Journal of Earth Science Research

To effectively prevent gas disasters and promote the development of coalbed methane resources, this study aims to systematically reveal the key geological control mechanisms of gas enrichment in the main B₄ coal seam of the Fengcheng mining area, Pingxiang-Le'an Depression, Jiangxi Province. The core scientific problem is to clarify the dominant geological factors controlling the heterogeneous gas occurrence in this mining area and their coupling relationships. This study adopted a multi-method integrated analysis approach, systematically combining regional geological exploration, borehole data, coal quality testing (including vitrinite reflectance determination and industrial analysis), and measured gas parameter data. The research focused on key geological gas-control factors such as roof and floor lithology, coal seam burial depth, coal seam thickness, coal metamorphism degree, and geological structures, conducting a comprehensive study that combined quantitative and qualitative analysis of gas occurrence patterns. The research indicates that gas occurrence in the B₄ coal seam is controlled by the synergistic effect of multiple factors: ① Lithological Control: Dense roof and floor strata (e.g., mudstone, siltstone) act as excellent seals, while the "thicker in the west, thinner in the east" distribution of the overlying S5 sandstone directly leads to a gas content pattern of "lower in the east, higher in the west." ② Burial Depth Effect: Gas content generally increases with burial depth, but anomalies occur in locally structurally complex areas (e.g., between exploration lines 2–5). ③ Coal Thickness Influence: Gas content is positively correlated with coal seam thickness. The coal seam distribution pattern of "thinner in the south, thicker in the north, thinner in the west, thicker in the east" highly aligns with the gas pattern of "lower in the south, higher in the north, lower in the east, higher in the west." ④ Coal Rank Effect: The B₄ coal seam is in a medium metamorphic stage (coking coal to lean coal, Ro=1.4%–1.895%). Its gas generation potential and strong adsorption capacity jointly promote gas enrichment. ⑤ Structural Control: Compressional structural areas such as the northern wing and axis of the Qujiang Syncline are gas enrichment zones, while open faults and the ancient weathering denudation zone in the southern wing facilitate gas escape. The gas enrichment in the B₄ coal seam of the Fengcheng mining area results from the combined effects of a dynamic "generation, storage, seal, and preservation" system. Its distribution pattern of "lower in the east and higher in the west, lower in the south and higher in the north" is comprehensively controlled by the gas generation potential of medium-metamorphic coal, the sealing capacity of the roof and floor, coal seam reservoir conditions, and structural preservation/escape effects. The findings of this study provide a key geological theoretical basis for the accurate prediction of gas occurrence patterns and the formulation of differentiated management strategies in the mining area.

Fengcheng mining area; Gas occurrence; Geological control; B₄ coal seam