Main control factors of coalbed methane occurrence differences in adjacent coal seams - a case study of Luling coal mine, Huaibei Coalfield, China

Coalbed methane (CBM) is a natural gas resource related with coal deposits. In general, Gas status parameters gradually with the depth of the stratum. However, in areas with complex geological structures and multiple coal seam occurrences, the gas storage situation in shallow coal seams is typically better than in deep coal seams. This research paper focuses on coal seams numbered 8, 9, and 10 within the Luling coal seam as the subject of study. The study combines the analysis of gas accumulation history, laboratory experiments, and field investigations to examine the differences in gas occurrence within the coal seam group. The findings suggest that the differences in gas occurrence state within each coal seam of the Luling coal mine is predominantly governed by tectonic processes. During the process of tectonic evolution, the thicker coal seams, such as Nos. 8 and 9, are more prone to fracturing, leading to the formation of widely distributed tectonic coal. These broken coal bodies exhibit a significant capacity to store gas, resulting in favorable gas storage conditions within these coal seams. On the other hand, the low permeability of the mudstone in the roof layer restricts the migration and seepage of gas in the No. 10 coal seam, leading to a comparatively lower sealing effect for gas. By providing a comprehensive understanding of the gas content differences in the coal seam group, this study highlights the significant influence of geological processes on the distribution and storage of gas. These findings contribute to understanding the characteristics of gas reservoirs under complex geological conditions and adopting corresponding measures to reduce the risk of coal and gas outbursts in coal seams.