Gas-bearing characteristics and its main controlling factors in low-rank coal seams of the Wujianfang Basin, North China

The Erlian Basin stands as a potential region for low-rank coalbed methane (CBM) exploration and development in China. Located within the western part of this basin in Ujimqin Banner, the Wujianfang Basin hosts six exploitable coal seams and demonstrates significant potential for low-rank CBM production. However, the current understanding of the geological characteristics of CBM in this area remains limited, a challenge compounded by the substantial differences in reservoir attributes between low-rank and medium-to-high-rank CBM systems. This study utilizes a comprehensive dataset obtained from exploration activities since 2007, integrated with core observations and laboratory analyses, to investigate the coal quality, pore structure, isothermal adsorption, and gas-bearing characteristics of the coal seams in the Wujianfang Basin. Key findings reveal that the measured gas content in the parameter well varies between 0.453 m3/t and 1.85 m3/t, with methane constituting 48.18% to 83.21% of the total gas volume, which reflects a heterogeneous gas accumulation pattern across the basin. Gas content is strongly influenced by trapping and preservation conditions, with high-gas-content potential being governed by the combined effects of gas generation, migration, trapping, and preservation processes. Through the application of partial least squares regression (PLSR), volatile matter content, porosity, and fixed carbon content were identified as the main geological factors controlling gas enrichment in the basin. This research provides a theoretical foundation for advancing the study of gas-bearing properties in low-rank coals and contributes to the basis for efficient CBM extraction under China’s dual-carbon strategy.