Directional fracturing technology for cliff horizontal wells to increase single well production of fragmented soft and low-permeability coal seam

In response to the problems of poor underground treatment effect and low gas production caused by low permeability and high gas content in the fragmented soft and low-permeability coal seam of Zhaozhuang Mine, as well as the difficulty in gas extraction due to low gas production in conventional vertical wells, directional fracturing technology for cliff horizontal wells is proposed to improve the efficiency of coalbed methane extraction and offer support for low-carbon green mining. Taking account of the drillability of cliff rock and hydration laboratory finds of mudstone, the well finish position of cliff horizontal well in mudstone or sandy shale neighbouring the coal seam is optimal. By combining well inclination, azimuth data, and near drill bit inclination data with directional operation software, precise control of wellbore trajectory is achieved, thus realizing safe and efficient drilling. Directional perforation fracturing is carried out in the horizontal section to effectively communicate the cliff horizontal wells with underlying coal seam. Adopting precise pressure control and extraction technology by screw pump enables long-term stable production of coalbed methane wells. The on-site test results show that by the end of 2024, the cumulative gas production of the experimental wells was 7.1156 million m³, with a maximum daily gas production of 11,200 m³/d. The daily gas production during the stable production period was 3,500-4,500 m³/d, keeping the stable production lasting for more than 5 years. This provides technical support and experience for advanced pre-extraction of coalbed methane and resource utilization in high gas, soft and low-permeability coal seams. It is recommended to further promote and apply coalbed methane development under similar geological conditions to improve the efficiency of coalbed methane extraction and boost the low-carbon and green development of the coal industry.