Fractal Characteristics of Different Tectonic Coals in the Yuwu Mining Area based on Mercury Intrusion Porosimetry

Tectonic coal is a product of intense deformation and transformation of coal under tectonic stress. The complexity of its pore structure directly affects the occurrence and migration efficiency of coalbed methane (CBM), which is one of the key factors restricting CBM development in high-stress mining areas. Located in the northeastern part of the Qinshui Basin, the Yuwu Mining Area is characterized by frequent regional tectonic activities, with various tectonic types such as faults and folds developed, resulting in the extensive distribution of tectonic coal and significant differences in metamorphic degree within the mining area. As an effective tool for quantifying the structural complexity of porous media, fractal theory has been widely applied in the characterization of coal pore structure. In this study, different types of tectonic coals (e.g., cataclastic coal, mylonitic coal) in the Yuwu Mining Area were selected as research objects. Combining low-temperature nitrogen adsorption experiments with the FHH fractal model, the fractal dimension characteristics of coal samples under different tectonic deformation intensities were systematically analyzed. The influence mechanism of tectonic activity on the fractal properties of coal pores was revealed, and the intrinsic correlation between fractal dimensions and pore structure parameters (specific surface area, pore volume, pore size distribution) was clarified. The research results can provide theoretical basis and data support for CBM reservoir evaluation and development plan optimization in the Yuwu Mining Area, while enriching the geological understanding of fractal evolution of tectonic coal pores.