3－Tutorial STARS BUILDER Revised Nov 2007

Introduction to STARS Introduction to CMG’s Thermal and Advanced Process Simulator

Computer Modelling Group Ltd. 2007

TABLE OF CONTENTS LIST OF FIGURES .................................................. ........................................................................... .................................................. ............................................ ...................3 3 REQUIRED FILES.......................................... FILES................................................................... .................................................. ................................................... ............................ .. 4 CREATING A MODEL FROM GEOLOGICAL GEOLOGICAL DATA USING BUILDER.....................................5 BUILDER..................................... 5 Starting CMG Launcher........... ............. ............. ............. ............. .............. ............. ............. ............. ............. .............. 5 Opening BUILDER............ ............. ............. .............. ............. ............. ............. ............. .............. ............. ............. ....... 5 Creating the Simulation Simulation Grid (structu (structural ral data) data) ............ ............. ............. .............. ............. ............. ............. ............. ... 5 Assigning Porosity & Permeability Permeability to the Model ............ ............. .............. ............. ............. ............. ............. .............. 9 Creating Fluid Model Data............. Data ............. ............. .............. ............. ............. ............. ............. .............. ............. ............. ..... 10 Creating Relative Relative Permeability Data................ Data... ............. ............. ............. ............. .............. ............. ............. ............. ............. . 12 Creating Initial Conditions ............. ............. .............. ............. ............. ............. ............. .............. ............. ............. ..... 13 Creating Numerical Controls....................... .............. ............. ............. ............. ............. .............. ............. ............. ..... 13 Incorporating Well Trajectories and Perforations.... Perforations................. ............. ............. ............. ............. .............. ............. ............. ..... 14 Adding Historical Production Data to the Model................... Model...... ............. ............. ............. ............. .............. ............. ............. ..... 17 Creating Average Average Monthly Monthly Production Production / Injection Recurrent Well Data Data ............. ............. ............. ............. ............. . 18 Creating Field Production History (*.fhf) for History Match............. Match ............. ............. ............. .............. ............. ............. ..... 18 Well Definition Definition and Constraints ............ ............. ............. ............. .............. ............. ............. ............. ............. ............ 19 Write Out Restart information to a Restart File............. File ............. ............. .............. ............. ............. ............. ............. ............ 23 Running the STARS Dataset...................... ............. .............. ............. ............. ............. ............. .............. ............. ....... 23 Reviewing the Simulation Simulation Results Results using RESULTS GRAPH and RESULTS RESULTS 3D ........................ ............. ............. ... 23 Using the Historical Data Data Restart File in a Prediction Prediction Run ............ ............. ............. ............. ............. .............. ......... 25 Adding Adding an Aquifer Aquifer ..................... ................................ ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ................... ........ 27 Analyzing the Data........... ............. ............. ............. .............. ............. ............. ............. ............. .............. ............. ....... 29 Further Analysis ............ ............. ............. ............. ............. .............. ............. ............. ............. ............. .............. ......... 29 Extra Exercises..................... ............. .............. ............. ............. ............. ............. .............. ............. ............. ............. ... 33 Who gets more oil????........ ............. ............. ............. ............. .............. ............. ............. ............. ............. ............ 33

CREATE A PATTERN STEAM MODEL .................................................. ........................................................................... .................................. ......... 34 Open BUILDER.............. BUILDER......................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ................... ........ 34 Create an STARS Heavy oil Dataset Using ‘Quick Pattern’........... ............. ............. ............. ............. .............. ......... 34 Generate STARS STARS Fluid Fluid Model Properties Properties From From Black Oil PVT PVT Correlations Correlations ............. .............. ............. ............. ..... 35 Creating Relative Relative Permeability Data................ Data... ............. ............. ............. ............. .............. ............. ............. ............. ............. . 39 Temperature Dependent Relative Permeability.............. Permeability. ............. ............. .............. ............. ............. ............. ............. ............ 40 Modifying Relative Relative Permeability Curves Curves for Steam Injection Injection (compositional (compositional dependence) ....................... ............. . 43 Creating Initial Conditions ............. ............. .............. ............. ............. ............. ............. .............. ............. ............. ..... 47 Create Numerical Controls....... ............. ............. ............. ............. .............. ............. ............. ............. ............. ............ 47 Tutorial STARS BUILDER_Revised_Nov_ BUILDER_Revised_Nov_2007.doc 2007.doc

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Complete the Well Perforations............... ............. ............. .............. ............. ............. ............. ............. .............. ......... 47 Adding Operating Constraints ............ ............. ............. ............. ............. .............. ............. ............. ............. ............. . 48 Adding Adding Dates................... Dates.............................. ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ................... ........ 49 Outputting Basic Properties and Well Information Information ............. ............. ............. ............. ............. .............. ............. ....... 49 Validate Dataset Using Builder............ ............. ............. ............. ............. .............. ............. ............. ............. ............. . 50 Running the Simulator....... Simulator.................... ............. ............. .............. ............. ............. ............. ............. .............. ............. ............. ..... 51 Buildin Building g a Cyclic Cyclic Steam Simu Simulat lation ion Model Model in STARS............... STARS............... ............. ............. ............. .............. ............. ............. ..... 54 Water Flood ............ ............. ............. .............. ............. ............. ............. ............. .............. ............. ............. ............. ... 57 Primary Primary Producti Production on ..................... ................................ ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ...................... ................. ...... 57

Tutorial STARS BUILDER_Revised_Nov_ BUILDER_Revised_Nov_2007.doc 2007.doc

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LIST OF FIGURES FIGURE 1: New Dataset with Contour Map Open ................................................................................................... 5 FIGURE 2: Contour Map with Orthogonal Corner Point Grid.................................................................................... 6 FIGURE 3: General Property Specification Spreadsheet ......................................................................................... 6 FIGURE 4: Specifying a Geological Map for a Property........................................................................................... 7 FIGURE 5: 3D View of Reservoir after Property Specification.................................................................................. 8 FIGURE 6: Removing the Contour Map from the Display ........................................................................................ 8 FIGURE 7: Property Specification Spreadsheet with Grid Top, Thickness & Porosity Specified ............................... 9 FIGURE 8: Components Tab in the Tree View ...................................................................................................... 10 FIGURE 9: Import Black Oil PVT Form.................................................................................................................. 11 FIGURE 10: Plots for RockType 1......................................................................................................................... 13 FIGURE 11: Trajectory Properties Window Step 1 of 3.......................................................................................... 14 FIGURE 12: Trajectory Properties Window Step 2 of 3.......................................................................................... 15 FIGURE 13: Trajectory Perforations Window ........................................................................................................ 16 FIGURE 14: Trajectory Perforations Window after Read in Perforation File ........................................................... 16 FIGURE 15: Step #2 of the Production Data Wizard.............................................................................................. 17 FIGURE 16: Average Production/Injection Data Plot ............................................................................................. 18 FIGURE 17: Well Events Window ......................................................................................................................... 19 FIGURE 18: Window for Copying/Deleting Well Events......................................................................................... 20 FIGURE 19: Well Completion Data Window.......................................................................................................... 21 Figure 20: Adding perforations to well ................................................................................................................... 22 FIGURE 21: Simulation Log File ........................................................................................................................... 23 FIGURE 22: Plot of Simulation Data versus Historical Data................................................................................... 24 FIGURE 23: Well Events Window with Updated BHP Constraint ........................................................................... 25 FIGURE 24: Well Events Window with ALTER 0 Constraint .................................................................................. 26 FIGURE 25: Plot of Simulation Data versus Historical Data with Future Prediction ................................................ 27 FIGURE 26: Select Aquifer Location Window........................................................................................................ 28 FIGURE 27: Aquifer Properties Window................................................................................................................ 28 FIGURE 28: Plot of Pressure Difference Due to Aquifer ........................................................................................ 29 FIGURE 29: Reservoir Showing High Oil Saturation (orange)................................................................................ 30 FIGURE 30: Areal View (IJ-2D) of Trajectory for W11 ........................................................................................... 31 FIGURE 31: Cross Section View (JK-2D) of Trajectory for W11............................................................................. 32 FIGURE 1: General Property Specification Spreadsheet ....................................................................................... 34 FIGURE 2: Thermal Rock Types........................................................................................................................... 35 FIGURE 3: Drop down box.................................................................................................................................... 48 FIGURE 4: Constraints and Injected Fluid............................................................................................................. 49 FIGURE 10: I/O Control ........................................................................................................................................ 50 FIGURE 5: Log File Summary............................................................................................................................... 51 Tutorial STARS BUILDER_Revised_Nov_2007.doc

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REQUIRED FILES TO10FLT.bna

Porosflt.bna

Thickflt.bna

viscosity.txt

TRAJ_Meter.wdb

PERFS_Meter.perf

production-history.prd

Tutorial_CYC_DEFINE.INC

Well-11.perf

Well-11.wdb

viscosity.xls

Tutorial STARS BUILDER_Revised_Nov_2007.doc

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Creating a Model From Geological Data using Builder Create a working directory somewhere on your disk and put the map files that accompany this tutorial in this directory.

Starting CMG Launcher 1. Start the CMG Launcher by using the icon on your desktop, or by going through the Start menu and selecting Programs/CMG/Launcher. 2. Select menu item Projects, then Add Project. 3. Browse for the directory where you stored the map files. 4. Call the project Tutorial. 5. Click OK to exit back to the Launcher. 6. You should now have this directory displayed.

Opening BUILDER 1. Open Builder by double clicking on the appropriate icon in the Launcher. 2. Choose: •

STARS Simulator, SI Units, Single Porosity

•

Starting date 1991-01-01

3. Click OK twice.

Creating the Simulation Grid (structural data) 1. Click on File (on the menu bar, top left), then “ Open Map File…”. 2. Choose “Map Type – Atlas Boundary format (.bna)” and m in “Units for X,Y coordinates in the files” box. 3. Select the Top-of-Structure map file called “TO10FLT.bna” by clicking on the Browse button and locating the file. 4.

Click OK

FIGURE 1: New Dataset with Contour Map Open Tutorial STARS BUILDER_Revised_Nov_2007.doc

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5. Maximize the screens for a better view by clicking on the window maximize button. 6. Click on the arrow next to the “Reservoir” (on the left menu bar) and select “Create Grid”. 7.

Select Orthogonal Corner Point and specify a 25 (I-direction) x 35 (J-direction) x 4 (K-direction) grid.

8.

Enter 25*110 in the I direction box (meaning all 25 columns in the I-direction will be 110 meters in length).

9.

Enter 35*125 in the J-direction box (meaning all 35 rows in the J-direction will be 125 meters in length).

10. Click OK. 11. Hold down Shift key and hold down left mouse button to move (pan) grid. 12. Hold down Ctrl key and hold down left mouse button to rotate grid.

FIGURE 2: Contour Map with Orthogonal Corner Point Grid 13. Align the grid with the fault so that a grid block boundary lies along it, and the grid covers the whole map area. 14. Change display control to Probe mode by clicking on this

toolbar button on top tool bar.

15. Click on the Specify Property button (top middle of screen) to open the General Property Specification spreadsheet as shown below.

FIGURE 3: General Property Specification Spreadsheet


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16. Select the box for layer 1 under the property column labeled Grid Top. Right click in this box and select the Geological Map option as the data source. 17. Click the Values in file1 button, then Browse and select the top-of-structure map file called TO10FLT.bna

FIGURE 4: Specifying a Geological Map for a Property 18. Click OK to return to the spreadsheet type window. 19. Repeat this action for Grid Thickness in layer1 box, but this time select Thickflt.bna in the Values in file1 box. Also, enter 0.25 in the times box (still on the property specification menu) in order to allocate 25% of the total thickness map to each of the 4 layers in the grid. 20. Finally, copy the layer1, Grid Thickness cell contents and paste it into the layer 2, layer 3 and layer 4 Grid Thickness cells to complete the specification of Grid Thickness source data for each of the 4 layers in the grid. You can use Ctrl-C and Ctrl-V keys to copy specifications for the first layer to the other 3 just as in a regular spreadsheet. . 21. Click OK to the Block / Corner Value Calculation button will pop up click OK to populate the grid with top-ofstructure and grid thickness data (this operation is performed by BUILDER using the specified map data to interpolate grid cell values). Also click OK to the pop-up window regarding clamping. 22. Change the view from IJ-2D Areal to 3D View (in the upper left corner!!).


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FIGURE 5: 3D View of Reservoir after Property Specification 23. Click on the Rotate (3D View) button

(from the toolbar) to rotate the display by holding down the left mouse

button and using the cursor to move the model. Hold down the Ctrl key with the left mouse button and move the mouse toward the bottom of the screen to zoom in or move the mouse to the top of the screen to zoom out. If a mouse has a scroll wheel, this can also be used to zoom in and out by scrolling the wheel forward (zoom out) or backward (zoom in) 24. To remove the contour map from the display, click the right mouse button while the cursor is anywhere in the display area. Select Properties from the displayed menu (bottom of list), Maps from the tree view; and (finally) uncheck the Show Map Contours Lines and Fault boxes. Press OK.

FIGURE 6: Removing the Contour Map from the Display


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Assigning Porosity & Permeability to the Model 25. Repeat the above process for Porosity (i.e. similar to step #19), but select the map porosflt.bna. Use the same map for each layer. This time, leave the value in the times box as 1.

FIGURE 7: Property Specification Spreadsheet with Grid Top, Thickness & Porosity Specified 26. Select Permeability I from the list on the panel and enter the following: Layer 1

50

Layer 2

250

Layer 3

500

Layer 4

100

27. Select Permeability J and right click in the Whole Grid box. Select EQUALSI then OK. 28. Do the same with Permeability K and select EQUALSI. In the first box select * and then enter a value of 0.1 in the second field (this applies a Kv/Kh ratio of 0.1). Press the OK button. 29. Press the OK button on the Block/Corner Value Calculation window. This window can also be accessed by clicking on the Calculate Property button at the top. 30. Double click on Thermal Rocktypes in the tree view menu, create a new thermal rock type, select the Rock Compressibility tab and input 2E-5 in the Formation compressibility box , 20000 kPa in the Porosity Reference Pressure box and click OK . Units will be applied automatically; you should now have the Green check mark for Reservoir section. 31. This would be a good point to save the data set you are working on. Click File then Save As. Save file as Tutorial.dat.


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Creating Fluid Model Data 1. Click the Components tab menu in the tree view (or use the top menu), and select Import Blackoil PVT…

FIGURE 8: Components Tab in the Tree View 2. Select SI units, then click the button “Launch the Black Oil PVT Graphical User Interface (GUI)”. 3. Click the Tools button and select the menu item “Generate PVT Table Using Correlations”. 4. Enter 70 (deg °C implied) in the Reservoir Temperature box. Generate Pressure data up to 35000 kPa. For Bubble Point Pressure , select the “Value Provided” option and enter a value of 6500 kPa. For the Oil Density option, select “Stock tank oil gravity (API)” as the type of gravity value you want to use and enter a value of 35 in data entry window. Change the Gas Density box to display Gas Gravity(Air=1) and type .65 in the data entry window. 5. Check the box at the bottom “Set/Update Values of Reservoir Temperarture, Fluid Densities in Dataset”, and click OK. Click Yes to the question about oil compressibility. 6. Select the General tab and click the Tools button and select the menu item “Generate Water Properties Using Correlations…”. In the Reference Pressure box, enter a value of 20000 kPa and leave the Water bubble point pressure value blank. Check the box at the bottom “Set/update values of TRES and REFPW in PVT Region dialog, then click OK. Click OK again to exit the black oil PVT form. Click OK to the message about bubble point. 7. The panel should look like the following: Tutorial STARS BUILDER_Revised_Nov_2007.doc

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FIGURE 9: Import Black Oil PVT Form 1. In the Bubble Point Pressure section of the panel, click on Select From Table and click on the grey box next to the 6500 kPa value in the pressure column. Click on Next> which take you to Step 2. Note the various elements that have been selected by default. We will accept these selections/values, but in reality, they may be changed by the user. 2. Assuming we have a measurement of dead oil viscosity of 420 cp and 5 cp at reservoir and maximum steam temperature 70 and 325, respectively. Enter these values in the table. Note that under the Component System part of the panel, we are creating a live oil system. Also in the Gas K Value Temperature Dependence part of the panel, we are accepting the default value. Click Next>. A message will appear regarding the thermal expansion coefficient with a default value that we will accept. Click OK which takes you to Step 3 (Check Matches of PVT Properties). 3. Move this panel to the side to enable viewing of the match plots. Note the Match error values shown in the Step 3 panel. Check the match quality by expanding and clicking on the various available plots. Matches are acceptable, given the limited PVT data available. Note that the Gas Viscosity plot appears not to match. This is because the STARS computes gas viscosity changes with temperature and/or composition, but


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does not compute gas viscosity change with pressure. If gas viscosities are important, then the user can select the option “Composition dependent gas viscosity” and click the Re-Match button. 4. On the Step 3 panel, select Next> and then Finish on the Step 4 panel which has come up. Note that in the tree, the Components tab now has a green checkmark. 5. Save your dataset.

Creating Relative Permeability Data 1. Click the Rock-Fluid button on the menu in the left handside. 2. Double click on Rock Fluid Types in the tree view. A window will open. Click on the

button and

select New Rock Type. 3. Press the Tools button (on the “Relative Permeability Tables” tab) and select Generate Tables using Correlations.

Enter the following parameters for the analytical relative permeability curves generation. SWCON

0.2

SWCRIT

0.2

SOIRW

0.4

SORW

0.4

SOIRG

0.2

SORG

0.2

SGCON

0.05

SGCRIT

0.05

KROCW

0.8

KRWIRO

0.3

KRGCL

0.3

KROGCG

0.8

All Exponents

2.0

4. Press Apply and then OK. Press OK again to get out of the Rock Types window. A graph containing the relative permeability curves will appear. 5. The Rock Fluid section should have a green check mark. Save the file at this time. Tutorial STARS BUILDER_Revised_Nov_2007.doc

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FIGURE 10: Plots for RockType 1

Creating Initial Conditions 1. Click the Initial Conditions button on the tree view of Builder. 2. Double click on Initial Conditions. 3. Select Depth-Average Capillary-Gravity Method option. 4. Type the following values in the available fields: 27600 (kPa implied) in the Reference Pressure (REFPRES) window 3050 (m implied) in the Reference Depth (REFDEPTH) window 3080 (m implied) in the Water-Oil Contact (DWOC) window Leave the Gas-Oil Contact (DGOC) window blank. 5. Leave the other boxes blank. 6. Click on Apply; then OK.

Creating Numerical Controls 1. Click the Numerical button in the Builder tree view and double click on Numerical Controls and click OK to the message about DTWELL. 2. Set the DTWELL value to be 1.0 day and click OK. 3. You should now be back in the main Builder window with all tabs showing a green checkmark in the tree view, except for the “Wells & Recurrent” tab. 4. At this point it is advisable to save the data again by selecting File from the top menu and Save. Tutorial STARS BUILDER_Revised_Nov_2007.doc

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Incorporating Well Trajectories and Perforations Once we have created the static model, we will now incorporate the trajectory and perforation information into the model . 1. Go to the main Builder menu and select Well / Well Trajectories / Well Trajectories…. The “Import well trajectory wizard. Step 1 of 3” window will pop up. 2. You need to choose Trajectory File Type and appropriate Units for it (3 Steps Wizard). 3. Choose Table Format and m for X, Y and Z,MD then browse for the file “TRAJ_Meter.wdb”, Open, and press Next >(Step 1 of 3)

FIGURE 11: Trajectory Properties Window Step 1 of 3 4. The following window will open. Make sure all wells are selected, and check the box Clear all existing trajectories then press Next> (Step 2 of 3).


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FIGURE 12: Trajectory Properties Window Step 2 of 3 5. Click Finish to complete Step 3 of 3. 6. This screen will create a vertical trajectory for each well that exists in the main contour map. 7. Now go back to top menu and select Well, Well Trajectories, click on Trajectory Perforation Intervals… a window will open (Figure 13): 8. Click on Read File and choose File unit selection option as SI then browse PERFS_Meter.perf. Press Open. 9. If this is done correctly, the window will be like Figure 14: 10. Press Apply and then OK. This completes the trajectories and Perforation of the wells in the model


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FIGURE 13: Trajectory Perforations Window

FIGURE 14: Trajectory Perforations Window after Read in Perforation File


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Adding Historical Production Data to the Model The last item we want to do is add historical rate data so that we can set up a history match run. 1. Go to the main Builder menu and select Well / Import Production/Injection Data (this is the wizard to import production/injection data into the well & recurrent data for the simulator and it also defines the status of each well!!). 2. STEP 1: First step of this wizard is to provide the type and name name of the the production file. In our case, we will will use General and General and choose a file in the tutorial directory named Production-history.prd Production-history.prd.. Press the Next button. [Use the Next/Back buttons Next/Back buttons on the panels to move forward/backward between each Step]. 3. STEP 2: Follow Follow the instructions instructi ons and highlight the first line containing the production data (top window) window) and well name (lower window) window) (as shown in the following figure). Press Next. Next.

FIGURE 15: Step #2 of the Production Data Wizard 4. STEP 3: 3: If the delimiters look good and separate the columns correctly, correctly , click Next to Next to go to STEP 4. 5. STEP 4: Go to Columns 3 to 5 and in the identifier row, choose Oil Produced, Produced, Water Produced and Produced and Gas Produced for Produced for each column. Leave others as they pop up then click Next to go to the next step. 6. STEP 5: This is the place showing you which well’s well’s production data has been picked picked up and which well well is not. For example, the program program could not find any production data from well 5, 7 and 9. 9. Since wells wells 5, 7 and 9 have no production production history, the easiest action is to delete them from the model. We will do this later. Other than that, click Finish. Finish. Also, close the Simulation Dates window that may pop up.


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Creating Average Monthly Production / Injection Recurrent Well Data Next thing we want to do is to generate the well recurrent data for every month. 1. Go back back to the main Builder menu and select Well / Average Production/Injection Production/Inj ection Data... Data.. . 2. Now, move your mouse and right click on the x-axis. x-axi s. A menu will show up to allow you to change the average interval from this point on to monthly, bi-annually, yearly, yearly , etc.

FIGURE 16: Average Production/Injection Data Plot 3. Select “Reset all intervals to every month” month” and press the OK OK button. Once again, click Close Close on the Simulations Dates window Dates window that pops up.

Creating Field Production History (*.fhf) for History Match 1. Next thing we want want to do is to create a field history file so so that we can make a comparison between the simulation run and the actual field history file. 2. Go to the top menu again again and select Well / “Create Field History File…” then File…” then provide a filename (or you can just use the default production-history.fhf production-history.fhf ). ). Press OK. OK.


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Well Definition and Constraints 1. For those wells that have no production history, we can either delete them or define them as a producer or injector and shut-in the wells so that they will not affect the history match. 2. In this tutorial, we will delete Well 5 and change Wells 7 & 9 so that they are injectors. To do that, open the tree view and press the Wells & Recurrent tab. Expand the Wells list by clicking on the +. Right mouse click on Well 5, select Delete and press Yes to the message that pops up. 3. Go to Well 7, right mouse click and select Properties. A new window will show up as follows:

FIGURE 17: Well Events Window 4. Click on ID & Type, check the Edit box for Type, and select INJECTOR MOBWEIGHT EXPLICIT. Check the “Auto-apply” check box. 5. Go to Constraints tab (say YES to apply changes if asked!!), and check the Constraint definition box. 6. Under select new (in the Constraint column of the table), select OPERATE. Then select BHP bottom hole pressure, MAX, 25000 KPa, CONT REPEAT. Press Apply. 7. Go to the Injected Fluid tab and choose Water as injection fluid, enter a mole fraction of 1.0 for the component Water, then enter a Temperature of 70 C and a Steam Quality of 0.0. Press Apply. 8. Go to the Options tab. Check the Status box and choose to SHUTIN the well at this time. Press Apply. 9. Now, we can copy all the above specifications to Well 9. To do that, make sure you are looking at “Well 7” in the Name/Date list. Then highlight the following Events (for Well 7) by clicking on them with your mouse and pressing down the Ctrl key to select multiple items: INJECTOR, constraints, injected fluid, stream quality, stream temperature and SHUTIN (all of them!!!).


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10. Press the Tools button at the bottom of the screen, and select Copy events using filter. This will open a new window. In the Select Wells tab, check on Well 9 and then go to the Select Dates tab. Check the date 1991-01-01 and press the Search & Add button. The window should look like this:

FIGURE 18: Window for Copying/Deleting Well Events Tutorial STARS BUILDER_Revised_Nov_2007.doc

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11. Click OK and the same constraint information created for Well 7 will now be copied to Well 9. If a message pops up requesting to change the well type for Well 9, say Yes. Press OK to close the Well Events window. 12. Make sure that the View Type is set to IK-2D X-Sec (located in the upper left hand corner of the main Builder window). 13. Even though we defined Well 7 as an injector, provided constraint information and defined the trajectory path, well completions (or perforations) might need to be defined along the trajectory path. If the well completions are not defined, then the simulator will not be able to properly recognize the well. To define some well completions, go to the Well menu and select Well Completions (PERF). The following window will open: a. Note: by default, Builder will provide one completion in Layer K=1. To use the following approach to Add a new completion, this single completion should first be deleted. Alternatively we can add to the existing completions as also described below. 14. Expand the Well & Date list and select “Well 7”. a. To delete the existing perforation date Press the

button and select Completion – Delete

Current. Answer “Yes” to delete the model well. All related information for this completion is also deleted and must be re-entered by reference to one of the other wells.

Press the

button and

select Completion – Add New. Press the OK button in the window that pops up regarding the “New Well Completion Date”.

FIGURE 19: Well Completion Data Window b. Select the Perforations tab and press the

button. This will allow you to use your

mouse to select the grid blocks where you want the well completions to be. Since the well will be SHUTIN right away anyway, the location where you click in the grid does not have to be exact. Tutorial STARS BUILDER_Revised_Nov_2007.doc

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Change the Plane Slider to 15 and zoom in to the section containing Well 7 so that you can see the trajectory for Well 7. Use your mouse to click two or three times somewhere along the Well 7 trajectory in the main Builder window. Press

when you are done. Your screen

should look similar to figure 20 below. Press Apply and then OK to close the window.

Figure 20: Adding perforations to well

c.

Alternatively, we can simply add to the existing completion, or change it, by going to the Perforations tab and Delete the existing completion with the [X] button and Add new completions with the mouse.

15. If everything is OK, all of the tabs in the tree view should have a green checkmark. The Dates under Wells & Recurrent tab may still have a yellow exclamation mark. This will not affect the simulation of the model, however it can be removed by adding a top date a day after the last date on the list. 16. Double click on Dates. The Simulation Dates window will pop up. Click on the Add new date button on the right handside and enter 1991-09-02 and click OK. Make sure this date is checked under the set STOP column. Click Close to close the window. 17. Please save the file one more time!!!


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Write Out Restart information to a Restart File 1. Click on the I/O Control tab in the tree view. 2. Double click on Restart. 3. Check 0n Enable Restart Writing. 4. Press the

button and select the first simulation date which is 1991-01-01. Press OK.

5. Set the “Writing Frequency Option” to Every TIME or DATE Keywords. 6. Click OK to close the window. 7. Click File in the main Builder menu and select Save As. Name this file Tutorial_hm.dat. 8. By enabling the restart feature, you will be able to make prediction runs without having to rerun the historical data portion.

Running the STARS Dataset 1. If everything is OK, you should be able to run the dataset using STARS. Click the Validate with STARS button, click Yes to the question about saving the data set, then click the Run button. 2. If there are no errors, a MS-DOS window will open up and show you the progress of the run. When finished, the MS-DOS window will be terminated and shows a brief summary of results.

FIGURE 21: Simulation Log File

Reviewing the Simulation Results using RESULTS GRAPH and RESULTS 3D We can now look at the simulation run and compare it with the historical data and see how the reservoir would perform . Tutorial STARS BUILDER_Revised_Nov_2007.doc

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1. From the CMG launcher, drag and drop Tutorial_hm.irf onto the Results Graph 2007.10 icon. 2. Select menu item File; then Open Field History. 3. Select the production-history.fhf file we created in the Creating Field Production History section of the tutorial. Click on the Add Curve icon

.

4. Select the file to display data from as Tutorial_hm.irf. Select curve parameter Oil Rate SC. Choose Well 3 for the Origin and then Click OK. 5. Now repeat the same steps but this time select the file as production-history.fhf , as we want to compare the simulated data with the historical input data. You should now see a plot similar to:

FIGURE 22: Plot of Simulation Data versus Historical Data 6. Repeat the same procedure as above except this time, plot the Water Rate SC & Gas Rate SC curves either in the same plot or separately. To add new plot, right click on the Plot 1, then click on Add Plot. 7. In order to view this plot for all the production wells you can use the Repeat origins button

.

8. In the Repeat Plots window, select the All Producers option and OK to generate the plots. 9. You should now have a series of plots showing the historical data and simulator calculation for each of your production wells. 10. You can now continue to investigate the results from these datasets in Results Graph and Results 3D, and interactively discover the large range of features that are available to you for analyzing your data. Exit Graph and save the template file.


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Using the Historical Data Restart File in a Prediction Run We want to predict the reservoir performance until 1/1/1993 if the producers are fixed to a minimum BHP of 15000 kPa . 1. Load the dataset tutorial_hm.dat back into Builder. 2. Click on the I/O Control tab in the tree view. 3. Double click on the Restart option. 4. Check the box for Restart from previous simulation run (RESTART) . 5. Browse to select Tutorial_hm.irf. Click “Record to restart from” (Note that a series of restart dates are now available). 6. In the “Record to restart from” field, select the date 1991/09/01 and then press OK to exit back to the main Builder window. Click OK to the builder message that pops up. 7. Click on the Well & Recurrent section in the tree view and expand the Dates. 8. Select the date to 1991-09-01, double click. 9. If the Set stop box is checked on this date, uncheck it. Then click the button Add a range of dates. 10. Change the range of dates so that the From date is 1991-09-01 and the To date is 1993-01-01. Press OK. Press Close. 11. Click on the Wells & Recurrent section in the tree view again. Expand the Well items in the tree view and double click on Well 1. 12. Change the date to 1991-09-01, check the Auto-apply check box, and click on the Constraints tab. 13. Check the Constraint definition box, then change OPERATE, BHP, MIN to 15000 kPa 14. The panel that is displayed should look similar to:

FIGURE 23: Well Events Window with Updated BHP Constraint


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15. Click Apply, a new constraint will be created in the date 1991-09-01 for Well 1. The next task will be to copy the same constraint to all the other wells to do the forecast. 16. Highlight the Well 1 constraints Event for 1991-09-01 (in the Name/Date list). Click the Tools button at the bottom of the screen and select Copy events using filter. 17. On the “Select Wells” tab; check Producers and Select, then on the “Select Dates” tab check on 199109-01. At this tab; make sure to check on “Do you want to create new dates?”. This option creates new date for wells which are already shut in because of production history event . Press the Clear List button. Press the Search & Add button, then OK. All the wells except wells 7 & 9 will have a new constraint starting 1991-09-01. 18. On the “Well Event” window; you might see ALTER event equal to 0 on 1991-09-01. This should be deleted from prediction data file (Figure 24).

FIGURE 24: Well Events Window with ALTER 0 Constraint 19. Right click on highlighted ALTER and select “Delete event using filter..” then repeat step 17 to fix it 20. Click OK and return to the main menu. 21. Save the new file as Tutorial_pred.dat. 22. We can now exit Builder and drag and drop the Tutorial_pred.dat file onto the STARS icon to run it. We can now look at the simulation run and compare it with the historical data and see how the reservoir would continue to perform . 23. Drag and drop Tutorial_pred.irf onto the Results Graph icon. 24. Select menu item File; then Open Field History. 25. Select the production-history.fhf file we created in the Creating Field Production History section of the tutorial. Tutorial STARS BUILDER_Revised_Nov_2007.doc

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26. Click on the Add curve icon

.

27. Select the file to display data from as Tutorial_pred.irf. Select curve parameter Oil Rate SC; then Click OK. 28. Now repeat the same steps, but this time select the file as production_history.fhf, as we want to compare the prediction run and the history match run. 29. To increase the size of the historical data markers select menu item View; Properties. 30. Select the Curve tab and increase the marker size from 4 to 8 and Click OK. 31. You should now see a plot similar to:

FIGURE 25: Plot of Simulation Data versus Historical Data with Future Prediction 32. Repeat the same procedure as above except this time plot the Water Cut variable. Save the file and exit.

Adding an Aquifer The next thing we want to do is add an aquifer, and compare the simulation runs with and without an aquifer to see the difference it makes. 1. Drag and drop Tutorial_hm.dat onto the Builder icon. 2. Once in Builder go to the Reservoir and select Create/Edit Aquifers…. (Alternatively, you can just click on the Create/Edit Aquifers button

from the top tool bar).

3. Select the first listed type – Bottom aquifer, and OK the panel.


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FIGURE 26: Select Aquifer Location Window 4.

Select Modelling Method – Carter-Tracey (infinite). Leave all other items blank.

FIGURE 27: Aquifer Properties Window 5. OK to exit the panel to return to the model display area. 6. Go to File; Save As and change the file name to be saved to Tutorial_hm_aq.dat. 7. OK to save the new file and exit Builder. You can now drag and drop Tutorial_pred_aq.dat onto the STARS icon. (To run simulation).


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Analyzing the Data 1. The file Tutorial_hm_aq.irf file can be dragged and dropped onto the Results Graph icon. 2.

Select File; Open CMG Simulation Results from the menu bar and select Tutorial_hm.irf.

3. We now have both simulation results loaded so that we can compare them. 4. Click on the + icon to add a curve

.

5. Select Origin Type – Sector (Region). 6. Parameter – Ave Pres HC POVO SCTR. 7. Click on OK to display the line. 8. Repeat the above except select the filename as Tutorial_hm_aq.irf. 9. We now have a comparison plot that should look similar to:

FIGURE 28: Plot of Pressure Difference Due to Aquifer 10. You can also enter the 3D display area from here and both types of display are linked together. When you exit Results 3D or Graph, the .ses (line plot) or .3tp (3D image) file referred to is a template that you can use to re-create the images that you have generated using the same or other input files. 11. Results are very intuitive and most things can be accessed by the menus or by right mouse clicking on the display areas.

Further Analysis When you view the ternary plot for Tutorial_pred.irf in Results 3D it seems that there is quite a bit of oil left in the southern anticline at the end of this simulation, especially in layer K = 2. As part of our reservoir plan we would like to put in a horizontal well on 1/1/1992 to access this ‘remaining’ oil.


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FIGURE 29: Reservoir Showing High Oil Saturation (orange) 1. Load the dataset Tutorial_pred.dat into Builder. 2. Make sure you have the IJ-2D areal view showing so that we can easily locate the well we are about to add. 3. Click on the Wells & Recurrent tab, then right click on Wells in the tree view. From the popup menu that appears, select New… 4. Name the new well W11, change Type to PRODUCER, and change the date to be 1991-12-01. 5. Select the Constraints tab and check the Constraint definition check box. 6. Enter the constraint OPERATE; BHP bottom hole pressure; MIN; 10,000; CONT REPEAT. 7. Click OK to exit from the Create New Well panel. 8. Well W11 should have appeared on the Well & Recurrent tree view. There should be an exclamation mark next to this well indicating that there is a data problem.

9. Right click on this well and select Validate to display any error or warning messages. The message should indicate that there are no valid perforations. Click Ok to close the window. 10. Click the + sign next to W11 and double click on 1991-12-01 PERF.


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11. In the Well Completion Data (PERF) panel that appears, select the Perforations tab.

12. Click the Begin button to Add perfs with the mouse, then click on the tool button for Advanced options for perforating intermediate blocks between mouse clicks. 13. Check the Perforate all intermediate blocks box, and check the box to Set constant well length and leave the well length at the default of 1000m. Then click OK. 14. Now, move the Well Completion Data (PERF) panel to the side so that the model grid can be viewed. Using the knowledge gained from the previously displayed oil saturation plot from RESULTS 3D, select an area in the model that has both high oil saturation, and low well density. Once the area for the new horizontal has been selected, click once to add the first perforation. Move the mouse to a position approximately near the end of the 1000m horizontal well and click a second time. Click OK to exit. 15. Well W11 should have appeared on your display. You can also view it in JK cross section around plane 12. Note, the exact grid block position may vary slightly from that displayed below:

FIGURE 30: Areal View (IJ-2D) of Trajectory for W11 Tutorial STARS BUILDER_Revised_Nov_2007.doc

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W11 3 , 0 0 0

0 0 0 , 3

3 , 1 0

0 0 1 ,

FIGURE 31: Cross Section View (JK-2D) of Trajectory for W11 16. Note that the perforation will appear and disappear depending on the date you have displayed in Builder.

Left double click on well W11 to see that there is one date associated with it 1991-12-01. If there is also the simulation start date 1991-01-01 then select this date in the tree view, right mouse click and select "Delete". This will remove this unwanted date. 17. “Well 11” is now fully defined. We save the dataset as Tutorial_Pred1.dat, and exit. Now run in STARS the dataset and compare it with tutorial_pred.dat. Look at the oil saturation at the end of the simulation in Results 3D and the Field oil production rate in Results Graph. Note the increased production when the horizontal well opens. Also, oil left in the southern anticline decreased when viewed in Results 3D.


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Extra Exercises

Who gets more oil???? Now we are going to apply what we have learned in this class. You should implement everything you have learned in order to get a history match and perform predictions to produce as much oil as you can at an economic rate. STEPS: 1. Get a History match until 1991-09-01, in order to do that you might consider using: a.

Aquifer

b. Volume Modifiers c.

Property modifications

2. After you get a "decent" history match you should create a restart file, so you can start doing predictions 3. Run your predictions up to 2005-09-01, and save the file as Predict_your_name.dat, so we can compare the results. 4. In order to run your predictions, consider: a. Drilling new wells b. Inject water c.

inject gas

d. Change well constrains 5. Remember, try to get as much oil out as possible, but don't go crazy drilling wells, the project has to be economic, so you are only allow to drill a max of 3 wells including injectors and producers.

GOOD LUCK !!


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Create a Pattern Steam Model Open BUILDER 1. Open Builder by double clicking on the appropriate icon in the Launcher. 2. Choose: •

STARS Simulator, SI Units, Single Porosity

•

Starting date 2005-01-01

3. Click OK twice.

Create an STARS Heavy oil Dataset Using ‘Quick Pattern’ 4. Click Reservoir (on the menu bar or in tree view) and Create Grid. 5. Select Quick Pattern Grid and enter the following: Note : units will be applied automatically Pattern Type: Normal 5-spot

Top of Reservoir: 500 (m)

Pattern Area: 10 (acres)

Approx. Block Thickness: 4 (m)

Thickness of Reservoir: 30 (m)

Approx. Block Size in X,Y: 6 (m)

6. Click Calculate. The results from your input will be displayed. 7. Click OK. 8. Click on the “Specify Property” button (top middle of screen) to open the General Property Specification spreadsheet as shown below.

FIGURE 1: General Property Specification Spreadsheet 9. In the box for whole grid , input 0.3 for Porosity, 400 (mD) for Permeability I and J, and 40 (mD) for Permeability K. 10. Press OK to leave the General Property Specification section and OK again to Calculate Property.

11. Under Reservoir in tree view menu, double click on Thermal Rock Types, click the botton at the top with the arrow and select New Thermal Rock Type. Then, select the Rock Compressibility


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tab and input 1.8E-5 in the Formation compressibility box, 8576 kPa in the porosity reference pressure box.

12. Go to the Thermal Properties tab and input the following: •

Volumetric Heat Capacity (ROCKCP) 2.35E+06 J/(m3*C)

•

Thermal Conductivity of Reservoir Rock (THCONR) 6.6E+05

•

Thermal Conductivity of Water (THCONW) 5.35E+04

•

Thermal Conductivity of Oil (THCONO) 1.15E+04

•

Thermal Conductivity of Gas (THCONG) 4000

FIGURE 2: Thermal Rock Types 13. Go to the Overburden Heat Loss tab and input the following for both Overburden & Underburden: •

Volumetric Heat Capacity: 2.35E+06 J/(m3*C)

•

Thermal Conductivity: 1.5E+05 J/(m*day*C)

Generate STARS Fluid Model Properties From Black Oil PVT Correlations 1. There are several options available for creating a fluid model. If a PVT analysis exists, the data may be entered directly or copied and pasted from a spreadsheet file. Alternatively, CMG's WINPROP software may be used to generate PVT data in a compatible format. Here, we will assume that limited data is available. 2. Given that a gas cap exists, it will be assumed the reservoir fluid is at saturated conditions and the initial measured datum pressure of 8576 kPa represents the bubble point. The API gravity is 21°, gas specific gravity is 0.65 and the live oil viscosity is 120 cp. Initial production testing showed a producing GOR of 30.7 m3/m3. Tutorial STARS BUILDER_Revised_Nov_2007.doc

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3. Click on the Components right arrow and select Import Blackoil PVT. Select Units SI, enter the reservoir temperature of 37.7778 C (100 F). Click the button Launch the Black Oil PVT Graphical User Interface (GUI) . 4. Click the Tools button and select Generate PVT Table Using Correlations . 5. Enter the reservoir temperature of 100 °F (37.7778 °C) and a maximum table pressure value of 12000 kPa (maximum expected pressure in the model). Initially, we will assume the bubble point pressure is valid and will enter 8576 kPa in row 3 from the drop down menu under Value provided. Select Stock tank oil gravity (API) from the drop down menu for row 4 and enter a value of 21. Similarly for row 5, select Gas gravity (Air=1) and enter a value of 0.65. Leave the rest as default, but make sure to check the box at the bottom Set/Update values of Reservoir Temperature, Fluid Densities in Dataset. The panel should look like the picture below..

6. Click OK and answer No to the question about using oil compressibility in the PVT table. The PVT table should now be generated. 7. Examine the PVT table values to check the values of Rsi and Boi. Note the value of Rsi is acceptably close to the field measured value of 30 m3/m3 at the bubble point of 8576 kPa. Note the oil viscosity is in the order of 10 cp, much lower than the data value of 120 cp.


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8. Click on the oil viscosity column (viso). Then select Tools and Shift Column values to Match and enter the Pressure and Column values as 8576 and 120, respectively. Note that in the PVT Table, there is a new row at a pressure of 8576. Note the values at the bubble point pressure are as expected. Select OK. 9. Select the General tab click the Tools button and select Generate Water Properties Using Correlations. Enter a Reference pressure of 8576 kPa and check the box Set/Update values of TRES and REFPW in PVT Region Dialog. The panel should look like the following.

10. Click OK to exit back to the IMEX Black Oil PVT dialog. Enter an Under Saturated Oil Compressibility of 1.0e-5 1/kPa and a value of 0.0 for the water viscosity pressure dependence. Click OK to exit back to the STARS Black Oil PVT Conversion wizard. The panel should look like the following:


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11. In the Bubble Point Pressure section of the panel, click on Select From Table and click on the grey box next to the 8576 kPa value in the pressure column. Click on Next> which take you to Step 2. Note the various elements that have been selected by default. We will accept these selections/values, but in reality, they may be changed by the user. 12. Assuming we have a measurements of dead oil viscosity as follows: Temperature, C

Dead Oil Viscosity, cp

37.0

420

50.0

340

70.0

250

Enter these values in the table. Note that under the Component System part of the panel, we are creating a live oil system. Also in the Gas K Value Temperature Dependence part of the panel, we are accepting the default value. This value controls the behavior of the bubble point and GOR when temperatures are changed. Click Next>. A message will appear regarding the thermal expansion coefficient with a default value that we will accept. Click OK which takes you to Step 3 (Check Matches of PVT Properties). 13. Move this panel to the side to enable viewing of the match plots. Note the Match error values shown in the Step 3 panel. Check the match quality by expanding and clicking on the various available plots. Matches are acceptable, given the limited PVT data available. Note that the Gas Viscosity plot appears not to match. This is because the STARS uses an effective liquid viscosity for gas in the liquid phase. Tutorial STARS BUILDER_Revised_Nov_2007.doc

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14. On the Step 3 panel, select Next> and note the mole fractions vs. pressure (bubble point pressure). You should find that the mole fractions appearing in the data set correspond to those in the table at a pressure of 8576 kPa (saturation pressure).

15. Click Finish. Note that in the tree, the Components tab now has a green checkmark. 16. Save your dataset as Tutorial_Stars.dat.

Creating Relative Permeability Data 1. Click the Rock-Fluid tab in the tree view. 2. Double click on Rock Fluid Types in the tree view. A window will open. Click on the

button and

select New Rock Type. 3. Press the Tools button (on the Relative Permeability Tables tab) and select Generate Tables Using Correlations.

Enter the following parameters for the analytical relative permeability curves generation: SWCON SWCRIT SOIRW SORW SOIRG SORG

0.3 0.3 0.0 0.4 0.0 0.45

SGCON SGCRIT KROCW KRWIRO KRGCL

0.00 0.05 1 1.0 0.3

All Exponents

2.0


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4. Press Apply and then OK. Press OK again to get out of the Rock Types window. A graph containing the relative permeability curves will appear. The Rock Fluid section should have a green check mark.

Temperature Dependent Relative Permeability 1. The relative permeability curve endpoints we have in the models are typical for reservoir temperature displacement, but may be a little pessimistic for hot water or steam. Since STARS can model this dependency, let’s add it to one of the models. From the top menu, select Rock-Fluid->Create/Edit Rock Types. 2. Note the value of Sorw & Swc @ 37.778 C.

Swc=0.3

Water oil table has an Sorw value of (1-0.60) = 0.40


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3. Do the same for the Liquid-Gas table

Sorg = Slc – Swc = 0.750 – 0.3

4. From the Rock Types panel that comes up, Click on the Relative Permeability End Points tab. 5. Ensure there are 2 Temperature Intervals specified and enter the minimum and maximum values for the temperature range as 37.7778 and 325.0, respectively. These temperatures will then show in the lower table. Comments may be added at this point. 6. To overwrite individual critical saturation and endpoints from the original tables, Click on the blue triangle for whichever parameter is to be changed and from the drop down menu, select Temperature dependence. Here, we will change SWR, SORW and KRWRO. The values at 37.7778C will be the ones in the original tables. The values at 325C are to account for changes due to steam injection. Columns will appear in the KRTEMTAB table and should be filled in as follows:


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Parameter SWR

SORW SORG KRWRO

T=37.7778 0.3

0.4

0.45

0.3

T=325.0

0.2

0.05

0.4

0.4

7. Click OK. To view the effect on the relative permeability curves as a function of temperature, Click on Rock-Fluid, then the right arrow and select Diagnostic Plots. Toggle the Oil Water and Gas Oil buttons. This allows you to see the effect of the endpoint changes. In the case of multiple rock types, if you click on Reservoir to display any property and have the Rock Fluid Diagnostics panel open, clicking on any block will change the diagnostic plot to show that corresponding to the UBA. 8. Pick the Ternary display. Note that only one temperature at a time can be selected. Check that the Kro (intermediate phase relative permeability) does not touch the zero oil saturation line at either temperature. If it does, the Stone 2 formulation has failed and another 3-phase relative permeability option should be chosen.


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9. Diagnostic plots at 325 C.

Check Kro is zero inside the graph boundary

10. If you wish, change the 3 phase relative permeability option and rerun the case and compare with the previous steam flood result.

Modifying Relative Permeability Curves for Steam Injection (compositional dependence) Note: With steam injection, it is usual to expect changes in end-point saturations as a function of temperature. This is accomplished using the tabs available in the Rock-Fluid section.


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Additionally, it is recognized that the flow properties of injected steam are much different than the flow properties of evolved solution gas. When gas comes out of solution, the smallest pores are occupied by gas first and have the highest gas saturation. When gas or steam is injected, it is the largest pores that are occupied first. Therefore, it is expected that flow properties between the two cases should be different. This is accomplished in STARS using relative permeability interpolation which is based on the composition of the water component in the gas phase as the interpolation parameter. If the composition of water in the gas phase (steam) is low, then the low relative permeability curves associated with gas evolution are used. If the composition of water in the gas phase is large, the high relative permeability curves associated with gas or steam injection are used. 1. Basically, the two curves generated by changing the temperature dependent endpoints represent two different temperature regions in the reservoir. They do not reflect the fact that phase composition may also affect relative permeability. At original reservoir temperature, the curves apply to a region in which steam is absent (solution gas only in the gas phase); at high temperature, the curves apply to the region heated by steam (which may, or may not, have a high concentration of the water component in the gas phase). Depending on whether or not a region contains principally water or solution gas in the gas phase, we would like to apply a different gas relative permeability curve. This is done using the interpolation option. Note that this option is currently only available for water-wet systems. 2. Click on Rock-Fluid and the right arrow to bring up Create/Edit Rock Types. Select the Rocktype Properties tab and check “Use Interpolation sets”. Also, enable interpolation components (INTCOMP) as shown in figure below. Set the component for interpolation as WATER and the Phase from which component's composition will be taken as gas mole fraction.


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3. Goto the “Interpolation set parameters” tab and input a value of 0.2 for DTRAPW and DTRAPN. This means if the water mole fraction in the gas phase is less than 0.2 (no contact with steam), the first table will be used.

4. Go to “Relative Permeability Tables” tab. Click on the arrow on the right of the “Interpolation sets” and select Copy Current Interpolation Set. This will create a second interpolation set which is a copy of the first which we can modify. 5. Now click on Relative Permeability Endpoints and for set #1 overwrite the table value of Krgcw with 0.01. For set #2, overwrite the table value of Krgcw with 1.0.

6. Keeping the “Interpolation sets” selected as 2, goto Relative Permeability End Points tab and input values of temperature dependence similar to step 4 described above.


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7. Also, input the interpolation set parameters for interpolation set 2. Set the DTRAP values to 0.6. This means if the water mole fraction in the gas is greater than 0.6, the second table will be used (with higher gas relative permeability as shown in the next step). For water mole fraction values between 0.2 and 0.6, an interpolation between the two relative permeability curves will be made. 8. Finally, apply cubic endpoint smoothing to all curves by selecting each set and setting the cubic smoothing option. Click OK to exit.

9. View the diagnostic plots from Rock-Fluid, right arrow for both Oil Water and Gas Oil buttons.

10. Save the data set.


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Creating Initial Conditions 1. Click the Initial tab on the tree view of Builder. 2. Double click on Initial Conditions. 3. Select Water, Oil, Gas as the initial fluid in the reservoir to perform a Gravity-Capillary Equilibrium Calculation. 4. Type the following values in the available fields: 8576 (kPa implied) for Reference Pressure 504 (m implied) for Reference Depth 526 (m implied) for Water-Oil Contact 504 (m implied) for Gas-Oil Contact 5. Click on Apply; then OK. You should now be back in the main Builder window with all tabs showing a green checkmark in the tree view, except for the “Wells & Recurrent” tab.

Create Numerical Controls 1. Go to the Numerical tab in the tree view. Double Click on Numerical Controls. Press OK to the warning that pops up. 2. In the DTWELL box, type 1E-3. 3. In the UPSTREAM box, select KLEVEL.

Complete the Well Perforations 1. In the tree view press the Wells & Recurrent tab. 2.

Expand Wells, expand Injector 1, and double click on 2005-01-01 PERF.

3. Go to the Perforations tab. 4. We want to limit the perforations for the injectors so that they do not inject at the top of the formation, since steam over-ride will always occur and it is better to inject steam lower down in the formation. Under User Block Address, by clicking with your mouse and holding down the Ctrl key to select multiple items, highlight layers 1 to 3. Click on the

button to delete these layers. Note: The deleted layers include the gas zone.

This is what we want to isolate. 5. Click Apply. 6. Repeat these steps to delete the top perforations for all other injectors (i.e. Injector 2 – 4) by selecting each well from the drop down box under Well& Date:.


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FIGURE 3: Drop down box 7. We want to limit the perforations of the producer so that production does not occur from either the gas cap or the water zone. Delete the perforations in layers 1 to 3 and layers 7 and 8. 8. Click OK and save your file.

Adding Operating Constraints 1. In the Wells & Recurrent tab, expand Wells and double click on Injector 1. 2. Check the Auto-apply box at the bottom of the window. This will insure that all changes are applied automatically.

3. Go to the Constraints tab. 4. Under select new (in the Constraint column of the table), select OPERATE. Then select BHP bottom hole pressure, MAX, 12000 kPa, CONT REPEAT. 5. Repeat the previous step to add another operate constraint, except this time select STW, MAX, 250 m3/d, CONT REPEAT. 6. Go to the Injected Fluid tab and choose Water as injection fluid. Enter the water composition as 1.0 for component Water. Enter the Temperature of 325 C and steam quality of 0.8. 7. Now, we can copy all the above specifications to the other injectors. To do that, make sure you are looking at “Injector 1” in the Name/Date list. Then highlight the following Events (for Injector 1) using your mouse and the Ctrl key: INJECTOR, constraints, and injected fluid. Press the Tools button at the bottom of the screen, and select Copy events using filter. This will open a new window


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FIGURE 4: Constraints and Injected Fluid 8. In the 1.-Select Wells tab, under Auto Select Wells, click on Injectors and press the Select button. 9. Then go to the 2.-Select Dates tab. Under Auto select dates, check All and press the Select button. Then press the Search & Add button. 10. Click OK and the same constraint information created for Injector 1 will now be copied to all injectors. Click OK again. 11. Now double click on Producer 1 and set the operate constraints the same way as in steps 2 – 5. •

BHP, MIN, 200 kPa, CONT REPEAT

•

STL, MAX, 100 m3/d, CONT REPEAT

12. Click OK.

Adding Dates 1. In the Wells & Recurrent tab, double click on Dates. 2. Click on

to Add a range of dates. Choose From: 2005-01-01, To: 2010-01-01, by Month. Click OK

and click OK again to the message that appears. 3. In the set STOP column, check on 2010-01-01 so the simulator knows to stop at this date. Click on Close.

Outputting Basic Properties and Well Information 1. Click on I/O Control in the tree view. 2. Double click on Simulation Results Output. 3. Under the OUTSRF section, change the “Well” Information to All well values (ALL). 4. For “Grid” Information press the Select button and a new window should pop up. 5. Check the boxes for the following (if not already checked): Oil saturation (SO) Comp. comp. in gas phase (Y) Gas saturation (SG) Comp. comp. in oil phase (X) Tutorial STARS BUILDER_Revised_Nov_2007.doc

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Water saturation (SW) Temperature (TEMP) Pressure (PRES)

Viscosity (VISO) Oil density (MASDENO) Water, oil, gas relative perms (KRW,KRO,KRG)

6. Review the variable description list and select any other output which may be of interest. Note that this will increase the size of the output files. 7. Click on the green + under OUTSRF and add Well information for COMPONENTS ALL. Do this again and add LAYER ALL.It should look like the figure below when you are done.

FIGURE 10: I/O Control 8. Press OK to get back to the main Builder. 9. All tabs in the tree view of Builder should now have green checkmarks. Save the file.

Validate Dataset Using Builder 1. Right click the white space in the tree view and select Validate. A window will pop up letting you know the status of your input information. 2. Another method can be used to validate your data file. Click the Validate With STARS button near the top of Builder. 3. A message will prompt you to save. Do so if you have not already saved and a new window will appear. 4. Check Validate and press the Run/Submit button. Note :

The simulator can also be fully run at this point by choosing Run normal instead of Validate ; however the results can only be viewed in this window.

5. A brief output will be displayed, listing any warnings or errors with the dataset. Press Close. 6. Fix any warnings or errors; otherwise save your dataset and exit Builder.


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Running the Simulator 1. Go to Launcher and drag & drop Tutorial_Stars.dat into the STARS 2007.10 icon. A new window will pop up. Press the Submit Job button. 2. On the CMG Job Scheduler, right click on the job and select “View Log File”. When the run is finished, a brief summary of results will be displayed.

FIGURE 5: Log File Summary 3. Check to make sure initial conditions are as expected by reviewing the .out file which was created during the run. The file can be viewed by using an editor (TextPad, PFE32 , or Notepad ). 4. Note that if you see the following message at the end of the run, that the data set should be re-run using higher values of ITERMAX and NORTH (numerical section). ============ WARNING (from subroutine: PRTOUT) ======================= Fraction of Newton iterations with matrix solver failures (38%) is too large. Simulation result may not be valid. ======================================================================

5. Open Results Graph and create 3 plots per page (Properties->Page Layout->Plots Per Page, 3 rows, 1 column), and show 1 curve in each plot: •

Cumulative Oil SC for group “Default-Field-PRO,

•

Water Cut SC for group “Default-Field-PRO”,

•

Cumulative Water SC for group “Default-Field-INJ,

Make sure to save the template file in Graph.


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Default-Field-PRO FiveSpot.irf 40,000

) 30,000 3 m ( C S l i O20,000 e v i t a l u m u10,000 C

FiveSpot.irf

0 2005-7

2006-1

2006-7

2007-1

2007-7 Time (Date)

2008-1

2008-7

2009-1

2009-7

2010-1

2009-7

2010-1

1.00

0.80 FiveSpot.irf

C S0.60 t u C r e0.40 t a W 0.20

0.00 2005-7

2006-1

2006-7

2007-1

2007-7

2008-1

20 08-7

2009-1

Time (Date) 2.00e+5

) 3 1.50e+5 m ( C S r e t a1.00e+5 W e v i t a l u 5.00e+4 m u C

FiveSpot.irf

0.00e+0 20 05-7

2006-1

2006-7

2007-1

2007-7

2008-1

2008-7

2009-1

2009-7

2010-1

Time (Date)

6. Open Results 3D and note the temperature distribution in the reservoir. Temperature (C) 2010-01-01

0

K layer: 5

100

200

0

0

Injector 1

Injector 4

325 296 267 239 1 0 0

0 0 1 -

Producer 1

210 181 152 123 95 66

2 0 0

Injector 3 0


Injector 2 100

0 0 2 -

37

200

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7. Examine the steam flood behavior in Results 3D. Change the view to be 3D, change the property to be temperature and use the cutting plane tool to cut the reservoir diagonally through 2 injectors and the middle producer.

8. Change the property to be Ternay. Probe the blocks and examine the saturations. Add extra properties onto the Probe display by selecting Properties->Probe Display, check the box Other spatial properties at the same time, and add: Gas Mole Fraction (SolnGas), Gas Mole Fraction (SolnGas), Gas Relative Perm, Oil Relative Perm, Ternary, Temperature and Water Relative Perm. Verify that the gas relative perms are the expected values based on the gas composition. Verify that the oil and water relative perms are the expected values based on temperature.


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Building a Cyclic Steam Simulation Model in STARS 1. For cyclic steam there must be an injection well and production well located in the same location. Therefore, rename the well “Producer 1” to “Producer 5”. Then from the wells menu select “Copy well”. Select “Injectors” and make sure all 4 injectors are selected. Click Next and make sure “Copy all perforations” is selected. Click Next. Check the “Copy Geometry” option and click Next and Next again. Select the option “I will manually enter the new well name on the next step”. Click Next. Enter the names Producer 1 through 4 as shown below and click Finish.

2. Repeat the above “Copy Well” procedure again but copy the well “Producer 5” and rename the new well to be “Injector 5”. 3. Now using the “Copy Events” tool, copy the injector definition, constraints, injected fluid, steam quality and steam temperature to the new well “Injector 5”. 4. Using the “Copy Events” tool, copy the producer definition and constraints to the 4 new producers. 5. Click OK and save the data set. 6. We now have a complete data set BUT - all the wells are open at the same time. 7. We can use this data set to create a number of data sets which can investigate both CSS and alternative processes such as primary, water flood, and steam flood 8. There is also some customizing we need to do depending on the process we are going to investigate. 9. We need to ensure that only one well in a pair is open at the start. SHUTIN all the producers. From Wells & Recurrent, double click Wells, select the first producer, select Options, and SHUTIN the well. Repeat for the other 4 producers, either by copying or doing each individually. 10. Make sure the data set is saved and exit Builder. 11. We need to define cyclic groups (producer/injector pairs). We need to do this in a text editor. We need to define cycle parameters for forecasting. 12. Find the data set in Launcher and open it in a text editor. 13. Search for the second DATE line. This should be DATE 2005 2 1. Immediately before this is where we want to add the cyclic information so that it is read at the start. There are four steps: •

Defining the groups

•

Setting cycle injection constraints

•

Setting cycle soak constraints

•

Setting cycle production constraints


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14. Note: if you are matching historical cycling data you would import these data into Builder in the normal way and the switching between injection and production will be controlled by the data. This is no different from any other history match and does not require a special approach. What we are doing is what is required in order to forecast cyclic steam performance. 15. For

cyclic

groups,

add

the

following

lines

(can

be

copied

and

pasted

from

the

file

“Tutorial_CYC_DEFINE.INC”: CYC_GROUP 1 INCLUDES 'Injector 1' 'Producer 1' CYC_GROUP 2 INCLUDES 'Injector 2' 'Producer 2' CYC_GROUP 3 INCLUDES 'Injector 3' 'Producer 3' CYC_GROUP 4 INCLUDES 'Injector 4' 'Producer 4' CYC_GROUP 5 INCLUDES 'Injector 5' 'Producer 5' ** Cyclic group injection controls INJ_C_SWT 1:5 TOT_TIME 60 **Maximum injection period, days DTWCYC 0.001 **Time step size for starting injection, days ** Cyclic group soak controls IN_PR_SHUT 1:5 **All wells shut TOT_TIME 5 **Soak time, days DTWCYC 0.01 **Initial time step size, days ** Cyclic group production controls PROD_C_SWT 1:5 TOT_TIME 730 **Maximum production period, days DTWCYC 0.01 **Time step size for starting production, days 16. Save the data set and close the editor. Load the data set into Builder. Click the Wells & Recurrent button, then right click in the white space in the tree view and select. Display dataset for section. Scroll down and note the Cyclic Group information is still there. Click “Validate with STARS” and run the data set.


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17. Open the Graph template previously saved with the steam flood injection run and add the curves from the cyclic steam injection case onto the plots so that the 2 cases can be compared. 18. Note that the cyclic steam injection case results in higher oil recovery than the steamflood case. Also note the behavior of cyclic steam in later cycles. What do you think will occur in later cycles of steam injection? Default-Field-PRO FiveSpot.irf 40,000

) 330,000 m ( C S l i O20,000 e v i t a l u m u10,000 C

FiveSpot.irf FiveSpot_CSS.irf

0 2005-7

2006-1

2006-7

2007-1

2007-7 Time (Date)

2008-1

2008-7

2009-1

2009-7

2010-1

2009-7

2010-1

1.00

0.80 FiveSpot.irf FiveSpot_CSS.irf

C S0.60 t u C r e0.40 t a W 0.20

0.00 2005-7

2006-1

2006-7

2007-1

2007-7 Time (Date)

2008-1

2008-7

2009-1

2.00e+5

) 3 1.50e+5 m ( C S r e t a1.00e+5 W e v i t a l u 5.00e+4 m u C

FiveSpot.irf FiveSpot_CSS.irf

0.00e+0 2005-7

2006-1

2006-7


2007-1

2007-7 Time (Date)

2008-1

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2009-1

2009-7

2010-1

56

Water Flood 1. Close the Validation window in Builder and close Builder. We now want to look at water flood with one central injector. To do this we can use the steam flood data set and change the water injection temperature to 37.7778 C and the quality to 0, so this is quite simple. 2. Open the steam flood data set in Builder and save it to a different name. From Wells & Recurrent, expand Wells and double click on “Injector 1”. Click “stream temperature” and change it to 37.7778 C. Change the ‘steam’ quality to zero. Click Apply, then copy the stream quality and steam temperature values to the 3 other injection wells. Save and run the data set. 3. Add this run to Graph using the template previously saved. Compare the water flood to the steam flood and cyclic steam results. 4. Close Graph and Results 3D. Back in Builder, close the Validation screen. We have now completed all the basic thermal requirements to build and run several models, including CSS, based on an inverted 5-spot configuration. There only one other thing we should do to complete the coverage of this topic: •

Model primary production from the 5-spot

Primary Production 5. Finally, let’s look at primary production to see how well the field performs under primary with no pressure support. For primary production we need to do two things: •

Shut in the injectors

•

Monitor the producers for a minimum oil rate and shut them in when it is reached

6. Open the data set “Tutorial_Stars_CycSteam.dat in Builder and save it with a new name. Go to the Wells tab and double click on one of the corner injection wells. •

Select the Options tab.

•

Check Status and change it to SHUTIN.

•

Repeat for the other injectors.

7. Open all producer wells by selecting the SHUTIN keywords for these wells in the tree view and select Tools->Delete Events Selected in the List. 8. To monitor oil rate we need to add a MONITOR constraint to each producer. •

When the oil rate falls to 1 m3/day for the central well, or ¼ of that for the corner wells, they should be SHUTIN

•

This constraint can be set immediately or after a period of time a. If set immediately, use of the STODWN keyword is recommended. This requires the well to exceed this rate before the constraint is activated. b. If set after a period of time, either the STODWN or STO constraint can be used. STO is effective immediately.

9. Select the Constraint tab for well Producer 1. Select the date 2005-01-01. Check “Constraint definition”. Add a new MONITOR constraint for STODWN of 0.25 m3/day with the action of SHUTIN. 10. Copy these constraints to other producers. In the tree view make sure “constraints” from well Producer 1 is selected, click the tools button and select “Copy events using filter”. Tutorial STARS BUILDER_Revised_Nov_2007.doc

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11. Select all producers, date at 2005-01-01, Search & Add, OK.


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3－Tutorial STARS BUILDER Revised Nov 2007

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