Research and application of two-stage and two-speed reaming technology in coal mine

Aiming at the problems of low comprehensive efficiency and poor safety of drilling tools, a two-stage and two-speed reaming method is developed. A two-stage and two-speed reaming drilling tool is developed, including a straight screw motor, a first-stage bit and a second-stage bit. Based on the theory of specific work of equal broken rock, the study of reaming classification is carried out. The cutting boundary diameter between the first and second drill bits is 157 mm, and the outer diameter of the first drill bit is 165～172 mm. The design and research are carried out from the aspects of shell, motor power assembly, cardan shaft assembly, transmission shaft assembly and connection module, and the 105 mm two-stage and two-speed screw motor is developed. By means of parametric design, various specifications of first and second stage bits are developed. The field test results show that the two-stage and two-speed reaming technology can increase the diameter of high-level directional drilling from JP3120 mm to 200 mm at one time, improve the comprehensive drilling efficiency, and provide a new method for the quick hole formation of directional long drilling with high-efficiency gas drainage under pressure relief.