Geologic controls of the production of coalbed methane in the Hancheng area, southeastern Ordos Basin

Abstract

The Hancheng area of the southeastern Ordos Basin is a sample area for coalbed methane (CBM) development in China. There are three target coal seams for CBM development in this area, but the gas production of the different coal seams varies significantly. This study investigates the controlling factors of CBM production in the Hancheng area. The results indicate that permeability has the main impact on CBM production in the Hancheng area. Coal types and stress are closely related to fracture development and further impact on the permeability of coal reservoirs in this area. According to the macroscopic coal petrography description, mercury porosimetry experiments and X-CT scanning, bright coal has the largest pore volume and average pore size diameter than those of the other coal types and developed fractures with good openness and connectivity, whereas dull coal has the most undeveloped macropores and fractures. The No. 3 coal seam always has a higher productivity because it mainly consists of bright coal and semi-bright coal and has a relatively shallow buried depth. Therefore, the No. 3 coal seam had the best physical properties as a whole compared to the other coal seams, providing the most favourable conditions for CBM production.