Structural and sedimentary control of coalbed methane enrichment areas in south exploration block of Wuxiang County, Qinshui Basin

The south exploration block of Wuxiang County in Qinshui Basin of Shanxi Province is one of the important coalbed methane resource rich areas in China. However, its complex geological structure features, especially the alternating distribution of folds and faults, greatly restrict the efficient development of CBM. Therefore, combined with the regional geodynamic background, the structural characteristics of folds and faults in this block are systematically analyzed, on the basis of detailed interpretation of 3D seismic, logging and drilling data, a 3D model of fault and coal seam in the study block is constructed, and the correlation of sedimentary and structural characteristics with the variation of coal thickness and CBM content in this block is analyzed emphatically. From the researched results, it can be concluded that: Firstly, according to the structural composition and occurrence characteristics, four different distribution regions are divided, and the nature, elements and distribution characteristics of the main structures in each region are discussed, which provides a scientific basis for the systematic classification of regional geological structures; Secondly, according to the structural geometry and dynamic classification method, the block coal-controlling structural styles are divided into 3 structural types (extension, extrusion, strike-slip fault) and 9 subtypes, and the influence mechanism of structure on CBM enrichment is further refined. Thirdly, through the analysis of sand-mud ratio, sediment, lithology and geological structure characteristics of Shanxi Formation and Taiyuan Formation, the correlation between sedimentary environment, lithology of top and floor and changes of coal seam thickness and gas content is briefly discussed, revealing that sedimentary environment has a direct control effect on the thickness of coal seam, and the thickness of coal seam further affects the distribution of gas content. The controlling effect of structure on gas abundance is further studied. On this basis, three CBM enrichment areas in No. 3 and No. 15 coal reservoirs are delineated respectively, and the distribution characteristics of CBM enrichment areas are drawn. The research results can provide a basis for the scientific selection of efficient CBM development in this block.