Technology and application of indirect fracturing in CBM vertical well of broken and soft coal seam with low permeability

In order to solve the problems of pulverized coal output and fracturing fracture not easy to extend during fracturing operation in the broken and soft coal seam with low permeability, the adaptability and fracturing fracture distribution of CBM during indirect fracturing are studied by means of in-situ stress and numerical simulation, and the engineering practice of indirect fracturing has been tested in Hongshandian mining area of Hunan Province. The results show that indirect fracturing can effectively improve the fracturing effect of the broken and soft coal seam with low permeability, and increase the fracture length. When the roof and floor are lithologicaly brittle sandstone, it is more conducive to indirect fracturing. Well HC01 has achieved a good gas production efficiency of 1 850 m³/d, indicating that the active water indirect fracturing technology of "large displacement, large sand volume, high prepad ratio and medium sand ratio" is suitable for fracturing of the broken and soft coal seam with low permeability. At the same time, the application of drilling bridge plug cable perforation technology can effectively shorten the construction period of multi-seam fracturing in CBM well and improve the efficiency of fracturing operation.