Abstract

Carbonate rocks interbedded within black shale sequences in the Wolfcampian to lower Leonardian section in the Permian Basin represent shelf detritus redeposited in basinal settings. Such carbonate sequences occur as slope and toe-of-slope wedges and aprons whose gross trends are discontinuously parallel to the shelf edge. Internally, these wedges and aprons are composed of discrete, yet anastomosing channels, lobes and dams consisting of shelf margin-derived carbonate megabreccias and sands. The trends of the channels and lobes are normal or oblique to the contiguous shelf margin. The most productive reservoirs in the lower Leonardian and Wolfcampian sections are those developed in the carbonate sands; low-yield reservoirs locally occur within the megabreccias. Porosity in the reservoirs is late secondary (postburial) in origin, and includes biomolds, vugs, circumgranular pores, and solution-enlarged fractures.