Factors affecting coalbed methane enrichment in Anze area, southeastern Qinshui basin

Through deepened analysis of CBM geological conditions and reservoir conditions in Anze block, the CBM enrichment law and its major influencing factors were discussed. The results show that coal petrology and structure of coal seam, as well as lithological characteristics of roof and floor rocks of coal seam are three key factors influencing gas content. Generally, gas content was manly controlled by coal rank. The higher coal metamorphic degree resulted in higher adsorption capacity of coal, and thus the greater gas content. Locally, gas content is also influenced by buried depth of coal, faults, folds and lithology of seam roof and floor. In structurally gentle zone, CBM content increased with burial depth. In faulting zone, gas content in the upthrow side of normal fault was obviously lower than that in the downthrown side. CBM dispersed obviously through faults. Mudstone and shale roof and floor of coal seam show better sealing capacity than that of sandstone roof and floor.