Process simulation and application of hydraulic cavitation while drilling technology

In improving the efficiency of gas extraction from soft and low permeability coal seams, the traditional hydraulic punching method requires drilling, lifting the auger, lowering the hole-making device, lifting the auger and then lowering the screen pipe for gas extraction. In order to solve the problems of its complicated process and high-risk factor, the technical parameters of hydraulic punching suitable for broken soft coal seam are determined by combining simulation results with field experiments based on Fluent and Ls-dyna simulation. The results show that the cavitation nozzle with nozzle diameter of 2.8 mm has better coal breaking ability than the common nozzle; the best effect of breaking coal is achieved when the punching time is maintained at 30 min/m, the pump pressure is kept in the range of 12 MPa to 20 MPa and the rotational speed is maintained in the range of 90 r/min to 110 r/min during the hole making period. A total of 136 drill holes were constructed, and the average coal punching volume of 1.07 t/m was calculated, and the coal seam permeability was greatly improved.