doi:10.16186/j.cnki.1673-9787.2021110078

Received:2021-11-19

Revised:2021-12-14

Online Date:2022-09-13

Differences of the pore characteristics and adsorption/desorption of coalbed methane of different coal macrolithotype in low-rank coal reservoirs(Online)

LI Weibo1，LI Fei1，SHI Liyan1，ZHOU Shaowei1，MA Dongmin2，WANG Chuantao3，CHEN Yue2

（1. Shaanxi Geological Science and Technology Center，Xi’an 710054，Shaanxi，China；2. College of Geology and Environment，Xi’an Universityof Science and Technology，Xi’an 710054，Shaanxi，China；3. School of Chemistry and Chemical Engineering，Yan’an University，Yan’an 716000，Shaanxi，China）

Abstract:Coal reservoirs are highly heterogeneous and different macrolithotypes of coal have differences in material composition and pore structure, resulting in different coalbed methane(CBM) adsorption/desorption performance and gas-water migration characteristics. The differences of pore development characteristics between vitrain and durain and its influence on adsorption and desorption were studied based on theelement analysis, mercury injection, low temperature liquid nitrogen adsorption,adsorption-desorption experiment of the coal samples of Yan’an Formation in Huanglong coalfield. The results show: (1) The contents of vitrinite, volatile matter and H, O, N and S elements of vitrain are higher than those of durain, while the contents of inertinite, chitinite, minerals, ash, fixed carbon and C elements are lower than those of durain. (2) The coal sample has a porosity of 2.92%-10.29%, and overall, the pores are relatively developed. The porosity of durain is slightly higher than that of vitrain. The pore throat of durain is thicker and the macropores pores are more developed, resulting in better connectivity. The BET specific surface area and BJH total pore volume of vitrain coal are slightly larger than durain, and the micropores are more developed, which are dominated by semi-closed and ink bottle shaped pores. (3) Compared with durain,vitrain has more micropores and mesopores, contributing more specific surface area and stronger adsorption capacity. Desorption hysteresis is common in the process of methane adsorption / desorption in coal, and the pore connectivity of durain is relatively better, resulting in the degree of desorption hysteresis weaker and the theoretical desorption efficiency higher than that of vitrain .

Key words:Huanglong coal field;low coal-rank;coal lithotype;pore structure;adsorption/desorption

CLC：P618.13