Significant New

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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

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Project Results

• 290,000 BO Incremental Production 1996 to present
• gt650,000 BO Incremental Reserves
• 3 Re-entries
• 4 New Drills
• gt12 Workovers
• Economic life of field extended from 9 to 16 years

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Sec 36 Production 1977 to 1993
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Bottom Line
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Learnings Came in All Areas

• Reservoir Characterization
• Well Testing
• Re-completions
• Production

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INTEGATED STUDY

• GEOLOGICAL MODEL
• 3D SEISMIC / INVERSION MODELING
• FLOW MODELING
• HISTORY MATCH
• SIMULATION
• WELL WORK, TESTING, AND MONITORING

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PROCEEDURES

• PRODUCTION TESTING
• PRESSURE TRANSIENT TESTING
• WATER CHEMISTRY
• WELL WORK

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Type Log

• Queen
• Upper Grayburg Main Pay
• Lower Grayburg Minor Pay
• San Andres Large OOIP

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FOSTER FIELD
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INTEGATED STUDY
Problems
Solutions

• 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 OIL COME FROM AND WHERE DID THE
  WATER GO?
• OPEN HOLES / CASED HOLES

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• Discovered 1939
• 40 Acre spacing
• Nitro Open Holes
• Waterflood 1962
• 20 Acres 1979
• Laguna 1992
• DOE 1994
• Oxy 2002

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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

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Porosity vs. Permeability
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Seismic Inversion Modeling
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Porosity - Inversion vs. log
Seismic Inversion
Well Log
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Well Testing

• Water Chemistry
• 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

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History Match
1939 Discovery
1961 Waterflood
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1979 20 Acre Infill
1996 Simulation
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BOTTOM HOLE PRESSURE TESTINGAND THE IMPACT OF
PERMEABILITY ON PRESSURE DISTRIBUTION
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Upper Grayburg wells 1320 apart
2124
544
1534
955
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Dual Zone Test
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After CIBP
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Same Well After Re-frac
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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

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Brock Lease Workover Results
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
BR6 Re-Frac 8/98 68.6 3 1 9
Post-Frac 38 10 220
6/02 9 2 62
BR7 Re-Frac 8/98 77.2 6 2 5
Post-Frac 44 6 242
6/02 15 5 178
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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!

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Bottom Line
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ucceful 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

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Acknowledgements

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