Directional drilling technology and equipment of pneumatic screw motor in soft seam

Aiming at the drilling problems of shallow depth, uncontrollable trajectory and blind area of extraction in soft coal seam, the directional drilling technology of pneumatic screw motor was invented, and the directional drilling equipment consisting of pneumatic screw motor, narrow structure directional drilling rig and MWD system were formed. The air directional drilling technology and hole-completion technology were studied and developed. The technology of drilling and hole-completion solves the problem of long-distance safe drilling and hole protection of directional drilling along soft coal seam. The technology has been successfully tested in a coal mine, Huainan, with 30 test boreholes with a maximum depth of 300 m, an average of coal-drilling rate of 92.9%, and screen pipes installed in the whole hole section, extraction gas volume of boreholes is 320 000 m³, and the average efficiency of coal roadway excavation in the test area is 9.3 m/d, achieving efficient and safe recovery of coal seams in the covered area. A new progressive gas control model of soft coal across working face has been preliminarily explored.