--> Abstract: Anthracite: A Promising New Target for Coalbed Methane Exploration, by D. K. Murray; #90952 (1996).

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Abstract: Anthracite: A Promising New Target for Coalbed Methane Exploration

D. Keith Murray

Until recently, anthracite was not considered to constitute a viable reservoir for coalbed methane production. However, in 1994 commercial rates of methane were recovered from Permo-Carboniferous anthracites in the southern part of the North China Basin complex, in Henan and Shanxi Provinces, People's Republic of China. During production tests of limited duration, shallow (approximately 1,200 to 1,600 ft) vertical wells flowed at rates exceeding 250 Mcf plus 200 bbls water per day.

The coal in these two areas ranges from semi-anthracite to metaanthracite, with vitrinite reflectances (R0) varying from 2.4 to 6.0 percent. In-situ gas contents of cored coals are as high as 1,000 s.c.f./short ton. The produced gas consists of approximately 95 percent methane, with traces of CO2 and other gases. Aggregate coal thickness in both areas is from 35 to 60 ft; some individual beds range from 10 to 20 ft in thickness. Cores of these anthracites are described as fractured and friable, exhibiting fair to good cleat development. These deposits occur in geologically complex areas within a zone of intersecting major tectonic elements that is characterized by high geothermal gradients.

An untested but highly prospective anthracite deposit occurs in the South Wales Coal Basin, United Kingdom. Detailed, innovative research underway at the University of Wales, Cardiff, in this deformed Variscan foreland basin is focused on such topics as thrust-related permeability of anthracite and its potential control over coalbed methane production. The highest rank coal and the highest measured gas contents of cores (more than 850 s.c.f./short ton) in the U.K. are found in the northwestern part of the South Wales coal field.

AAPG Search and Discovery Article #90952©1996 AAPG Rocky Mountain Section Meeting, Billings, Montana