Progressive gas extraction technology in broken soft coal seam of Qinglong coal mine, Guizhou Province

Aiming at the problems of uncontrollable trajectory, shallow borehole depth and poor gas extraction effect in gas treatment drilling of broken soft coal seam in Qinglong coal mine, the regional progressive gas extraction technology in broken soft coal seam based on compressed-air directional drilling was proposed, on the basis of analyzing the technical bottleneck of existing gas extraction borehole with rotary drilling. The principle and advantage of the technology was expounded, the technology of directional drilling by compressed-air, the technology of long distance in-seam drilling, and the technology of compound slag discharge by double power were integrated. The field test was carried out in roadway 21606 of Qinglong coal mine, 253 boreholes were drilled in the broken soft coal seam with a protodyaknove's number of 0.37.95% of the boreholes, reached the design depth, and the cumulative footage was more than 30 000 m. The single-hole gas extraction purity is 10 times of that of the ordinary rotary boreholes, and the single-hole gas extraction concentration increased by about 50%. The application test shows that the regional progressive gas extraction technology has the advantages of great hole depth, high drilling efficiency and no blind extraction zone, which can effectively relieve the tension situation of mining replacement, improve the level of mine gas treatment technology, and provide a new technical way for the gas treatment of broken soft coal seam.