Geologic Challenges and Opportunites of the Cherokee Group Play (Pennsylvanian): Anadarko Basin, Oklahoma

The Middle Pennsylvanian Cherokee Group composes one of the most active natural gas plays in the Anadarko Basin of Oklahoma, having produced more than 1.2 Tcf from major (> 10 Bcf cumulative production) Cherokee reservoirs in Beckham, Custer, Roger Mills, and Washita Counties, the area currently experiencing the most active Cherokee development activity. Preliminary geologic study and telephone survey of 15 Cherokee operators satisfied three primary project objectives: (1) to summarize both the geologic characteristics of the Cherokee Group and the production highlights in the four-county area of current activity; (2) to summarize what current Cherokee producing companies perceive to be the primary geologic challenges they face in developing the Cherokee play; and (3) to suggest geologic strategies to help respond to these challenges. Geologic questions related to Cherokee gas-production enhancement are fundamental, and answers to these questions have the potential to alter current production strategies, reduce risk, and ultimately to increase natural gas reserves. Most of the surveyed Cherokee operators acknowledge that they have only a partial understanding of regional facies relations within the Cherokee depositional systems tracts. Moreover, there is no clear and integrated perspective of depositional systems, reservoir geometry, and diagenesis among all Cherokee fields in the play area. Reservoir geometry is complex and not readily predictable; therefore, drilling of infill wells, which characterizes the current development strategy of the Cherokee play, is fraught with uncertainty. The high degree of variation in porosity and permeability cannot be predicted from current knowledge of reservoir-quality patterns. A limited per-well drainage area suggests internal compartmentalization of sandstone reservoirs. Investigations at several scales can provide needed information. Improved and more precise modeling of (1) the regional spectra of Cherokee depositional settings at the play scale, (2) depositional facies and geometry at the field scale, and (3) facies architecture, diagenesis, and fracture distribution at the reservoir scale would aid the efficient exploitation of the remaining natural gas resources in the Cherokee play.