Regularities of variability of methane content in the coal layers of the Western Donbass

Abstract

The article considers the factors that contribute to the accumulation and preservation of methane in the coal seams of the Western Donbass. Mines of the district develop lower and middle carbon bituminous coal. It is characterized by a low degree of catagenetic transformations, increased collector properties. Regional regularities of change of methane bearing capacity of coal seams and content of free methane in them are established. In tectonic terms, the area is a monoclinal with domed and brachyform local structures associated with rupture. Methane-bearing anomalies, in turn, are associated with the vaults of such structures, both anticlinal and synclinal types. When bending into the anticlinal fold, the fracture of the rocks increases in the upper part of the formation, which increases their filtration rates. Roof rocks are characterized by high permeability and this leads to degassing of the anticline fold. During the formation of synclines, fractured zones are formed in the bottom of the coal seams and the screen for methane migration becomes directly the coal seam, which contributes to the preservation of methane in such structures. As a result, local synclines mostly have positive methane and free methane content and local anticline bends are mostly negative. It is established that the methane reservoirs in the study area are coal seams, argillites and siltstones with high reservoir properties, which are located in the vaults of plicative structures. The established patterns will improve reliability of the forecast of methane accumulations within coal deposits Keywords: methane bearing capacity, local folding, syncline structures, free methane, reservoir properties.