Abstract

Production from Permian Council Grove Group carbonates in the Hugoton Embayment was established on a regional basis in the mid 1950's. Panoma field extending from Kearny County, Kansas, to Texas County, Oklahoma, currently has 2,482 active wells that have produced over 2.4 trillion cubic feet (TCF). Historically wells generally were fracture stimulated and 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 revised completion technique of limiting the perforations to only a specific reservoir and then using an acid stimulation or small frac has reduced the amount of associated water production.

Depositional cycles interpreted as fourth-order parasequence sets in the Council Grove Group are characterized by coarsening-upward carbonate shoals overlain by terrestrial redbeds. Shoal and shoal-flank lithofacies generally consist of skeletal grainstones, packstones, and wackestones respectively. Dissolution of carbonate allochems and matrix by meteoric diagenesis created porosity that averages 15%. Pore types range from intergranular to touching vugs with permeability ranging from 0.01 to 200 millidarcies.

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 result in high water-saturation calculations. A cementation exponent (m) of 1.8 in the standard Archie water saturation equation is more appropriate for the skeletal wackestones.