Since 1981, an active oil and gas play has developed in Upper and Middle Devonian fine-grained clastics above the Onondaga Limestone and Huntersville Chert in part of northwestern West Virginia. Activity has been greatest in Ritchie and Pleasants Counties, but Wood, Wirt, Roane, and Calhoun Counties are also involved.

Recent drilling activity has facilitated a more detailed understanding of the Upper and Middle Devonian stratigraphy of the area. The section thickens from west to east, from about 2,000 ft to more than 4,000 ft. To the west, it is composed primarily of interbedded basinal organic dark-brown and gray to black shales and inorganic lighter gray and gray-green shales.

This section is also equivalent to the coarser grained clastic units of the Catskill delta to the east. As the section thickens to the east in the study area, the influence of the delta can be seen in the decrease of organic shale content and the progradation of siltstone bundles into the area. These delta-front siltstones are probably of predominantly turbidite origin and can be correlated with the well-known Upper Devonian drillers' "sands" of central West Virginia.

These facies changes across the area can be used to divide the area into three oil and gas plays: (1) The area west of the Burning Springs anticline, where gas is produced primarily from inorganic and organic shales. (2) The area immediately east of the Burning Springs anticline, where oil and gas are produced from transitional facies including inorganic and organic shales and siltstone. (3) The eastern fringe of the study area, where gas produced primarily from siltstone bundles has been the significant exploration result to date.

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