xTHT4) TORQS4 = (y1, y2, … , YTHT4) ! !************************************************************************************************* 696 / 769

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! Table for two phase head multiplier !************************************************************************************************* VOID = (x1, x2, … , xHV) HEADM = (y1, y2, … , YHV) ! !************************************************************************************************* ! Table for two phase torque multiplier !************************************************************************************************* VOID = (x1, x2, … , xTV) TORQM = (y1, y2, … , YTV) ! !************************************************************************************************* ! End of the table !************************************************************************************************* END ! NOTE ! The number of elements for each curve is limited to 10.

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Pump Data Table for Displacement Pumps The back flow rate, Qb , is a function of PI , DP, aI, nl , and N. In order to define Qb a complete table with 5 independent variables and one dependent variable should be defined. Linear interpolation is used to calculate the Qb-value and its partial derivatives at the operating point. The default units of the variables in the table: PI, - Pa; Pump inlet pressure DP - Pa; Pump pressure increase 3 Qb - m / s; Volumetric back flow nl - m2 / s; Liquid kinematic viscosity aI - (-); Gas volume fraction N - rpm. Pump speed The units can also be specified by users. The structure of the table is as shown in the example below. The reading of the input is based on keywords, but the sequence of the keywords must be as shown in the example. The structure of the table is: !************************************************************************* ! Pump type and label !************************************************************************* TYPE = DISPLACEMENT, LABEL = Label of the table ! !************************************************************************* ! First pump speed (1) !------------------------------------------------------------------------------------PUMPSPEED = N1 ! !************************************************************************* ! First suction pressure (2) !------------------------------------------------------------------------------------INPRESSURE = Pl,1 ! !************************************************************************* ! Lists of voidfractions and deltap for first pump speed and ! suction pressure. (3) !------------------------------------------------------------------------------------VOIDFRACTION = (aI,1, aI,2, … , aI,J) ! DELTAP = (DP1, DP2, … , DPK) ! !************************************************************************* ! First viscosity (4). ! ! For each viscosity back flow is listed as function of void! fraction and DP. Each BACKFLOW entry is for one ! DP and runs over all voidfractions. !------------------------------------------------------------------------------------VISCOSITY = nl,1 698 / 769

OLGA 7

! BACKFLOW BACKFLOW : :

= (Qb,1,1, Qb,1,2, … , Qb,1,J) = (Qb,2,1, Qb,2,2, … , Qb,2,J)

BACKFLOW = (Qb,K,1, Qb,K,2, … , Qb,K,J) ! !************************************************************************* ! Second viscosity. !------------------------------------------------------------------------------------VISCOSITY = nl,2 : : ! !************************************************************************* ! (2)+(3)+(4) is repeated for each suction pressure ! associated with the first pump speed. ! Different values for voidfraction, deltap and viscosity can ! be used for each suction pressure. !------------------------------------------------------------------------------------INPRESSURE = Pl,2 ! : : ! !************************************************************************* ! (1)+(2)+(3)+(4) is repeated for each pump speed. ! Different values for suction pressure, voidfraction, deltap ! and viscosity can be used for each suction pressure. !------------------------------------------------------------------------------------PUMPSPEED = N2 ! : : !************************************************************************* ! End of the table !------------------------------------------------------------------------------------ENDTABLE ! NOTE! The number of pump speeds and suction pressures is limited to 5, while the number of voidfraction, deltap and viscosity entries is limited to 10.

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Restrictions and Limitations Memory consumption Fluid properties Input/Output Limitations Standard Conditions in OLGA Two-Phase Model Limitations Important Numerical Recommendations

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Memory consumption OLGA will allocate memory for the simulation as needed. The memory usage will be a function of the total number of pipe sections in the case, any special modules used (for instance: slug-tracking, inhibitor tracking, compositional tracking) and to some extent the number of plot variables (TREND, PROFILE). In particular, it is important to be aware that the amount of memory required during the simulation will roughly be proportional to the total number of sections in the network. That is, double the number of sections for a given case, and you will double the memory usage. If the machine running the simulation is short on physical and virtual memory, this will ultimately lead to an unexpected program termination.

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Fluid properties All fluid properties are normally assumed to be unique functions of temperature and pressure, and have to be input to OLGA in a particular file. Thus, the total composition (the mole fractions of the components) of the multiphase mixture is assumed to be constant both in time and space. This limitation is important for mixtures with pronounced compositional dependent properties. Note, however, that one may use different fluid properties in different branches in a pipeline network. Network simulations are special cases where total compositional changes in the pipeline may be important. Due to the phase velocity differences, the fluid composition in a pipe is generally different from the fluid compositions used in the PVT table (for example during the depressurisation of a pipeline). If only gas is released from the pipe, the total composition in the pipe will change. Condensate may accumulate in the lower parts of the pipe and result in large compositional differences between sections. This difference will not affect the steady state results provided that the inlet flowing fluid has the same composition as in the PVT table. In transient simulations the fluids in the pipes have different compositions. Thus, changes in physical properties and equilibrium mass fractions due to changes in temperature and pressure will be different from the values in the PVT table. These differences are usually small. As an alternative to PVT tables, it is possible to perform a simulation using compositional tracking, where the compositional data is provided in a feed file and the code calculates the fluid properties internally. This means that the total composition may vary both in time and space, and that no special consideration is needed for a pipeline network. This procedure is also more accurate in simulations where the fluid composition will change considerably with time, e.g., blowdown of pipelines. However, compositional tracking is more CPU demanding and may prolong the simulation time significantly. The gas and liquid phases are assumed to be in thermodynamic equilibrium; the temperature and pressure are equal in both phases, and any interface mass transfer occurs instantaneously. The latter has important implications for the pressure wave propagation (or speed of sound); if normal condensation takes place, the mixture will appear too compressible in OLGA and the pressure wave velocity will be smaller than if the mass transfer rate was finite.

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Input/Output Limitations Input pre-processor The input pre-processor that checks the input data for inconsistencies is not foolproof. Although the most frequent input errors are found, there may be cases with faulty input that are not detected. Initial value pre-processor OLGA contains a steady state pre-processor, that computes values to be used as initial conditions in dynamic computations. The pre-processor uses the OLGAS interface iteratively over all pipe sections to calculate pressure gradients and other parameters in the flow network until a consistent steady-state solution has been found. However, the solution computed by the steady state pre-processor and the solution obtained when simulation with the dynamic solver until a steady-state is achieved may not be equal. See limitations in the steady state pre-processor chapter for an explanation for this. Printed output As this is a user specified quantity, care must be taken to avoid a paper or file ”explosion”. The amount of printed output is proportional to the number of output intervals and to the number of output variables and sections specified in the keyword statement OUTPUT. Output postprocessor The output postprocessor summarizes the simulation results. Some of the information is dedicated to steady state cases. Other items, like the minimum and maximum variable values, are interesting also for transient simulations. The postprocessor will not give any information on any process equipment that is simulated. Plot file sizes There are no formal program restrictions regarding the size of these files. The user implicitly controls the size through the data specified in the keyword statements PLOT, TREND and PROFILE. The size is determined by the number of variables, sections and output time intervals. The file size limitation will be system dependent. For 32-bit operating systems, a rule-of-thumb says that files should not exceed 2GB.

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Standard Conditions in OLGA ”Standard conditions” are often defined in SI units as 1 bara and 15 °C, but the default value in OLGA it is defined as 1 atm/14.7 psia and 15.56 °C/60 F. This definition is the most commonly used in the petroleum industry. The default value can only be overridden when using keyword based PVT table. ”Stock tank conditions” are also used in the industry, but this phrase is often perceived to mean dry oil and gas. Therefore, the term ”standard conditions” is used in OLGA. Also, ”volume rates at standard conditions” are sometimes expressed as simply the in-situ mass rate divided by the density at standard conditions (for liquid), but in OLGA this definition is not used. Output variables for volume rates at standard conditions assume that a single stage flash from in-situ to standard conditions has been performed. That is, mass transfer between the phases from in-situ to standard conditions is taken into account. The gas is not dehydrated unless FLASHMODEL = HYDROCARBON is specified in the keyword OPTIONS. For table-based simulations, OLGA uses the gas mass fractions and densities from the fluid property file to perform the conversion (requires that the tables contain standard conditions). For Compositional tracking simulations a flash is performed for the in-situ fluid to standard conditions for each section and time the output variables are to be reported. This can increase the simulation time as a flash is CPU demanding, and such output variables should therefore be used with care for Compositional tracking simulations.

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Flow Model Limitations Generally, these limitations are difficult to assess. Their possible consequences, however, will normally not be influenced by the user input. An exception is the correlation for the void fraction in liquid slugs. An average correlation based on the diesel, naphtha and stanco experiments at the SINTEF loop is applied by default. The actual correlation quite significantly influences the transition from stratified to slug flow. The selected correlation yields good agreement for all the above experiments. For air/water, another correlation should be applied and OLGA provides an alternative which may be activated by specifying the key SLUGVOID in the keyword OPTIONS. Unless the slug tracking option is used, OLGA applies an average slug flow description. That is, if slug flow is predicted at a section boundary, the flow parameters at that boundary, such as slug bubble velocity and volume fraction, slug fraction, etc., are computed based on the assumption of fully developed slug flow with an infinite number of identical slug cells. The detailed flow parameters at another point along the pipeline will normally differ as the average flow parameters (pressure, hold-up, etc.) differ. The average description implies that if slug flow occurs in two adjacent sections, the detailed slug flow parameters at one section do not explicitly influence those in the section following it. The flow history at a pipe location is to a small extent considered in the flow regime determination. For example, if slug flow is predicted in an upward sloping pipe and stratified flow in a following downward sloping pipe, all slugs die at the entrance of the latter pipe. In reality, slug flow may persist some distance downstream since a slug needs some time to disintegrate. Eventually, one slug may proceed downstream and cause liquid blockage at a bend in a riser connection with possible build-up of a terrain slug. This special type of mechanism for the onset of terrain slugging is not represented in the standard OLGA model. To simulate this phenomenon accurately the SLUGTRACKING model with HYDRODYNAMIC=ON should be used.

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Important Numerical Recommendations Time step OLGA has time step control based on several criteria. They can all be given at user specified sections through the keyword statement DTCONTROL. The first time step control is based on the transport criterion of Courant-Friedrich-Levy (CFL): This criterion is by default switched on. This means that the time step is limited so that no mass is trans ported across a whole section in one time step. This is the maximum time step allowed if a mass transient is to be followed correctly. The second time step control, SOUND_CFL, (default OFF) uses the same principles as the CFL but is based on the speed of the pressure wave instead of the fluid velocity. It has been introduced to better calculate shock waves (e.g. due to water hammer). The third time step control, PRESSURE, (default OFF) is based on the second order time derivative of the pressure. The fourth time step control, GRADPRESSURE, (default OFF) is based on the first order time derivative of the pressure. This has been introduced to be able to reduce the time step earlier for quick pressure changes, e.g. a pipeline with high pressure is opened into a small closed volume. If all time step control criteria are switched on, OLGA will choose the minimum time step from the activated time steps controls. The upper and lower limit for the time step is the user-given MINDT and MAXDT in the keyword statement INTEGRATION. Additional time step controls are activated when process equipment is simulated, or the slug tracking option is activated. Section Lengths For a pipeline of fixed length the simulation time increases roughly quadratically with the number of sections in the pipeline. First, the number of arithmetic operations per time step increases proportionally to the number of sections. Second, the time step decreases with decreasing section length if the CFL transport criterion is switched on. The accuracy of the solution increases with smaller sections but in a complex manner that is difficult to estimate quantitatively. The numerical solution should, however, approach the analytical one as and approach zero. Variable Mesh Length Past experience indicates that the section lengths should not differ too much along the pipeline. A factor of 2 or less in length ratio between adjacent sections is recommended although factors of 5-10 might work in some cases. Pipe-Section Discretisation In general, if either the inclination angle or the diameter of the pipes varies, each pipe should be divided into at least two sections to ensure meaningful results, i.e. to reduce numerical 'smearing out' of these effects. Wall Layer Thickness The numerical solution of the wall temperatures in the wall layers is dependent on the wall layer discretisation. For steady state calculations, the wall layer discretisation can be quite coarse, one layer for each material layer. For transient calculations when the heat storage in the pipe walls can be important (cool down or heat up) a finer discretisation of the pipe walls may be necessary. 706 / 769

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up) a finer discretisation of the pipe walls may be necessary. Very thin layers, such as paint etc., should be included in a neighbouring layer by adjusting the thickness and conductivity of that layer. If the thermal conductivity of the thin layer is fairly close to the conductivity of one of the neighbours, only the thickness needs to be adjusted.

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Sample cases The OLGA 6 installation includes a set of sample cases. These are located in the .\SPT Group\OLGA 6.2\Samples\OLGA 6 folder in the installation directory (by default this is either C:\Program Files or C:\Program Files (x86) depending on the Windows installation). All sample projects can also be started from the start menu (All Programs > SPT Group > OLGA 6.2 > OLGA 6 Samples). The sample cases are organized in projects as follows: Advanced Thermal project: Fluid bundle Solid bundle Compositional project: Blackoil Compositional Tracking MEG Tracking CO2 Tracking (Single component) H2O Tracking (Single component) H2O Tracking (Steam/Water–HC) Tracer Tracking FA-Models project: 2nd-order scheme Advanced Well Corrosion Drilling Fluid Hydrate Kinetics Network Wateroptions Waxdeposition Pigging project: Pigging (with and w/o tracking of slug and with and w/o compositional tracking) Process project: Process Equipment PID Controller Simplified Pump Centrifugal Pump Displacement Pump Pump Battery Separator Source, Leak and Choke Slugging project: Start-up slug (with and w/o compositional tracking) Hydrodynamic slugging (with and w/o compositional tracking)

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Sample case: 2nd-order scheme The case Second-order-MEGsteps.opi illustrates the improved accuracy that can be achieved by applying a 2nd-order scheme when solving the mass equations. The pipeline is 100 m long with a 50 m gain in elevation. Initially, the first 100 m of the pipe is filled with oil whereas the rest of the pipe is filled with water. Within the water, there are three regions with various amounts of MEG, see Figure 1. As the simulation starts, oil is injected at the inlet, pushing the water out of the pipeline. What should be noted are the differences in results when running the case using a 2ndorder scheme for the mass equations as compared to a 1st-order scheme. While numerical diffusion rapidly smears out the MEG using the 1st-order scheme, pronounced peaks are preserved throughout the simulation using the 2nd-order scheme, see Figure 2.

Figure 1 Initial MEG fractions.

Figure 2 MEG fractions 85 s into the simulation. The black curve is using a 1st-order scheme for the mass equations whereas the red curve illustrates the use of a 2nd-order scheme.

Case Comments: CaseDefinition: OPTIONS: The discretization scheme applied when solving the mass equations is determined by the key MASSEQSCHEME. 709 / 769

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FlowComponent: FLOWPATH — Boundary&InitialConditions — INITIALCONDITIONS: The first 100 m of the pipe is filled with oil whereas the rest of the pipe contains only water. Within the water, three regions containing different amounts of MEG are set up. FLOWPATH — Boundary&InitialConditions — SOURCE: The mass source is ramped up to a steady mass flow of 53.34 kg/s over the first 8.5 seconds of the simulation. The source temperature is 30°C. FLOWPATH — Piping: The branch is a single pipe, 1 km long with an elevation of 50 m. FLOWPATH — Output — PROFILEDATA: Variables of interest are hold-ups and inhibitor fractions. NODE: The inlet node is closed. The outlet boundary condition is set to a constant pressure of 4.5 MPa and a temperature of 30°C. Output: OUTPUT: OLGA variables are printed to the output file every 100 seconds. TREND: Trend variables are plotted every 0.1 seconds. PROFILE: Profile variables are plotted every 5 seconds.

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Sample case: Advanced well The case AdvancedWell.opi demonstrates some of the features in the advanced well functionality. A 3500 m vertical well is producing from a gas reservoir through a 5.5" ID tubing. The formation has a permeability of 500 mD and the Forchheimer inflow correlation is applied. This is a typical inflow correlation for a gas reservoir where the non-linear behavior between the produced gas rate and flowing bottom hole pressure is important. A wellhead choke is placed at the last section boundary of the branch.

Case Comments: CaseDefinition: OPTIONS: The steady state pre-processor is deactivated. The heat transfer number outside the wall have to be given. INTEGRATION: The case is simulated form 0 to 5 hours with a maximum time step of 2 seconds. The minimum time step is set to 0.001 seconds. FlowComponent: FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: A linear ambient temperature profile is used for the well. An overall heat transfer coefficient of 10 W/m2K has been used. FLOWPATH — Boundary&InitialConditions — INITIALCONDITIONS: The pipeline is initialized with gas at 30°C. The mass flow is set to zero throughout the pipeline. The pressure is set to 400 bar at the inlet, 300 bar at the outlet, and is interpolated vertically in between. FLOWPATH — Boundary&InitialConditions — WELL: A gas well with reservoir pressure of 412 bara and reservoir temperature of 43.5°C is placed at the branch inlet. The well production is calculated using the Forchheimer model and the linear model is used for injection. The reservoir permeability is 500 mD and the net pay from the zone is 14 m. The mechanical skin is 3, and a turbulent non-Darcy skin of 0.01 1/mmscf/d is used. FLOWPATH — ProcessEquipment — VALVE: A wellhead choke with 10% opening is placed at the outlet. NODE: The inlet node is closed and the inlet flow is specified with a productivity correlation based on physical reservoir properties (see WELL). The outlet node is of type pressure. The boundary conditions are constant through the simulation. FLOWPATH — Piping: The 3500 m long vertical well is described by 9 pipes. Output: OUTPUT: OLGA variables are printed to the output file every 10000 seconds. TREND: Trend variables are plotted every 100 seconds. PROFILE: Profile variables are plotted every 6000 seconds. 711 / 769

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Sample case: Blackoil The case Blackoil.opi demonstrates the blackoil module. The case comprises of a single branch with one ascending pipe. The pipeline is 400 meters long and has an elevation of 10 meters. The pipeline is divided into 10 sections.

Case Comments: CaseDefinition: OPTIONS: To activate the blackoil module, the key COMPOSITIONAL has to be set to BLACKOIL. INTEGRATION: The simulation end time is set to 100 seconds. The maximum and minimum time steps are 5 s and 0.01 s, respectively. Compositional: BLACKOILCOMPONENT: One gas component and one oil component is defined. The oil component is defined by a specific gravity of 0.8 whereas the gas component is defined by a specific gravity of 0.7. The gas component is given a CO2 mole fraction of 0.1, and an N2 mole fraction of 0.02. BLACKOILFEED: The BLACKOILFEED combines the two BLACKOILCOMPONENTs. The two components are combined to give a GOR of 200 Sm3/Sm3 at standard conditions. FlowComponent: FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: A constant ambient temperature of 6°C and an ambient heat transfer coefficient of 6.5 W/m2K is used. FLOWPATH — Boundary&InitialConditions — SOURCE: The source has a constant flow rate throughout the simulation. The name of the fluid (feed) is given by the key FEEDNAME. The flow rate is set to 1000 STB/d (in the FEEDSTDFLOW keyword). FLOWPATH — Output — TRENDDATA: Pressure, volumetric oil holdup and volumetric water holdup are plotted at the first and last section of the pipe. The overall content of oil, and overall content of water are plotted. The content is given as cubic meters for the entire pipeline. FLOWPATH — Output — OUTPUTDATA: Pressure, temperature, volumetric holdup, gas mass flow and overall mass flow are written to the output file. NODE: There is a mass source at the inlet, the inlet node is therefore closed. There is a constant pressure condition at the outlet. The outlet node uses the BLACKOILFEED (set in the FEEDNAME keyword). Output: OUTPUT: OLGA variables are printed to the output file every hour. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes. 712 / 769

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PROFILEDATA: Pressure, temperature, liquid holdup, overall mass flow and gas mass flow are plotted.

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Sample case: Centrifugal Pump The case Pump-Centrifugal.opi demonstrates how how OLGA can be used to model a centrifugal multiphase pump with recycle function and bypass lines. The system consists of a 100 m long horizontal wellhead pipe followed by a 300 m m long pipe containing a pump inlet valve, a centrifugal pump, a pump outlet valve, and a check valve at the outlet of that pipe. Following this is a 100 m long pipe leading up to a 200 m tall riser to the topside. A bypass pipeline is connected to the pump pipeline. This line has a bypass valve on the inlet and a check valve on the outlet. A sketch of the model is shown in Figure 1. Operation scenario: In the first hour, the system's inlet pressure is 8 bar higher than its outlet pressure. The production is to go through the bypass line and the total flow rate is about 45 kg/s. In the second hour, the inlet pressure is reduced to be the same as the outlet pressure so that no production is expected without a pump. Then, the pump line is opened, the bypass line closed, and the centrifugal pump starts to increase the pump speed in order to yield the flow rate 50 kg/s.

Figure 1 Sketch of the model.

Case Comments: CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through the pipe walls is used. The steady state pre-processor is turned off. FILES: The characteristic data of the pump is found in the file ol-pumpc-2.tab. Controller-models: PIDCONTROLLER: C-PUMP-C-SP: This controller is required by the pump module. In this sample case, the pump speed is controlled by the total mass flow rate (PUMPGT) through the pump. 714 / 769

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case, the pump speed is controlled by the total mass flow rate (PUMPGT) through the pump. PIDCONTROLLER: C-PUMP-C-RE: This controller is required by the pump module. In this case, the pump recycle flow is controlled by the pump inlet pressure. The pump inlet pressure is measured by Transmitter TRAN-B-PL-PT, and if the pump inlet pressure is lower than 38.12 bara, the recycle flow will be started. If no recycle flow is required, a manual controller with SETPOINT=0 can be used for the recycle controller or the recycle diameter, RECDIAMETER, can be set to zero. MANUALCONTROLLER: C-PUMP-C-BY: This controller is required by the pump module. However, the built-in bypass function of the pump module is obsolete since any bypass line can be modeled using an additional flow-path. In this sample case, the bypass controller is a manual controller with set-point 0, which means that the built-in bypass line is closed. MANUALCONTROLLER: C-PUMP-V-1: This controller is optional. The controller is used to control the built-in valve in the centrifugal pump module to stop the flow if the pump is deeded, e.g., if the pump is shut down and no back flow is allowed. In this sample case, this controller is defined as TYPE=MANUAL and SETPOINT=1, which means that the valve is fully opened. FlowComponent: FLOWPATH — Boundary&InitialConditions — INITIALCONDITIONS: Since the steady state preprocessor is not used, the initial conditions have to be given. FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: The ambient temperature is set to 15°C. The heat transfer coefficient on outer walls is set to 500 W/m2K. The minimum heat transfer coefficient on inner walls is set to 10 W/m2K. FLOWPATH — ProcessEquipment — PUMP: The centrifugal pump is defined by following parameters: DENSITYR=900 kg/m3; EFFIMECH=0.7; FLOWRATED=0.15 m3/s; HEADRATED=150 m; SPEEDR=1500 rpm; MAXSPEED=8000 rpm; RECDIAMETER=0.1 m (diameter of the built-in recycle pipe); BYDIAMETER=0 (bypass diameter, zero means no bypass flow through the built-in bypass). FLOWPATH — Piping: The pipeline consists of a 500 m long pipe horizontal pipe with a 0.2 m diameter which leads up to a 200 m tall riser. At topside a 100 m pipe leads to the outlet. The bypass line, constituted by six sections, is 300 m long and has the same diameter, 0.2 m, as the rest of the pipe. FLOWPATH — Output — TRENDDATA: Pump variables are plotted. NODE: Both the inlet and outlet nodes are pressure nodes. The inlet pressure is 47 bara over the first hour and is then reduced to 39 bara. The inlet temperature is held constant at 30°C. The outlet pressure is held constant at 39 bara and the temperature is 20°C. Two internal nodes are used to connect the bypass around the pump. Output: OUTPUT: OLGA variables are printed to the output file every 10 hours. TREND: Trend variables are plotted every second. PROFILE: Profile variables are plotted every 30 minutes.

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Sample case: CO2 Tracking (Single component) Case: Single-CO2.opi Purpose: "Walk around" the critical point. Fluid: 100% CO2 The transient starts in the gas region, T=5°C and P=30 bar. After 60 seconds, the inlet temperature is increased and reaches 50°C after 120 seconds. A corresponding increase in outlet temperature follows. A temporary small increase in outlet flow rate occurs due to the lower density of gas at the increased temperature. The lower gas density leads to an increase in volumetric flow rate. After 10 minutes, the outlet pressure is increased to 80 bar, thereby moving into the dense phase region on the gas side. A temporary increase in outlet temperature occurs due to compression of the gas and a temporary reduction in outlet flow rate can also be seen. After 20 minutes, the inlet temperature is reduced to 5°C, thereby moving into the liquid side of the dense phase region. This leads to condensation of gas which slows down the reduction in outlet temperature (release of heat due to condensation). The outlet flow rate of gas shows an oscillatory behavior and finally goes to zero when all the vapor is either condensed or has left the pipe. After half an hour, the outlet pressure is reduced to 30 bar, thereby crossing the saturation line from the liquid side to the gas side. A temporary drop in outlet temperature down to about saturation temperature occurs due to the evaporation of water. There is also an overshoot in gas flow rate due to the volume increase.

Case Comments: CaseDefinition: OPTIONS: The single component module is activated by setting COMPOSITIONAL=SINGLE. TEMPERATURE=ADIABATIC (no heat exchange with walls) Compositional: SINGLEOPTIONS: CO2 is activated by setting COMPONENT=CO2. Time constants are set: TCONDENSATION=1.0, TBOILING=1.0. FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: Liquid source delivering 2 kg/s. Temperature and pressure varies with time. FLOWPATH — Piping: 100 m horizontal pipe, diameter=0.12 m, 20 sections NODE: A closed node is placed at the pipe inlet. The outlet is a pressure boundary.

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Sample case: Compositional tracking The case CompTrack.opi comprises one branch with ascending and descending pipes. Initially the pipeline is filled with live crude and the fluid is under-saturated throughout the pipeline. After 30 hours, the system is shut-in and cooled down due to a low ambient temperature. Then, gas pockets are generated at the highest points of the pipeline. After 50 hours, oil is injected at the inlet. This fluid is the same as the one the pipeline was filled with initially. The gas is dissolved in the undersaturated oil. After 51 hours all the gas has disappeared and the system returns to the original steady state.

Figure 1 Schematic view of the pipeline geometry.

Case Comments: CaseDefinition: OPTIONS: To activate compositional tracking, the key COMPOSITIONAL has to be set to ON. FILES: A feed file generated with PVTSim has be specified using the key FEEDFILE. The feed file contains information about the fluids and the components used in the simulation. INTEGRATION: The simulation end time is set to 70 hours. The maximum and minimum time steps are 20 s and 0.1 s, respectively. FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: The source produces the same fluid throughout the simulation, but the source flow rate and temperature changes. The name of the fluid (feed) is given by the key FEEDNAME. The flow rate is specified in FEEDMASSFLOW. After 30 hours, the production is shut-in and the pipeline is closed. After 50 hours the source is restarted. FLOWPATH — Output — PROFILEDATA: Standard variables are plotted. Mole fractions in the gas phase, liquid phase and overall are plotted. FLOWPATH — Output — TRENDDATA: Mass fractions in the gas and liquid phases are plotted at the inlet and outlet. The overall mole fraction is also plotted at these positions. NODE: The inlet node is closed since there is a mass source at the inlet producing at varying flow rate. At the outlet, a constant pressure condition is applied. The same fluid is used at both nodes (given by the key FEEDNAME). 717 / 769

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Output: OUTPUT: OLGA variables are printed to the output file every hour. TREND: Trend variables are plotted every three minutes. PROFILE: Profile variables are plotted every hour.

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Sample case: Corrosion The case Corrosion.opi is an example illustrating the use of the corrosion model. The main pipeline starts with a 3.3 km long horizontal pipe ending in a 90 m riser followed by a short horizontal pipe. The inner diameter of the pipe is 0.41 m. Heat transfer through pipe walls is calculated. The fluid composition is of a gas condensate type. The water cut is about 80%.

Case Comments: Library: WALL: The pipe walls consist of steel (two layers) covered by one layer of insulation. CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through pipe walls is used. INTEGRATION: The simulation runs for five hours using a minimum time step of 0.01 s and a maximum one of 10 s. The initial time step is set equal to the minimum one. FA-models: WATEROPTIONS: Water flash and water slip are turned on. FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: The inlet boundary condition is a constant mass source with mass flow of 34.181 kg/s and temperature of 60°C. The mass fraction of free water is set to 0.3. Since water flash is active, see WATEROPTIONS keyword, there is additional water in the vapor phase given by the water vapor mass fraction in the PVT table. By default, the equilibrium is used to determine the gas source at the inlet. FLOWPATH — FA-models — CORROSION: Both Model1 (NORSOK) and Model3 (de Waard 95) are activated on flow path B-INLET. The CO2 fraction, i.e., the ratio of CO2 partial pressure to total pressure in the gas, is set to 5%. The fraction of glycol in the glycol/water mixture is set to 50% and the inhibitor efficiency is set to 90%. The presence of glycol yields a reduction factor of the corrosion rate. The effect of a second inhibitor is given directly though the key INHIBITOREFFICIENCY. For the NORSOK model, only the largest of these two factors is multiplied with the corrosion rate while for the de Waard 95 model, both factors are multiplied with the corrosion rate. FLOWPATH — Piping: The pipeline is 3.3 km long. The total number of pipes, including topside, is 9. The pipes are divided into 58 sections. The pipe walls consist of steel (two layers) covered with a layer of insulation. FLOWPATH — Output — PROFILEDATA: Pressure, temperature, overall mass flow, gas velocity, and oil and water hold-up and velocities are profile plotted for all pipelines. NODE: The inlet node is closed. The outlet boundary condition is to a constant pressure of 24 bara and a temperature of 26°C. Output: 719 / 769

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OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 10 seconds. PROFILE: Profile variables are plotted every 50 seconds.

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Sample case: Displacement Pump The case Pump-Displacement.opi demonstrates how how OLGA can be used to model a displacement multiphase pump with recycle function and bypass lines. The system consists of a 100 m long horizontal wellhead pipe followed by a 300 m m long pipe containing a pump inlet valve, a displacement pump, a pump outlet valve, and a check valve at the outlet of that pipe. Following this is a 100 m long pipe leading up to a 200 m tall riser to the topside. A bypass pipeline is connected to the pump pipeline. This line has a bypass valve on the inlet and a check valve on the outlet. A sketch of the model is shown in Figure 1. Operation scenario: In the first hour, the system's inlet pressure is 4 bar higher than its outlet pressure. The production is to go through the bypass line and the total flow rate is about 22.2 kg/s. In the second hour, the inlet pressure is reduced to be the same as the outlet pressure so that no production is expected without a pump. Then, the pump line is opened, the bypass line closed, and the displacement pump starts to increase the pump speed in order to yield the flow rate 30 kg/s.

Figure 1 Sketch of the model.

Case Comments: CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through the pipe walls is used. The steady state pre-processor is turned off. FILES: The characteristic data of the pump is found in the file ol-pump1-2.tab. Controller-models: PIDCONTROLLER: C-PUMP-D-SP: This controller is required by the pump module. In this sample case, the pump speed is controlled by the total mass flow rate (PUMPGT) through the pump. 721 / 769

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case, the pump speed is controlled by the total mass flow rate (PUMPGT) through the pump. PIDCONTROLLER: C-PUMP-D-RE: This controller is required by the pump module. In this case, the pump recycle flow is controlled by the pump inlet pressure. The pump inlet pressure is measured by Transmitter TRAN-PUMP-IN-PT, and if the pump inlet pressure is lower than 38.2 bara, the recycle flow will be started. If no recycle flow is required, a manual controller with SETPOINT=0 can be used for the recycle controller or the recycle diameter, RECDIAMETER, can be set to zero. MANUALCONTROLLER: C-PUMP-C-BY: This controller is required by the pump module. However, the built-in bypass function of the pump module is obsolete since any bypass line can be modeled using an additional flow-path. In this sample case, the bypass controller is a manual controller with set-point 0, which means that the built-in bypass line is closed. FlowComponent: FLOWPATH — Boundary&InitialConditions — INITIALCONDITIONS: Since the steady state preprocessor is not used, the initial conditions have to be given. FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: The ambient temperature is set to 15°C. The heat transfer coefficient on outer walls is set to 500 W/m2K. The minimum heat transfer coefficient on inner walls is set to 10 W/m2K. FLOWPATH — ProcessEquipment — PUMP: The centrifugal pump is defined by following parameters: SPECAPACITY=0.01 m3/R; PREFSPEED=3000 rpm; MAXSPEED=8000 rpm; RECDIAMETER=0.1 m (diameter of the built-in recycle pipe); BYDIAMETER=0 (bypass diameter, zero means no bypass flow through the built-in bypass). FLOWPATH — Piping: The pipeline consists of a 500 m long pipe horizontal pipe with a 0.2 m diameter which leads up to a 200 m tall riser. At topside a 100 m pipe leads to the outlet. The bypass line, constituted by six sections, is 300 m long and has the same diameter, 0.2 m, as the rest of the pipe. FLOWPATH — Output — TRENDDATA: Pump variables are plotted. NODE: Both the inlet and outlet nodes are pressure nodes. The inlet pressure is 43 bara over the first hour and is then reduced to 39 bara. The inlet temperature is held constant at 30°C. The outlet pressure is held constant at 39 bara and the temperature is 20°C. Two internal nodes are used to connect the bypass around the pump. Output: OUTPUT: OLGA variables are printed to the output file every 10 hours. TREND: Trend variables are plotted every second. PROFILE: Profile variables are plotted every 30 minutes.

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Sample case: Drilling Fluid The case DrillingFluid.opi demonstrates how how OLGA models drilling fluid in a well clean-up case. The system consists of a well tubing pipeline with 1875 m TVD and 2725 m MD and a 150 m long wellhead pipe. A source injects water based drilling mud from the well bottom hole to fill-in the well tubing. The well production will push the drilling mud out of the tubing and start normal production. A sketch of the model is shown in Figure 1. Operation scenario: Water based drilling mud is injected from the well bottom hole during the first hour in order to fill-in the well tubing. The mud is then reduced to zero over half an hour. The well production will push the drilling mud out of the tubing and start normal production. Trend plots of the total mass flow rate at topside (GT), the total well flow rate (GTWELL), and mud source mass flow rate (GTSOUR) show the flow rate changing. Profile plots of the mass fraction of mud (MFAMUD), liquid density (ROL) and hold-up show changes in the amount of mud and liquid in the pipeline.

Figure 1 Sketch of the model.

Case Comments: Library: DRILLINGFLUID: The drilling fluid, DRFL_LIQ_1, is defined with TYPE=WATER, MINDENSITY=600 kg/m3, MAXDENSITY=2400 kg/m3, MINVISCOSITY=10-4 Ns/m2 and MAXVISCOSITY=1 Ns/m2 CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through the pipe walls is used. The steady state pre-processor is used to generate initial conditions. 723 / 769

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steady state pre-processor is used to generate initial conditions. FlowComponent: FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: The ambient temperature is vertically interpolated from 80°C at the bottom of the borehole to 20°C at the wellhead. The heat transfer coefficient on outer walls is set to 500 W/m2K. The minimum heat transfer coefficient on inner walls is set to 10 W/m2K. FLOWPATH — Boundary&InitialConditions — SOURCE: The mass source injects water based mud at the well bottom hole at a rate of 60 kg/s over the first hours. Over the next half an hour, the rate is reduced to zero. FLOWPATH — Boundary&InitialConditions — WELL: The reservoir pressure is 200 bara and reservoir temperature 80°C. Production and injection type is LINEAR. AINJ=APROD=0, BINJ=108 kg/s/Pa and BPROD=3.5·10-6 kg/s/Pa. FLOWPATH — Output — TRENDDATA: The mass fraction of mud is plotted. NODE: The outlet pressure held constant at 30 bara and the temperature is 4°C. Output: OUTPUT: OLGA variables are printed to the output file every 10 hours. TREND: Trend variables are plotted every 10^#160;seconds. PROFILE: Profile variables are plotted every 6 minutes.

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Sample case: Fluid bundle The case FluidBundle-converted.opi demonstrates how OLGA can be used to simulate how a bundled pipeline initially filled with gas is heated up before production is started. N.B., when importing similar cases from OLGA 5, a certain amount of manual labor is required. Please refer to the conversion documentation for a detailed description. The pipeline consists of a 5480 m long pipe along the seabed followed by a 162 m vertical riser and a 100 m horizontal topside pipe. The pipe has a hydraulic diameter of 30.48 cm. The part of the pipeline which is on the seabed is contained within a bundle where the carrier line contains heated water injected on the platform end. The carrier line water returns to the platform through the return line before it is heated up again and reinjected into the carrier line. The bundle also contains a methanol line. A sketch of the cross-section of the bundle is shown in Figure 1.

Figure 1 Cross-section of the bundle.

Case Comments: Library: MATERIAL: Carbon steel is the only material used in the pipe walls. WALL: The flow line pipe wall is 2.54 cm thick and has been divided into 4 layers. CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through the pipe wall has been used as this is required by the bundle module. The steady state initialization has been turned off. FlowComponent: FLOWPATH — Boundary&InitialConditions — INITIALCONDITIONS: The flow line is initially filled with gas and the pressure is set equal to the outlet pressure. The initial temperature is 4°C both in the pipeline and bundle lines. FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: The ambient conditions are constant along the whole system. For the part of the pipeline contained in the bundle, the ambient conditions are exterior to the flow line. FLOWPATH — Boundary&InitialConditions — SOURCE: During the initial heating up of the system, the source is turned off. Ramping up to a steady production flow rate is commenced after 10 hours. 725 / 769

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FLOWPATH — Piping: The pipeline along the seabed (5480 m) is described by seven pipes whereas the riser and topside are single pipes. FLOWPATH — Output — OUTPUTDATA: In addition to standard OLGA variables, TBUN is printed to the output file. FLOWPATH — Output — TRENDDATA: In addition to standard OLGA variables, TBUN is trended for the bundle lines at selected positions. FLOWPATH — Output — PROFILEDATA: In addition to standard OLGA variables, TBUN is profiled for all bundle lines. NODE: The flow line has a closed inlet node whereas the methanol line has a mass flow node on the inlet. Both these lines have pressure boundaries specified at the outlet. Inlet temperatures are specified for the bundle lines. An internal node is used for the crossover from the carrier line to the return line. The water is going in a loop consisting of the carrier and return lines where constant pressure and temperature is set on the platform side. ThermalComponent: FLUIDBUNDLE: The bundle consists of four pipelines (BundleComponents). One is defined as a FLOWPATH and the other three as LINEs. The pipe defined as FLOWPATH defines that the bundle starts at the beginning of the second pipe and ends at the riser base. The data of both fluid and line pipe walls are given so that OLGA calculates a u-value for each of the lines. The flow in the carrier line is counter current to the flow in the other lines and in the flowpath. Output: OUTPUT: OLGA variables are printed to the output file, every 10th hour. TREND: Trend variables are plotted every minute. PROFILE: Profile variables are plotted every hour.

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Sample case: H2O Tracking (Single component) Case: Single-H2O.opi Purpose: "Walk around" the critical point. Fluid: 100% H2O The transient starts in the gas region, T=360°C and P=150 bar. After 60 seconds the inlet temperature is increased and reaches 450°C after 120 seconds. A corresponding increase in outlet temperature follows. A temporary small increase in outlet flow rate occurs due to the lower density of gas at the increased temperature. After 10 minutes, the outlet pressure is increased to 227 bar, thereby moving into the dense phase region on the gas side. A temporary increase in outlet temperature occurs due to compression of the gas and a minor reduction in outlet flow rate can also be seen. After 20 minutes, the inlet temperature is reduced to 360°C, thereby moving into the liquid side of the dense phase region. This leads to condensation of gas which slows down the reduction in outlet temperature. The outlet flow rate of gas shows an oscillatory behavior and finally goes to zero when all the vapor is either condensed or has left the pipe. During the oscillations in outlet flow of vapor negative values can be seen, which is due to the oscillations being of numerical nature. The conditions are quite close to the critical point where the behavior of the fluid properties is highly nonlinear. After half an hour, the outlet pressure is reduced to 150 bar, thereby crossing the saturation line from the liquid side to the gas side. A temporary drop in outlet temperature down to about saturation temperature occurs due to the evaporation of water. There is also an overshoot in gas flow rate due to the volume increase.

Case Comments: CaseDefinition: OPTIONS: The single component module is activated by setting COMPOSITIONAL=SINGLE. TEMPERATURE=ADIABATIC (no heat exchange with walls) Compositional: SINGLEOPTIONS: H2O is activated by setting COMPONENT=H20. Time constants are set: TCONDENSATION=1.0, TBOILING=1.0, TVAPORIZATION=1.0 FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: Water source delivering 2 kg/s. Temperature and pressure varies with time. FLOWPATH — Piping: 100 m horizontal pipe, diameter=0.12 m, 20 sections NODE: A closed node is placed at the pipe inlet. The outlet is a pressure boundary.

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Sample case: H2O Tracking (Steam/Water–HC) Case: SteamWater-HC.opi Purpose: "Walk around" the critical point. Fluid: 100% H2O The transient starts in the gas region, T=360°C and P=150 bar. After 60 seconds the inlet temperature is increased and reaches 450°C after 120 seconds. A corresponding increase in outlet temperature follows. A temporary small increase in outlet flow rate occurs due to the lower density of gas at the increased temperature. After 10 minutes, the outlet pressure is increased to 227 bar, thereby moving into the dense phase region on the gas side. A temporary increase in outlet temperature occurs due to compression of the gas and a minor reduction in outlet flow rate can also be seen. After 20 minutes, the inlet temperature is reduced to 360°C, thereby moving into the liquid side of the dense phase region. This leads to condensation of gas which slows down the reduction in outlet temperature. The outlet flow rate of gas shows an oscillatory behavior and finally goes to zero when all the vapor is either condensed or has left the pipe. During the oscillations in outlet flow of vapor negative values can be seen, which is due to the oscillations being of numerical nature. The conditions are quite close to the critical point where the behavior of the fluid properties is highly nonlinear. After half an hour, the outlet pressure is reduced to 150 bar, thereby crossing the saturation line from the liquid side to the gas side. A temporary drop in outlet temperature down to about saturation temperature occurs due to the evaporation of water. There is also an overshoot in gas flow rate due to the volume increase.

Case Comments: CaseDefinition: OPTIONS: The steam\water–HC module is activated by setting COMPOSITIONAL=STEAMWATER-HC. TEMPERATURE=ADIABATIC (no heat exchange with walls) Compositional: COMPOPTIONS: Time constants are set: TCONDENSATION=1.0, TBOILING=1.0, TVAPORIZATION=1.0 FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: Liquid source delivering 2 kg/s. Temperature and pressure varies with time. FLOWPATH — Piping: 100 m horizontal pipe, diameter=0.12 m, 20 sections NODE: A closed node is placed at the pipe inlet. The outlet is a pressure boundary.

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Sample case: Hydrate Kinetics The case HydrateKinetics.opi demonstrates how the hydrate kinetics model can be used in an OLGA simulation. The hydrate kinetics model enables approximate predictions of where hydrate plugs might form in oil and gas pipelines. The system consists of a well tubing pipeline with a 1875 m true vertical depth (TVD) and a 2725 m measured depth (MD), a 150 m long wellhead pipe, a 3150 m pipeline leading up to a 391.2 m vertical riser and a 100 m long horizontal topside pipe. The total production is controlled by the wellhead choke. A sketch of the model is shown in Figure 1. Operation scenario: The well is a gas well. The fluid temperature may be below the hydrate temperature in the flow line. In order to avoid hydrate plugs, regions where the conditions might cause hydrate plugs to form can be detected.

Figure 1 Sketch of the model.

Case Comments: Library: HYDRATECURVE: Definition of hydrate curve used by HYDRATECHECK. CaseDefinition: OPTIONS: Temperature calculations use heat transfer on the inside and outside of pipe walls as well as heat conduction, but no heat storage is accounted for. The initial conditions are generated by the steady state pre-processor.

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FlowComponent: FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: The inlet ambient temperature of the well is 50°C and outlet ambient temperature is 4°. The code will do a vertical interpolation on ambient temperature along the tubing. In the flow line and riser, the ambient temperature is 4°C. The heat transfer coefficient on outer wall is set to 500 W/m2K. The minimum heat transfer coefficient on inner wall is set to 10 W/m2K. FLOWPATH — Boundary&InitialConditions — WELL: The reservoir pressure is 200 bara and reservoir temperature 50°C. Production and injection type is LINEAR. AINJ=APROD=0, BINJ=107 kg/s/Pa and BPROD=2.5·10-6 kg/s/Pa. FLOWPATH — FA-models — HYDRATECHECK: Hydrate checking is activated in all flow-paths. FLOWPATH — FA-models — HYDRATEKINETICS: The hydrate kinetics model is applied for all flowpaths. FLOWPATH — Output — TRENDDATA: Hydrate variables are plotted. FLOWPATH — Output — PROFILEDATA: Hydrate variables are plotted. NODE: The outlet pressure held constant at 50 bara and the temperature is 20°C. Output: OUTPUT: OLGA variables are printed to the output file every 10 hours. TREND: Trend variables are plotted every 10 seconds. PROFILE: Profile variables are plotted every hour.

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Sample case: Hydrodynamic slugging The cases HydrSlug-pvt.opi and HydrSlug-comp.opi illustrate slug-tracking using hydrodynamic slug initiation with and without and with compositional tracking, respectively. A platform to platform transportation is simulated where the fluid enters into a short horizontal pipe before descending down a 173 m long riser. A 7.5 km pipeline through slight uphill terrain leads up to the second, 140 m high, riser and a short horizontal topside pipe. A sketch of the pipeline geometry is shown in Figure 1.

Figure 1 Schematic illustration of the pipeline geometry.

Case Comments: CaseDefinition: OPTIONS: The two cases run with COMPOSITIONAL=OFF/ON, respectively. Temperature exchange with the walls are not accounted for, adiabatic flow is assumed. FILES: The fluid is described by either a pvt-file or an equivalent feed-file depending on the type of simulation. FA-models: SLUGTRACKING: Hydrodynamic slug initiation is enabled (HYDRODYNAMIC=ON) is enabled through the entire simulation. FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: The source introduces fluid into the pipeline at a constant rate of 130200 kg/h. The fluid temperature is 72.2°C. FLOWPATH — FA-models — SLUGILLEGAL: The sections in the pipe TO-SEP are declared as illegal sections, i.e., no slugs can be initiated or propagate through these sections. FLOWPATH — ProcessEquipment — VALVE: A valve with constant valve opening is put in the middle of the top-side pipe at the outlet. FLOWPATH — Output — TRENDDATA: In addition to standard plotting variables such as liquid content, pressure, hold-ups, etc., various slug related properties are plotted. E.g., variables like HOLEXP show the instantaneous holdup at the position specified. NODE: The inlet node is closed. The outlet boundary condition is set to a constant pressure of 68.3 bara and a temperature of 20°C. Output: OUTPUT: OLGA variables are printed to the output file every hour. 731 / 769

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OUTPUT: OLGA variables are printed to the output file every hour. TREND: Trend variables are plotted every second. PROFILE: Profile variables are plotted every 10 minutes. TRENDDATA: In addition to standard plotting variables, the number of slugs in the pipeline (NSLUG) and the accumulated number of slugs initiated (SLUPRO) are plotted.

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Sample case: MEG Tracking The case Meg-Tracking.opi demonstrates the features of the inhibitor tracking module. A horizontal pipeline with a source at the inlet is used to show that the concentration of MEG can be changed during the simulation and how this can be tracked through the pipeline.

Case Comments: FA-models: WATEROPTIONS: Water flash and water slip are turned on. CaseDefinition: OPTIONS: To activate MEG tracking, the key COMPOSITIONAL has to be set to MEG. FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: A mass source with constant mass flow is placed at the inlet. The MEG concentration in the aqueous phase changes from 60% to 30% after 1.5 hours. FLOWPATH — Piping: The branch consists of 11 pipes. FLOWPATH — Output — TRENDDATA: The mole fractions of all three components in the gas and water phases are plotted. FLOWPATH — Output — PROFILEDATA: The mole fraction of MEG in the water phase is plotted. NODE: A closed node is placed at the pipe inlet. A constant pressure is applied at the outlet. Output: OUTPUT: OLGA variables are printed to the output file every 2 hours. TREND: Trend variables are plotted every 6 minutes. PROFILE: Profile variables are plotted every 15 minutes.

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Sample case: Network The case Network.opi is a network case. Five wells merge into two different wellheads. The fluid is transported through two pipelines, one from each wellhead, to a processing platform. Here, the flow merge into a common header and then flows through some horizontal piping before reaching the outlet. Two wells merge at the first wellhead and the other three wells at the second one. Two slightly different geometries are used for the wells. The boundary conditions vary between given pressure, given mass flow, and well productivity index. The two pipelines have identical geometries.

Figure 1 Schematic view of the network.

Case Comments: CaseDefinition: OPTION: Temperature option "ADIABATIC" has been chosen. No heat transfer through the pipe walls is assumed. INTEGRATION: The simulation end time is set to 3 hours. The maximum and minimum time steps are 10 seconds and 0.01 seconds, respectively. FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: Branches 1 and 5 use constant mass sources. N.B., for Branch 1, the mass flow is specified in terms of volumetric flow rate of liquid at standard conditions. FLOWPATH — Boundary&InitialConditions — WELL: The reservoir pressure and temperature are given together with a linear productivity index for gas and liquid flow at the midpoint of the first section in branch 3. FLOWPATH — ProcessEquipment — VALVE: The wellhead choke in Branch 3 is fully open during the entire simulation. FLOWPATH — Piping: The number of pipes and their coordinates are defined for each branch, x and z represent horizontal coordinates whereas y is the vertical axis. As a verification of the input, the user 734 / 769

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represent horizontal coordinates whereas y is the vertical axis. As a verification of the input, the user may note the length and inclination of each pipe section as printed to the output file at the end of the initialization. Toward the end of the flow lines, the section lengths are gradually reduced to the values in the riser. NODE: Branches 1, 3 and 5 have closed nodes at the inlets. Branches 2 and 6 have constant pressure nodes at the inlets. Branches 4 and 7 are connected to internal nodes and have no terminal nodes. Branch 8 has a constant pressure node at the outlet. Output: OUTPUT: OLGA variables are printed to the output file at the end of the simulation. TREND: Trend variables are plotted every 30 seconds. PROFILE: Profile variables are plotted every 15 minutes.

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Sample case: PID Controller The case PID-Controller.opi demonstrates pressure control at a riser base. The pipeline consists of 5 pipes. First a horizontal pipe and two weakly descending pipes before a vertical pipe and a short horizontal pipe. A valve is used to control the pressure at the riser base.

Case Comments: CaseDefinition: OPTIONS: Temperature option ADIABATIC has been chosen. The pipeline is simulated without heat transfer through the pipe walls. INTEGRATION: The simulation starts at t=0 s, and ends at time t=1.5 h. The time step starts at the minimum value of 0.01 s and is limited to a maximum value of 25 s. Controller: PIDCONTROLLER: A pressure control valve is used to control the pressure at the riser base. A PID controller is used to regulate the valve opening, which is 0.1 initially (see the BIAS key). The pressure setpoint is 75 bara. The measured value is taken from the transmitter. A range of 50 bara is set for the controller (NORMRANGE key). FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: The inlet boundary condition is a constant mass source with mass flow 10.0 kg/s and a temperature of 62°C. The mass fraction of free water is set to 0. By default, the equilibrium is used to determine the gas source at the inlet. FLOWPATH — FA-models — DTCONTROL: The CFL criterion is used to limit the simulation time step. A safety margin of 20% is added to the CFL criterion to get a stable simulation (CFLFACTOR = 0.8). FLOWPATH — ProcessEquipment — TRANSMITTER: A transmitter is positioned at the riser base. The transmitter is used to collect the pressure from the pipeline, whcih is transmitted to the controller. The section pressure is transmitted with unit bara. FLOWPATH — ProcessEquipment — VALVE: A valve is placed before the riser but downstream the transmitter. The valve has the same maximum cross section as the pipeline. The valve opening is regulated by the pressure controller. FLOWPATH — Output — TRENDDATA: The valve opening is plotted. FLOWPATH — Output — PROFILEDATA: Profiles of pressure, temperature, liquid holdup, liquid mass flow and gas mass flow are plotted. NODE: The inlet node is closed. The outlet boundary condition is a constant pressure of 55 bara. Output: OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every second. 736 / 769

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PROFILE: Profile variables are plotted every 6 minutes.

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Sample case: Pigging The following cases illustrate the following pigging scenarios: Pigging of a pipeline using standard OLGA without tracking the liquid slug in Pig-noSlug-pvt.opi front of the pig. Pig-TrackSlugPigging of a pipeline using standard OLGA tracking the liquid slug in front of the pvt.opi pig. Pig-noSlugPigging of a pipeline using compositional tracking without tracking the liquid slug comp.opi in front of the pig. Pig-TrackSlugPigging of a pipeline using compositional tracking, also tracking the liquid slug in comp.opi front of the pig. The pipeline has pressure nodes both on the inlet and outlet. At the inlet, the pressure is 117 bara and the temperature is 10°C. The temperature at the outlet is the same, but the pressure is 100 bara. The pig is launched 1500ɢm into the pipeline and it is trapped at 75 m into the topside pipe. The geometry is shown in Figure 1.

Figure 1 Illustration of the pipe geometry. The launch and trap positions are indicated.

Case Comments: CaseDefinition: OPTIONS: The two cases run with COMPOSITIONAL=OFF/ON, respectively. Temperature exchange with the walls are not accounted for, adiabatic flow is assumed. FILES: The fluid is described by either a pvt-file or an equivalent feed-file depending on the type of simulation. Controller-models: PIDCONTROLLER: A PID controller regulates the opening of the outlet valve based on the gas mass flow. FlowComponent: FLOWPATH — FA-models — PIG: A pig is launched after 300 s. Whether the liquid slug in front of the pig is tracked or not is determined by the key TRACKSLUG. FLOWPATH — ProcessEquipment — TRANSMITTER: A transmitter is located in the second last boundary on topside, providing the PID controller with its input signal. FLOWPATH — ProcessEquipment — VALVE: An outlet valve controlled by the PID controller is situated at the end of the topside pipe. FLOWPATH — Piping: The branch is split into three pipes. A 10 km long horizontal pipe leads up to a 500 m riser. At topside, there is a 100 m horizontal pipe, in which the trap position is located. 738 / 769

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FLOWPATH — Output — TRENDDATA: In cases where the slug in front of the pig is tracked, its length is plotted. NODE: Both the inlet and outlet nodes are pressure nodes. The inlet pressure is 117 bara and the outlet pressure is 100 bara. Both nodes have a temperature of 10°C. Output: OUTPUT: OLGA variables are printed to the output file every 2 hours. TREND: Trend variables are plotted every 3 seconds. PROFILE: Profile variables are plotted every 30 seconds. TRENDDATA: The velocity of the pig and its are plotted.

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Sample case: Process Equipment The case Process-Equipment.opi is an example of a simulation with process equipment. The case shows examples of several types of process equipment, e.g., separator, valves, compressor, and heat exchanger. A total of 5 PID controllers are used to stabilize the process. Figure 1 shows the process flow sheet. One pipeline feeds the separator with a mixture of gas and liquid. This pipeline is 15100 meters long divided into 12 sections, and a diameter of 0.5 meters. The pipeline has a valve close to the outlet. The valve is used to control the overall flow into the separator. The separator has a gas and liquid outlet. The gas outlet is 400 m long, has a diameter of 1.0 m, and is divided into 7 sections. The gas line contain a compressor with recycle and anti-surge control. The compressor speed is used to control the separator pressure. Downstream the compressor, a heat exchanger is included to cool the gas. The heat exchanger is connected to a temperature controller. The liquid outlet is 100 m long and has a diameter of 0.12 m. The liquid line contains a valve that is used for level control of the separator. The pipe has only two sections. The simulation time is 20 hours. After 10 hours the separator feed is dropped from 70 to 50 kg/s.

Figure 1 Process flow sheet.

Case Comments: CaseDefinition: OPTION: Temperature option UGIVEN has been chosen. The pipelines are simulated with a constant outer heat transfer coefficient. The steady state pre-processor is deactivated. INTEGRATION: The simulation start at t=0 s and ends at time t=20 h. The time step starts at the minimum value of 0.01 s, and is limited to a maximum value of 10 s. Controller: 5 controllers are used to stabilize the process. All controllers are of type PID. One controller (FC) is used to manipulate the feed flow rate of the separator. One pressure controller (PC) is used to control the pressure in the separator. A level controller (LC) is used to stabilize the liquid level of the separator. An

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pressure in the separator. A level controller (LC) is used to stabilize the liquid level of the separator. An anti-surge controller (ASC) is used to stabilize the operation of the compressor. The ASC is an asymmetric PID controller, i.e., it has two amplification factors. A temperature controller is used to control the temperature at the outlet of the gas pipeline. FlowComponent: FLOWPATH — ProcessEquipment — COMPRESSOR: The compressor is used to lift the gas from the separator. At steady state, the compressor lift from approximately 71 to 110 bara. A recycle valve with diameter 0.25 m is controlled by the ASC controller. FLOWPATH — ProcessEquipment — HEATEXCHANGER: A controlled heat exchanger is used to manipulate the pressure out of the gas pipeline. The heat exchanger is given a capacity of -3 MW. FLOWPATH — ProcessEquipment — TRANSMITTER: Transmitters are used to transmit the temperature and overall flow from the pipeline to the controllers. FLOWPATH — ProcessEquipment — VALVE: One valve is placed before the riser, but downstream the transmitter. The valve has the same maximum cross section as the pipeline. A pressure controller is connected to the valve to manipulate the valve opening. FLOWPATH — Output — TRENDDATA: Gas volume flow at the compressor boundary and the compressor surge flow setpoint for the ASC controller (QGSURGE) are trended. NODE: The case has three nodes, all of type pressure. The inlet boundary condition is a constant pressure of 108 bara and temperature 40°C. The mass fraction of free water is set to 0 and the gas faction to 0.7. The outlet boundary conditions for the gas and liquid outlets are constant pressures of 110 bara and 65 bara, respectively. ProcessEquipment: SEPARATOR — Output — TRENDDATA: SEPARATOR: The separator is horizontal with length 15 m and diameter 2 m. It separates gas and liquid. Output: Pressure, temperature, and liquid level are trended. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 20 seconds. PROFILE: Profile variables are plotted every 30 minutes.

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Sample case: Pump Battery The case Pump-Battery.opi demonstrates how how OLGA can be used to model a pump battery. The system consists of a 2 km long well tubing followed by a 150 m long wellhead pipe. A pump battery is installed downstream of the well bottom hole in order to increase the production. The pump battery speed is controlled by the flow rate at the wellhead. A sketch of the model is shown in Figure 1. Operation scenario: Due to the reservoir conditions, this well can only produce a flow of 6 kg/s. After the pump battery is installed near the well bottom hole, the production can be increased to 10 kg/s or higher.

Figure 1 Sketch of the model.

Case Comments: CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through the pipe walls is used. The steady state pre-processor is turned off. Controller-models: PIDCONTROLLER: C-PUMP-SP: This controller is required by the pump module. In this sample case, the pump speed is controlled by the total mass flow rate at the wellhead as measured by Transmitter TRAN-WH-TT. FlowComponent: FLOWPATH — Boundary&InitialConditions — INITIALCONDITIONS: Since the steady state preprocessor is not used, the initial conditions have to be given. 742 / 769

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FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: The ambient temperature is vertically interpolated from 80°C at the bottom of the borehole to 20°C at the wellhead. The heat transfer coefficient on outer walls is set to 500 W/m2K. The minimum heat transfer coefficient on inner walls is set to 10 W/m2K. FLOWPATH — Boundary&InitialConditions — WELL: The reservoir pressure is 200 bara and reservoir temperature 80°C. Production and injection type is LINEAR. AINJ=APROD=0, BINJ=107 kg/s/Pa and BPROD=10-6 kg/s/Pa. FLOWPATH — ProcessEquipment — PUMP: The pump battery is defined by following parameters: MAXCAPACITY=0.06 m3/s; MINCAPACITY=0 m3/s; MAXPRESSURE=230 bara; MAXSPEED=8000 rpm; MINSPEED=0 rpm. FLOWPATH — Output — TRENDDATA: Pump variables are plotted. NODE: The outlet pressure held constant at 60 bara and the temperature is 20°C. Output: OUTPUT: OLGA variables are printed to the output file every 10 hours. TREND: Trend variables are plotted every second. PROFILE: Profile variables are plotted every 30 minutes.

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Sample case: Separator The case Separator-converted.opi illustrates the use of a separator. N.B., when importing similar cases from OLGA 5, a certain amount of manual labor is required. Please refer to the conversion documentation for a detailed description. A 4100 m long pipe leads up to a 300 tall riser. On topside a 120 m pipe leads into a separator. The separator is 4 m long and has a diameter of 2.5 m. The separator has three outlets, a gas outlet, an oil outlet, and an emergency drain. On the separator outlets, valves controlled by controllers are applied. The pressure is 50 bara at the gas outlet and 20 bara; at the oil outlet and emergency drain outlet.

Case Comments: CaseDefinition: OPTIONS: Full temperature calculations are enabled. FlowComponent: FLOWPATH — Boundary&InitialConditions — INITIALCONDITIONS: The first 100 m of the pipe is filled with oil whereas the rest of the pipe contains only water. Within the water, three regions containing different amounts of MEG are set up. FLOWPATH — Boundary&InitialConditions — SOURCE: The mass source is ramped up to a steady mass flow of 53.34 kg/s over the first 8.5 seconds of the simulation. The source temperature is 30°C. FLOWPATH — Piping: The branch is a single pipe, 1 km long with an elevation of 50 m. FLOWPATH — Output — PROFILEDATA: Variables of interest are hold-ups and inhibitor fractions. NODE: The inlet node is closed. The outlet boundary condition is set to a constant pressure of 4.5 MPa and a temperature of 30°C. Output: OUTPUT: OLGA variables are printed to the output file every 100 seconds. TREND: Trend variables are plotted every 0.1 seconds. PROFILE: Profile variables are plotted every 5 seconds.

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Sample case: Simplified Pump The case Pump-Simplified.opi demonstrates how to model a simplified pump in OLGA. The system consists of a 500 m long horizontal pipe followed by a 250 m tall vertical riser, and a 100 m long horizontal topside pipe. The inlet pressure is only 5 bara and the outlet pressure is 50 bara. A pump is installed in order to deliver the water to a higher pressure tower. No speed controller is required for a simplified pump. A valve and check vale are placed at the topside pipe. A sketch of the model is shown in Figure 1.

Figure 1 Sketch of the model.

Case Comments: CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through the pipe walls is used. The initial conditions are determined by the steady state pre-processor. FlowComponent: FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: The ambient temperature is 20°C. The heat transfer coefficient on outer wall is set to 500 W/m2K. The minimum heat transfer coefficient on inner wall is set to 10 W/m2K. FLOWPATH — ProcessEquipment — PUMP: The simplified pump is defined with following parameters: DENSITYR=1000 kg/m3; FLOWRATED=600 m3/h; SPEEDR=2000 rpm; DPRATED=70 bara. It is assumed that the pump pressure only dependeds on the pump flow rate. FLOWPATH — Piping: Three pipes are defined for the geometry. The first pipe is a 500 m long horizontal pipe and the pump is placed at the second section boundary. Downstream of the horizontal pipeline is a 250 m high vertical riser. At the top of riser is a 100 m long horizontal topside pipe. Pipe 745 / 769

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pipeline is a 250 m high vertical riser. At the top of riser is a 100 m long horizontal topside pipe. Pipe diameter is 12" and roughness 0.001 m FLOWPATH — Output — TRENDDATA: Mass flow rates and pump variables are plotted. NODE: Both the inlet and outlet nodes are pressure nodes. The inlet pressure is 5 bara and the outlet pressure is 50 bara. Both nodes have a temperature of 20°C. Output: OUTPUT: OLGA variables are printed to the output file every 10 hours. TREND: Trend variables are plotted every second. PROFILE: Profile variables are plotted every 30 minutes.

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Sample case: Solid bundle The case SolidBundle-converted.opi demonstrates how OLGA can be used to simulate the transient and spatial distribution of temperatures in the solid interior of a complex bundle by means of finite element calculations. N.B., when importing similar cases from OLGA 5, a certain amount of manual labor is required. Please refer to the conversion documentation for a detailed description. The branches 1 and 2 are identical with a 12.0 cm inner diameter. They consist of a 4300 m long pipeline on the seabed, a 300 m vertical riser, and a 100 m horizontal topside pipe. They merge into branch 3, a 100 m horizontal topside pipe The riser of branch 1 is contained within the inner fluid bundle where the carrier line contains heated water. The water is heated at the platform end, sent down into the carrier line, and back up to the platform through the return line. This fluid bundle is contained within a solid bundle together with branch 2 and a methanol line. A sketch of the cross-section of the bundle is shown in Figure 1.

Figure 1 Cross-section of the bundle. The outer border, i.e., the border of the solid bundle, is given by the shape specified under Library. The fluid bundle contained within the solid bundle is marked in gray shading.

Case Comments: Library: MATERIAL: Carbon steel (MATER-1) and insulation (MATER-2) are the materials used for the pipe walls. HEATING and METHANOLFLUID are fluids used by the bundle module. SHAPE: The shape defining the solid bundle, in this case a circle with radius 80 cm made of insulation. WALL: Five different walls are used in the flowpaths and lines specified. CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through the pipe wall has been used as this is required by both the bundle and FEMTherm modules. The steady state initialization is turned on. FlowComponent: 747 / 769

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FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: The ambient conditions are defined for all branches. The ambient heat transfer coefficient for the solid bundle is assumed constant along the length of it. Its value is taken from the first component in the solid bundle definition, more specifically from its first section entering into the solid bundle. The ambient temperature, on the other hand, may vary along the length of the solid bundle and the values are taken from its first constituent branch. FLOWPATH — Boundary&InitialConditions — SOURCE: The sources at the inlet of each seabed pipeline is kept at a constant low rate for the first three hours, before being ramped up to a higher rate during 10 minutes. FLOWPATH — Piping: The pipeline along the seabed (4300 m) is described using three pipes whereas the riser and topside as single pipes. The topside branch consists of a single pipe. FLOWPATH — ProcessEquipment; VALVE: One valve is installed at the outlet of each of the parallel pipelines just upstream of the internal node. They are both fully open throughout the simulation. NODE: The two inlet nodes for the seabed branches are closed. These two branches lead up to an internal node where they merge into the topside branch which has a pressure boundary at the outlet. Inlet temperatures are specified for the bundle lines. An internal node is used for the crossover from the carrier line to the return line. The water is going in a loop consisting of the carrier and return lines where constant pressure and temperature is set on the platform side. ThermalComponent: SOLIDBUNDLE: The shape of the solid bundle containing all the pipes is defined through the Library keyword SHAPE. The shape is one out of four BundleComponents in this case. The other components are a FLOWPATH, a LINE, and a FLUIDBUNDLE. The meshfineness (recommended value is between 128 and 640), calculation time step (DELTAT), and time step for saving thermal data (DTPLOT) define the FEMTherm calculations.

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Sample case: Source, Leak and Choke The case Src-Leak-Choke.opi is a simple demonstration of a the simulation using a choke, a controlled sources and a leak. A horizontal pipe is initially at high pressure and closed at both ends. The choke with a constant diameter is positioned at the middle of the pipe, the leak at the end and the source at the inlet. The outside pressure of the source is set constant and equal to the initial pipe pressure. The outside pressure of the leak is also constant, but very low. All three devices are given a constant flow area. The simulation starts with a rapid blow down of the pipe with critical flow in the leak. Inlet mass flow starts when the pipe pressure decreases and a steady state is obtained when the mass flows of the source and the leak are equal. The temperature in the pipe decreases during the blow down and increases slowly as warm fluid enters through the inlet.

Figure 1 Schematic illustration of the the simulated pipeline. The pipe is divided into four sections.

Case Comments: CaseDefinition: OPTION: The steady state pre-processor is not used since the initial state of the closed pipe is a fluid at rest. The temperature calculation is performed without heat transfer through the wall. Controller: MANUALCONTROLLER: The controllers for the source (C-502) and the leak (C503) are specified as manual ones. The controller signals determine the flow area and are specified using time series. The time that the devices need to adjust to a new set point (the actuator time) is 33.33 seconds. FlowComponent: FLOWPATH — Boundary&InitialConditions — INITIALCONDITIONS: The fluid is initially at rest with constant pressure, void fraction and temperature. FLOWPATH — Boundary&InitialConditions — SOURCE: The controller reference number for the source is C-502. The maximum flow area in the source equals the pipe area. The outside pressure is held constant at 168 bar and the temperature is held constant at 73°C. The negative value of the gas mass fraction indicates that the phase mass fractions are computed from the equilibrium gas mass fraction values in the fluid properties tables. FLOWPATH — ProcessEquipment — LEAK: The controller reference number for the leak is C-503. The maximum flow area in the leak equals the pipe area. The relative leakage area is increased from 0.03 to 0.1 after 35 seconds. Due to the actuator time, the leak will use 2.33 seconds before it reaches a relative opening area of 0.1. The outside pressure is held constant at 2 bar. FLOWPATH — ProcessEquipment — VALVE: The choke is positioned at boundary number 3. A time series for the flow area is given. The maximum flow area in the choke equals the pipe area. The flow area specified is 3% of the maximum. 749 / 769

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FLOWPATH — Piping: Only four sections are specified in the horizontal pipe. The pipe is 80 m long and parallel to the x-axis. NODE: The pipe is closed at both ends. Output: OUTPUT: OLGA variables are printed to the output file every 10 seconds.

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Sample case: Start-up slug The cases StartupSlug-pvt.opi and StartupSlug-comp.opi illustrate tracking of a start-up slug without and with compositional tracking, respectively. The pipeline is symmetric with two 200 meter long horizontal pipes leading up to a 50 meter long and 2 meter deep dip. The dip is filled with liquid and the pipe leading from the dip to the outlet is half filled. The pipe leading up to the dip is filled with gas and the inlet is a gas source. The geometry and initial condition is shown in Figure 1.

Figure 1 Illustration of the pipe geometry and initial condition.

Case Comments: CaseDefinition: OPTIONS: The two cases run with COMPOSITIONAL=OFF/ON, respectively. Temperature exchange with the walls are not accounted for, adiabatic flow is assumed. FILES: The fluid is described by either a pvt-file or an equivalent feed-file depending on the type of simulation. FA-models: SLUGTRACKING: Level slug initiation is enabled (LEVEL=ON). The initiation of slugs is limited to initiate a single start-up slug (MAXNOSLUGS=1) at the start of the simulation (STARTTIME=0 s and ENDTIME=0.1 s). FlowComponent: FLOWPATH — Boundary&InitialConditions — INITIALCONDITIONS: The pressure and temperature in the branch is set constant and equal to the conditions at the output node. The pipe leading up to the dip is filled with gas, the dip is filled with liquid, and the pipe leading from the dip to the outlet is half filled. FLOWPATH — Boundary&InitialConditions — SOURCE: The gas source is ramped up to a steady mass flow of 5.325 kg/s over the first 8.5 seconds of the simulation. The source temperature is 30°C. FLOWPATH — Piping: The branch is split into five pipes. A 200 m long horizontal pipe split into 20 sections lead up to the dip. The dip is constituted by two 25 meter long pipes split into 5 m sections and the lowest point 2.17 m below the horizontal pipes. Two horizontal pipes, each 100 m and split into 20 sections, lead from the dip to the outlet. FLOWPATH — Output — TRENDDATA: Various properties for the slug are plotted. Furthermore, the instantaneous values of the droplet volume fraction and droplet velocity are plotted at boundaries NODE: The inlet node is closed. The outlet boundary condition is set to a constant pressure of 4.5 MPa and a temperature of 30°C. Output: 751 / 769

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OUTPUT: OLGA variables are printed to the output file every minute. TREND: Trend variables are plotted every 0.5 seconds. PROFILE: Profile variables are plotted every 2.5 seconds. TRENDDATA: The number of slugs in the pipe is plotted. PROFILEDATA: Integrated additional pressure drops are plotted.

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Sample case: Tracer Tracking The case KHI-TracerTracking.opi demonstrates how OLGA can be used to model an inhibitor tracer tracking case. The system consists of a well tubing pipeline with a 1875 m true vertical depth (TVD) and a 2725 m measured depth (MD), a 150 m long wellhead pipe, a 3150 m pipeline leading up to a 391.2 m vertical riser and a 100 m long horizontal topside pipe. The KHI inhibitor is injected into the first section of the wellhead pipe. A wellhead choke and a check vale are placed at the wellhead pipeline downstream of the KHI injection position. The total production is controlled by the wellhead choke. A sketch of the model is shown in Figure 1. Operation scenario: The well is a gas well. The fluid temperature may be below the hydrate temperature in the flow line. Therefore, a KHI tracer is injected at the wellhead to prevent hydrate formation. The KHI flow rate and mass fraction in the water phase can be checked for different KHI age groups along the pipeline.

Figure 1 Sketch of the model.

Case Comments: Library: HYDRATECURVE: Definition of hydrate curve used by HYDRATECHECK. TRACERFEED: Definition of the tracer feed TR-KHI. CaseDefinition: OPTIONS: Temperature calculations use heat transfer on the inside and outside of pipe walls as well as heat conduction, but no heat storage is accounted for. The steady state pre-processor is turned off. 753 / 769

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FlowComponent: FLOWPATH — Boundary&InitialConditions — INITIALCONDITIONS: Since the steady state preprocessor is not used, the initial conditions have to be given. FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: The inlet ambient temperature of the well is 50°C and outlet ambient temperature is 4°. The code will do a vertical interpolation on ambient temperature along the tubing. In the flow line and riser, the ambient temperature is 4°C. The heat transfer coefficient on outer wall is set to 500 W/m2K. The minimum heat transfer coefficient on inner wall is set to 10 W/m2K. FLOWPATH — Boundary&InitialConditions — WELL: The reservoir pressure is 200 bara and reservoir temperature 50°C. Production and injection type is LINEAR. AINJ=APROD=0, BINJ=107 kg/s/Pa and BPROD=2.5·10-6 kg/s/Pa. FLOWPATH — Boundary&InitialConditions — SOURCE: The tracer source injects tracer at a rate of 1 kg/s. FLOWPATH — FA-models — HYDRATECHECK: Hydrate checking is activated in all flow-paths. FLOWPATH — Output — TRENDDATA: Tracer variables are plotted. FLOWPATH — Output — PROFILEDATA: Tracer variables are plotted. NODE: The outlet pressure held constant at 30 bara and the temperature is 20°C. Output: OUTPUT: OLGA variables are printed to the output file every 10 hours. TREND: Trend variables are plotted every 10 seconds. PROFILE: Profile variables are plotted every hour.

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Sample case: Wateroptions The case WaterOptions.opi is an example of a three phase simulation using WATEROPTIONS. The main pipeline starts with a 3.3 km long horizontal pipe ending in a 90 m riser followed by a short horizontal pipe. The inner diameter of the pipe is 0.41 m. Heat transfer through pipe walls is calculated.

Case Comments: Library: WALL: The pipe walls consist of steel (two layers) covered by one layer of insulation. CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through pipe walls is used. INTEGRATION: The simulation runs for five hours using a minimum time step of 0.01 s and a maximum one of 10 s. The initial time step is set equal to the minimum one. FA-models: WATEROPTIONS: Water flash and water slip are turned on. FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: The inlet boundary condition is a constant mass source with mass flow of 34.181 kg/s and temperature of 60°C. The mass fraction of free water is set to 0.3. Since water flash is active, see WATEROPTIONS keyword, there is additional water in the vapor phase given by the water vapor mass fraction in the PVT table. By default, the equilibrium is used to determine the gas source at the inlet. FLOWPATH — Piping: The pipeline is 3.3 km long. The total number of pipes, including topside, is 9. The pipes are divided into 58 sections. The pipe walls consist of steel (two layers) covered with a layer of insulation. NODE: The inlet node is closed. The outlet boundary condition is to a constant pressure of 24 bara and a temperature of 26°C. Output: OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 10 seconds. PROFILE: Profile variables are plotted every 50 seconds.

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Sample case: Wax deposition The case WaxDeposition.opi demonstrates a simulation of wax deposition. The pipeline consists of an 8 km long horizontal pipe, a 110 m vertical riser, and 60 m long horizontal topside pipe. The inner diameter is 0.17 m throughout the pipeline. The fluid enters the pipeline with a temperature of 70°C, which is above the wax appearance temperature. On its way through the pipeline, the fluid is cooled and wax precipitation and deposition starts once the temperature is low enough. This happens about 2 km from the inlet. Due to the thermal insulation effect of the wax layer, the fluid temperature increases in the parts of the pipeline where wax is deposited. Furthermore, the wax layer makes the effective area of the pipe decreases, resulting in an increasing inlet pressure in order to maintain a constant flow rate.

Case Comments: Library: WALL: The pipe wall consists of steel, concrete, and an insulating polypropylene layer. CaseDefinition: FILES: The wax properties are defined in the file wax_tab-1.wax. OPTION: The steady state pre-processor is activated to generate the initial conditions. N.B., wax is not accounted for in the pre-processor. Full temperature calculation (TEMPERATURE=WALL) is required when simulating wax deposition. INTEGRATION: Since wax deposition is a slow process, the simulation time is set to 10 days. This is sufficient for a wax layer to start appearing. FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: The flow rate at the inlet is set to 17.51 kg/s with a temperature of 70°C. FLOWPATH — FA-models — WAXDEPOSITION: Deposition of wax is allowed in the entire pipeline. The wax porosity is set to 0.6 and the built in routine for calculating the viscosity of oil with precipitated wax is used. Wax properties are taken from the table WAXTAB in the file wax_tab-1.wax. Contribution to the wall roughness from deposited wax is not considered (WAXROUGHNESS=0 by default). FLOWPATH — Output — PROFILEDATA: Variables of interest are pressure and temperature in addition to wax related variables, such as wax layer thickness (DXWX), mass of wax dispersed and dissolved in oil (MWXDIP and MWXDIS, respectively) and the wax appearance temperature (WAXAP), which is pressure dependent. FLOWPATH — Piping: For the horizontal part of the pipeline, sections of length 250 m are used. If higher accuracy of the position where the wax starts depositing is needed, shorter sections should be used. NODE: The inlet node is closed. A constant outlet pressure of 20 bara is applied. Output: 756 / 769

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OUTPUT: Pressure and temperature in all sections are written every 10&#days. Four columns of results are printed on each page. TREND: Trend variables are plotted every hour. PROFILE: Profile variables are plotted every day.

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Troubleshooting Below is a list of problems with some suggestion of what has gone wrong and/or how to solve the problem. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Simulation state is not runnable Simulation state is runnable, but the simulation will not run Geometry Editor problems Problem showing the graphics Update Graphical driver GUI uses a lot of Memory Plots - no units are shown What to do when the layout gets screwed up License issues Inp files associated with GUI Mouse pointer changed to an unrecognize symbol

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Geometry Editor problems Below is a list of scenarios with some suggestion on how to solve: 1. Problem entering new values for existing pipes. Check that none of the filters are turned on, X-Bound/Y-Bound/X Fixed/Y Fixed. 2. Update geometry? is not asked on exit. The Geometry Editor needs to be associated to a flowpath to be able to update the correct flowpath. If you do not get the question about updating the geometry on exit, the reason might be that you opened the Geometry Editor without being connected to a flowpath and a geometry. In this case you need to use the exchange geometry option to be able to update the geometry of a given flowpath. Exchange geometry can be accessed while the Geometry Editor is open by right clicking on the flowpath which you want to update the geometry for. 3. The geometry editor does not start (possibly with the error message 'Geometry Editor is not registered). Start the Windows Explorer and locate the file Geometry.exe. The file is located in the \SPT Group\OLGAGeoEditor subfolder where you installed OLGA. Double click on this exe. If the geometry editor starts then close it again and try to start it from the OLGA GUI. If none of the above scenarios covers your request please send an e-mail to olgasupport@sptgroup.com.

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GUI Memory Requirement The OLGA GUI can in some cases use up to 50% of the memory, even if it is not active. A solution to this problem can be to updated the driver on the video card.

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Inp files are associated to OLGA GUI The installation starts the GUI with the /Register switch, so the files mentioned are after the installation associated with the GUI. If you want to remove all the associations you can launch the OLGA GUI.exe from DOS window with the /Unregister switch. (The GUI won't open, only the file associations are removed) e.g "OLGA GUI.exe" /Unregister OR Through the windows explorer and "Folder Option" to remove selected file associations, i.e only the .inp

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License issues Specifying the OLGA license file: 1. Start the License Handler from the start menu -> All programs -> SPT Group-> License Handler. 2. In the license handler select the type of license you use. Then click 'Configure' 3a) If you are using a local license server, specify the location of the license folder. This folder should contain your license file(s). As long as you have the .lic extension on your license file you can have several license files.NB! Make sure you do not have any invalid licenses in the license folder (e.g. expired licenses) 3b) If you are using a network license server, specify the location of the license server on the format @. Please note that OLGA licenses by default does not specify a port number (previously they used port 7570). I.e. the location of the license server will normally be on the format @ (e.g.: @myserver). 3c) If you are using a demo license file, specify the full path to the license file, including the name of the license file. 4. If the local license server status is green (up and running), you press close. However, if it is not, you can try to select the Restart license server and/or Uninstall license server followed by Install license server (for local license servers only). 5. If you still cannot get the local license server status green (up and running), please contact olgasupport at olgasupport@sptgroup.com. Specifying the PVTsim license file: 1. Start the license Manager from the start menu -> All programs -> Calsep -> License Manager -> Calsep License Manager. 2. Choose FlexLm and press OK. 3. Next time you start PVTsim you will be asked to give the path to the license file.

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Mouse pointer changed to an unrecognize symbol If one within the graphical user interface (GUI) press e.g. the combination space + N, the mouse pointer becomes a knife. To get rid of this symbol one have to press space. There are several symbols that can be accessed by pressing space + a character. However, by pressing space one will return to the standard mouse pointer.

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Plots - no units are shown What to do if no units are shown in the plots. 1. Check that cached static data is turned on. This can be checked by selecting Tools -> Options from the GUI main menu. Cached static data should always be turned on. GUI should be restarted if the cached static data had to be turned on. 2. Try to restart GUI. If you still have a problem please contact olgasupport@sptgroup.com.

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Problems showing the graphics 1. The OLGA GUI complains about that the hardware acceleration must be turned on. This error may arise in at least 3 different circumstances. * The hardware acceleration is manually been turned off. a. Open the Display properties (i.e. right-click on the desktop and select ;Properties”). b. Select the ”settings” tab. c. Click on the ”Advanced” button. The page that appears here is created by the graphics card vendor, and may very a lot from one pc to the other. It is difficult to say what to look for in general, but maybe ”Troubleshoot”. When you locate it, it should state pretty clear that the property is ”r;hardware acceleration”. d. Set the hardware acceleration to full. * The current graphics driver don't support hardware acceleration for OpenGL. a. Update the graphics driver * The pc is used through Remote Desktop. The OLGA GUI won't work! 2. When starting the OLGA GUI all is ok. But when I try to load an old case or create a new one, no graphics are presented for that case. I only get a gray box with a white ellipsis inside, and some text inside that again. This problem is due to some graphics settings no complying with the gui's graphical engine. It can happen in at least 2 different situations. * The display color quality is less than the minimum 32 bit. a. Open the Display properties (i.e. right-click on the desktop and select ”Properties”). b. Select the ”settings” tab. c. The "Color Quality" must be set to at least 32 bit. d. Re-start the GUI. * The graphics card is to old. The gui is tested with graphics card as low as 16MB of graphics RAM. This is, however well below our recommended size. But there is a lot of uncertainty we respect to the driver for such a card. The only thing to do is to update to the newest available driver for that specific card.

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What to do when the layout gets screwed up 1. You can restore the original layout by selecting the Restore to factory settings. This option can be accessed from the Tools -> Options menu. PS. This option requires GUI to close to take action. 2. If it is just a floating window, e.g. the property dialog, double click on the top of floating window, and the window will dock itself were it last was docked. 3. If a window is missing from the layout. It can be reopened from the View menu.

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Simulation state is runnable, but the simulation will not run 1. Check that a simulation engine is defined. Click Tools -> Options and select the OLGA Version tab. Verify that a version number is listed and selected. If not, click the Advanced button and add an 'OLGA engine/rules'. You can also add an OLGA 5 engine (refer to the installation guide for a description on how to set up OLGA 5 engines in the OLGA 6 GUI). 2. Try to run the case in batch (F4). If the case runs in batch then inspect the genkey file. The genkey file can be viewed by right clicking the case name in the file view window and selecting Open as text file. If the .genkey file shows keys that you didn't think you had specified, check that the write default values are not turned on. To check this go to Tools -> Options and see if Write default values to OLGA is turned on. If so, uncheck the option and try to start the simulation again. 4. If you still cannot find out what is wrong please send the case and the associated files to olgasupport@sptgroup.com.

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Simulation state is not runnable Normally, when the simulation state is "not runnable", there is something wrong with the input. Press F7 or the Verify button to verify the case. The output window will display a list of errors and warnings related to the given input. 1. Fix the errors that are displayed in the Output window. 2. If an error message states that something is wrong even though it appear to be correct (e.g. An error claims that the list of specified keys are not of the same length even though they are) try to define one of the keys over again. If this doesn't help you can try to define the keyword over again starting from an empty keyword. 3. If no error message appear, check that the Error button on the upper left corner of the output window is turned on. This is a filter button that removes all error messages reported to the output window if it is turned off. 4. If you still have a problem, send the opi file and the associated files (like the .tab file) to olgasupport@sptgroup.com. 5. Generate a genkey file by selecting the File view, right click on the filename and select -> Open as text file. A genkey file is now saved on the same location as the opi file. Rename the *.genkey file to *.key. Close the opi file that you are having trouble with and open the newly created *.key file. If you still get a simulation state that is not runnable, wait for the reply from olgasupport.

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Update Graphical driver This is a short guide to how you can check and/or update your graphics driver. OLGA has some requirements with regard to the PC's graphics driver. In order to make OLGA work properly, you have to make sure your graphics card comply with these requirements. 1. Identify your graphics driver. a. Open the Display properties (i.e. right-click on the desktop and select ”Properties”). b. Select the ”settings” tab. c. Click on the ”Advanced” button. The page that appears here is created by the graphics card vendor, and may very a lot from one pc to the other. It is difficult to say what to look for in general, but if you have an ”Adapter” tab here, that’s a start. What you need is the properties of the adapter, which in turn should list what driver the pc currently uses. d. The graphics driver should be provided by the graphics cards manufacturer. On some older pc’s it is likely that Microsoft has provided the driver, if so it must be updated. 2. Update the graphics driver. a. Open the graphics cards manufacturers’ homepage. b. Try to find ”Download” or ”Driver” or something. If you find a newer driver for your specific graphics card, download it and install. c. If you can't find the correct driver, try the pc manufacturers homepage, and try to locate a new graphics driver there. 3. Reboot the pc (if necessary).

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