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

Paul C. Lyons
Open-File Report 96-735

Introduction

Over the past decade in the United States, coalbed methane (CBM) has become an increasingly important unconventional source of fossil fuel, which also includes gas shales and tight gas sands. In 1994, unconventional natural gas accounted for 3,609 billion cubic feet (Bcf) and about 20 percent of U.S. gas production; of this total, tight gas sands contributed 2,492 Bcf (~14%), CBM 858 Bcf (~5%), and gas shales 259 Bcf (1%) (Kuuskraa and Stevens, 1995). According to Rogers (1994), CBM accounts for a significant part of the gas reserves of the United States, which has been estimated by Rice (1995) as 6 percent..

For many years CBM was primarily an underground coal-mine safety problem and a large body of literature exists on this subject (e.g., see Finfinger, 1995). Over the last decade there has been a rapid acceleration of symposia, conferences, literature, and technological and scientific studies on CBM as an unconventional fossil fuel. In addition, a new periodical--Quarterly Review of Methane from Coals Seams Technology, which is produced by the Gas Research Institute--emerged about a decade ago. These activities have paralleled accelerated exploration and development of CBM in the United States. CBM exploration and development during this decade was stimulated by the federal Windfall Profit Act of 1980 (Nonconventional Fuels Tax Credit under Section 29) for wells drilled between December 31, 1979 and December 31, 1992. Coalbed methane (also called ìcoalbed gasî by Rice et al., 1993) represented in 1994 approximately 3% of natural gas production. The most significant CBM production occurs in the San Juan Basin, Colorado and New Mexico and Warrior Basin, Alabama, which collectively accounted for about 94% of CBM production in the United States in 1995 (Stevens et al., 1996). According to the latter authors, the Appalachian basin accounted for 4% of U.S. CBM production during 1995, and, according to these authors, accounts for an estimated 12% of the U.S. reserves of CBM. Thus, Appalachian CBM deserves special attention as a mainly undeveloped, clean-burning fossil fuel.

In addition, decreasing the venting of CBM to the atmosphere from coal mines by extracting it through wells may help to reduce global warming (Rogers, 1994). According to Clayton et al. (1995), methane is an important greenhouse gas and ventilation from underground coal mines is the largest source of atmospheric methane from coal. Kelafant and Boyer (1988) reported several coal mines in their study area in the central Appalachian basin venting 3 million cubic feet of gas per day, which is equivalent to 6 Bcf of CBM per year lost to the atmosphere. This loss to the atmosphere does not include natural degassing along hillsides with outcropping coal beds.

This paper is an overview of the potential of coal beds of the central Appalachian basin (Virginia, West Virginia, Kentucky, and Tennessee) and northern Appalachian basin (Pennsylvania, West Virginia, Ohio, and Maryland) for CBM exploration and development (see also Stevens et al., 1996). The Cahaba coal field of Alabama in the southern Appalachian basin also contains CBM at depths of about 2500-9000 ft (Rice, 1995; Pashin et al., 1995). The Cahaba coal field is usually considered with the Black Warrior Basin of Alabama, which has a similar section of Pottsville strata. Various aspects of Appalachian CBM are summarized in this paper including legal and economic constraints, CBM fields and stratigraphy, depth to coal beds and coalification, cleats, CBM composition and desorption data, production, and CBM potential of different areas of the central and northern Appalachian basin. Additional references on the subject appear in a selected bibliography of Appalachian coalbed methane by Lyons and Ryder (1995).

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