CBM enrichment mechanisms in the Southern Qinshui Basin: A synergistic role of tectonic-lithological-hydrodynamic coupling

The Qinshui Basin is renowned for its thick, laterally extensive coal seams, high thermal maturity, and significant coalbed methane (CBM) potential. However, reservoir heterogeneity resulting from multi-stage tectonic activity leads to pronounced variability in CBM enrichment, posing challenges for efficient development. This study examines the influence of individual and coupled tectonic, roof–floor lithological, and hydrodynamic factors on CBM accumulation in the southern Qinshui Basin, using seismic data, well logs, and gas content analysis. Four distinct CBM enrichment models are identified from north to south: in shallow seams, atmospheric precipitation-driven groundwater recharge, coupled with anticlinal structures, controls the spatial distribution of gas; with increasing burial depth, reduced groundwater mobility and improved roof–floor sealing shift the dominant control from hydrodynamic to lithological factors; in structural slope zones, gas enrichment is governed by the coupling of nose structure and hydrodynamic sealing; In fault-dominated areas, gas migration along faults and the sealing capacity of fault zones are the primary controls. These findings provide a scientific basis for optimizing CBM exploration and development in geologically complex basins.