Review and Outlook on Simulation Studies of Fracture Propagation in Segmented Multi-Cluster Fracturing of Coal Seam Roofs

As a clean and efficient unconventional natural gas resource, coalbed methane serves as a vital safeguard for China's energy transition and coal mine safety. Over 95% of China's high-gas mines face technical bottlenecks in low-permeability coalbed methane extraction efficiency, where conventional underground extraction technologies struggle to meet development demands in deep, fragmented, and soft coal seams. The horizontal top-wall multi-cluster fracturing technology for coal seams-involving horizontal well placement in the roof and multi-cluster segmented fracturing-induces fractures to penetrate and extend into the coal seam, forming complex fracture networks that enhance gas migration pathways. This has become one of the core technologies for efficient development of low-permeability coalbed methane. The fracture propagation patterns-including initiation locations, propagation paths, fracture network morphology, and interlayer penetration capabilities-directly determine fracturing effectiveness. Numerical simulation has become a core research tool in this field due to its ability to quantify coupled geological-engineering factors and dynamically reproduce fracture propagation processes.