High-power nitrogen directional drilling ina broken soft coal seam with low permeability in Huayang No.2 Mine

CHENG Zhuoer; LI Quanxin; FANG Jun; LIU Fei; YANG Weifeng; LI Shuaishuai; GUO Lijia

doi:10.11799/ce202507009

Abstract：Aiming at the difficulties for gas control in Yangquan Mining Area,such as soft and broken coal seam,low permeability,high gas content,difficult long-distance bedding drilling and poor extraction effect,we took Huayang No.2 Mine as a demonstration mine,proposed the overall scheme of gas drainage drilling construction using high-power nitrogen directional drilling technology and equipment on the basis of analyzing the mine gas geology and gas control status.The technical principle and technical advantages were introduced,and the key technologies of nitrogen directional drilling,such as composite directional trajectory control technology,composite high-efficiency slag discharge technology,long-distance drilling along the seam,and long-distance sieve tube hole protection technology for directional drilling,were developed.The core equipment of high-power directional drilling equipment,such as high-power directional drilling rig,nitrogen making device,high-torque and long-life pneumatic screw motor,were studied and selected.The overall test scheme of drilling field design,drilling design,equipment matching and drilling tool combination design was formulated.The high-power nitrogen directional drilling test of bedding drilling was carried out in the No.81511 drilling field of Huayang No.2 Coal Mine.According to the test results,the high-power nitrogen directional drilling technology and equipment can realize the efficient directional drilling and gas drainage in the soft and low permeability coal seam.The construction completed 7 main holes and 13 branch holes of directional drilling,in which 5 holes were deeper than 350 m,the maximum hole depth reached 506 m,and the total footage was 3363 m.The diameter of the drilling hole was 120 mm,with Φ32 mm sieve tube deployed into the whole hole.The test drilling field has been stably extracted for over half a year,the gas extraction concentration was maintained over 50%,the maximum gas extraction purity has reached 3.43 m3/min,and the cumulative gas extraction purity has reached 689.9 thousand m3.It provides a new technical way for the efficient extraction and control of gas area in broken soft and low permeability coal seam of Yangquan mining area,which can be used for reference in mines with similar conditions.