OLGA Sample Cases

DYNAMIC MULTIPHASE FLOW SIMULATOR

OLGA 2015 Version 2015.1

Sample cases

Table of contents

Table of contents Copyright notice ................................................................................................. 4 Sample cases..................................................................................................... 5 Basic case .......................................................................................................... 8 Basic network case ............................................................................................ 9 Empty Case...................................................................................................... 10 Blackoil ............................................................................................................. 11 Compositional mud tracking ............................................................................. 13 Compositional tracking ..................................................................................... 15 Tracer tracking ................................................................................................. 17 MEG tracking ................................................................................................... 19 Compositional - Single-CO2 ............................................................................. 20 H2O tracking (Single component) ..................................................................... 22 Compositional - Steam/Water-HC .................................................................... 23 Drilling .............................................................................................................. 25 Advanced well .................................................................................................. 26 Corrosion.......................................................................................................... 28 Drilling fluid....................................................................................................... 30 Hydrate kinetics ................................................................................................ 32 Network ............................................................................................................ 34 Particle flow ...................................................................................................... 36 2nd-order scheme ............................................................................................. 37 Water options ................................................................................................... 40 Wax deposition ................................................................................................. 41 Backpressure IPR ............................................................................................ 42 Well Forchheimer IPR ...................................................................................... 43 Linear IPR ........................................................................................................ 44 Normalized backpressure IPR .......................................................................... 45 Quadric IPR...................................................................................................... 46 Single Forchheimer IPR ................................................................................... 47 Tabular IPR ...................................................................................................... 48 Undersaturated IPR ......................................................................................... 50 Vogels IPR ....................................................................................................... 51 Network server ................................................................................................. 52 PID-net-gainsched-normrange-server .............................................................. 53 Server demo with OPC..................................................................................... 56 Pigging ............................................................................................................. 57 Sand in water ................................................................................................... 64 OLGA Compressor control ............................................................................... 68 Compressor manual controls ........................................................................... 69 Jet pump .......................................................................................................... 70 PID controller ................................................................................................... 72 Process equipment .......................................................................................... 74 Centrifugal pump .............................................................................................. 76 Displacement pump ......................................................................................... 78 Simplified pump ................................................................................................ 80 Separator ......................................................................................................... 82 OLGA Single separator 3-phase compressor................................................... 83

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OLGA GUI user manual

Source, leak and choke .................................................................................... 85 Well ESP .......................................................................................................... 87 Well-GLV .......................................................................................................... 91 Well-pressure boost ......................................................................................... 93 Pump battery .................................................................................................... 95 Centrifugal pump .............................................................................................. 97 Displacement pump ......................................................................................... 99 Simplified pump .............................................................................................. 101 OneSubsea pump .......................................................................................... 103 OneSubsea pump - Start-up procedure ......................................................... 106 OneSubsea pump - Trip procedure ................................................................ 108 Hydrodynamic slugging .................................................................................. 109 Start-up slug ................................................................................................... 111 Submodelling ................................................................................................. 113 Fluid bundle.................................................................................................... 115 Solid bundle ................................................................................................... 117 Valve model ................................................................................................... 120 Critical two-phase valve flow .......................................................................... 122 Subcritical valve flow of a flashing liquid ........................................................ 123 Valve recovery ............................................................................................... 124 Valve slip ........................................................................................................ 125 Thermal equilibrium in valve flow ................................................................... 126 Gas lift well casingheading ............................................................................. 127 Gas well liquid loading.................................................................................... 129 Well clean-up ................................................................................................. 131 Well dry tree ................................................................................................... 133

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Table of contents

OLGA Sample cases manual The complete program documentation includes: 

OLGA Release notes

 

OLGA user manual OLGA GUI user manual

 

OLGA Sample cases (this document) Well editor user manual

 

OLGA Viewer user manual Pipeline editor user manual

 

Profile generator user manaul FEMTherm editor user manual

 

OLGA OPC server guide OLGA Submodelling guide

 

OLGA Namespace Explorer guide Installation guide



Rocx User manual

All documents listed above are available from the Start menu (Start - All Programs - Schlumberger - OLGA x.x.- Documentation). The OLGA User manual is also available from the Help menu in the GUI. User Manuals for other tools included with the installation (e.g. FEMTherm, Rocx, OLGA Namespace Explorer, etc.) are available from the Help menus in the tools. Release information Please refer to the Release notes for detailed release information. Online help OLGA is equipped with a context sensitive help document which can be opened directly from the user interface. The help can be reached in several ways: 

Click the Properties view and press F1 -> leads to the information on the relevant model

 

Select Help from the File menu Select the Help icon in the upper right corner of the OLGA main window.

Operating system The program is available on PCs with Microsoft Windows operating systems (Windows Vista, Windows 7, Windows 8, Windows Server 2008 and 2012). Several versions of OLGA may be installed in parallel. Support centre The Support Portal provides useful information about frequently asked questions and known issues. Please contact OLGA support if problems or missing functionality are encountered when using OLGA or any of the related tools included in the OLGA software package.

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Copyright notice Copyright © 2015 Schlumberger. All rights reserved. This work contains the confidential and proprietary trade secrets of Schlumberger and may not be copied or stored in an information retrieval system, transferred, used, distributed, translated or retransmitted in any form or by any means, electronic or mechanical, in whole or in part, without the express written permission of the copyright owner. Trademarks & Service Marks Schlumberger, the Schlumberger logotype, and other words or symbols used to identify the products and services described herein are either trademarks, trade names or service marks of Schlumberger and its licensors, or are the property of their respective owners. These marks may not be copied, imitated or used, in whole or in part, without the express prior written permission of Schlumberger. In addition, covers, page headers, custom graphics, icons, and other design elements may be service marks, trademarks, and/or trade dress of Schlumberger, and may not be copied, imitated, or used, in whole or in part, without the express prior written permission of Schlumberger. Other company, product, and service names are the properties of their respective owners. An asterisk (*) is used throughout this document to designate a mark of Schlumberger. Security Notice The software described herein is configured to operate with at least the minimum specifications set out by Schlumberger. You are advised that such minimum specifications are merely recommendations and not intended to be limiting to configurations that may be used to operate the software. Similarly, you are advised that the software should be operated in a secure environment whether such software is operated across a network, on a single system and/or on a plurality of systems. It is up to you to configure and maintain your networks and/or system(s) in a secure manner. If you have further questions as to recommendations regarding recommended specifications or security, please feel free to contact your local Schlumberger representative.

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Sample cases

Sample cases The OLGA installation includes a set of sample cases. They can be accessed from the New page in the GUI. The sample cases are organized in projects as follows: Basic projects Basic case Basic network case Basic empty case Compositional projects Blackoil Compositional tracking Compositional mud tracking Tracer tracking MEG tracking CO2 tracking (Single component) H2O tracking (Single component) H2O tracking (Steam/Water–HC) Drilling projects Drilling FA-Models project Advanced well Corrosion Drilling fluid Hydrate kinetics Network Particle flow 2nd-order scheme Water options Wax deposition IPR projects Backpressure IPR ForchheimerIPR LinearIPR Normalized Bakpressure IPR Quadric IPR SingleForchheimerIPR Tabular IPR Well Undersaturated IPR Vogels IPR

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OPC server projects Network server PID controller Server demo with OPC Pigging projects Pigging (with and w/o tracking of slug and with and w/o Compositional Tracking) Plug-in projects Plug-in hydrate formation Plug-in_sand in water Process projects Compressor control Compressor manual control Jet pump PID controller Process equipment ESP Separator Single separator 3-phase compressor Source, Leak and Choke Well GLV Well and Pressure Boost Pump projects Pump battery Centrifugal pump Displacement pump Simplified pump OneSubsea pump OneSubsea pump: Start-up procedure OneSubsea pump Stop procedure OneSubsea pump: Trip procedure Slug tracking projects Hydrodynamic slugging (with and w/o Compositional tracking) Start-up slug (with and w/o Compositional tracking) Submodelling projects Submodelling Thermal Advanced projects Fluid bundle Solid bundle

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Sample cases

Valve project Valve samples Well project Gas lift well casing heading Gas well liquid loading Well Clean-up Well Dry Tree

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Basic case This sample case generates a complete basic case - ready for simulation. The case consists of a single flowpath with a closed inlet node and a pressure outlet node. A source is defined in the first section of the pipeline.

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Basic network case

Basic network case This sample case generates a simple network case consisting of two flowpaths leading into an internal node which again is connected to a third flowpath. There are no sources, instead the inlet nodes are massflow nodes.

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Empty Case The OLGA Empty case sample is used to create new case with no predefined content. All information must be given from scratch.

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Blackoil

Blackoil The case Blackoil.opi demonstrates the Blackoil model. 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 model, 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file every hour.

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TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes. PROFILEDATA: Pressure, temperature, liquid holdup, overall mass flow and gas mass flow are plotted.

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Compositional mud tracking

Compositional mud tracking The sample case CompositionalMudTracking.opi simulates a gas kick in a well filled with oil based mud. Activating the compositional option allows for modelling of the partial dissolution of gas in the mud. The system consists of a 3000 m deep well and two sources near the bottom of the well. The bottom most source S-OBM produces a stable flow of oil based mud. The other source, S-KickGas, releases a gas flow in a given period. Operation scenario: The Steady state preprocessor is run with flow of mud only, and then the dynamic simulation is started with the same stable flow of mud. In the period 3-6 minutes after start, gas is released through a separate source to simulate a kick. The simulation continues until the gas has reached the surface. The transport of the kick gas as partially free gas and partially dissolved gas can be seen by inspecting the PROFILE plot variables CGG_METHANE and CGHT_METHANE, respectively.

Case comments CaseDefinition OPTIONS: The Steady state preprocessor is applied. In order to have a compositional description of mud and reservoir fluids, the drilling and compositional options are activated. FILES: A feed file, CompositionalMudTracking.mfl, generated with the Multiflash PVT package, has be specified using the key FEEDFILE. The feed file contains information about the fluids and the components used in the simulation. FlowComponent FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: A linear temperature gradient from 50°C to 4°C is assumed. FLOWPATH — Boundary&InitialConditions — SOURCE: The source S-OBM produces a steady flow of oil based mud (no gas) at 1891.43 Sm3/d. FLOWPATH — Boundary&InitialConditions — SOURCE: The source S-KickGas ramps up a flow of gas (methane) from zero to 5.14 in the period from 3-4 minutes. The rate is kept until 5 min, and is then ramped down to zero flow again at 6 min.

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FLOWPATH — Piping: The well consists of a 3000 m vertical pipe with inner diameter 0.12 m. FLOWPATH — Output — PROFILEDATA: Component mass flow rates in gas and oil phases are plotted NODE: The inlet node is closed, while the outlet node is defined with a pressure of 1 atm. Output TREND: Trend variables are plotted every 10 seconds. PROFILE: Profile variables are plotted every minute.

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Compositional tracking

Compositional tracking The sample 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 20 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 under-saturated oil. After 51 hours all the gas has disappeared and the system returns to the original steady state.

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 Multiflash 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 0.01 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 20 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.

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FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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).

Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Tracer tracking

Tracer tracking The sample 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 below. 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.

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.

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

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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=10 -7 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 flowpaths. FLOWPATH — Output — TRENDDATA - Tracer variables are plotted. FLOWPATH — Output — PROFILEDATA -Tracer variables are plotted. FLOWPATH — Output —SERVERDATA - Server variables are available for plotting in interactive simulations. NODE - The outlet pressure held constant at 30 bara and the temperature is 20°C. Output ANIMATE - 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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MEG tracking

MEG tracking The sample 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. NODE: A closed node is placed at the pipe inlet. A constant pressure is applied at the outlet. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Compositional - Single-CO2 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 FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. NODE: A closed node is placed at the pipe inlet. The outlet is a pressure boundary.

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Compositional - Single-CO2

Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file every 600 seconds. TREND: Trend variables are plotted every second. PROFILE: Profile variables are plotted every 5 minutes. PROFILEDATA: Pressure, temperature, liquid holdup, overall mass flow and gas mass flow are plotted.

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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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. NODE: A closed node is placed at the pipe inlet. The outlet is a pressure boundary.

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Compositional - Steam/Water-HC

Compositional - 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. FLOWPATH — Output —SERVERDATA - Server variables are available for plotting in interactive simulations.

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NODE - A closed node is placed at the pipe inlet. The outlet is a pressure boundary. Output ANIMATE - 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT - OLGA variables are printed to the output file every 600 seconds. TREND - Trend variables are plotted every seconds. PROFILE - Profile variables are plotted every 5 minutes.

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Drilling

Drilling The sample case Drilling.opi gives an example of a simple drilling case. The configuration includes the minimum configuration (three flowpaths) as described in the Drilling fluid - How to use section in the OLGA user manual. In this case, we have also included an internal node to connect the annulus to a return line.

The case is configured to start drilling from the top. After it reaches the bottom, the drill string is pulled up again. An oil-based mud is injected from the top, while the two wells at the bottom start producing as the corresponding sections are activated.

Case comments In order to couple the STANDNODE to the drill string, DRILLSTRING = DrillString1 is set under the STANDNODE keyword. Two ANNULUS components are defined for this case: one going from the top to the middle of the drill string geometry (ANNULUS_1), and another one going from the middle to the bottom (ANNULUS_2). It is worth remembering that Annulus1 and DrillString1 have equivalent geometries, and that the corresponding positions in Annulus1 have been used to define the ANNULUS components. Under the BITNODE keyword, we specify the drilling path by listing the mentioned ANNULUS components: ANNULUSLIST = (ANNULUS_2, ANNULUS_1). We start the case with an initial drilled depth of one meter (INITDRILLEDMD = 1 m), and we place the BITNODE at the bottom of the drilled part (INITBITMD = 1 m). The rate of penetration is defined so that after 200s the bit drills at a rate of 0.1 m/s, and then after 2000s the bit is moved up at a rate of 0.1 m/s. For this we use a time series: TIME = (0, 200, 2000) s, ROP = (0, 0.1, -0.2) m/s.

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Advanced well The sample 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations.

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Advanced well

Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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.

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Corrosion The sample 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations.

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Corrosion

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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Drilling fluid The sample case DrillingFluid.opi demonstrates 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 below. 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.

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.

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Drilling fluid

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=10 -8 kg/s/Pa and BPROD=3.5·10-6 kg/s/Pa. FLOWPATH — Output — TRENDDATA: The mass fraction of mud is plotted. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. NODE: The outlet pressure held constant at 30 bara and the temperature is 4°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Hydrate kinetics The sample 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 below. 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.

Case comments Library HYDRATECURVE: Definition of hydrate curve used by HYDRATECHECK.

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Hydrate kinetics

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. 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=10 -7 kg/s/Pa and BPROD=2.5·10-6 kg/s/Pa. FLOWPATH — FA-models — HYDRATECHECK: Hydrate checking is activated in all flowpaths. 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. NODE: The outlet pressure held constant at 50 bara and the temperature is 20°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Network The sample 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.

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.

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Network

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 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Particle flow The sample case ParticleFlow.opi demonstrates how OLGA simulates particle deposition and entrainment in a horizontal pipeline. The case consists of a horizontal pipeline with a fixed outlet pressure. A source injects water, oil, gas and particles at the inlet. The mass flow is initially reduced. Consequently, a bed is formed. After some time, the mass flow is increased again, entraining the particles from the bed and making the latter disappear.

Case comments Library PARTICLES: Default values are used for the properties of the particle phase. CaseDefinition OPTIONS: We set PARTICLEFLOW=ADVANCED to enable bed formation. FA-models PARTICLEOPTIONS: We set BEDPOROSITY=0.3 and leave the default value for the rest. FlowComponent: FLOWPATH — Boundary&InitialConditions — SOURCE: The mass source injects oil, water, gas and particles. The mass flow rate is reduced linearly from 18 kg/s to 2 kg/s in 800s and then increased again to 18kg/s with the same slope. The mass fraction of particles being injected is kept constant at one percent. NODE: The outlet pressure held constant at 50 bara and the temperature is 22°C. Output OUTPUT: OLGA variables are printed to the output file every 1 hour. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes.

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2nd-order scheme

2nd-order scheme The sample 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 See " Initial MEG fractions." on page 37. 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 2nd-order 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 See " 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." on page 38.

Initial MEG fractions.

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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. 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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: ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds.

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2nd-order scheme

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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Water options The sample 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. FLOWPATH — Output —SERVERDATA - Server variables are available for plotting in interactive simulations. 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 ANIMATE - 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Wax deposition

Wax deposition The sample 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 — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Backpressure IPR The sample case Well-BackpressureIPR.opi is constructed to show how to model well production using backpressure reservoir inflow option. The well geometry and components are shown in the figure below.

The system consists of a 1000 m vertical well with a well module located at the bottom. The reservoir pressure and temperature are 80 bara and 62°C respectively. The PRODOPTION and INJOPTION are chosen as BACKPRESSURE with positive production and negative injection coefficient C =100 scf/d/psi2. The exponent constant n=1. Library WALL: The simple tubing wall consists of two material layers. CaseDefinition OPTIONS: The STEADYSTATE preprocessor is ON. INTEGRATION: The simulation runs for 100 seconds using a minimum time step of 0.01 s and a maximum one of 5 s. The initial time step is set equal to the minimum time step. Flow Component: FLOWPATH(s): The well consists of one flowpath: Well OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 50 bara, temperature of 22°C. Output: ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes.

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Well Forchheimer IPR

Well Forchheimer IPR The sample case Well-ForchheimerIPR.opi is constructed to show how to model a well production using Forchheimer reservoir inflow option. The well geometry and components are shown in the figure below.

The system consists of a 1000 m vertical well with a well module located at the bottom. The reservoir pressure and temperature are 80 bara and 62°C respectively. The PRODOPTION and INJOPTION are chosen as Forchheimer with positive production and negative injection coefficients B=1 e-6 Psi2 –d/scf and C =1e-10 Psi2 –d2/scf2. Library WALL: The simple tubing wall consists of two material layers. CaseDefinition OPTIONS: The STEADYSTATE preprocessor is ON. INTEGRATION: The simulation runs for 100 seconds using a minimum time step of 0.01 s and a maximum one of 5 s. The initial time step is set equal to the minimum time step. Flow Component FLOWPATH(s): The well consists of one flowpath: Well OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 50 bara, temperature of 22°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes.

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Linear IPR The sample case Well-LinearIPR.opi is constructed to show how to model a well production using the linear reservoir inflow option. The well geometry and components are shown in the figure below.

The system consists of a 1000 m vertical well with a well module located at the bottom. The reservoir pressure and temperature are 85 bara and 62°C respectively. The PRODOPTION and INJOPTION are chosen as linear with positive production and negative injection coefficient B=1 e-6 kg/s/Pa. Library WALL: The simple tubing wall consists of two material layers. CaseDefinition OPTIONS: The STEADYSTATE preprocessor is ON. INTEGRATION: The simulation runs for 100 seconds using a minimum time step of 0.01 s and a maximum one of 5 s. The initial time step is set equal to the minimum time step. Flow Component FLOWPATH(s): The well consists of one flowpath: Well OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 50 bara, temperature of 22°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes.

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Normalized backpressure IPR

Normalized backpressure IPR The sample case Well-NormalizedBackpressureIPR.opi is constructed to show how to model a well production using normalized backpressure reservoir inflow option. The well geometry and components are shown in the figure below.

The system consists of a 1000 m vertical well with a well module located at the bottom. The reservoir pressure and temperature are 80 bara and 62°C respectively. The PRODOPTION and INJOPTION are chosen as NORMALIZEDBACKPRESSURE with exponent constant=1, QMAX=50000 STB/d and PHASE=OIL Library WALL: The simple tubing wall consists of two material layers. CaseDefinition OPTIONS: The STEADYSTATE preprocessor is ON. INTEGRATION: The simulation runs for 100 seconds using a minimum time step of 0.01 s and a maximum one of 5 s. The initial time step is set equal to the minimum time step. Flow Component FLOWPATH(s): The well consists of one flowpath: Well OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 50 bara, temperature of 22°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes.

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Quadric IPR The sample case Well-QaudraticIPR.opi is constructed to show how to model a well production using Qaudratic reservoir inflow option. The well geometry and components are shown in the figure below.

The system consists of a 1000 m vertical well with a well module located at the bottom. The reservoir pressure and temperature are 80 bara and 62°C respectively. The PRODOPTION and INJOPTION are chosen as QUADRATIC with AINJ=APROD=0 Pa2 and BINJ=BPROD=0 Pa2s/kg and CINJ=CPROD=50000000 Pa2s2/Kg2. Library WALL: The simple tubing wall consists of two material layers. CaseDefinition OPTIONS: The STEADYSTATE preprocessor is ON. INTEGRATION: The simulation runs for 100 seconds using a minimum time step of 0.01 s and a maximum one of 5 s. The initial time step is set equal to the minimum time step. Flow Component FLOWPATH(s): The well consists of one flowpath: Well OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 50 bara, temperature of 22°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes.

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Single Forchheimer IPR

Single Forchheimer IPR The sample case Well-SingleForchheimerIPR.opi is constructed to show how to model a well production using Single Forchheimer reservoir inflow option. The well geometry and components are shown in the figure below.

The system consists of a 1000 m vertical well with a well module located at the bottom. The reservoir pressure and temperature are 80.5 bara and 62 C respectively. The PRODOPTION and INJOPTION are chosen as SINGLEFORCHHEIMER with BINJ=BPROD=1e-6 psi-d/scf and CINJ=CPROD=1e-11 psid2/scf. Library WALL: The simple tubing wall consists of two material layers. CaseDefinition OPTIONS: The STEADYSTATE preprocessor is ON. INTEGRATION: The simulation runs for 100 seconds using a minimum time step of 0.01 s and a maximum one of 5 s. The initial time step is set equal to the minimum time step. Flow Component FLOWPATH(s): The well consists of one flowpath: Well OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 50 bara, temperature of 22°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes.

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Tabular IPR The sample case Well-TabularIPR.opi is constructed to show how to model a well production using Single tabular inflow option. The well geometry and components are shown in the figure below.

The system consists of a 1000 m vertical well with a well module located at the bottom. The reservoir pressure and temperature are 80 bara and 62 C respectively. The PRODOPTION and INJOPTION are chosen as TABULAR. The production table given at three DELTAP (PR- Pwf) (bar) provides the production mass flow (kg/s) from the reservoir. The table is shown in See " Production table" on page 48.

Production table Library WALL: The simple tubing wall consists of two material layers. CaseDefinition OPTIONS: The STEADYSTATE preprocessor is ON.

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Tabular IPR

INTEGRATION: The simulation runs for 100 seconds using a minimum time step of 0.01 s and a maximum one of 5 s. The initial time step is set equal to the minimum time step. Flow Component FLOWPATH(s): The well consists of one flowpath: Well OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 50 bara, temperature of 22°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes.

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Undersaturated IPR The sample case Well-UndersaturatedIPR.opi is constructed to show how to model a well production using Undersaturated reservoir inflow option. The well geometry and components are shown in the figure below.

The system consists of a 1000 m vertical well with a well module located at the bottom. The reservoir pressure and temperature are 80 bara and 62°C respectively. The bubble point pressure is set as 79 bara while INJECTIVY= 0 scf/d/psi and PRODI= 42 scf/d/psi. Library WALL: The simple tubing wall consists of two material layers. CaseDefinition OPTIONS: The STEADYSTATE preprocessor is ON. INTEGRATION: The simulation runs for 100 seconds using a minimum time step of 0.01 s and a maximum one of 5 s. The initial time step is set equal to the minimum time step. Flow Component FLOWPATH(s): The well consists of one flowpath: Well OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 50 bara, temperature of 22°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes.

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Vogels IPR

Vogels IPR The sample case Well-VogelsIPR.opi is constructed to show how to model a well production using Vogels reservoir inflow option. The well geometry and components are shown in the figure below.

The system consists of a 1000 m vertical well with a well module located at the bottom. The reservoir pressure and temperature are 80 bara and 62°C respectively. QMAX in Vogels equation is set to 50000 STB/D. Library WALL: The simple tubing wall consists of two material layers. CaseDefinition OPTIONS: The STEADYSTATE preprocessor is ON. INTEGRATION: The simulation runs for 100 seconds using a minimum time step of 0.01 s and a maximum one of 5 s. The initial time step is set equal to the minimum time step. Flow Component FLOWPATH(s): The well consists of one flowpath: Well OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 50 bara, temperature of 22°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 15 seconds. PROFILE: Profile variables are plotted every 5 minutes.

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Network server The case Network-server.opi is an OPC server version of the demo case Network.opi.

Case comments Only server specific items are commented here. For other comments see the Network.opi sample which apart from server specific items is identical, except for the ANIMATE keyword which is turned off in the OPC server version of the case. CaseDefinition: SERVEROPTIONS : A model name “NetworkDemo” is specified. Defining this keyword is all that is needed to start the built-in OPC server in OLGA. INTEGRATION: SIMULATIONSPEED is set to 15, indicating the model is requested to simulate at 15 times real-time speed. Further, SIMULATIONSPEED and MINDT are selected in the EXPOSE key, which gives the possibility to change these input values using a connected OPC client. FlowComponent: FLOWPATH : BRAN-3-ProcessEquipment-VALVE: The valve OPENING is selected in the EXPOSE key. Thus, the valve opening can be set from a connected OPC client. NODE: NODE-2: The node PRESSURE is exposed. FLOWPATH : BRAN-1-Boundary&InitialConditions-SOURCE: SOUR-1-1: All possible keys are selected as exposed. OLGA will automatically filter out any keys that cannot be exposed and issue a harmless warning when the case starts. In this case the keys STDFLOWRATE, TEMPERATURE and WATERCUT are ultimately exposed on the OPC server. FLOWPATH : BRAN-5-Boundary&InitialConditions-SOURCE: SOUR-2-1: MASSFLOW is exposed. FLOWPATH – Output – SERVERDATA: VALVOP is selected for the valve. HOL and PT profile is selected for BRAN-8. GT trend is selected for position TOPSIDE-OUT in BRAN-8. Output: SERVERDATA: SIMTIME, TIME, HT, SPEED, LAGFACT, LAGIND is set. These will be visible on the OPC server.

OPC Interactivity: Fiddling with the exposed input parameters, the running case can be manipulated. For instance, lowering Toolkit.NetworkDemo.NODE-2.PRESSURE from 243 to 40 will cause the holdup in BRAN-8 to drop, setting the pressure back to 243 causes the same holdup to rise again.

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PID-net-gainsched-normrange-server

PID-net-gainsched-normrange-server PID-net-gainsched-normrange-server.opi is a simple case with one flowpath modeling a pipeline riser system. At the bottom of the riser a valve labeled CHOKE-1-1 is included. Upstream the valve a pressure transmitter is included. A controller C-1 acts on the valve CHOKE-1-1 to control the pressure upstream the valve. The purpose with this sample case is to demonstrate the possibilities to interact with a PID controller through the OLGA OPC Server and exemplify how vectors can be addressed through the OLGA OPC Server.

Case comments CaseDefinition SERVEROPTIONS : The model name sub-key is set to “TEST” and the server name is set to OLGAOPCServer INTEGRATION: SIMULATIONSPEED is set to 10, indicating the model is requested to simulate at 10 times real-time speed. Further, SIMULATIONSPEED is set in the EXPOSE key, which gives the possibility to change the requested simulation speed through the OPC server. Controller: PIDCONTROLLER C-1: Controller C-1 is used to control the pressure at riser base (upstream the valve CHOKE-1-1) by adjusting the opening. The set-point to the controller is 75e5. The controller measures the pressure in unit Pa. Note the use of controller sub-key NORMRANGE which is set to 1e5. The controller C1 is a scheduling controller. It uses a table of amplification factors, integral constants and derivative constants rather than one value for each. For further description of PID controller with scheduling functionality refer to the OLGA PID controller documentation. The EXPOSE key of controller C-1 is set to ALL. The OPC Server will then expose all input keys that are explicitly set in the controller. In this case the following keys are exposed as input items on the OPC Server: MAXSIGNAL, MINSIGNAL, AMPLIFICATION, BIAS, DERIVATIVECONST, ERROR, INTEGRALCONST, NORMRANGE, SETPOINT, MODE, MANUALOUTPUT, OPENINGTIME, CLOSINGTIME For further information of these keys see the description of PID controller. Note that the keys: AMPLIFICATION, ERROR, INTEGRALCONST and DERIVATIVE CONST are vectors of size four in the definition of controller C-1.

FlowComponent FLOWPATH P1: One horizontal pipe followed by two downwards inclined pipes and a vertical riser, see figure below. CHOKE-1-1: controller C-1 manipulates the CHOKE-1-1 and the initial output of the controller is 0.5 PTSIG: Measures the pressure upstream CHOKE-1-1. PTSIG is connected to the MEASRD terminal of controller C-1. The signal is pressure in unit Pa.

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Output Global SERVERDATA keyword: Variables VOLGBL, HT, TIME, SPEED and SIMTIME are defined to be updated on the OPC server with DTPLOT set to 10 seconds. SERVERDATA keyword defined on controller C-1: Variables CONTR, MEASVAR, SETPVAR, ERRVAR are defined to be updated on the OPC server with DTPLOT set to 10 seconds.

OPC Interactivity: Manipulation of input items Start simulating the OLGA case by pressing one of the run buttons in the OLGA GUI. Then launch MatrikonOPC Explorer, connect to SPT.OLGAOPCServer.1, add a group and add all items to the provided by the OLGA OPC server to the group. Then one will obtain a display similar to the one below.

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PID-net-gainsched-normrange-server

Note that the values on the exposed keys automatically comes up with the values set in the model. Manipulation of server inputs The engineer has the possibility to change the values of all the exposed keys. For instance decreasing the set-point of controller C-1 to 74e5 causes the controller to open the valve from 5.8% to 6.6%. By further reduction in the set-point to 73e5 causes the controller to open the valve to 8.1%, etc. Through the OPC Server the maximum, minimum constraint on the controller output can be changed through the MAXSIGNAL and MINSIGNAL keys. The rate of change constraints on the output can be changed through OPENINGTIME and CLOSINGTIME. The engineer can detune the controller either by reducing the amplification factors or increasing the integral constants. The amplification factor is scaled by dividing by the NORMRANGE. By increasing the NORMRANGE the controller is thus detuned for all ERROR ranges. If the engineer wants to detune the controller for a specific error range one need to adjust the corresponding element in the array of amplification factors or integral constants. By changing the elements in the array exposed as ERROR the engineer can change the error ranges.

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Server demo with OPC Server-demo-with-opc.opi is a simple case with one horizontal flowpath, an ESD controller and a valve. There is a 50 bara pressure difference between the boundary nodes driving the fluid towards the outlet. The ESD controller is set to close the valve whenever the upstream holdup goes above 0.8. Without user interaction the holdup stays around 0.65, leaving the valve completely open.

Case comments CaseDefinition SERVEROPTIONS : A model name “ServerDemo” is specified. Defining this keyword is all that is needed to start the built in OPC server in OLGA. INTEGRATION: SIMULATIONSPEED is set to 100, indicating the model is requested to simulate at 100 times real-time speed. Further, SIMULATIONSPEED is selected in the EXPOSE key, which gives the possibility to change the requested simulation speed using a connected OPC client. Controller: ESDCONTROLLER: An emergency shutdown controller is used to close the valve whenever the holdup upstream goes above the controller setpoint, which is set to 0.8. The set point of the controller is selected in the EXPOSE key, meaning that it is possible to dynamically change the setpoint using an OPC client connected to the OLGA OPC server. FlowComponent: FLOWPATH –ProcessEquipment-VALVE: The valve is initially fully open and is regulated by the ESD controller. Output: SERVERDATA: SIMTIME, TIME, HT, SPEED is set. These will be visible on the OPC server. OPC Interactivity Manipulation of input items: Using a standard OPC client, the setpoint for the controller is changed to 0.5. This causes the valve to close. Manipulation of server commands: Saving a snap file: Specify a filename in the OPC item Toolkit.ServerDemo.SaveSnap.File, for instance “snap.rsw”. Then toggle the command item Toolkit.ServerDemo.SaveSnap to ‘true’. This causes a snapfile (a.k.a. restart file) to be saved to disk. Loading a snap file into the running server: Specify the same filename as in the save-snap command argument, e.g. set Toolkit.ServerDemo.LoadSnap.File to “snap.rsw” and toggle Toolkit.ServerDemo.LoadSnap to ‘true’. The snap-file is then loaded and the simulator state from the snap file is restored. Toggeling Toolkit.ServerDemo.Stop to ‘true’ causes the simulation to shut down.

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Pigging

Pigging The following cases illustrate the following pigging scenarios: Pig-noSlug-pvt.opi Pigging of a pipeline using standard OLGA without tracking the liquid slug in front Pig-TrackSlug-

of the pig. Pigging of a pipeline using standard OLGA tracking the liquid slug in front of the

pvt.opi Pig-noSlug-comp.opi

pig. Pigging of a pipeline using Compositional Tracking without tracking the liquid

Pig-TrackSlug-

slug in front of the pig. Pigging of a pipeline using Compositional Tracking, also tracking the liquid slug

comp.opi

in 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 See " Illustration of the pipe geometry. The launch and trap positions are indicated." on page 57

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.

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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. FLOWPATH — Output — TRENDDATA: In cases where the slug in front of the pig is tracked, its length is plotted. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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 trend data are plotted.

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Pigging

Hydrate formation Hydrate model TESTCASE This is an example case for a pre-defined plug-in dll with a hydrate formation model. The case consists of a single 500 m horizontal pipe. The pipe diameter is 0.11 m. A hydrate phase has been added to calculate the following effects: 

Tracking the hydrate particles forming and following the flow



Calculating the effects of hydrates on the viscosity of the water film

Case description The physical models needed to handle the tasks listed above are included in the plug-in DLL “OlgaPlugInHydrateTutorialStructDat.dll” which is included in the executable folder for the OLGA X.x installation package. 1. The case name is HydrateTutorial.opi. 2. The DLL to use in this case is specified as follows: In the GUI, under CaseDefinition, UDOPTIONS has been added. The dll name “OlgaPlugInHydrateTutorialStructDat.dll” has been entered in the PLUGINDLL field. The dll is located in the same folder as the OLGA X.x engine executable, and it is thus not necessary to include path in this case. 3. The hydrate phase which is recognized by the DLL has been defined as follows: The case uses internal models from the plug-in for hydrate heat capacity, enthalpy, density, thermal conductivity, and viscosity. Therefore we don’t need to give values for heat capacity in the UDPHASE field. We do, however, need to set a dummy value for the hydrate particle density to bypass the input error check. The value is overridden by the density model in the plug-in DLL. The “dummy” hydrate density is set to 940 kg/m3. The hydrate particle diameter is 0.001 m. See section 1.2.4 for further info about the plug-in DLL PVT-property models. Under Library, UDPHASE has been added. LABEL has been set to “HYDRATE”, TYPE=PARTICLE, PARTDIAMETER = 0.001 m and PARTDENSITY = 940 kg/m3. 4. The case is set up to use INITIALCONDITIONS. Initially the pipe is filled with gas, oil and water, and no hydrates. Thus, it is not necessary to specify any initial conditions for hydrates in this case. However, in order to illustrate the use of initial conditions, the model has explicitly been set to start with zero hydrates at time = 0. At case level, UserDefined/UDGROUP has been added. UDGROUP label =” HYDRATE -INIT” Under UDPhasesAndDispersions, UDFRACTION has been added: LAYER=WALL, PHASE=HYDRATE, MASSFRACTION=0.0

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Under FLOWPATH:BRAN-1/Boundary&InitialConditions/INITIALCONDITIONS[1]/User Defined, UDGROUP= HYDRATE-INIT has been chosen. 5. There is no inflow of hydrates in this case. Only hydrate formation within the pipeline. It is thus not necessary to specify hydrate inflow for the source. However, In order to illustrate how to enter hydrates from a source, the hydrate inflow has explicitly been defined to zero for the source in the first pipe section, by using a zero hydrate fraction for all layers. At case level, UserDefined/UDGROUP has been added. UDGROUP label =” HYDRATE-SOURCE” Under UDPhasesAndDispersions/UDFRACTION[1], TIME = 0, MASSFRACTION = 0 has been set. LAYER = GAS has been chosen. For PHASE, HYDRATE has been chosen. Under UDPhasesAndDispersions, UDFRACTION[2 ] has been added, TIME = 0, MASSFRACTION = 0. LAYER = OIL has been chosen. For PHASE, HYDRATE has been chosen. Under UDPhasesAndDispersions, UDFRACTION[3 ] has been added, TIME = 0, MASSFRACTION = 0. LAYER = WATER has been chosen. PHASE = HYDRATE. Source entry: At FLOWPATH: BRAN-1/Boundary&InitialConditions/SOURCE:SOURCE-1-1, UDGROUP= HYDRATE -SOURCE has been chosen. 6. The hydrate curve information is provided through a table file which is read by the plug-in DLL. The format of the table file is dictated by the plug-in DLL. The hydrate curve is given through the OLGA input in the FILES UDPVTFILE field. FILES UDPVTFILE is a string vector, so it is possible to give multiple input files in a simulation. BRANCH and NODE both have a key named UDPVTFILE where the user can select which file is used. It is therefore possible to use different hydrate curves in different branches of a network simulation. Under CaseDefinition/FILES, “HydrateTutorial.tab” has been chosen through the UDPVTFILE file browser. 7. In order to refer to the hydrate curve for the fluid in a given branch, it is necessary to refer to the table file used by the plug-in DLL which is applied for the specific branch. Under FlowComponent/FLOWPATH:BRAN-1/Piping/BRANCH, UDPVTFILE= HydrateTutorial.tab has been chosen. 8. Plotting of results: The variables P-G, P-HOL, P-M, P-Q, P-U, P-US have been specified for FLOWPATH: BRAN-1/Output, PROFILEDATA. PHASE = HYDRATE. As we are going to inspect the oil layer, FLOWLAYER = OIL has been specified in this case. The hydrate formation and propagation through the pipeline can be inspected by plotting e.g. the following profile variable: P-HOL_HydrateInOil. The variable name is a composite name based on the generic PHOL (holdup for UD dispersed phase), the UD dispersion phase name (Hydrate) and the layer where it is located (InOil). The other “P-“ variables have the same composite structure.

The effect of hydrate particles on oil viscosity can be seen by plotting the following profile variables in the same plot: VISHLEFF and VISHL.

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Pigging

Physical effects modelled The hydrate reaction: 1) (1.1)

The value chosen for a is 6.87. Hydrate equilibrium curve The hydrate equilibrium is given as a tabulation of temperature and pressure. The hydrate curve must be user given. The following format is chosen: 31 -10.00 -8.00

3.29 3.59

………. Here “” is a tag telling how the temperature and pressure data is given. “31” is the number of data points given. An example of a hydrate curve is given in the HydrateTutorial.tab. The HydrateTutorial.tab is used in the HydrateTutorial.opi.

Formation of hydrate if the temperature drops below the hydrate equilibrium temperature When the fluid temperature ( ) drops below the hydrate equilibrium temperature ( hydrate particles will form according to the hydrate reaction.

),

Reaction rate: (1.2)

Here,

is the gas mass reacted per time and section volume.

Mass limitation for hydrate formation rate: (1.3)

(1.4)

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(1.5)

Here is the stoichiometric constant in the hydrate reaction. mass per section volume.

is the time step and

is the phase

Distribution of phase mass on fields: The reacted mass rates are given as overall phase values. These phase values must be distributed to fields. To distribute the phase values, we use the following logic:  

The hydrate particles is only present in the oil layer. Gas and water field masses are distributed based on field mass fractions (field mass / phase mass).



If the gas or water phase mass is missing, the mass is distributed equally on all fields.

Increased oil viscosity The effective viscosity of the hydrate-oil dispersion is higher than the pure oil viscosity. The effective viscosity is used in the friction calculations in OLGA, and the dispersion viscosity will give a higher pressure drop over the pipeline. The effective oil viscosity will be modeled with the Krieger-Dougherty correlation. Krieger-Dougherty correlation: (1.6)

Where

is the oil viscosity without particles,

is the particle volumetric concentration in water and

is the maximum concentration set to 0.65.

Hydrate PVT properties Hydrate enthalpy: (1.7)

Where is the enthalpy and is the constant heat of reaction assumed to be 4.088e6 J/kg. The heat capacity, partial enthalpy with respect to pressure, partial enthalpy with respect to temperature and entropy is derived from the enthalpy equation. Hydrate heat capacity:

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Pigging

(1.8)

Hydrate density: (1.9)

Hydrate thermal conductivity: (1.10)

Hydrate viscosity: (1.11)

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Sand in water The case consists of a single 2000 m pipe with an elevation of 150 m. The pipe diameter is 0.2 m. The case name is SandInWater.opi. Water and sand is injected in the first pipe section. The case is set up to use INITIALCONDITIONS. Initially the pipe is filled with water only. The tasks in this case are as follows:  

Tracking the sand particles following the flow in the water layer Tracking the sand forming a bed.

 

Calculating the effects of sand on the viscosity of the water film Calculating the slip velocity between suspended sand particles and the water in the water layer

Case description The physical models needed to handle the tasks listed above are included in the plug-in DLL “OlgaPlugInSandWaterTutorialStructDat.dll”, which is included in the executable folder for the OLGA X.x installation package. The UD phase specific input is described below: 1. The DLL is specified as follows: In the GUI, under CaseDefinition, UDOPTIONS, the dll name “OlgaPlugInSandWaterTutorialStructDat.dll” has been entered in the PLUGINDLL field. The dll is located in the same folder as the OLGA X.x engine executable, and it is thus not necessary to include path in this case. 2. The phase which is recognized by the DLL is defined as follows. Under Library, UDPHASE has been added. LABEL has been set to “SAND”, TYPE=PARTICLE, PARTDIAMETER = 0.001 m and PARTDENSITY = 2000 kg/m3. The case uses OPTIONS TEMPERATURE=OFF, and therefore we don’t need to model the sand heat capacity and enthalpy. The sand density is 2000 kg/m3. The sand particle diameter is 0.001 m. Other sand properties are not required. 3. The case is set up to use INITIALCONDITIONS. Initially the pipe is filled with water only. Thus, it is not necessary to specify any initial conditions for sand in this case. 4. Sand is injected together with water in the first pipe section, with a constant mass fraction of sand = 0.1. At case level, UserDefined/UDGROUP has been added. UDGROUP label =” SAND-SOURCE” Under UDPhasesAndDispersions/UDFRACTION[1], TIME = 0, MASSFRACTION = 0.1 has been set. LAYER = WATER has been chosen, as the sand should enter in the water layer. The PHASE is referring to a UD phase, SAND has been chosen. Source entry: At FLOWPATH: BRAN-1/Boundary&InitialConditions/SOURCE:SOURCE-1-1,

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Sand in water

UDGROUP=SAND-SOURCE has been chosen. 5. Plotting of results: Sand propagates through the pipeline and forms an expanding bed, and the velocity of the sand particles in the water film is different from the water velocity. This can be seen by inspecting e.g. the following profile plot variables: P-HOL_SandInWater, P-HOL_SandAtBed, P-U_SandInWater, ULWT. The variable name PU_SandInWater is a composite name based on a generic name, P-U, the defined UD phase, (Sand), and the specified layer: (InWater). The other UD phase output variables have the same composite structure. At FLOWPATH: BRAN-1/Output, PROFILEDATA, the variables P-HOL, P-U for FLOWLAYER = WATER, BED and PHASE = SAND have been specified to get the output variables described above. The effect of sand on water viscosity can be seen by plotting the effective viscosity of the water layer, VISWTEFF, and pure water viscosity from tables, VISWT in the same plot. Physical effects modelled The three following physical effects has been modeled: 

Sand offset velocity due to density differences



Increased friction due to sand particles in the water



Bed formation

Sand offset velocity due to density differences The density of the sand particles are larger than the water density, and the particles will, due to the pipe inclination, get a negative offset velocity. The offset velocity will be calculated by Stokes’ law. Stokes’ law: 1) (1.1)

Where ufall is the terminal settling velocity, ρp is the particle density, ρf is the fluid density, µf is the fluid viscosity, g is the gravity constant and rp is the particle radius. The offset velocity then becomes: (1.2)

Where uOffset is the offset velocity which will be used by OLGA, and θ is the pipe angle with the gravity vector. The sand velocity (uSand) will then be: (1.3)

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Where uWater is the water film velocity.

Increased friction due to sand particles in the water The effective viscosity of the water-sand dispersion is higher than the pure water viscosity. The effective viscosity is used in the friction calculations in OLGA, and the dispersion viscosity will give a higher pressure drop over the pipeline. The effective water viscosity will be modeled with the Krieger-Dougherty correlation. Krieger-Dougherty correlation: (1.4)

Where and

is the water viscosity without particles,

is the particle volumetric concentration in water

is the maximum concentration set to 0.65.

Bed formation A dummy bed formation model is used to demonstrate how to set mass transfer rates. A fixed deposition rate to the bed is used. If the bed height is lower than 15% of the pipeline diameter, sand mass will deposit on the bed. As a result, the bed should build up from zero to 0.03 m, in the SandAndWater.opi case. The deposition rate can therefore be expressed as: (1.5)

Where

is the deposition rate [kg s-1 m-3],

is the mass [kg m-3] of sand particles, and

is the

current time step [s]. Note that in OLGA the masses are divided with the section volume, and thus are in units of [kg m-3]. The deposition rate is fixed to “0.1”, but the deposition rate is limited. A maximum of 50 mass percent of the particle mass can be deposited over the next time step. For the tutorial case remember that the pipeline initially is filled with only water, i.e. there is no sand that can deposit and make a bed. When the bed height is 15% of the pipeline diameter or higher, the deposition rate is set to zero. The bed height is calculated from the “Wetted angle”, β, that are given as input to the entrainment/deposition and flash interface.

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Sand in water

“Wetted angle”, β, and height, h, of water bed interface. The bed height, h, is calculated as (See Figure 15): (1.6)

Where rp is the pipe diameter.

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OLGA Compressor control OLGA Compressor Control is a sample case for a compressor with anti-surge and pressure performance controllers.

Case description Model consists of a single branch with compressor CMPR-1. PID controller C-PT controls compressor suction pressure by adjusting compressor speed. Note the speed signal is normalized in range 0 – 1 corresponding to range MinRPM - MaxRPM. Anti-surge controller C-ASC adjusts the opening of the recycle valve to avoid the compressor surges. Signal connections CMPR-1 ACSIG (compressor input) is connected to C-ASC CONTR (controller output). CMPR-1 SPEEDSIG (compressor input) is connected to pressure controller C-PT CONTR (controller output). Speed signal range 0 to 1. The terminal signal adjusts the compressor speed: CompressorSpeed = MinRPM + (MaxRPM - MinRPM) * Speed Signal C-PT MEASRD (controller input) is connected to transmitter PT-1 with variable PT in unit bar. C-ASC MEASRD (controller input) is connected to transmitter QG with variable QG in unit m3/s. Transmitter QG is placed at the same section boundary as the compressor. The set point terminal of C-ASC SETPOINT (controller input) is connected to transmitter TM-3 with variable QGSURGE in unit m3/s. This is the set point to the anti-surge controller and is the surge point for the compressor at the current operating conditions. Dynamic simulation To test the performance of the compressor control set point, changes to the pressure controller C-PT are introduced at times 200 and 400 seconds. The controller set point is changed from 33 bar to 30 bar at time 200 seconds and from 30 to 25 bar at time 400 seconds. To test the anti-surge controller, the flow through the compressor is lowered (changed in the source, SOUR-1). The source flow rate is lowered from 100 to 50 MMscf/d in the time interval 800 to 900 seconds and from 50 to 30 MMscf/d in the time interval 1200 to 1300 seconds.

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Compressor manual controls

Compressor manual controls Compressor Manual Controls is a simple model to demonstrate compressors with a manual speed controller and a manual controller attached to the compressor recycle valve.

Case description The model consists of a single branch with a compressor CMPR-1. A manual controller C-MAN-SPEED adjusts the speed of the compressor. The controller C-SCALE-SPEED normalizes (scales the speed from rang MinRPM–MaxRPM to range 0-1) the speed input to the compressor. The manual controller CMANRECYCLE adjusts the opening of the compressor recycle valve. Signal connections CMPR-1 ACSSIG – terminal for compressor anti-surge controller. Anti –surge signal in range 0 to 1. The terminal signal adjusts the compressor recycle valve. CMPR-1 SPEEDSIG – terminal for compressor speed controller. Speed signal range 0 to 1. The terminal signal adjusts the compressor speed: CompressorSpeed = MinRPM + (MaxRPM - MinRPM) * Speed Signal Dynamic simulation To test the performance of the compressor the speed is changed (set-point change in controller C-MANSPPED) at time 100 and 200 seconds and the recycle valve opening is changed for closed to 0.1 at time 500 seconds.

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Jet pump The sample case Jetpump.opi defines how water at low pressure can flow towards a higher outlet pressure using a Jet pump with water as power fluid.

Case comments Case definition OPTIONS: The Steady state preprocessor is used to generate initial conditions.

INTEGRATION: The simulation end time is set to 30 minutes. This will allow the system to stabilize. Controller: PIDCONTROLLER: PID-LP: The opening of the valve in the Jet pump outlet branch is adjusted by a PID controller connected to a transmitter in the low pressure flowpath to keep the pump suction pressure at 60 bara. The BIAS is set to 0.05 to give proper starting conditions for the system. The purpose of the controller system is to ensure well balanced pressure conditions in the Jet pump. Flow components FLOWPATH: LP-LINE — Boundary and Initial Conditions — SOURCE: LP-SOUR: A mass source is included in the first section of the low pressure (suction) flowpath. The source supplies water at a constant mass flow rate of 20 kg/s and a temperature of 10 oC.

FLOWPATH: LP-LINE — Process Equipment — TRANSMITTER: TM-LP: Transmits the variable PT [bara](pressure) from the pump suction to controller PID-LP. FLOWPATH: MIXED — Process Equipment — VALVE: VALVE-1: A valve with the same diameter as the pipe diameter is positioned in the middle of the Jet pump outlet branch.

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Jet pump

NODE: HP-INLET: A pressure node is placed at the inlet of the high pressure (power) flowpath. The node is specified with a pressure of 135 bara, a WATERFRACTION of 1 and a temperature of 10oC.

NODE: OUTLET: A pressure node is placed at the system outlet. The node is specified with a pressure of 40 bara, a WATERFRACTION of 1 and a temperature of 10oC. Output: PROFILE: Profile variables are plotted every 15 minutes. TREND: Trend variables are plotted every 30 seconds. Process Equipment: JETPUMP: The diameters of the Jet pump inlets and outlet are set equal to the diameters of incoming and outgoing pipes. Loss coefficients are specified for the nozzle, throat (mixing tube) and diffuser. JETPUMP: Output: All TRENDDATA variables available for the Jet pump are selected.

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PID controller The sample 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, which 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. NODE: The inlet node is closed. The outlet boundary condition is a constant pressure of 55 bara.

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PID controller

Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every second. PROFILE: Profile variables are plotted every 6 minutes.

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Process equipment The sample 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. See " Process flow sheet." on page 74 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.

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.

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Process equipment

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 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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. ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Centrifugal pump The sample case Pump-Centrifugal.opi demonstrates 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 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 the figure below. 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.

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 Multiphase pump module. In this sample case, the pump speed is controlled by the total mass flow rate (PUMPGT) through the pump. The total mass flow rate is measured by and defined in the Transmitter TM-2. PIDCONTROLLER: C-PUMP-C-RE: This controller is required by the Multiphase 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.

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Centrifugal pump

MANUALCONTROLLER: C-PUMP-C-BY: This controller is required by the Multiphase pump module. However, the built-in bypass function of the Multiphase 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 withSETPOINT=0, which means that the built-in bypass line is closed. MANUALCONTROLLER: C-PUMPV-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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Displacement pump The sample case Pump-Displacement.opi demonstrates 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 below. 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.

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 Multiphase pump module. In this sample case, the pump speed is controlled by the total mass flow rate (PUMPGT) through the pump. The total mass flow rate is measured by and defined in the Transmitter TM-2. PIDCONTROLLER: C-PUMP-D-RE: This controller is required by the Multiphase 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 Multiphase pump module. However, the built-in bypass function of the Multiphase pump module is obsolete since any bypass line

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Displacement pump

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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Simplified pump The sample 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 below.

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 depends 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 diameter is 12" and roughness 0.001 m FLOWPATH — Output — TRENDDATA: Mass flow rates and pump variables are plotted.

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Simplified pump

FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Separator The sample case Separator.opi illustrates the use of a separator. 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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OLGA Single separator 3-phase compressor

OLGA Single separator 3-phase compressor OLGA Single Separator 3-Phase Compressor is a sample case for a three phase separator with a compressor at the gas outlet.

Case description Single three phase separator model with compressor CMPR-1 at gas outlet. PID controller C-PT-SEP controls separator pressure by adjusting compressor speed. Note the speed signal is normalized in range 0 – 1 corresponding to range MinRPM - MaxRPM. Anti-surge controller C-ASC to adjust the opening of the recycle valve to avoid that the compressor surges. PID controllers C-LC-OIL and C-LC-WAT controls separator levels by adjusting valves at separator liquid outlets. Signal connections CMPR-1 ACSSIG (compressor input) is connected to C-ASC CONTR (controller output). CMPR-1 SPEEDSIG (compressor input) is connected to pressure controller C-PT-SEP CONTR (controller output). Speed signal range 0 to 1. The terminal signal adjusts the compressor speed: CompressorSpeed = MinRPM + (MaxRPM - MinRPM) * Speed Signal C-PT-SEP MEASRD (controller input) is connected to transmitter TM-3 with variable PTSEP in unit bar. C-ASC MEASRD (controller input) is connected to transmitter QG with variable QG in unit m3/s. Transmitter QG is placed on the same section boundary as compressor. C-ASC SETPOINT (controller input) is connected to transmitter TM-5 with variable QGSURGE in unit m3/s, the set point to the anti-surge controller is the surge limit for the compressor at the current operation conditions. C-LC-OIL MEASRD (controller input) is connected to transmitter TM-1 with variable OILLV in unit mm. C-LC-WAT MEASRD (controller input) is connected to transmitter TM-2 with variable WATLV in unit mm. V-LV-OIL INPSIG (valve input signal) is connected to C-LV-OIL CONTR V-LV-WAT INPSIG (valve input signal) is connected to C-LV-WAT CONTR

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Dynamic simulation To test the performance of the compressor, control set-point changes to the pressure controller C-PT-SEP are introduced at times 300, 1800 and 3600 seconds. The controller set-point is changed from 25 bar to 20 bar at time 300 seconds, from 20 to 18 bar at time 1800 seconds and 18 to 16 bar at time 3600 seconds. The anti-surge controller keeps the recycle valve slightly open to achieve sufficient constant margin to the surge line.

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Source, leak and choke

Source, leak and choke The sample 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.

Schematic illustration of 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 (C-503) 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.

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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. FLOWPATH — Piping: Only four sections are specified in the horizontal pipe. The pipe is 80 m long and parallel to the x-axis. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. NODE: The pipe is closed at both ends. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file every 10 seconds. TREND: Trend variables are plotted every 0.1 second. PROFILE: Profile variables are plotted every 6 seconds.

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Well ESP

Well ESP The sample case Well-ESP.opi is a simple demonstration of an Electric Submersible Pump (ESP) in a well. The ESP is used to increase production (reduce BHP) and push fluids up the well. The well is deviated and has a profile as shown below.

The model, as shown in See "The model" on page 88, shows the bottom well section with 3 WELL keywords with linear well flow equations with reservoir pressures at 216 bara and at 102 degC. Above the casing shoe, two flowpaths are modelled where the annulus (B-CASING) is sealed off by a valve. The tubing (B-WELL-TUBING) includes an ESP close to the shoe and ends up with a small horizontal section with a valve (open). The ESP is controlled by a manual controller (MANUALCONTROLLER_1) which is set to respectively 0,0.5 and 1 (SETPOINT) at time 0, 5000 and 10000 seconds.

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The model The response after simulation shows an increased total mass flow rate at the well head as the pump is turned on and the setpoint is changed in time. The figure below (See "Interactive mode" on page 89) shows the case run in interactive mode giving the results in the embedded plots.

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Well ESP

Interactive mode

Case comments Library: WALL: The well contains 3 walls. The first is the annulus which consists of a steel layer and multiple formation layers. The second is the tubing with only a steel layer. The third is the well head with a steel layer and some insulated coating. Case Definition: OPTIONS: The full heat transfer calculation option with heat transfer through pipe walls is used. INTEGRATION: The simulation runs for four hours using a minimum time step of 0.01 s and a maximum one of 5 s. The initial time step is set equal to the minimum one. Flow Component: FLOWPATH(s) - The well consists of 4 flow paths: The well flow path, with 3 WELL sources with linear well flow equations with reservoir pressures at 216 bara and at 102 degC; the casing flow path, with a

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closed valve on top; the tubing section placed within the casing with the ESP; and the horizontal well head flowpath. OUTPUT: Multiple variables have been set up for output such as trend variables, profile variables and server variables. The server variables are available for plotting in interactive simulations. (Only Pumpspeed for ESP, BHP and BHT on at the beginning of the well section and volumetric flow rates at the well head are set up in the sample case). NODE: The inlet node is closed. The casing outlet boundary condition is set to a constant pressure of 14.8 bara and a temperature of 22°C. The wellhead (tubing) outlet boundary condition is set to a constant pressure of 14.8 bara and a temperature of 4°C Output: ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 5 seconds. PROFILE: Profile variables are plotted every 100 seconds. Thermal Component: ANNULUS: The tubing is placed inside of the casing using the ANNULUS keyword.

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Well-GLV

Well-GLV The sample case Well-GLV.opi is a demonstration of a well with a gas lift system installed. The gas lift system comprises of two gas lift valves (GLV) as illustrated in the well schematic below. The upper most GLV is used for unloading the well and the bottom GLV is the operational valve. The well is highly deviated and the OLGA model has an annulus, used to transport the gas down the well and a production tubing with the completion at botttom.

The simulation scenario is the following: The model represents a newly completed well that is filled with water in both casing (annulus) and tubing. The well is unable to start up by itself and requires gas-lift in order to do so. The casing head pressure cannot exceed the operational rating of 120 bara. A first simulation attempt with only the bottom operational valve was unsuccessful as the gas was not able to reach the GLV (orifice). An unloading valve above was used and the well was able to start up within 10 hours.

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Case comments Library: WALL: Two walls are present in the model. First is the steel wall of the tubing and the other is the casing wall which includes the casing steel, the cement and the formation. CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through pipe walls is used. INTEGRATION: The simulation runs for ten hours using a minimum time step of 0.01 s and a maximum time step of 5 s. The initial time step is set equal to the minimum time step. Flow Component: FLOWPATH(s): The well consists of two flowpaths: The annulus which is used to transport the lifting gas from surface down to the two GLVs and the tubing which is receiving the reservoir inflow and the gas from the two GLVs. The reservoir is modelled with linear IPR with a reservoir pressure of 198 bara and 123 degC. The inflow coefficients are 0 for A and BINJ= 7e-006 and BPROD=7e-007 and the phase distribution is set to 85% water fraction. The initial conditions are set so that the well’s annulus and tubing is filled with water. Two LEAK components are used for the GLVs and both are of type GASLIFTVALVE and uses the DEMO GLV gas lift valve model. The unloading valve (top) has a port size of 12, PTRO set to 125 bara and the operational valve (bottom) has a port size of 24 and a PTRO set to 0 bara. OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. Numerous variables related to the LEAK keyword has been included and can be seen in the sample case. NODE: The bottom of the casing and tubing have two closed nodes. The casing outlet boundary condition is set to a constant pressure of 125 bara, temperature of 4°C and 100% gas fraction. The wellhead (tubing) outlet boundary condition is set to a constant pressure of 13.5 bara and a temperature of 28°C. Output: ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 5 seconds. PROFILE: Profile variables are plotted every 100 seconds. Thermal Component: ANNULUS: The tubing is placed inside of the casing using the ANNULUS keyword.

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Well-pressure boost

Well-pressure boost The sample case Well-PressureBoost.opi is a simple demonstration of a controlled PressureBoost pump. A typical geometry from well to platform is used. The PressureBoost pump is used to increase the production. A controller is used to achieve a desired flow rate.

Case Comments CaseDefinition OPTION The steady state pre-processor is enabled. The temperature calculation is performed using a constant overall heat transfer coefficient (UGIVEN). INTEGRATION The steady state pre-processor is enabled. The temperature calculation is performed with a heat transfer through the wall and heat accumulation in the wall. Controller PIDCONTROLLER: The flow controller, FC, is used to achieve the desired flow rate of 10 kg/s. A flow transmitter, FT, is connected to the MEASRD terminal, supplying the measured flow rate in the pipeline. The controller output is connected to the PressureBoost pump. The controller bias is set to zero, and the pressure increase of the Pressureboost pump is therefore zero at time 0. The AMPLIFICATION and INTEGRALTIME is tuned to get a stable simulation. FlowComponent FLOWPATH — Boundary&InitialConditions — HEATTRANSFER: A constant ambient temperature of 6°C, and a constant ambient heat transfer of 6.5 W/m 2/°C is used.. FLOWPATH — Boundary&InitialConditions — WELL: The reservoir pressure is set to 150 bara, and the reservoir temperature is set to 68°C. The production and injection model is linear with AINJ = APROD = 0 and BINJ = BPROD = 6.0e-6. FLOWPATH — ProcessEquipment — PRESSUREBOOST: The pump is given a maximum pressure increase of 60 bar. The isentropic efficiency is set to 0.9. FLOWPATH — ProcessEquipment — TRANSMITTER: The flow transmitter, FT, is positioned close to the PressureBoost pump. FT measures the overall mass flow (GT) in the pipe.

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FLOWPATH — Piping: 9 pipes is used to describe the pipeline from the well to the platform. The pipeline is 6500 m long, and have an overall elevation of 1800 m. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. NODE: The pipe is closed the inlet. The outlet node is a PRESSURE node, setting a pressure of 50 bara. Gas at 22°C is used as boundary fluid. Output OUTPUT OLGA variables are printed to the output file every 10 seconds. ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. The controller output CONTR and the pressure increase PUMPDP is included among the TREND variables.

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Pump battery

Pump battery The sample case Pump-Battery.opi demonstrates 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 below. 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.

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 Multiphase 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.

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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=10 -7 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. NODE: The outlet pressure held constant at 60 bara and the temperature is 20°C. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Centrifugal pump

Centrifugal pump The sample case Pump-Centrifugal.opi demonstrates 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 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 the figure below. 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.

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 Multiphase pump module. In this sample case, the pump speed is controlled by the total mass flow rate (PUMPGT) through the pump. The total mass flow rate is measured by and defined in the Transmitter TM-2. PIDCONTROLLER: C-PUMP-C-RE: This controller is required by the Multiphase 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.

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MANUALCONTROLLER: C-PUMP-C-BY: This controller is required by the Multiphase pump module. However, the built-in bypass function of the Multiphase 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 withSETPOINT=0, which means that the built-in bypass line is closed. MANUALCONTROLLER: C-PUMPV-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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Displacement pump

Displacement pump The sample case Pump-Displacement.opi demonstrates 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 below. 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.

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 Multiphase pump module. In this sample case, the pump speed is controlled by the total mass flow rate (PUMPGT) through the pump. The total mass flow rate is measured by and defined in the Transmitter TM-2. PIDCONTROLLER: C-PUMP-D-RE: This controller is required by the Multiphase 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 Multiphase pump module. However, the built-in bypass function of the Multiphase pump module is obsolete since any bypass line

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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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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Simplified pump

Simplified pump The sample 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 below.

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 depends 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 diameter is 12" and roughness 0.001 m FLOWPATH — Output — TRENDDATA: Mass flow rates and pump variables are plotted.

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FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. 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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OneSubsea pump

OneSubsea pump The OneSubsea pump example case is meant for training purposes and presents typical pump start-up, pump stop and pump trip operations. The sequence of events for these operations may differ in real life operations. The OneSubsea pump is used to increase, prolong and/or enable the production of hydrocarbons by lowering and/or maintaining the subsea pressure. The OneSubsea pumps will give stable and flexible operation due to a wide operation envelope, the possibility to operate at all gas volume fractions and to handle different flow regimes. The example case is a setup with 2.7 km flowline (profile given in See " Flowline geometry" on page 103) and a OneSubsea multiphase pump (OneSubsea-Hx310-700-45). The flowline is divided into 27 sections (each section is 100 meter long).

Flowline geometry The model, as illustrated in See "Illustration of the sample case." on page 104 includes a closed inlet node followed by a pressure driven source with a pressure of 90 bara at 50 °C. The pressure driven source represents the wellhead. The OneSubsea multiphase pump is located 500 meters from the wellhead. Two manual controllers are connected to the pump; V1 (MANUALCONTROLLER: V1) and V3 (MANUALCONTROLLER: V3). V1 is the pump inlet valve and V3 is the pump bypass valve (see See ": The OneSubsea pump station for the sample case." on page 104. A pressure node with a pressure of 55 bara is located at the outlet. The outlet node is elevated 200 meters to represent a riser.

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Illustration of the sample case.

: The OneSubsea pump station for the sample case.

Case comments Library: WALL: The case contains one wall of steel layer. Case definition: INTEGRATION: The largest time-step allowed is 1 second and the smallest is 0.001 second. The initial time step is set equal to the minimum time step. OPTIONS: Heat transfer on the inside and outside wall, wall heat conduction and heat storage is accounted for in the temperature calculation. Flow Component: FLOWPATH: Flowline:

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OneSubsea pump

Boundary and Initial Conditions: The source is pressure driven with a pressure of 90 bara, temperature of 50 °C, gas mass fraction in gas and oil mixture of 0.1 and a mass fraction of free water in the total source flow mixture of 0.1. Output: Multiple trend variables can be added for the pump, such as pump differential pressure (PUMPDP), GVF mix (GVFMIX), total volume flow through the pump (PUMPQT), total pump power (PUMPTT), pump speed (PUMPSPEED) and total volumetric recirculation flow (PUREQT). Trend variables (pressure and total volume flow) have also been added in the section upstream of the pump. Piping: The flowline consists of three pipes (PIPE-1, -2 and -3) with an internal diameter of 6 inches and an absolute roughness of 2.8E-05 m. Process equipment: The OneSubsea-Hx310-700-45 pump is used in the example case. It is a helicoaxial multiphase pump with a nominal flow rate of 700 Am3/h and a maximum differential pressure of 45 bars. The choice of pump is based on the natural well flow and GVF at pump location conditions and the required differential pressure. The flow rate gives an indication of the pump size. The OneSubseaMIXER with a typical mixer volume of 1 m3 is used in the example case. The size of the recirculation choke (CHOKECV = 70) is based on a simplified control valve sizing equation (see Eq. 1) and the operational envelope for the pump.

(Eq. 1) is the valve flow coefficient, Q [ ] is the total flowrate, SG is the specific gravity of the flow mixture and ΔP [bar] is the differential pressure over the recirculation choke. NODE: The inlet node is closed. The outlet boundary condition is set to a constant pressure of 55 bara and a temperature of 15 °C. Output: TREND: Trend variables are plotted every 5 seconds.

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OneSubsea pump - Start-up procedure The case pump_start.opi presents a simplified demonstration of a start-up procedure for a OneSubsea pump. Before pump start-up V1 (inlet valve) is closed, V3 (bypass valve) is open and V4 (choke) is open. All flow is produced through the bypass line and flow is stable. The start-up sequence starts with opening V1, and then the OneSubsea pump is started with a speed of 1500 rpm. The pump speed is ramped up until the pump capacity is larger than the total well flow. Hence the total flow from the wells passes through the pump and not through the bypass line. V3 is then closed and the choke is set to close shortly after. When the choke is fully closed, the pump is set in suction pressure control. Further, the pump speed is ramped up through a stepwise reduction (2 bars per 20 min) in suction pressure control set point until the desired suction pressure control set point is reached. Trend variables and pump envelope operating points for the start-up procedure are given respectively in See " Trend variables throughout the start-up procedure" on page 106 and See " Pump envelope operating points throughout the start-up procedure" on page 106:

Trend variables throughout the start-up procedure

Pump envelope operating points throughout the start-up procedure The simulation shows an increased total volume flow of 55% by lowering the subsea pressure with 5 bar.

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OneSubsea pump - Start-up procedure

Case comments Case Definition: INTEGRATION: The duration of the simulation is five hours. RESTART: Restart data is written to file. Controller: MANUALCONTROLLER: V1: The inlet valve is opened at 50 minutes. Typical opening time for V1 is 60 seconds. MANUALCONTROLLER: V3: The bypass valve is closed at 82 minutes when the total well flow passes through the pump. Typical closing time for V3 is 60 seconds. Flow Component: FLOWPATH: Flowline: Process equipment: The pump is started at 51 minutes with a start speed of 1500 rpm. At 80 minutes the pump speed is ramped up to 2400 rpm and the choke is set to close at 83 minutes. Typical closing time for the choke is approximately 50 minutes. The suction pressure control is initiated at 140 minutes with a pressure set point of 85 bara. The suction pressure control set point is lowered in intervals of 2 bars per 20 minutes to the desired set point of 80 bara (the last reduction is only 1 bar).

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OneSubsea pump - Trip procedure The case pump_trip.opi is a demonstration of a trip procedure for a OneSubsea pump. The case is restarted from the start-up procedure, with simulation start at five hours. The MPP is initially operating at steady state when a trip is initiated. The inlet- and bypass valves go to their fail-safe positions, i.e. V1 (inlet valve) closes and V3 (bypass valve) opens. See See " Trend variables throughout the trip procedure" on page 108 for trend variables throughout the trip procedure.

You must run the start-up procedure before this procedure can be run.

Trend variables throughout the trip procedure

Case comments Case Definition: INTEGRATION: The start time for the simulation is at five hours and the simulation end time is seven hours. RESTART: No restart data is written to file and the pump start-up procedure is used to restart the simulation. Flow Component: FLOWPATH: Flowline: Process equipment: At 360 minutes a trip is initiated.

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Hydrodynamic slugging

Hydrodynamic slugging The sample 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 below.

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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds.

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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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Start-up slug

Start-up slug The sample 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 below.

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 FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds.

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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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Submodelling

Submodelling This sample case is a combination of two cases, mastermodel and submodel_1. Together they form an integrated OLGA model consisting of two cases demonstrating the submodelling features of OLGA. The case submodel_1 represents a simplified well using a SOURCE feeding flow into the master model that represents a 3-phase separator. It is similar to the sample case Separator in functionality that can be found in the Process category. Two connections has been made between the two cases: 1.

A flow connection between NODE N-OUTLET-PIPELINE-1 in submodel_1 and SOURCE SPIPELINE-1 in mastermodel.

2.

A signal connection between TRANSMITTER PT-1301 in submodel_1 and MANUALCONTROLLER SC-PT-101 in mastermodel.

The PIDCONTROLLER PIC-101 located in the master model is regulating the pressure in the outlet of FLOWPATH B-PIPELINE-1 located in submodel_1. The two other PIDCONTROLLER’s LIC-104 and LIC105 are controlling the oil level and oil/water interface level in the separator.

Case definition SCHEDULER: This keyword is required for enabling OLGA to schedule two or more submodels. Can be configured in a separate case or as in this example configured as part of a OLGA case including a submodel. SERVEROPTIONS: The submodels communicate via OPC, so both submodels needs to be configured as OPC servers. Flow component NODE N-OUTLET-PIPELINE-1: GASCMASS: 21 kg/m3 OILCMASS: 11 kg/m3 WATERCMASS: 21 kg/m3 PRESSURE: 2500000 Pa TEMPERATURE: 15 C SOURCE S-PIPELINE-1: GASCMASSFLOW: 8 kg/s OILCMASSFLOW: 5 kg/s WATERCMASSFLOW: 2 kg/s PRESSURE: 2500000 Pa TEMPERATURE: 15 C Output The following global output SERVERDATA keys are required: HT, MAXSPEED, SIMTIME, TIME Submodelling Two SUBMODELS keywords are added:

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SUBMODEL: mastermodel. The key LOCATION is set to INTERNAL (internal to the OLGA case). SUBMODEL: submodel_1. The key LOCATION is set to LOCAL (local to the computer running OLGA). Required SERVERDATA keys NODE N-OUTLET-PIPELINE-1: PRESSURE, TEMPERATURE, GASCMASS, OILCMASS, WATERCMASS, DPDGG, DPDGLTHL, DPDGLTWT and HTEXT. SOURCE S-PIPELINE-1: PRESSURE, TEMPERATURE, GASCMASSFLOW, OILCMASSFLOW, WATERCMASSFLOW, DGGDP, DGLTHLDP, DGLTWTDP and HTEXT Required SERVERDATA keys NODE N-OUTLET-PIPELINE-1: CGGBOU, CGLTHLBOU, CGLTWTBOU, PTBOU, TMBOU, DGGDPB, DGLTHLDPB, DGLTWTDPB and HT. SOURCE S-PIPELINE-1: CMG, CMLTHL, CMLTWT, PT, TM, CMG, CMLTHL, CMLTWT and HT. Required submodel connections: Flow: submodel_1.OUTLET-PIPELINE-1 coupled to mastermodel.PIPELINE-1 Signal: submodel_1.SIGNALOUT-1 coupled to mastermodel.SIGNALIN-1

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Fluid bundle

Fluid bundle The sample case FluidBundle.opi demonstrates how OLGA can be used to simulate how a bundled pipeline initially filled with gas is heated up before production is started. Note, 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 See "Cross-section of the bundle." on page 115.

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.

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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. 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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 ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file, every 10 th hour. TREND: Trend variables are plotted every minute. PROFILE: Profile variables are plotted every hour.

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Solid bundle

Solid bundle The sample case SolidBundle.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 See "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." on page 117.

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.

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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 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. FLOWPATH — Output —SERVERDATA: Server variables are available for plotting in interactive simulations. 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. Output ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file every 5 hours. TREND: Trend variables are plotted every 10 seconds. PROFILE: Profile variables are plotted every 20 minutes. 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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Solid bundle

OneSubsea pump - Stop procedure The case pump_stop.opi is a simplified demonstration of a stop procedure for a OneSubsea pump. The case is restarted from the start-up procedure, with simulation start at five hours. The MPP is initially operating at steady state. The stop sequence is initiated by reducing the pump speed by increasing the suction pressure control set point in intervals of 2 bars per 20 min (the last increase is only 1 bar). When the differential pressure is approximately 5 bars, the pump is stopped. At the same time V3 (bypass valve) opens. V1 (inlet valve) closes after a time delay of 20 seconds. See See ": Trend variables throughout the stop procedure" on page 119 for trend variables for the stop procedure.

You must run the start-up procedure before this procedure can be run.

: Trend variables throughout the stop procedure

Case comments Case Definition: INTEGRATION: The start time for the simulation is at five hours and the simulation end time is 7.5 hours. RESTART: No restart data is written to file and the pump start-up procedure is used to restart the simulation. Controller: MANUALCONTROLLER: V1: The inlet valve starts to close 20 seconds after the pump stop has been initiated. Typical closing time for V1 is 30 seconds. MANUALCONTROLLER: V3: The bypass valve is opened at the same time as the initiation of the pump stop. Typical opening time for V3 is 30 seconds. Flow Component: FLOWPATH: Flowline: Process equipment: At 340 minutes the suction pressure control set point is increased in intervals of 2 bars per 20 minutes until a pump differential pressure of approximately 5 bars is reached (suction pressure control set point of 85 bara). The pump is then stopped.

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Valve model To demonstrate some of the model options for the valve, five simple valve cases have been created: Sub_Critical_Valve_Flashing_Liquid.opi - Sub critical valve flow of a flashing liquid Critical_Valve_Two_Phase.opi - Critical two phase valve flow. Valve_Recovery.opi - Sub critical none flashing liquid valve flow. Valve_Slip.opi - Two phase sub critical valve flow. Valve_Termal_Equilibrium.opi - Three phase sub critical valve flow. All these cases have the same geometry and configuration. The left boundary condition is a closed node and a mass flow source in the first section. The right boundary condition is a gas pressure node. The geometry is described with one pipe divided in 10 equal sections. The pipeline is 400 m long and have an elevation of 10 m. The diameter is 0.12 m. The cases differ in: 

source mass flow, phase fractions and temperature

 

outlet pressure valve opening



fluid table

GUI snapshot from the Sub_Critical_Valve_Flashing_Liquid.opi case.

Case comments CaseDefinition: OPTION: The steady state pre-processor is enabled. There are no heat transfer to the surroundings. The simulation is adiabatic. INTEGRATION: The simulation time is 3 minutes with a maximum time step of 5 seconds. FlowComponent:

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Valve model

FLOWPATH — Boundary&InitialConditions — Source: A constant mass source is positioned at the first section of the pipeline. FLOWPATH — ProcessEquipment — Valve: The valve is positioned at the middle of the pipeline. The valve diameter is identical to the pipeline diameter. The HYDROVALVE model is used. FLOWPATH — Piping: One pipe is used to describe the pipeline. The pipeline is 400 m long, and have an overall elevation of 10 m. The pipeline diameter is 0.12 m. The pipeline is split in 10 sections. NODE: The pipe is closed at the inlet. The outlet node is a PRESSURE node. Gas at 25°C is used as boundary fluid. Output: OUTPUT: OLGA trend variables are printed to the output file every 15 seconds. Profile variables are plottet at the start and end of the simulation. Valve TREND variables included: ICRIT, PVALVE, TVALVEOUT, VALVDP, THROATSLIP, TVALVE

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Critical two-phase valve flow This sample case is created to demonstrate the possible effect of the valve model option EQUILIBRIUMMODEL. Running the case with EQUILIBRIUMMODEL FROZEN, HENRYFAUSKE and EQUILIBRIUM will give a large difference in pressure drop. The EQUILIBRIUM option gives the largest pressure drop over the valve, and the FROZEN option gives the lowest pressure drop. The HENRYFAUSKE option lies between the FROZEN and EQUILIBRIUM option.

Pressure profile for EQUILIBRIUMMODEL FROZEN/HENRYFAUSKE/EQUILIBRIUM at critical valve flow.

Case comments See Valve Model for a more detailed description of the case.

CaseDefinition: Files: 2phase.tab FlowComponent FLOWPATH — Boundary&InitialConditions — Source: Mass flow is set to 22 kg/s. The temperature is set to 90ºC, and the gas fraction is 0.1. No water is included in the source. FLOWPATH — ProcessEquipment — Valve: The valve opening is set to 0.03. NODE: The outlet node pressure is set to 50 bar.

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Subcritical valve flow of a flashing liquid

Subcritical valve flow of a flashing liquid This sample case is constructed to demonstrate the possible effect of the valve model option EQUILIBRIUMMODEL. Running the case with EQUILIBRIUMMODEL FROZEN, HENRYFAUSKE and EQUILIBRIUM, EQUILIBRIUM will give a large difference in pressure drop. The reason for the difference in pressure drop, is due to the flashing of the liquid. The EQUILIBRIUM option includes flashing, the HENRYFAUSKE option has a correction for the gas fraction in the throat while the FROZEN option do not include any flashing. In a non-flashing case the models will give very similar results. The pressure drop with the EQUILIBRIUM option is larger than with the FROZEN option.

Pressure profile for EQUILIBRIUMMODEL FROZEN, HENRYFAUSKE and EQUILIBRIUM.


CaseDefinition: FILES 2phase.tab FlowComponent FLOWPATH — Boundary&InitialConditions — Source: Mass flow is set to 18 kg/s. The temperature is set to 90ºC, and the gas fraction is 0. No water is included in the source. FLOWPATH — ProcessEquipment — Valve: The valve opening is set to 0.05. NODE: The outlet node pressure is set to 95 bar.

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Valve recovery This sample case is constructed to demonstrate the effect of the valve model option RECOVERY. Running the case with RECOVERY YES/NO will give a difference in pressure drop over the valve. The pressure drop over the valve will without recovery always be greater with recovery.

Trend plot of VALVDP with and witout pressure recovery.

Case comments See Valve Model for a more detailed description of the case. CaseDefinition: Files 3phase.tab FlowComponent FLOWPATH — Boundary&InitialConditions — Source: Mass flow is set to 20 kg/s. The temperature is set to 50ºC, and the gas fraction is 0. No water is included in the source. FLOWPATH — ProcessEquipment — Valve: The valve opening is set to 0.25. NODE: The outlet node pressure is set to 160 bar.

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Valve slip

Valve slip This sample case is constructed to demonstrate the possible effect of the valve model option SLIPMODEL. Running the case with SLIPMODEL NOSLIP and CHISHOLM will give a large difference in pressure drop. The CHISHOLM model will apply a slip between gas and liquid in the valve.

Pressure profile for SLIPMODEL NOSLIP and CHISHOLM.

Trend plot of THROATSLIP (The slip ratio in the throat) for SLIPMODEL NOSLIP and CHISHOLM.

Case comments See Valve Model for a more detailed description of the case. CaseDefinition: Files 2phase.tab FlowComponent FLOWPATH — Boundary&InitialConditions — Source: Mass flow is set to 22 kg/s. The temperature is set to 30ºC, and the gas fraction is 0.1. No water is included in the source. FLOWPATH — ProcessEquipment — Valve: The valve opening is set to 0.05. NODE: The outlet node pressure is set to 50 bar.

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Thermal equilibrium in valve flow This sample case is constructed to demonstrate the possible effect of the valve model option THERMALPHASEEQ. Running the case with THERMALPHASEEQ YES and NO will give a difference in pressure drop due to the change in gas density for the valve model. This model option will affect the throat gas temperature (TVALVE) . For this case, the valve pressure drop (VALVDP) change when applying thermal equilibrium is approximately 0.5 bar. The change in the lowest gas temperature in the valve (TVALVE) is almost 16ºC.

Trend plot of VALVDP for THERMALPHASEEQ YES and NO.

Trend plot of TVALVE for THERMALPHASEEQ YES and NO.


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Gas lift well casingheading

Gas lift well casingheading The sample case Gas-lift-well-casingheading.opi is a demonstration of a gas lift well. The well geometry and components are shown in the figure below. The gas lift system is built using a LEAK inserted at 2350 m that provides communication between the annulus and tubing. The gas enters the annulus with a “Sourceinflow” at 0 m depths with a constant 0.7 kg/s.

The simulation requires flow in annulus which is only available through the OLGA Well module. The simulation scenario is the following: The total simulation time is 24 hours. If no gas is injected by for instance setting the SourceInflow to 0 kg/s, the well will not be able to produce. The well quickly fills up with liquid and stops producing. If 0.7 kg/s is used, the well will cyclically unload and allow for intermittant production. If the rate however is set a bit higher (for instance 1.5 kg/s), the well will unload and eventually stabilize the production at a given rate. The case can be used to play with variables like production pressure, gas lift rates, tubing diameters etc. in order to optimize the production. See also the output variable GTLEAK’s Casing Heading (or Slugging) Outflow to the Tubing, despite the output variable GTSOUR’s Constant Inflow. This occurs since the Gas Lift LEAK needs a smaller hole (and more Orifice dP) to Stabilize its Gas Lift Dynamics Library: WALL: Multiple walls are present in the model to accurately represent the various sections of the well. The walls are built up by many layers of material including casing steel, cement, fluid behind casing and formation. As can be seen in the well schematic, there is not always cement behind the casing and the wall will therefore include a defined “fluid above cement” instead. CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through pipe walls is used. INTEGRATION: The simulation runs for 24 hours using a minimum time step of 0.001 s and a maximum one of 100 s. The initial time step is set equal to the minimum one.

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Flow Component:

FLOWPATH(s): The well consists of two main flowpaths: The tubing section with the well bore section and the separate annulus flowpath. The reservoir inflow is modeled using a linear equation with 150 bara Pressure, 100 degC and a PI of 10 Sm3/d/bar. The initial conditions are set so that the well is filled with gas. OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore as well as the top and bottom of the annulus is modeled with closed nodes. The tubing outlet boundary condition is set to a constant pressure of 20 bara, temperature of 15°C and 100% gas fraction. Output:

ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file every 1 hour. TREND: Trend variables are plotted every 5 sec. PROFILE: Profile variables are plotted every 1 hour. Thermal Component:

ANNULUS: The tubing is placed inside of the casing using the ANNULUS keyword.

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Gas well liquid loading

Gas well liquid loading The sample case Gas-well-liquid-loading.opi is a demonstration of a liquid loading situation in a well. The well geometry and components are shown in the figure below.

The simulation does not include flow in annulus so the space between the tubing and casing is only modelled as part of the tubing wall. The simulation scenario is the following: The total simulation time is 48 hours and illustrates how the well starts producing but eventually stop producing due to high liquid content in the well.

Library: WALL: Multiple walls are present in the model to accurately represent the various sections of the well. The walls are built up by many layers of material including casing steel, cement, fluid behind casing and formation. As you see in the well schematic, there is not always cement behind the casing and the wall will therefore include a defined “liquid behind tubing” instead. CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through pipe walls is used. INTEGRATION: The simulation runs for 48 hours using a minimum time step of 0.001 s and a maximum one of 100 s. The initial time step is set equal to the minimum time step. Flow Component: FLOWPATH(s): The well consists of two flowpaths: The tubing section and the well bore section. The reservoir inflow is modelled using the Forchheimer equation that starts of at time 0 with 35 bar Pressure, 100 degC and a B coefficient of 0.000298 psi2 / (scf/d). After 2 days (24 hours), the pressure is lowered to 30 bar. The initial conditions are set so that the well is filled with gas. OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables.

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NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 20 bara, temperature of 15°C and 100% gas fraction. Output: ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 10 min. PROFILE: Profile variables are plotted every 24 hour.

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Well clean-up

Well clean-up The sample case Well-Clean-Up.opi is a simple demonstration of cleaning scenario in a well. The well geometry and components are shown in the figure below.

The simulation scenario is as follow: The wellbore is initially filled with different types of fluid (see above). At the bottom-hole, the wellbore is filled with Mud. Above the Mud the wellbore is filled with Brine, and on the top the wellbore is filled with Baseoil. The simulation starts from a restart file where the well is settled, the wellbore fluid is in thermal balance with the formation and the pressure profile is established in the wellbore. The inflow zone at the bottom of the wellbore is at P=235.5 bar and T= 106°C, and will not flow when the topside pressure is 20 bara. In order to get the well to produce, nitrogen lift gas is injected at the rate of 5 kg/s for about 5 hours through the Nitrogen source. The lift gas assist in the clean-up process, and the well starts to produce.

Library: WALL: Multiple walls are present in the model to accurately represent the various sections of the well. The walls are built up by many layers of material including formation, spacer between formation and casing, casing steel, cement, fluid behind casing and formation. As you see in the well schematic, there is not always cement behind the casing. DRILLINGFLUID: 4 different drilling fluids are created for this task. Nitrogen for the lifting process, brine, oil-based mud, water-based brine and base oil. CaseDefinition: OPTIONS: The full heat transfer calculation option with heat transfer through pipe walls is used.

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RESTART: The case is restarted from a settled wellbore restart solution (CLEANUPINI.rsw) INTEGRATION: The simulation runs for 10 hours using a minimum time step of 0.001 s and a maximum one of 1 s. The initial time step is set equal to the minimum time step. Flow Component: FLOWPATH(s): The well consists of two flowpaths: The tubing section and the well bore section. The reservoir inflow is modelled using the linear equation with INJECTIVITY and PRODI= 115 Sm3/d/bar. OUTPUT: Multiple variables have been set up for output such as trend variables and profile variables. NODE: The bottom of the wellbore is a closed node. The tubing outlet boundary condition is set to a constant pressure of 20 bara, temperature of 15°C and 100% gas fraction. Output: ANIMATE: 3D plot of holdup for liquid along the pipeline is plotted every 10 seconds. OUTPUT: OLGA variables are printed to the output file at the start and end of the simulation. TREND: Trend variables are plotted every 5 seconds. PROFILE: Profile variables are plotted every 30 seconds.

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Well dry tree

Well dry tree The sample case Well-Dry-Tree.opi is a demonstration of a dry tree well. The case is very simple and is similar to one of the sample cases. The only difference being that the well head is of type dry tree. As shown in See "Well dry tree" on page 133, the well riser and tubing starts from depth 0 in air and goes through water at MSL of 50m and into the formation at 150m. The casing model includes several surface casings and there is no flow in the annulus (packer) which means that the casing, cement, fluid behind casing and formation are all part of the WALL.

Well dry tree There is no particular simulation scenario and no special parameters compared to the sample well cases.

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OLGA Sample Cases

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