The purpose of this exercise is to utilize WinProp in building a Heavy Oil Model. Commonly, such models will be used in STARS for thermal applications. Because of this thermal properties may play a larger role than observed in Black-Oil fluid models (such as Exercise 3). This fluid model will be created by incorporating similar techniques implemented in Exercise 3, including matching laboratory data, as well as some new concepts, such as Plus Fraction Splitting.
Setup of WinProp model with Plus Fraction Splitting
1. Open WinProp through CMG launcher.
2. In the Titles/EOS/Units form insert a title: “Fluid Model for STARS” and select PR (1978), kPa & deg C, and feed as moles.
3. In the Component Selection/Properties add the library component C1. Open the Composition form and add the composition for C1 as given in the file “Heavy Oil for STARS-Data1.xls”. (The mole fraction of C1 is 0.08223).
4. The laboratory has supplied a C6+ component which now needs to be split into pseudocomponents.
In order to split the C6+ fractions, insert a Plus fraction Splitting form in the WinProp interface after the Composition form. The first single carbon number in plus fraction should be 6. Specify the number of Pseudo-components to 4 and select Gamma, Gaussian Quadrature, and Lee-Kesler (Figure 57).
Figure 57: Plus Fraction Splitting for Heavy Oil
45 | P a g e 5. In the Sample 1 tab, input SG+ as 0.989 and the global mole fractions and molecular
weights for liquid component as given in the file “Heavy Oil for STARS-Data.xls” (Figure 58).
Figure 58: Plus fraction splitting for Heavy Oil
6. Add a Saturation Pressure form (Figure 59). Save the dataset as ‘S1-char.dat’ and Run it. After running the data set, Update component properties and Save the data set as
‘S2-regression psat.dat’.
You will now notice that 4 hypothetical pseudo components have been added in the components form.
46 | P a g e Figure 59: Saturation Pressure Calculation added per Step 6
Matching of WinProp Model to Laboratory Results
Due to splitting the component into 4 pseudocomponents a regression/tuning must be performed to match the WinProp model to the experimental data.
1. The first experimental value to match is the Saturation Pressure. Delete Plus Faction Splitting, and then add Regression Parameters below Composition.
Then select Saturation Pressure and Delete/Cut and click Regression Parameters and Paste into Reg-Block.
On the Regression Parameters form, select Pc and Tc for the heaviest pseudocomponent. In the Interactions Coefficients tab select the hydrocarbon interaction coefficient exponent.
Run the dataset. After running the dataset, Update component properties and Save the data set as ‘S3-lumping.dat’.
2. Delete Regression Parameters, than add a Component Lumping form and lump the last three heavy components by highlighting all three then selecting the bottom-most component. The Component Lumping form should look like Figure 60.
47 | P a g e Figure 60: Component Lumping form for Heavy Oil
3. Run the dataset. After running the dataset, Update component properties and Save the data set as ‘S4-regression.dat’.
4. Delete Component Lumping and add Regression Parameters. Then select Saturation Pressure and Delete/Cut and click Regression Parameters and Paste into Reg-Block.
Select Regression Parameters and Add into Reg-Block -> Lab -> Separator. Enter saturation pressure, reservoir temperature, GOR and API data from “Heavy Oil for STARS-Data1.xls” (Figures 61-63).
Figure 61: Saturation Pressure Form Populated with Excel Values
48 | P a g e Figure 62: Separator Form Populated with values from Excel File
Figure 63: Separator Form Experimental Tab Populated with Excel Values
49 | P a g e 5. In Regression Parameters under the Component Properties tab select Pc and Tc for the
Heaviest component, and Vol. shift for the 2 Heaviest components. Run the dataset.
Check for match in regression summary. After running the dataset, Update component properties and Save the data set as ‘S5-regression_visc.dat’.
Figure 64: Regression Parameters Set per Step 11
Matching of WinProp Model Viscosity to Laboratory Viscosity
We will repeat the regression to match Viscosity at 10 deg C (Figures 65 and 66) and 100 deg C (Figures 67 and 68) as given in “Heavy Oil for STARS-Data.xls”.
1. Insert 2 Two Phase Flash forms to input experimental viscosity data (Figures 65 and 66)
Figure 65: Two-Phase Flash Calculations for viscosity data of Heavy Oil (10 deg)
50 | P a g e Figure 66: Two-Phase Flash Experimental Data viscosity of Heavy Oil (10 deg)
Figure 67: Two-Phase Flash Calculations viscosity data of Heavy Oil (100 deg)
51 | P a g e Figure 68: Two-Phase Flash Experimental Data viscosity of Heavy Oil (100 deg)
2. In Component Selection/Properties on the Viscosity tab, set viscosity model type to Pedersen Corresponding State Model and the corresponding states model to Modified Pedersen (1987), (Figure 69).
In Regression Parameters, Viscosity Parameters tab, select all check boxes. Run the dataset. After running the dataset, check for a match.
You may have to change variable bounds to improve the match.
When an acceptable match has been found Update component properties and Save the data set as ‘S6-STARS PVT.dat’.
52 | P a g e Figure 69: Viscosity Component Definition Tab showing changes to Modified Pedersen
Creating a STARS PVT Model from WinProp
1. Delete Regression Parameters then insert 2 CMG STARS PVT Data forms from the Simulator PVT drop down menu.
2. On the first CMG STARS PVT Data form, on the Calc. Type tab select “Basic STARS PVT Data”. Then on the Basic PVT tab enter the initial reservoir conditions (3200 kPa and 12 C) as the reference conditions.
Generate a Component liquid viscosity table from 10 C to 360 C with 8 steps and use the WinProp viscosity model (Figure 70). Set lower pressure at 500 kPa, upper pressure at 5500 kPa and number of steps as 10.
53 | P a g e Figure 70: STARS PVT Data Generator with Initial Reservoir Conditions
3. On the second CMG STARS PVT Data form, on the Calc. Type tab select “Gas-Liquid K-value Tables.” On the K-Value tab enter 500 kPa for both the Pressure and Pressure Step and 11 for the No. of pressure steps. Also enter 10 C for Temperature, 50 C for Temperature Step, and 8 for No. of temperature steps.
Entering a minimum K-value threshold of 1.0E-06 will improve STARS numerical stability without materially affecting the simulation results (Figure 71). This option sets any K-Value less than this threshold to 0.
54 | P a g e Figure 71: STARS PVT Data Generator K-Value Data Entries
4. Save the dataset under a new name and Run it. The information obtained is now capable of being imported to a STARS dataset and Ran.