Prediction of Solution Gas drive reservoir performance

1. Prediction of Solution Gas drive reservoir performance

2. Tarner Methods for Predicting Solution gas drive reservoir • First of all Recall the MBE for this drive mechanisms • @> Pb

3. Instantaneous GOR (I.G.O.R)

4. Oil Saturation

5. First of all we have to draw the past production history versus pressure • Also, PVT versus Pressure and • So Vs Kg / Ko

7. Select Pressure and Assume Np • At Pressure we assume three Np • Px Np1 Np2 Np3 • Solve NPRP from MBE at each Np • We calculate the NPRP from MBE at pressure before Px Represents the amount of gas produced during the time interval required for decreasing the reservoir pressure from Px-I to Px

8. Using the assumed values of Np1,Np2 and Np3 solve the oil saturation for So1, So2 and So3 at each Np assumed respectively. • Using the calculated values of oil saturation determine relative permeability ratio (kg/Ko)1, (kg/Ko)2& (kg/Ko)3 at each saturation from the relative permeability ratio saturation curve. • Calculate R1,R2 and R3 from I.G.O.R equation

9. Calculate the amount of gas produced during the period (Px-1, Px )as follow

10. The values of amount of gas produced during interval pressure calculated by both methods ( MBE and IGOR) are then plotted on a graph Vs Np • The plot of the two lines will intersect. This intersection is only place where one value of Np will satisfy both equation.

11. Example • Table below lists reservoir data necessary for depletion drive reservoir

12. Assume that Swi= 15 % and N = 96.55 x10^6 STB . • Calculate Rp and Np at P = 400 psia

13. Solution • As Np = 0.1578 N at P= 700 psia, then assume. • Np = 0.17 N, Np = 0.175 N and Np = 0.18 N

14. Calculate the amount of gas produced during the period (P700, P400)as follow from MBE

15. Oil Satyration

16. From data given and plot the relation between relative permeability ratio versus oil saturation • From this figure we can obtained the values of (kg/Ko)1,=1.28 (kg/Ko)2= 1.314 and(kg/Ko)3=1.395

17. We can conclude the results obtained in the following table

18. The results: Npc=0.1716 N , DG= 202 N : Npc= 16.56x!0^6 STB Using DG relation ship of DG 202N= (0.1716N-0.1578N)x(13010+Rc)/2 then Rc= 16265.3 SCF/STB

19. Problem 1 • Given the following data for an oil reservoir

20. Determine : (neglecting Cw &Cf) • The fractional oil recover at the bubble point presssure. • The original oil in place • The reservoir drive mechanism • The STB of oil that would have been recovered at 1050 psia if all the gas produced except 170 SCF/STB on a cumulative basis had injected back into the reservoir • Using the following permeability relationship:

21. Find by Tarner’s metjhod the fractional oil recovery (Np/N) and R at pressure 750 psia assuming that Swi= 0.2