Abstract

Basinal dark-gray to black marine shales in the New Mexico part of the Permian Basin that have been traditionally correlated as the Barnett Shale (Upper Mississippian) are Late Mississippian to Morrowan (Early Pennsylvanian) in age. The Upper Mississippian part of the shale sequence is correlated as the Barnett Shale and consists of 200 to 400 ft of dark-gray to black shale with minor thin sandstones and minor thin limestones. The overlying Morrowan (Lower Pennsylvanian) shales are 200 to 1200 ft thick. The Barnett Shale was deposited in a Late Mississippian basin and intertongues to the north and northwest with Upper Mississippian shelf limestones.

The Barnett Shale contains mature, organic-rich petroleum source rocks. Total organic carbon (TOC) content ranges from 0.85 to 4.9 percent. The kerogen population is dominantly gas prone. The Barnett Shale is thermally mature throughout its extent in the New Mexico part of the Permian Basin. A northwest-southeast trending depth-independent fairway for Barnett shale gas exploration extends throughout the western portion of the New Mexico part of the basin. This fairway is defined by the most thermally mature source rocks with TOC contents greater than 2 percent. The Barnett is within the upper part of the condensate and gas windows along this fairway. Gas shows along the axis of the fairway are characterized by methane. Heavier gases characterize gas shows outside of the fairway.