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Cross Timbers Oil Company, Fort Worth, Texas

Abstract: Reservoir Characterization of the Council Grove Group, Texas County, Oklahoma

Production from Permian age Council Grove Group carbonates was established on a regional basis in the mid-1950s. Panoma Field, extending from Kearny County, Kansas to Texas County, Oklahoma currently has 2482 active wells that have produced over 2.4 TCF. Wells were generally fracture stimulated and then brought on production with a substantial amount of water production. Operators involved in recent exploration plays in Texas County have discovered new reserves in the Beattie, Neva and Howe Limestones. A completion technique of limiting the perforations to only a specific reservoir and then using an acid stimulation or small frac has cut the amount of water production.

Sedimentation patterns for the 4 th order sequence sets in the Council Grove Group are characterized by coarsening upward carbonate shoals overlain by terrestrial redbeds. Shoal lithofacies generally consist of skeletal grainstones, packstones, and wackestones. Dissolution of carbonate allochems and matrix by meteoric diagenesis creates porosity that averages fifteen percent. Pore types vary from intergranular to touching vugs with .01 to 200 millidarcies of permeability.

A more accurate prediction of hydrocarbon and water productive reservoirs can be achieved if each reservoir is evaluated by lithofacies. A case history of constructing pickett plots and bulk volume water plots on the basis of lithofacies in the Beattie Limestone illustrates how a silty carbonate matrix can cause high water saturation calculations. A cementation exponent of 1.8 in the standard Archies equation is more appropriate for the skeletal wackestones.

AAPG Search and Discovery Article #90921©1999 AAPG Mid-Continent Section Meeting, Wichita, Kansas