Coal Engineering ›› 2025, Vol. 57 ›› Issue (7): 60-66.doi: 10. 11799/ ce202507009

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

  

  • Received:2024-08-30 Revised:2024-11-23 Online:2025-07-11 Published:2025-08-14

Abstract:

Aiming at the problems of soft coal seam, low permeability, high gas content, difficult long-distance drilling along the seam and poor drainage effect in Yangquan mining area, taking Huayang No.2 Mine as a demonstration mine, based on the analysis of mine gas geology and drainage treatment status, the overall scheme of gas drainage drilling construction using high-power nitrogen directional drilling technology and equipment is proposed. The technical principle and technical advantages are 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, are 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, was 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 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, of which 5 holes were more than 350 m deep, the maximum hole depth reached 506 m, and the total footage was 3363 m. The diameter of the drilling hole is 120 mm, and the Φ32 mm sieve tube is put into the whole hole. The test drilling field has been stably extracted for nearly half a year, the gas extraction concentration has exceeded 50 %, the gas extraction purity has reached 2.46 m3/min, and the cumulative gas extraction purity has reached 56.06 million 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.

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