1. Rejuvenation of a mature oil field: Underground Gas Storage and Enhanced Oil Recovery, Schönkirchen Tief Field, Austria IEA-EOR Conference 2009
Torsten Clemens, Joop de Kok, Yannick Yanze

2. Gas supply shortage in 2008

3. Outline Reservoir overview
Concept Underground Gas Storage (UGS) + Enhanced Oil Recovery (EOR)
Simulation setup
Optimization of UGS
Dewatering
Cycling
EOR
Conclusions

4. Reservoir overview Highly fractured dolomite Water- to mixed wet
19 mn Sm3 STOIIP
GOC at 2550 mss
OWC 2740 mss
Producing since 1962
Current recovery factor 59 %
Water flooded

5. Historical production – initial conditions

6. Historical production – initial oil production phase

7. Historical production – initial oil production phase

8. Historical production – perforation higher

9. Historical production – water injection

10. Historical production – current conditions

11. Historical production – current conditions
Sorw = 25%

12. Underground Gas Storage & EOR - fractures

13. Underground Gas Storage & EOR - fractures

14. Underground Gas Storage & EOR - fractures

15. Underground Gas Storage & EOR - matrix
Sorg = 15%
Sorw = 25%

16. Simulation setup
Is it possible to build up the required volumes of gas?
How long does it take to build up the UGS?
Is dewatering required?
How much cushion gas is required to safely produce the gas volumes?
How many wells are necessary to inject and produce the required gas volumes?
Where to place the injection / production wells?
What are the risks and uncertainties?
Is there any EOR potential?
Is there an opportunity to accelerate current production?

17. Simulation setup Dual-permeability approach: two superimposed grids
Matrix grid
Fracture grid
km, fm
kf, ff, σ
input
properties
fracture-fracture exchanges
matrix-matrix exchanges
matrix-fracture exchanges
Pm, Sm
Pf, Sf
unknowns

18. History match
Multiple history matches
Multiple predictions

19. Optimization of UGS – phased approach3
Phase 1 2
Total injected gas [billion m³] 1
Time in years

20. Optimization of UGS – phased approach3
Phase 1
Monitoring phase 2
Total injected gas [billion m³] 1
Time in years

21. Optimization of UGS – phased approach3
Phase 1
Monitoring phase 2
Total injected gas [billion m³] 1
Time in years

22. Dewatering to increase gas volume
1.8
1.5
1.2
Without dewatering
0.9
Total injected gas [billion m³]
0.6
0.3
Time in years

23. Dewatering to increase gas volume
1.8
With dewatering
1.5
1.2
Without dewatering
0.9
Total injected gas [billion m³]
0.6
0.3
Time in years

24. Dewatering to increase gas volume
Water injection into sandstone
Horizontal gas injection wells
Original oil/water contact
Vertical dewatering wells

25. Gas/liquid contact movement in the fractures

26. UGS & EOR - concept Crestal gas injection wells Oil rim
Residual oil 15 %
Residual oil 25 %
Original oil/water contact
Downdip production wells

27. Enhanced Oil Recovery (EOR)
2008
2030

28. Enhanced Oil Recovery (EOR)
Production of incremental oil after several cycles
Up to 5 % recovery of incremental oil in place

29. Effect of gas cycling on oil production

30. Gas/Oil Contact in Fractures and Matrix
Gas Injection
Gas Production
Gas invasion in matrix
Gas invasion in matrix
Gas/Oil Gravity Drainage in Matrix
Gas/Oil Gravity Drainage in Matrix
Gas/Oil Contact in Fractures
Well
Well
Water/Oil Contact in Fractures

31. Conclusions
Schönkirchen Tief is good candidate reservoir for high performance Underground Gas Storage
1.5 bn m³ gas can be injected in phase one and 3 bn m³ gas in phase two (dewatering required)

32. Conclusions
Schönkirchen Tief is good candidate reservoir for high performance Underground Gas Storage
1.5 bn m³ gas can be injected in phase one and 3 bn m³ gas in phase two (dewatering required)
De-watering can be optimised by drilling vertical wells deep below the original oil/water contact
Enhanced Oil Recovery can be achieved due to the difference in residual oil saturation towards water and gas
Up to 5 % incremental oil can be recovered

33. Acknowledgements Thanks to:
OMV E&P for the permission to publish this paper