Regional Controls of Gas Accumulation in Oriskany Sandstone, Central Appalachian Basin

Abstract

Available literature and production data were used to compile maps of stratigraphic relationships, structural configuration, and production trends of the Oriskany (Ridgeley) Sandstone, Lower Devonian (Deerpark Stage). Many of the Oriskany gas fields that occur in the western basin and northern portions of the Low Plateau and High Plateau provinces are stratigraphic traps associated with the Oriskany pinch-out. This pinch-out is a result of pre- and/or post-Oriskany unconformities, which are more pronounced along the basin margin. Pinch-out fields are characterized by intergranular porosity that probably developed soon after deposition on pre-Middle Devonian topographic highs. Entrapment generally results from an updip permeability barrier against the pinch-out. Oriskany fields that are not associated with the pinch-out are in structural traps characterized by fracture porosity and entrapment along anticlinal highs or against faults. Fields of this type are more common in the central and eastern parts of the basin, especially in the High Plateau province and the Valley and Ridge. Oriskany production is generally absent from areas within the Low Plateau province that are not in proximity to the pinch-out. This unproductive trend coincides with an area of gentle structural deformation and the occurrence of Huntersville Chert directly above the Oriskany.