Abstract: Continuous-Type (Basin-Centered) Gas Accumulation in the Lower Silurian "Clinton" Sands, Medina Group, and Tuscarora Sandstone in the Appalachian Basin

R. T. Ryder, J. R. Sanfilipo, R. D. Hettinger, C. W. Keighin, B. E. Law, V. F. Nuccio, W. J. Perry Jr., C. J. Wandrey

Following earlier interpretations by Davis (1984), Zagorski (1988,1991), and Law and Spencer (1993), investigations at the U.S. Geological Survey (USGS) suggest that natural gas trapped in the Lower Silurian "Clinton" sands, Medina Group, and Tuscarora Sandstone of the Appalachian basin constitute a regionally extensive continuous-type (basin-centered) gas accumulation. Based on the USGS 1995 National Assessment of United States oil and gas resources (Gautier and others, 1995, USGS DDS-30), this accumulation contains, at a mean value, several tens of trillion cubic feet of recoverable gas estimated as undiscovered.

Important characteristics of continuous-type (basin-centered) gas accumulations, such as low-permeability reservoir, abnormal formation pressure, gas fields that tend to coalesce with additional exploration, gas shows or production in most holes drilled, low water yield, lack of well-defined downdip gas-water contacts, production "sweet spots", and a general lack of structural control on entrapment are all present in the proposed "Clinton"/Medina/Tuscarora gas accumulation. A 17,000 square mile region of western New York, northwestern Pennsylvania, eastern Ohio, and a small area of westernmost West Virginia--part of which is already gas productive in the "Clinton" sands and Medina Group--is the most favorable corridor for future continuous-type gas resources. Oil and gas produced in e st-central Ohio from "Clinton" sands since the early 1880's, located updip from the most favorable corridor of continuous-type gas resources, are considered conventional-type hydrocarbon accumulations because of their tendency to exist as discrete fields with well-defined oil- and gas-water contacts. The boundary between the conventional- and continuous-type accumulations is transitional and poorly defined.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas