ENHANCED PHASE-CHANGE FRACKING GAS EXTRACTION METHOD FOR LOW-PERMEABILITY COAL BED

摘要

An enhanced phase-change fracking gas extraction method for a low-permeability coal bed, comprising: injecting water at room temperature into a coal bed (1) through a drilling hole, and shutting off a valve after water injection is complete; freezing the coal bed around the water injection hole (2) using a refrigeration and freezing technique, the free water inside the coal bed fractures gradually transitioning from a liquid state to a solid state during the freezing process to expand and break the coal mass and promote generation and expansion of fractures inside the coal mass; after the freezing process is complete, the coal bed absorbs underground environmental heat and melts, further promoting coal mass pore interconnection and fracture expansion, and enhancing the effect of phase change fracking; after the melting process is complete, connecting the water injection hole to a gas extraction pipe and extracting gas, or drilling a gas extraction drilling hole in the coal bed in a phase-change fracking area and extracting gas. In the gas extraction process, phase-change fracking can be applied repeatedly to the drilling hole depending on gas extraction results, thus achieving objectives of improving coal bed permeability and efficiently extracting gas.