Some parameters of coal methane system that cause very slow release of methane from virgin coal beds (CBM)

Abstract

In some worldwide hard coal basins recovery of methane from virgin coal beds is difficult. In general, mentioned difficulties are related to geo-mechanical, petrographical and physical-chemical properties of coals in question, occurring for example in the Bowen Basin (Australia) or the Upper Silesian Coal Basin (Poland). Among numerous properties and parameters, the following are very essential: susceptibility of coal beds to deformation connected with coal stress state change and contemporary shrinkage of the coal matrix during methane desorption. Those adverse geo-mechanical and physical-chemical effects are accompanied by essential change of the porous coal structure, which under these disadvantageous conditions is very complex. This study aims to show difficulties, which occur in phase of recognition of the methane-reach coal deposit. Volume absorbed methane (not surface adsorbed) in sub-micropores having minimal size comparable with gas molecule diameter must possess energy allowing separation of the nodes and methane release to micropores. Keywords: Coal bed methane, Porosity, Slow desorption, Diffusion, Virgin bed