Hydraulic fracturing and punching integration enhanced permeability gas extraction technology

The existing hydraulic fracturing, hydraulic punching, hydraulic slotting, hydraulic cutting and other underground hydraulic permeability enhancement technologies in coal mines have complex processes, single adaptability conditions, and high labor intensity. However, drilling and punching integration, drilling and expansion integration, hydraulic punching/fracturing integration and other technologies are not ideal for enhancing the permeability of hard coal. There are problems such as cumbersome processes and inability to operate continuously. In order to solve the above problems, a hydraulic fracturing and punching integration enhanced permeability gas extraction technology is proposed. During the drilling process, high-pressure water jet is used to perform hydraulic enhanced permeability operations on coal seams at fixed points (directional, segmented). It can achieve integrated drilling, hydraulic punching of soft coal, and hydraulic injection fracturing of hard coal. The study reveals the principle of hydraulic fracturing and punching integration permeability enhancement. The hydraulic punching is used to flush out part of the coal body in soft coal seams, achieving pressure relief and permeability enhancement of soft coal seams. The fixed-point hydraulic jet fracturing is performed on hard coal seams, achieving fracture formation and permeability enhancement in hard coal seams. The drilling tool of hydraulic fracturing and punching integration is developed to meet the requirements of high pump pressure and large displacement. The drilling tool has strong rock breaking and chip removal capabilities. The process is simple and controllable. The drilling tool control methods for high-pressure water jet punching and hydraulic jet fracturing are provided. The stamping process during drilling and stamping process during drill withdrawal are discussed. The on site engineering tests are conducted using fracturing and punching integration drilling tools in the 16101 bottom drainage roadway of a coal mine. The results show that hydraulic punching operation in the soft coal section shortens the time by 60% to 80% compared to traditional hydraulic punching. The coal output from a single hole increases by about 2 times, and the average gas extraction purity per 100 meters per hole increases by 1 time. The hydraulic jet fracturing operation is carried out in the hard coal section. The average gas extraction purity per 100 meters per hole increases by 2 times compared to traditional hydraulic punching.