Research on nitrogen/air composite directional drilling technology in high-order broken soft coal seam
Aiming at the problems of difficult construction,low hole-forming rate,CO overrun and fire in the hole of gas extraction borehole in the soft area of anthracite in Jincheng mining area,a nitrogen/air composite directional drilling technology is proposed.Starting from the technical principle and process method,the influence of process parameters such as air pressure and air supply on the construction of composite directional drilling is analyzed.The field test was carried out in 4326 working face of Changping Coal Mine.A total of 42 main holes were completed,and the cumulative footage was 6454.5 m.The hole forming rate of 300 m and above was 79.5％,the hole forming rate of 200 m and above was 85.7％,and the hole forming rate of 150 m and above was 94.5％.The effect was remarkable.
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