Recovery And Use Of Coalbed Methane
Authors: Sturgill Carl L. 
Published: December 2007

1.0 INTRODUCTION

Interest in the so called unconventional gas sources is currently in a period of rapid growth. One of these sources, coal bed methane, is known to exist in large quantities within and around most coal seam formations. Numerical estimates of the extent of this resource have been placed as high as 800 trillion cubic feet, with perhaps 300–400 trillion cubic feet recoverable. At today's prices for conventional energy sources, and projected escalations of those prices, coalbed methane is becoming a strong candidate, in many cases, for actual recovery and use as an auxiliary energy source. Historically methane has been recovered and used extensively for many years in other countries;1 particularly in conjunction with coal mining operations. These uses have included pipeline injection, industrial process heat generation and gas turbine-generator conversion to electricity. The technology for converting methane to useful energy forms, then, is not a limiting factor, and has, in fact, been around for many years. The principal factors which appear to influence the extent to which this resource can be recovered and used in this country include:Institutional barriers; particularly the question of methane ownership.Conflicting philosophies on how to recover, collect and use the resource.Economic considerations.

The question of methane ownership has already been discussed this morning. To what has already been said I would only add that the ownership issue is in many cases, apparently the single most important factor in delaying the application of existing technology to the actual recovery and use of this resource.

In the case of the second point noted above, a coal bed methane resource of several hundred trillion cubic feet an quickly suggest a large scale, regionally oriented recovery approach with interconnecting pipeline systems for collecting and delivering large gas flows to the users. This approach would seem to be an unlikely candidate for success with coal bed methane. On the contrary, technological, institutional and economic factors all weigh heavily in favor of a relatively small, individual site development approach.

Finally, economic viability has, and will most likely continue, to control the extent to which the private business sector is willing to make the necessary investments required to recover and use the coal bed methane resource. On this basis the system requirements will include:Predictable gas flows which can be sustained for long periods of time.Recovery, collection and conversion equipments which are reliable, safe, and environmentally acceptable to operate.Initial investment and operation/maintenance costs which are compatible with reasonable system payback periods and acceptable returns on investment.

With this background, I would now like to present a summary of two programs now underway at Westinghouse. The Department of Energy, through the Morgantown Energy Technology Center, is the primary sponsor for both programs, with additional support provided by the United States Army Corps of Engineers, Bethlehem Mines Corporation and the Commonwealth of Pennsylvania. These programs are both based on the concept of recovering, collecting and using the methane within a relatively small geographic area.

In one case, the methane is being extracted from virgin coal which is considered too thin to be mined. The end use of the methane in this case is gas fired boilers used to make industrial process and habitable space heat. In the second case, methane recovered from an active coal mining operation is intended to serve as the primary fuel for gas turbine-generator conversion to electricity for use by the mining operation. In what follows, these programs are referred to as Case No. 1 and Case No. 2, respectively.