Potentially recoverable quantities of methane from unconventional sources such as coalbeds have been largely excluded from potential gas supply surveys. This is attributable to the lack of data about the resource, technology and economics of its recovery. In order to provide answers, DOE initiated the Methane Recovery from Coalbeds Project (MRCP) to characterize the gas-in-place for various coalbeds and associated sediments. After the 1977 initiation of the MRCP, several other interested groups have supported various aspects of the project.

Results are presented from the first phase of a joint effort between DOE (METC), TRW, GRI, and Industry to investigate the coalbed methane resource in the Arkoma basin. This elongated narrow east-west sedimentary basin is located in east-central Oklahoma and in west-central Arkansas and contains extensive gaseous bituminous coal reserves of Pennsylvanian age. Preliminary gas-in-place resource estimates were made based on the volume of coal in-place and on direct methane desorption data. It has been conservatively estimated that the total coal resource of the basin is about 7.9 billion tons. Seven individual coal seams have been identified as being the most likely candidates to contain potential coalbed gas reservoirs. The majority of these coalbeds are continuous, but these beds do not maintain a constant thickness throughout the basin. Total gas contents, as determined by desorption tests on coal cores, range from 73 cubic feet per ton to 576 cubic feet per ton. The estimated unsealed in-place methane resource is 1.6 Tcf and is considered a low volumetric assessment for the basin. The estimated depth scaled in-place methane resource is 2.7 Tcf, 82 percent of which is contained in the Hartshorne coalbeds. Analyses of gas produced from the Hartshorne coals/Hartshorne Formation show a range of Btu values from 993 to 1118 in the western part of the basin.

A viable exploration rationale has been established for the Arkoma basin, based on various geological aspects, such as stratigraphy and structure, the depth of the coalbeds and the recent MRCP well tests. The described methodology of methane exploration is present along with the results. Redefined target-test areas in the basin have been delineated and are discussed.

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