Factors influencing the methane content of coal beds of the Czech part of the Upper Silesian Coal Basin, Czech Republic

The article is one of the results of long-term efforts of the team of authors to evaluate the reserves of raw materials for energy purposes in the Czech part of the Upper Silesian Coal Basin and to assess possibilities of their realistic utilisation. A relatively large program of exploratory drilling to determine the content of coal bed methane (CBM) in the Czech part of the Upper Silesian Coal Basin (upper Mississippian to lower Pennsylvanian) was undertaken in the 1990s. The possibility of extracting CBM from coal beds undisturbed by mining was also investigated. Numerous analyses of the gas contents of coal beds by the Borowski and USBM methods and other parameters that affect the sorption of CBM were made. The relationships between these factors are described and discussed in the present paper. Factors governing the occurrence and spatial distribution of CBM in the Czech part of the Upper Silesian Coal Basin are divided into those of primary nature (the degree of coalification, the chemical and physical properties of the coal, its maceral composition and pore structure) and those of secondary nature (gas migration, erosion, tectonic setting). The ten most important factors are defined. However, in the area of all the Czech part of the Upper Silesian Coal Basin, the degree of their importance, which varies in individual boreholes, cannot be unambiguously determined. Future geological exploration for CBM in coal basins should be guided by the essential factors identified in this study. The application of them could contribute to solving a long-term known discrepancy between the amount of reserves and the question of their exploitability.