Workflow for creating a PVTi project, tuning EoS and generating output for compositional and blackoil simulation(Based on PVTi Tutorials 2-4) This exercise describes how to specify fluid properties in PVTi. It covers the basic functionality of PVTi; The PVT report for this fluid contains details of three experiments: a Constant Composition Expansion experiment, a Differential Liberation experiment, and a Bubble Point experiment. The later steps describe how the experimental results may be used to fit an equation of state to the experimental behavior, and how this fitted equation of state can be used to generate PVT tables for use in reservoir simulations. Creating a fluid system This part of the exercise shows how to set up basic fluid properties in PVTi and how to display the phase envelope for the defined fluid. 1. Start PVTi. 2. Select PVTi: File | New... 3. Enter BLACK.PVI as the project name in the file selection window. The Fundamentals panel opens so that basic project information can be entered. 4. Enter CO2, N2, C1 and C6 into the Components column. 5. Click Apply. 6. Click Yes so that PVTi fills in the library component names. 7. Enter the mole fractions from figure and the details for the C7+ component into the Fundamentals panel and click OK. Note The components for which no mole weight or specific gravity has been specified are automatically set to use the PVTi component properties library. The component properties can be examined by selecting PVTi: Edit | Fluid Model | Components.... This panel can also be used to add additional components, the select alternative characterization methods and to manually defined component properties Selecting an equation of state Three-parameter Soave-Redlich-Kwong equation of is fitted to the results of experiments carried out on the defined fluid. The Lohrenz-Bray-Clark correlations is used for viscosity. 8. PVTi: Edit | Fluid Model | Equation Of State... This opens the Equation of State and Viscosity Correlation panel. 9. Select the 3-parameter Soave-Redlich-Kwong equation of state (SRK3). 10. Click on OK. 11. Click on OK to change the parameters to SRK3 defaults. Program options 12. PVTi: Utilities | Program | Options... This opens the Program Options panel. 13. Set the Separator GOR calculation to use Liquid at Stock Tank Conditions. 14. Set the Temperature-dependence for volume shifts to be calculated by Polynomial correlations. 15. Set Treatment of Volume Shifts to Independent and click on OK. 1. the second is a phase plot. . First is the fingerprint plot of mole fraction versus molecular weight. Right-click on ZI in the project tree-view and select Fingerprint Plot from the popup menu.View fluid attributes Now that a fluid has been defined. there are two plots available to review the fluid we have entered. 16. The plot should look like Figure 5. saves a history of the project... 21. Saving the SYSTEM section for future use 22. The complete project can be saved using PVTi: File | Save. This. Set Mole Fraction or Percentage to Percentage 28. Set Absolute or Gauge Pressure to Gauge.. 5 quality lines. Call the file FLUID_DEF. 20.. effectively. PVTi: View | Samples | Phase Plot..PVI. Set the Temperature Unit Type to Fahrenhei 27.. Click on OK. PVTi: File | Save (Concise). Simulating experiments This step describes how experimental observations can be entered into PVTi and how the experiments can then be simulated from an existing fluid definition. 29. Setting units 24. 25.17. The plot should look like Figure ?. 18. Click on OK. Request Sample ZI. Set the Unit Type to Field 26. . Utilities | Units. 23. 19... 35.. Select the Observations folder. In the General folder. 38. 32. 39. from the drop-down list. enter the temperature (220 F). The table now shows two folders. 34. the General folder now shows an entry field to select fluid type and another to enter the temperature of the experiment. 30. Click in the top left cell of the table and select Pressure from the dropdown list in that cell. PVTi: Edit | Experiments. The Experiment Entry window now shows three folders: General.Defining experiments for simulation In this section data from a constant composition expansion experiment are brought into PVTi... The Components folder has disappeared as there were no component observations selected. 33. 31. 36. Observations and Components. These folders are used to define the experiment entry form.. In the second column select Relative Vol. Experiment Entry: Add | Pressure Depletion | Constant Composition Expansion. . The ability to tailor the table means that data entry can then be further accelerated by importing observations from a text file or the clipboard. 37. Click on Next. 47. Table is provided in the file CCE_TABLE.TXT and click on Open.TXT 42. Note The error message “Cannot delete rows from this table” appears This is because the table has a fixed length and the file we are importing from has fewer rows than the table. 45.. 44. 41. Click on OK.40. Click on Next to create the experiment. 43.. This message can be safely ignored. The Observations folder now shows a two-column table with the columns selected previously. Select CCE_TABLE. . In the Text Import Wizard turn on Ignore Records and set the number of records to ignore to 1 (since we want to ignore the column headings). Select the Observations folder. The view of the table should no longer contain the first row. Click on OK to remove the message “Cannot delete rows from this table”. Right-click in the table and select Table Import | From file. 46. Click on the Relative Vol. PVTi: Edit | Experiments.The data tree now shows the created experiment (CCE1). Differential liberation experiment 50. 52.. The asterisk (*) next to the experiment’s name means that it is active. The Main Plot Window should now look like Figure 5.. Vapor Z-factor. In the Observations folder. CCE1 has one observation node. Liquid Density. Plotting simulation results 49. set the table headings to match those in Table Pressure. .. for the relative volume measurements. 48.. Oil Rel. Gas-Oil ratio. Click Close to shut the panel.. Vol. Gas Gravity. Experiment Entry: Add | Pressure depletion | Differential Liberation.3. 51. Gas FVF. observation in the Data Tree and drop it over the Main Plot Window. 56. which contains column headings.53. remembering to ignore the first line. Import the file DL_TABLE. Click on Next 54. . 55. Enter 220 F as the temperature in the General folder. Click on Next to create the experiment.TXT into the table in the Observations folder. Experiment Entry: Add | Single Point | Bubble Point. Defining the bubble point experiment Finally.. Pressure and the second to Liquid Density 59. 61. Enter the temperature. . there is a bubble point experiment at 220o F to be added. Select the Observations folder. 57.The Experiment Entry panel now shows that there are 2 experiments defined.. In the Observations folder set the first column heading to Sat. 220o F in the General folder. 58. Click on Next 60. Click on Next to create the experiment. 68. Simulating all the experiments All the experiments have now been entered. 69. is displayed in the Output Display panel. 65.PVI.62. 72. to describe experimental results. opens the Regression panel. Enter the saturation pressure as 2516. Call the file SIMULATE_SECTION. PVTi: View | Observations. Sensitivity analysis Sensitivity analysis is used to establish which fluid properties most affect the difference between the observed and simulated values. Output Display: File | Close Plotting all observations for an experiment 67. Fitting an equation of state to experimental results This part of the exercise shows how a fluid definition can be fitted. Saving the project for future use 71. PVTi: File | Save (concise).. Click OK. The most sensitive attributes are then adjusted slightly by regression to improve the equation of state model of the fluid. showing information on all the experiments.. 63. Select the Differential Liberation (DL1) experiment.11 lb/ft3. 64.. The equation of state is fitted to the observation data to produce a better representation of the fluid. 70. PVTi: Run | Regression. This plots each observed data set (as points) for the differential liberation experiment and each calculated data set (as lines) generated by simulation.7 psig and the liquid density as 45. . Double-clicking on one of the small plots swaps it with the large plot. 66. 73. Click Close. Examine each of the plots and note how well (or badly) the simulation has matched the data.. A sensitivity analysis is carried out to determine which attributes of the fluid components improve the solution by the smallest change. by regression... PVTi: Run | Simulate A simulation report. NC5 and C6 groups those components into the first regression variable. Click Variables. NC4. Entering 1 in the critical pressure (Pcrit) column in the rows corresponding to C3.74. Fill in the table in the Select EOS parameters for regression panel with the following data: . The regression variables are numbered for each property. IC4. Select Normal as the Type of regression variables in the Variables section of the panel. 76. 75. IC5. The values in the leading diagonal dominate the matrix.77. Click on OK. The sensitivities for the first Pcrit parameter are generally lower than for the other regression variables. 78. except in the first row. • Select the Covariance folder In this table the largest value is for the first Pcrit parameter. designed to give the best possible insight into creating a fluid model. Click Regression in the Report section of the panel 80. • Select the Hessian folder. indicating that it is the least well determined by the regression. 79. the row relating the first Pcrit parameter. Leave the second part of the Select EOS parameters for regression panel blank. . • Select the Sensitivities folder. The Regression Report panel provides several views of the regression problem. Fill in the columns to describe the reduced set of regression variables with the following data: . 81. 84. Click Variables in the Regression panel. Close the Regression Report panel. From an examination of the information in the Regression Report panel. and it may hinder it. 82. Consequently that regression variable is removed before regression is started. There is a strong negative correlation between the two Pcrit parameters.• Select the Correlation folder. it can be seen that the first Pcrit parameter is not likely to aid the regression. indicating that the regression would proceed better if only one of those two parameters were used. 83. In the Select EOS parameters for regression panel click on Reset to clear all the cells in the table. 85. Click on OK 86. . Repeat steps 90-91 and compare. Right-click on experiment DL1 in the project tree-view and select Plot from the pop-up menu. 90. Select the Modifiers folder. 91. 88. This starts the regression. Click on Regression in the Report section of the Regression panel. The difference between the final and initial value of each regression variable is displayed. Click Run in the Regress section of the Regression panel.Viewing the regression progress 87. . 89. The observed data are plotted as points and the simulated data before and after regression are plotted as lines.. it may be used in a reservoir simulation. Enter a reservoir temperature of 220 F and an initial reservoir pressure of 2500 psig. Call the file REGRESS_SECTION. Examine the plots in the main window. This is effectively separate from the fluid model. An observation-by-observation breakdown of the final fit is shown. Select the Details folder. The regression has improved the equation of state model.92.. Click Accept in the Regress section of the Regression Panel. PVTi facilitates the transition between a fluid description and the PVT keyword description required by the ECLIPSE family of simulators. so the regression results can be accepted. Close the Regression Report panel. 94. PVTi: Save (concise). 96. Exporting water properties The water properties exported from PVTi are generated by correlation. . 93. along with the total fit to all data (both unweighted and incorporating the observation weights). 97.. PVTi: File | Export Keywords | Water. 99. 98. 95. 100. Information can be exported either to the blackoil or compositional simulator.PVI Exporting ECLIPSE Black Oil PVT tables Once the fluid description has been fitted to the experimental observations.. . . The PVT tables are generated off either of these experiments.PVO for the water keyword Close Output Display panel.. Generating ECLIPSE Black Oil PVT tables In order to generate ECLIPSE BlackOil simulation PVT tables. Select PVTO and PVDG (Live oil and dry gas) on the radio button menu. Right-click on experiment DL1 in the sample tree and select Export Keywords. 103. 105. PVTi requires either a Differential Liberation experiment or a Constant Volume Depletion experiment to be simulated from the fitted equation of state.from the drop-down menu. 102. 104.101. Click on OK Enter the filename PVTW. Click OK 107. The keywords are generated and the Display Output module shows the generated keywords. . enter ECLIPSE100 as the name of the export file.106. In the File Selection box. PVTi: File | Export Keywords | ECLIPSE Compositional Fluid Model.. This is the correct selection in this case as the equilibration (RSVD) is used to create a composition versus depth table (ZMFVD).Generating Compositional Fluid Model (Optional) In this part of the exercise. 111. 109. Select the fluid {None}. Click OK. 112. Enter the reservoir temperature as 220o F. This means that PVTi does not write out a ZI keyword for the ECLIPSE Compositional fluid model. Export the fluid model to FLUID.PVO .. Exporting the fluid model 108. 110. full compositional model and composition versus depth table (ZMFVD) are exported if a compositional model is required. . from the drop-down menu.PVO. PVTi: File | Exit (There is no need to save the PVI file as it can be created from the ECLIPSE Office case). 117. In PVTi. 116. 118. Exporting equilibration keywords 114. In the COMPG1 export panel. 115. right-click on the composition versus depth experiment COMPG1. . Export the keyword to the file ZMFVD. Click OK. select ZMFVD (Compositional) on the radio button.113.. Select Export keywords. 119. . Save the file and Exit.