Influence of geological factors on gas content of the deep coal seam in the northern DJ block, Southeast Ordos Basin, China

DJ block, located in the southeast of the Ordos Basin, is rich in coalbed methane (CBM) resources. A systematic investigation was performed to study the variation of gas content of the Benxi Formation coal seam and its geological controls. The results show that: 1) the gas content ranges from 19.80 cm3/g to 33.90 cm3/g and shows an increasing from west to east; 2) the key factors that control gas content are coal quality, sealing unit characteristics, and small-scale structures; 3) the gas content is mainly controlled by three geological models. The first model suggests that there is less storage space in small synclines structure, and CBM is more likely to escape from steeply dipping areas. The second model indicates that small anticlines are more likely to develop cracks, which expand the reservoir space. The third model suggests that the saddle of deep burial is more conducive to the enrichment of CBM.