Abstract: Variability of Gas Production in the Ohio Part of the Lower Silurian Regional Oil and Gas Accumulation, Appalachian Basin, As Indicated By Distributions of Estimated Ultimate Recovery (EUR) Per Well

RYDER, R. T.
U.S. Geological Survey (USGS), Reston, VA
R. A. RILEY and L. H. WICKSTROM
Ohio Department of Natural Resources, Division of Geological Survey (ODGS), Columbus, OH

Estimated ultimate recovery (EUR) of gas per well is an essential parameter for assessing recoverable gas resources in the Lower Silurian regional oil and gas accumulation (LSRA) in the Appalachian basin. Basically, an EUR probability distribution for a set of wells in the regional accumulation can be projected to undrilled parts of the accumulation for the calculation of remaining recoverable resources.

A recent investigation of the production history of the Ohio part ("Clinton" sands) of the LSRA by the USGS and the ODGS has provided new production data and EURs that better characterize variability of the resource. Over 100,000 monthly and annual production records for 2,000 wells were added to an existing ODGS database of over 410,000 records for 43,000 wells. EURs were calculated for about 400 wells using standard decline-analysis software. Also, about 200 EURS were obtained from the literature and M.S. theses.

Probability distributions of EURs of wells in about 15 localities in eastern Ohio range from median (F₅₀) EUR values less than 75 MMCFG per well in Lake/Geauga Cos. to approximately 250 MMCFG per well in western Noble Co. Geologic factors that may control the volume of recoverable gas include: regional trapping mechanisms; reservoir thickness; reservoir depositional environment; basement-involved structures and associated natural fractures; and diagenetic history. Ravenna (Portage Co.) (F₅₀ ~ 300 MMCFG) and Sharon (Noble Co.) (F₅₀ ~ 250 MMCFG) gas fields are production "sweet spots" that may be controlled by basement-involved faults.

AAPG Search and Discovery Article #90930©1998 AAPG Eastern Section, Columbus, Ohio