Research status and prospect of coal expansion fracturing and permeability improvement

Safely and effectively increasing the permeability of coal seams and improving the efficiency of coalbed methane extraction is the key to promoting efficient energy utilization. With the increase of coal mining depth in China, the difficulty of coalbed methane mining is increasing, and the risk of gas outbursts is becoming more and more serious. The expansion fracturing technology has the unique advantages of no noise, no vibration, and no dust, which makes it have broad application prospect in the field of coal seam permeability enhancement. Through the investigation and analysis of the existing research results, the reaction mechanism of static expansion materials and the mechanism of expansion cracking and permeability improvement were analyzed, and the influence of parameters such as borehole diameter, spacing, and shape on the cracking effect of the coal body was combed, and the mechanical models of coal damage (coal damage fracture model and crack propagation model) in the process of expansion cracking were summarized, and the application status of expansion cracking technology in the field of coal seam permeability enhancement was expounded, and the research direction and development suggestions of expansion fracking technology in the field of coal seam permeability enhancement were proposed.