Coalbed methane potential in the Appalachian states of Pennsylvania, West Virginia, Maryland, Ohio, Virginia, Kentucky, and Tennessee; an overview

Abstract

This report focuses on the coalbed methane (CBM) potential of the central Appalachian basin (Virginia, eastern Kentucky, southern West Virginia, and Tennessee) and the northern Appalachian basin (Pennsylvania, northern West Virginia, Maryland, and Ohio). As of April 1996, there were about 800 wells producing CBM in the central and northern Appalachian basin. For the Appalchian basin as a whole (including the Cahaba coal field, Alabama, and excluding the Black Warrior Basin, Alabama), the total CBM production for 1992, 1993, 1994, and 1995, is here estimated at 7.77, 21.51, 29.99, and 32 billion cubic feet (Bcf), respectively. These production data compare with 91.38, 104.70, 110.70, and 112.11 Bcf, respectively, for the same years for the Black Warrior Basin, which is the second largest CBM producing basin in the United States. For 1992-1995, 92-95% of central and northern Appalachian CBM production came from southwestern Virginia, which has by far the largest CBM production the Appalachian states, exclusive of Alabama. For 1994, the average daily production of CBM wells in Virginia was 119.6 Mcf/day, which is about two to four times the average daily production rates for many of the CBM wells in the northern Appalachian basin. For 1992-1995, there is a clear increase in the percentage of CBM being produced in the central and northern Appalachian basin as compared with the Black Warrior Basin. In 1992, this percentage was 8% of the combined central and northern Appalachian and Black Warrior Basin CBM production as compared with 22% in 1995. These trends imply that the Appalachian states, except for Alabama and Virginia, are in their infancy with respect to CBM production. Total in place CBM resources in the central and northern Appalachian basin have been variously estimated at 66-76 trillion cubic feet (Tcf), of which an estimated 14.55 Tcf (3.07 Tcf for central Appalachian basin and 11.48 Tcf for northern Appalachian basin) is technically recoverable according to Ricei s (1995) report. This compares with 20 Tcf in place and 2.30 Tcf as technically recoverable CBM for the Black Warrior Basin. These estimates should be considered preliminary because of unknown CBM potential in Ohio, Maryland, Tennessee, and eastern Kentucky. The largest potential for CBM development in the central Appalachian basin is in the Pocahontas coal beds, which have total gas values as much as 700 cf/ton, and in the New River coal beds. In the northern Appalachian basin, the greatest CBM potential is in the Middle Pennsylvanian Allegheny coal beds, which have total gas values as much as 252 cf/ton. Rice (1995) estimated a mean estimated ultimate recovery per well of 521 MMcfg for the central Appalachian basin and means of 121 and 216 MMcfg for the anticlinal and synclinal areas, respectively, of the northern Applachian basin. There is potential for CBM development in the Valley coal fields and Richmond basin of Virginia, the bituminous region of southeastern Kentucky, eastern Ohio, northern Tennessee, and the Georges Creek coal field of western Maryland and adjacent parts of Pennsylvania. Moreover, the Anthracite region of eastern Pennsylvania, which has the second highest known total gas content for a single coal bed (687 cf/ton) in the central and northern Appalachian basin, should be considered to have a fair to good potential for CBM development where structure, bed continuity, and permeability are favorable. CBM is mainly an undeveloped unconventional fossil-fuel resource in the central and northern Appalachian basin states, except in Virginia, and will probably contribute an increasing part of total Appalachian gas production into the next century as development in Pennsylvania, West Virginia, Ohio, and other Appalachian states continue. The central and northern Appalachian basins are frontier or emerging regions for CBM exploration and development, which will probably extend well into the next century. On the basis of CBM production