Methane Recovery And Utilization From Coalbeds
Authors: Wise Robert L. , Rightmire Craig T. 
Published: December 2007

Unconventional sources of natural gas already provide over 0.03 Tm3 (1 Tcf) annually to the domestic gas provide over 0.03 Tm3 (1 Tcf) annually to the domestic gas production and could ultimately provide a much larger production and could ultimately provide a much larger share of the natural gas supply. The Methane Recovery from Coalbeds Project has estimated the coalbed methane resource from 8.5 to 19.8 Tm3 (300 to 700 Tcf).

This paper presents project progress in resource verification, research and development, and technology systems tests. The resource verification activities involve major coal deposits throughout the U. S. The test projects feature various combinations of recovery and utilization systems including vertical and directional drilled boreholes, pipeline injection, mine power generation and space heating/boiler applications. power generation and space heating/boiler applications

Introduction

Natural gas accounts for about one-fourth of the nation's energy requirements. In recent years, demand for natural gas has been restrained to the level of available supply by non-market factors such as residential hookup moratoria, regulations on industrial and electric utility use, and, in extreme cases, curtailments. Recent projections agree that while constrained gas demand will remain at the current level of about 0.6 Tm3 (20 Tcf) at least through the 1990s, unconstrained demand could reach 0.7–0.9 Tm3 (25–30 Tcf) by 1990. Thus, gas consumption is expected to hold constant or to increase, depending on availability of supply and gas-use regulations.

However, domestic production and reserves dominated by conventional gas resources have declined steadily. Production in 1978 was 0.55 Tm3 (19.3 Tcf), down from the 1973 peak of 0.64 Tm3 (22.6 Tcf). Reserves have dropped to 5.7 Tm3 (200 Tcf) from their 1967 peak of 8.3 Tm3 (293 Tcf). Reserve additions (excepting Prudhoe Bay) have replaced only 46% of withdrawals during the 1970s.

This serious decline in production and reserves has continued despite a nearly tripling of average natural gas price (in real terms) since 1973, the emergence of still higher price intrastate markets, and a corresponding doubling of exploratory effort.

Recent data point to sharply declining availability and rapidly increasing costs of conventional gas production from the contiguous United States. The production from the contiguous United States. The phased decontrol and special provisions of the Natural phased decontrol and special provisions of the Natural Gas Policy Act of 1978 provide incentives for accelerated exploration, but the apparent decline in the number and quality of conventional gas prospects suggests that numerous supplementary gas sources will be required to meet the demand for gas.

The supplemental sources that may be needed to balance supply and demand include imports of oil and gas; gas from environmentally hostile, fragile or costly areas; surface gasification of coal; or by the unconventional gas resources, including underground coal gasification.

In light of the continuing demand and declining conventional supply and the fact that unconventional gas sources all require considerable lead times and capital commitments, all supplemental sources must be examined with care.

Analyses to date have concluded that the potential of the unconventional gas resources could be substantial. Numerous studies have attempted to estimate the magnitude of the resource-in-place and the portion of that which is technically recoverable. A range of these estimates are shown in Table 1. These broad ranges illustrate the vast uncertainty surrounding the potential of these resources. While the economically potential of these resources. While the economically recoverable portion of the resources, or reserves, would be considerably smaller than the technically recoverable resource estimates, the potential of the unconventional sources is still significant.

Some of the unconventional gas sources are relatively near to commercial status, so may contribute to domestic supply while the longer term alternatives are being developed. The geologically more favorable portions of the tight gas formations and eastern gas portions of the tight gas formations and eastern gas shales already produce nearly 0.03 Tm3 (1 Tcf/year), or about 5% of total supply. Thus, the unconventional sources could play an important role in the nation's energy supply within the near term.