Abstract: Coalbed methane (CBM) is a hazardous gas that leads to gas explosions, coal and gas outbursts, and contributes to atmospheric greenhouse effects in coal mines. At the same time, CBM is a clean and efficient energy source. Developing CBM in coal mining areas offers significant benefits for enhanced safety, energy production, and environmental protection. In China, the estimated CBM resource is 32.86 × 10¹² m³ at depths shallower than 2 000 meters and 40.71 × 10¹² m³ at depths beyond 2 000 meters. Since the “12th Five-Year Plan”, an extraction model of “four-zone coordination” has been developed through practical exploration to ensure both CBM resource development and the safe, efficient operation of coal mines. This model is tailored to mining engineering deployment, mining-induced disturbances, and coal seam geological conditions. It involves coordinated CBM development in planning, preparation, production, and goaf areas, demonstrating significant effectiveness in practice. The key outcomes include: (1) Three technologies have been developed for use in planning areas, namely, surface vertical well fracturing, staged fracturing in coal-seam horizontal well, and staged fracturing and extraction. In the Haishiwan Mine of Yaojie, Gansu, vertical well interlayer temporary plugging and diverting fracturing technology is used in the target coal seam, and the CBM well production reaches 2 607 m³/day. In Sihe mine of the Jincheng Mining Area, Shanxi, bottom-sealed coiled tubing pulling hydraulic jet and annulus sand fracturing technology is used in coal seam 15. The length of the horizontal well is 820.53 m with 8 fracturing sections. The maximum well production is 9 100 m³/day, and the stable gas production is 7 000-8 000 m³/day. U-shaped horizontal well staged fracturing is used in the roof of fragmented and soft coal seam 8 of Luling Mine in the Huaibei Mining Area, Anhui Province. The horizontal well length is 585.96 m with 7 fracturing sections. The maximum well production is 10 760 m³/day, and the total production is 7.5 million m³. (2) Directional long borehole staged fracturing and extraction technology in underground coal mines have been developed in preparation areas. In the Dafosi Mine of Binchang, Shaanxi Province, long borehole staged fracturing is used in coal seam 4. The horizontal well length is 600 m with 8 fracturing sections. The maximum pure gas production is 3 600 m³/day, and the average is 1 000-2 500 m³/day. Pure gas production per 100 meters is 4.9-11.0 times that of unfractured boreholes in the same area. In the Xinjing Mine of the Yangquan Mining Area, Shanxi Province, the roof of fragmented and soft coal seam 3 is sand fractured in stages. The drilling length reaches 609 m with 10 fracturing sections. The maximum pure gas production is 2 811 m³/day, and the pure gas production per 100 meters is 5.6-15.4 times that of unfractured boreholes in the same area. (3) For fragmented and soft coal seams, technologies such as high-pressure sand hydraulic fracturing and pneumatic directional drilling have been developed in production areas. In the Pansan Mining Area, Anhui Province, sand hydraulic fracturing technology is used in coal seam 13-1. The pure gas production per 100 meters of sand-fractured borehole is 2.38 times that of conventional water fracturing. In the No.2 Mine of Yangquan, Shanxi Province, to address the difficulties of drilling in fragmented and soft coal seams and the tendency of borehole collapse upon encountering water, pneumatic directional drilling drainage technology is used in coal seam 8. The drilling depth is 607 m, and the pure gas production is 971.6 m³/day. (4) A ground vertical well and L- shaped horizontal well gas extraction model is developed for goaf areas in coal mines. In the Panyi Mine of the Huainan Mining Area, Anhui Province, due to the depressurization mining of coal seam 11-2, ground vertical wells are used to drain gas from coal seam No.13-1, and gas production reaches 50 000 m³/day. In the Sihe Mine, Jincheng Mining Area, Shanxi Province, the L-shaped horizontal well is used in the roof coal seam 3, and the pure gas production is 30 000 m³/day. Innovative technologies such as large-scale staged fracturing both at the surface and underground and deep CBM development have been proposed to promote technological advancement in coal mining areas and ensure the safe mining and efficient development of CBM resources.

Key words: coal mining area, coalbed methane (CBM), four-zone coordination, staged fracturing, fragmented and soft coal seam