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Significant New “Learings” From Significant New “Learings” From An Integrated Study Of An Old An Integrated Study Of An Old
Field, Foster/South Cowden Field Field, Foster/South Cowden Field (Grayburg & San Andres), Ector (Grayburg & San Andres), Ector
County, TexasCounty, TexasDE-FC22-93BC14982DE-FC22-93BC14982
Robert C. Trentham, DGSCenter for Energy and
Economic DiversificationUniversity of Texas of the
Permian Basin
Project ResultsProject 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• Sold to Oxy for well above decline curve price.
““Learnings” Came in All Learnings” Came in All AreasAreas
• Reservoir Characterization• Well Testing• Recompletions • Production
Type LogType Log• Queen
• Upper Grayburg –Main Pay
• Lower Grayburg – Minor Pay
• San Andres – Large OOIP
INTEGATED STUDYINTEGATED STUDY
• GEOLOGICAL MODEL
• 3D SEISMIC / INVERSION MODELING
• FLOW MODELING• HISTORY MATCH• SIMULATION• TESTING, WELL
WORK, MONITORING
• OLD WATERFLOOD• CROSS FLOW
BETWEEN ZONES• NO FRACTURE
STIMULATIONS• BHP DISCREPANCIES• LOW PERMEABILLLTY• WHERE DID THE
WATER GO?• OPEN HOLES / CASED
HOLES
Problems Solutions
Discovered 193940 Acre spacingNitro Open HolesWaterflood 196220 Acres 1979Laguna 1992DOE 1994Oxy 2002
Reservoir CharacterizationReservoir 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
Well TestingWell Testing
• Water Chemistry – Inefficient sweep– Backup for well testing & workover
results
• Bottom Hole Pressure Test results– Complex layering of reservoir– Cross flow– Low permeability = Longer test duration
• Production tests– 3 day minimum
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
Recompletions/WorkoversRecompletions/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
Brock Lease Workover Brock Lease Workover ResultsResults
Well Work Date $$ BOPD MCFPD BWPD
BR #5
Re-Frac
8/98 58.5 6 1 6
Post-Frac
72 10 200
6/02 13 3 71
BR#6 Re-Frac
8/98 68.6 3 1 9
Post-Frac
38 10 220
6/02 9 2 62
BR#7 Re-Frac
8/98 77.2 6 2 5
Post-Frac
44 6 242
6/02 15 5 178
ProductionProduction• Outcome of fracture stimulation is
proportional to bottom hole pressure and Oil/Water production rates prior to treatment
• Flowing water recoveries do not condemn a well. Some wells produce many times load and have to have fluid level drop below 1000’ from surface before producing OIL!
$ucce$$ful Project?$ucce$$ful Project?
• PRODUCTION BEFORE WELL WORK (UPPER GRAYBURG ONLY) 37 BO, 9 MCF, 181 BW
• INITIAL PRODUCTION AFTER WORK 467 BO, 145 MCF, 3167 BW
• CURRENT PRODUCTION RATE 280 BO, 65 MCF,
2323 BW