Abstract

Hydrocarbon reservoirs in carbonate rocks in the Permian Basin are developed in a myriad of trapping styles, including structural, paleogeomorphic, stratigraphic, and hydrodynamic traps. In this mature hydrocarbon province the subtle paleogeomorphic and stratigraphic traps offer the greatest potential for future energy reserves. Subtle, subunconformity paleogeomorphic traps are most common in pre-Pennsylvanian carbonate fields in this area, and basically include three types of reservoir systems: (1) those developed in heavily dissected karst terrains such as in sinkholes and caverns (Ellenburger); (2) erosional truncation or depositional pinchout of porous zones beneath unconformities (Silurian-Devonian), and: (3) reservoirs in meteorically altered, non-karst terrains (Mississippian). By contrast, subtle stratigraphic traps of combination depositional-diagenetic origin are common in Pennsylvanian and Permian rocks in this basin. Reservoirs in this trap type include various reefs and other organic buildups, carbonate sand shoals, dolomitized lagoonal mudstones, and peritidal facies deposited in shallow platform settings; subaerially exposed islands also comprise reservoirs in platform areas. Reservoirs in contiguous slope and basinal facies include in situ reefs, atolls, and resedimented, platform-derived carbonate debris.