Study on Coalbed Methane Extraction Mode of Cracked Soft Coal Seam with Sectional Hydraulic Fracturing in the Rock of Coal Seam Roof

A coalbed methane extraction model using sectional hydraulic fracturing in the rock of the coal seam roof has been proposed to effectively manage soft, low-permeability coal seams in the Huaibei mining zone. The model utilizes stress-seepage-damage coupling to simulate the hydraulic fracturing process and the resulting fracture propagation. Numerical simulations have demonstrated that cracks in the rock of the roof can extend to the coal seam, allowing for effective extraction of coalbed methane.Physical similarity simulations were conducted to verify the effectiveness of the proposed sectional hydraulic fracture method. The results showed that hydraulic fractures could develop in the roof rock both vertically and downwards, penetrating the soft and fractured coal seam. Productivity simulations were then used to analyze the efficiency of coalbed methane extraction and determine the optimal number of fracturing stages. The best drainage effect was achieved with a fracture spacing of 72~83 m.Engineering verification experiments were conducted, confirming the effectiveness of the sectional hydraulic fracture method for coalbed methane extraction in the Huaibei mining area where the coal is soft, cracked, and has weak permeability. Overall, the proposed method provides an effective solution for the extraction of coalbed methane from low-permeability, soft coal seams, with potential to benefit the energy industry in the Huaibei mining zone and beyond.