Oriskany Sand Gas in Western Pennsylvania, Eastern Ohio, and Northern West Virginia

John T. Galey

Gas has been found only on structural closures in the Lower Devonian Oriskany, east of the stratigraphic accumulations in Ohio and West Virginia and west of the faulted areas of Pennsylvania, Maryland, and West Virginia. Structural closures occur where the rate of west reversal of the surface rocks exceeds the rate of eastward thickening of the Devonian section. This shifts the basal Devonian structural high west of that at the surface. Without such a rate of reversal, there would be no closure and, therefore, no gas.

The first structural closure discovered in western Pennsylvania was in Beaver County in 1935 where projection of the Mississippian structure to the Oriskany by convergence revealed a low-relief closure. Although reliable control for the rate of Devonian section thickening at that time was sparse and widespread, the predicted Oriskany datum for the discovery was within a few feet of that actually found, demonstrating the relatively uniform rate of Devonian thickening. Development of the feature revealed slightly subnormal thickening over the Oriskany high and slightly abnormal thickening under the highest part of the surface, but this was insufficient to give greater structural relief to the Oriskany than that found at surface. Four pools, in addition to that in Beaver County (one in W st Virginia and three in eastern Ohio), were discovered by the same means. Of the many wells in this area drilled to test the Oriskany but not meeting the conditions described, all without exception have been failures.

AAPG Search and Discovery Article #91041©1987 AAPG Eastern Section Meeting, Columbus, Ohio, October 7-10, 1987.