1. Significant New “Learnings” From An Integrated Study Of An Old Field, Foster/South Cowden Field (Grayburg & San Andres), Ector County, Texas.
Robert C. Trentham, DGS
Center for Energy and Economic Diversification
University of Texas of the Permian Basin

2. Project Results 290,000 BO Incremental Production 1996 to present
>650,000 BO Incremental Reserves
3 Re-entries
4 New Drills
>12 Workovers
Economic life of field extended from 9 to 16 years

3. Sec 36 Production 1977 to 1993

4. Bottom Line

5. “Learnings” Came in All Areas
Reservoir Characterization
Well Testing
Re-completions
Production

6. INTEGATED STUDY GEOLOGICAL MODEL 3D SEISMIC / INVERSION MODELING
FLOW MODELING
HISTORY MATCH
SIMULATION
WELL WORK, TESTING, AND MONITORING

7. PROCEEDURES PRODUCTION TESTING PRESSURE TRANSIENT TESTING
WATER CHEMISTRY
WELL WORK

8. Type Log Queen Upper Grayburg –Main Pay Lower Grayburg – Minor Pay
San Andres – Large OOIP

9. FOSTER FIELD

10. INTEGATED STUDY Problems Solutions OLD WATERFLOOD
CROSS FLOW BETWEEN ZONES
NO FRACTURE STIMULATIONS
BHP DISCREPANCIES
LOW PERMEABILLLTY
WHERE DID THE OIL COME FROM AND WHERE DID THE WATER GO?
OPEN HOLES / CASED HOLES
GEOLOGICAL MODEL
3D SEISMIC / INVERSION MODELING
FLOW MODELING
HISTORY MATCH
SIMULATION
TESTING, WELL WORK, MONITORING

11. Discovered 1939
40 Acre spacing
Nitro Open Holes
Waterflood
20 Acres
Laguna
DOE
Oxy

13. Reservoir Characterization
San Andres Reservoir – Over Estimates and Under Achievement
Barriers to vertical flow
Inversion Modeling to porosity maps
Seismic Velocity related to Neutron Density Porosity

14. Porosity vs. Permeability

16. Seismic Inversion Modeling

18. Porosity - Inversion vs. log
Seismic Inversion
Well Log

19. Well Testing Water Chemistry Bottom Hole Pressure Test results
Inefficient sweep
Backup for well testing & workover results
Carryover and Makeup water
Bottom Hole Pressure Test results
Complex layering of reservoir
Cross flow
Low permeability = Longer test duration
Production tests
3 day minimum

20. HC03 S04 CL CA MG NA TDS UPPER GRAYBURG 170 2990 13500 1530 450
HC03
S04 CL CA MG NA
TDS
UPPER GRAYBURG
170
2990
13500
1530
450
7750
26390
LOWER GRAYBURG
386
2632
20295
1889
664
11245
37332
SAN ANDRES
980
3881
33846
2507
762
19855
61831
INJECTION WATER
793
3100
32000
2646
947
17757
57244
CANYON
329
1104
76532
5880
692
42193
126693
ELLENBURGER
439
1459
63917
3840
972
36064
106691

24. History Match
1939 Discovery
1961 Waterflood

25. Acre Infill
1996 Simulation

26. BOTTOM HOLE PRESSURE TESTING AND THE IMPACT OF PERMEABILITY ON PRESSURE DISTRIBUTION

27. Upper Grayburg wells 1320’ apart
2124 #
544 #
1534 #
955 #

28. Dual Zone Test

29. After CIBP

30. Same Well After Re-frac

31. Recompletions/Workovers
1955 to 1982 Fracture Stimulation are closed, healed or scaled over
Acid Stimulations unsuccessful in contacting reservoir
Success rate can be estimated and candidates ranked by Bottom Hole Pressure, Water Chemistry and Production Tests

32. Brock Lease Workover Results
Well
Work
Date $$
BOPD
MCFPD
BWPD
BR #5
Re-Frac
8/98
58.5 6 1
Post-Frac 72 10
200
6/02 13 3 71
BR#6
68.6 9 38
220 2 62
BR#7
77.2 5 44
242 15
178

33. Production
Outcome of fracture stimulation is proportional to bottom hole pressure and Oil/Water production rates prior to treatment
Flowing water recoveries do not condemn a well. Some wells produce many times load and have to have fluid level drop below 1000’ from surface before producing OIL!

34. Bottom Line

35. $ucce$$ful Project?
PRODUCTION BEFORE WELL WORK (UPPER GRAYBURG ONLY) BO, 9 MCF, 181 BW
INITIAL PRODUCTION AFTER WORK BO, 145 MCF, 3167 BW
CURRENT PRODUCTION RATE BO, 65 MCF, 2323 BW

36. Acknowledgements Dick Weinbrandt Bill Robinson DOE Tulsa office
The Staff of Laguna Petroleum
Baker-Hughes (previously Scientific Software Intercorp)
Paul Laverty