There are two basic steps to work on compositional simulation. One is the PVT match, the other is the simulation of the compositional model. The following are the step-wise procedures and the corresponding data files. DESKTOP_PVT package was used for PVT match, compositional simulator is VIP. Data are from “Third SPE Comparative Solution Project: Gas Cycling of Retrograde Condensate Reservoirs”1 (we name this paper as SPE3).
1- Heavy Ends Characterization. This is the first step for PVT matching. The following procedure is to be followed:
a- Invoke DESKTOP_PVT. The Peng-Robinson EOS is selected by picking CONFIG from the main menu, then EOS submenu, then typing PR. (noted as CONFIG/EOS, PR).
b- Turn on heavy end characterization by choosing CONFIG/Heavy, Y.
c- Enter heavy end parameters by selecting (from main menu) HEAVY/Parameter. At least three numbers must be input to complete this step, they are: molecular weight, specific gravity, and mole fraction of C7+ . These numbers can be found in SPE3.
d- Specify the names and number of heavy component groups by choosing PSEUDO-COMPONENT NO. AND NAME.
e- Select “cut-off molecular weights” and specify 130 for bracket 1 and 180 for bracket 2.
f- After inputting these data, you click CALCULATE option in the HEAVY menu.
g- Inspect the data by selecting HEAVY/Review.
h- Save the calculated EOS parameters by selecting HEAVY/Save EOS. Name the file
“heavy.eos”.
i- Save the data by choosing FILE/Save and name the file “heavy.dat”.
Molecular Weight = 140 Specific gravity = 0.774 Mole Fraction = 0.0659 Cut-off Molecular Weight 130 180
Names of Heavy Components: HVY1 HVY2 HVY3 Output: HEAVY.DAT, HEAVY.EOS
2- Default Fluid Predictions. At this step, all components from SPE3 should be input except heavy components. The following procedure is to be followed:
a- Choose CONFIG/Test Type.
b- Select, Cnst Composition, Cnst Volume, and/or Swelling.
c- Choose CONFIG/Heavy, N, to turn off the heavy components option.
d- Choose COMPONENT/System, and highlight the components required (do not include the C7+).
e- Load The EOS for the heavy component by choosing COMPONENT/Append EOS,
“heavy.eos”.
f- Enter pure component mole fraction by choosing COMPONENT/Composition.
g- Enter the data for the tests by choosing TESTS/Cnst Composition.
h- Repeat for the Cnst Volume and Swelling tests.
i- Run the program by Chooing RUN/Go.
j- View the data by choosing REPORT/Graphics.
k- Save the data by choosing FILE/Save. Name the file “default.dat”.
Components: CO2,N2,C1,C2,C3,NC4,IC4,NC5,IC5,NC6,HVY1,HVY2,HVY3 Test Types: Constant Composition Expansion, Constant Volume Depletion and Swelling
Output: default.dat
3- Pre-regression. Before pseudoization, we make regression for EOS properties. We call this step as pre-regression. We first need to pick regression variables, then run the program based on the previous data file default.dat. After doing this, we save two files. One is regress.dat, and the other is regress.eos. The updated EOS properties are included in regress.eos. The following procedure is to be followed:
a- Choose CONFIG/Regression, Y, to turn on regression.
b- Choose (from main menu) REGRES/Variable. Choose EOS Property and enter the number for the regression variable in the appropriate place. Then Choose Binary Coeff and enter the number for the regression variable in the appropriate place. Then Exit.
c- Choose REGRES/Limits and change the minimum to 0.7 and maximum to 1.3.
d- Choose REGRES/Control and change the no. of iterations to 20.
e- Run the program by Choosing RUN/Go.
f- View the data by choosing REPORT/Graphics.
g- Save the calculated EOS parameters by selecting REPORT/Save EOS. Name the file
“regress.eos”.
h- Save the data by choosing FILE/Save and name the file “regress.dat”.
Components: CO2,N2,C1,C2,C3,NC4,IC4,NC5,IC5,NC6,HVY1,HVY2,HVY3 Regress Variables:
C1-OMEGAA 1 C1-OMEGAB 2
HVY1-OMEGAA 3
HVY2-OMEGAA 4
HVY3-OMEGAA 5
HVY1-OMEGAB 6
HVY2-OMEGAB 7
HVY3-OMEGAB 8
DJK C1-HVY1 9
DJK C1-HVY2 10
DJK C2-HVY3 11
Output: REGRESS.DAT, REGRESS.EOS
4- Component Pseudoization. This step is called the pseudoization. The pseudo components are listed below. Once you give the names of pseudo components and components included in them, the program is capable of calculating regrouped lab data. Test data must be reentered for the new pseudo components. New files will be generated: “pseudo.dat” and “pseudo.eos”. The following procedure is to be followed:
a- Choose COMPONENT/Load EOS, “regress.eos”. This will load the regressed EOS.
b- Turn off regression by choosing CONFIG/Regression, N.
c- Turn Pseudoization on by selecting CONFIG/Pseudoization, Y.
d- Choose PSEUDO/Pseudo Name. Give names to the new pseudo components.
e- Choose PSEUDO/Parameter. Specify the components in Pseudo-COMP P1 Lump.
Repeat for all pseudo components.
f- Choose PSEUDO/Calculate.
g- Save the calculated EOS parameters by selecting PSEUDO/Save EOS. Name the file
“pseudo.eos”.
h- Choose PSEUDO/Replace EOS. This replaces the active EOS.
i- Turn off pseudoization by choosing CONFIG/Pseudoization, N.
j- Reenter the test data by choosing TESTS/Const Composition. Press F2 and load the global reference composition. Repeat for other tests.
k- Run the program by selecting RUN/Go.
l- Save the data by choosing FILE/Save and name the file “pseudo.dat”.
Pseudo Components:
Test Types: Constant Composition Expansion, Constant Volume Depletion and Swelling
Output: PSEUDO.DAT, PSEUDO.EOS
5- Regression. This is the final step for PVT match. Procedures are the same as we did in the step 3. Regression is based on the data obtained in the step 4. The main problem is the selection of variables to be regressed in order to obtain a good match. There is no definite way to proceed.
In this case trial and error method was used to get a good match. Selecting proper variables is a time consuming effort. The following procedure is to be followed:
a- Choose CONFIG/Regression, Y, to turn on regression.
b- Choose (from main menu), REGRES/Variable. Choose EOS Property and enter the number for the regression variable in the appropriate place (delete old numbers if present). Then Choose Binary Coeff and enter the number for the regression variable in the appropriate place. Then Exit.
c- Choose REGRES/Limits and change the minimum to 0.7 and maximum to 1.3.
d- Choose REGRES/Control and change the no. of iterations to 20.
e- Run the program by Choosing RUN/Go.
f- View the data by choosing REPORT/Graphics.
g- Save the calculated EOS parameters by selecting REPORT/Save EOS. Name the file
“final.eos”.
h- Choose COMPONENT/Load EOS, final.eos. This will overwrite the old EOS.
i- Choose CONFIG/Regression, N, to turn off regression.
j- Run the program by Choosing RUN/Go.
k- Save the data by choosing FILE/Save and name the file “final.dat”.
Pseudo Components:
6- Initialization Data for Compositional Simulation. After step 5, the adjusted EOS properties are obtained. These data are considered as the "correct values" and input in the initialization file along with other data from SPE3. The format of initialization file is attached in the following pages. VIP will create a spe3i.rst file when you type: "corerun" in the terminal. It should be noted that you should check the "corefil.dat" in the current directory before you type command
"corerun."
Data Sources: SPE12278 paper, FINAL.DAT File Name: spe3i.dat
7- Run Data for Compositional Simulation. This is the last step for compositional simulation.
After creating the simulation run data file-spe3r.dat and having a proper restart file-spe3i.rst from step 6. you can type the command "execrun", VIP will automatically produce the information specified by the user in the spe3r.dat. The format of the run data file spe3r.dat is attached in the following pages.
Data Sources: SPE12278, Final.dat File Name: spe3r.dat