Study of Devonian Shale Gas Geology and Production in West Virginia, Kentucky, and Ohio

Abstract

Summary Gas Research Inst. (GRI) is sponsoring research by the West Virginia, Kentucky, and Ohio state geologic surveys so that they may provide Appalachian basin operators with studies of Devonian shale geology, completion techniques, and gas production. The study area encompasses 16 West Virginia, 25 Kentucky, and 5 Ohio counties. Major portions of the investigation are complete and can be obtained from the respective state surveys. Introduction Each state involved in the research is digitizing and evaluating pertinent well information from hard-copy state survey records, pertinent well information from hard-copy state survey records, operators' files, and county courthouse records in a study area that has significant historical levels of commercial production. Additional information is being acquired from GRI's Eastern Gas Data System, which contains detailed records on more than 2,100 shale gas wells. Computer hardware and software, common to each survey, are being used to facilitate exchange of information, and to allow integration of individual studies into an improved basinwide understanding of the Devonian shale and the factors correlating with best production. West Virginia has completed three oil and gas reports (Pleasants, Wood, and Ritchie counties; Mingo, Lincoln, and Logan counties; and Wirt, Roane, and Calhoun counties). Kentucky has completed six geologic and hydrocarbon reports (individual reports on Letcher, Knott, Floyd, Martin, and Pike counties, and a combined report covering Whitley, Knox, Bell, and Harlan counties). Ohio has finalized reports on Lawrence and Meigs counties. These reports include geologic cross sections and well locations, structure, isopach, and isopotential maps. These reports, plus detailed computer-drawn maps and data printouts, can be used directly by industry to improve exploration and production rationales, to locate well sites, to determine appropriate total depths, and to select completion zones. The Devonian shale of the eastern United States has been an important supplemental source of natural gas, and has the potential to become a major source in the future. Research by the U.S. DOE and others shows that the shale contains reserves throughout its areal extent, much of it at shallow drilling depths. Estimated in-place reserves range from 225 to 1,861 Tcf [6.37 times ten to the twelve to 52.7 times ten to the twelve Meters cubed]. However, the low reserves produced to date (3 Tcf [85 times ten to the nine meters cubed]) and the annual rate of production (0.1 Tcf [2.8 times ten to the nine meters cubed]) indicate the problem of per-well productivity. Flow rates and reserves of Devonian shale per-well productivity. Flow rates and reserves of Devonian shale wells are quite variable. U.S. DOE has reported that the average rate for a well during its first year is 200,000 ft3 cubed per D [5663 meters cubed per d], declining to a stable production rate of 10,000 to 50,000 ft cubed per D [283 to 1416 meters cubed per d] for as long as 30 to 40 years. This variability and generally low production rate is a result of several factors:there is little technical basis for choosing well sites;there is difficulty in evaluating the wellbore and selecting completion intervals; anda number of varied stimulation methods are being used, which are poorly understood. Additionally, the data needed to resolve these problems either are not available to the operator or are not problems either are not available to the operator or are not readily accessible. The three-state study area is shown in Figs. 1 and 2. This area covers the core of the Devonian-shale producing trend and generally corresponds to the U.S. DOE's Province 1-highly productive Appalachian producing area. productive Appalachian producing area.