Abstract
Methane gas retained in gassy coal seams is a valuable source of clean energy. However, methane is also a potential safety hazard. Its removal prior to mining improves mine safety by reducing the potential for explosions as well as economics by decreasing ventilation costs. A method of field evaluation of methane content in some Western US coal seams is presented. Results of pre-mining degasification in seams of similar methane content are described. The results indicate that degasification, or methane drainage, depends heavily on coal permeability. Since the permeability is affected by the presence of joints, fractures and cleats in coal and associated strata, their influence on the optimum direction of boreholes was studied. The results of methane drainage are discussed and recommendations as to the orientation of boreholes with respect to the main cleat systems in coal are suggested. 18 refs., 8 figs., 2 tabs.
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