Coal Engineering ›› 2025, Vol. 57 ›› Issue (2): 103-111.doi: 10. 11799/ ce202502015

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Deep directional borehole “drilling-punching-protection” technology for permeability enhancement in gas extraction of soft coal seam

  

  • Received:2024-04-16 Revised:2024-07-16 Online:2025-02-10 Published:2025-04-28
  • Contact: Gaojian LI E-mail:yxyxyx20242024@163.com

Abstract:

In order to achieve accurate, efficient and stable gas drainage in soft coal seams, in view of the problems of large drift of deep borehole drilling trajectory in soft coal seams, low permeability, poor drainage effect, and high scrapping rate of boreholes that are easy to collapse, Deep borehole directionally integrated technology, "drilling-punching-protection " to enhance permeability and promote drainage in soft coal seam was proposed. The technology realizes the directional drilling process through the combination of sliding drilling and composite drilling, changes the stress environment of the coal body through the hydraulic punching process to achieve enhanced permeability and promotes drainage, and provides a certain support for the borehole wall through the screen tube protection technology to ensure gas drainage mining channel. On the basis of directional drilling technology theory, hydraulic punching enhances permeability mechanism, borehole collapse failure characteristics and influencing factors, the technical equipment and process were introduced, and the key parameters of the "drilling-punching-protection" integrated technology were simulated and studied, and the "drilling-punching-protection" integrated enhance permeability and pumping promotion tech-nology was applied in Shanxi Changping Coal Industry Co., Ltd. Engineering practice shows that: in the soft coal seam, the deep borehole directional "drilling-flushing-protection" integrated anti-reflection enhancement and drainage technology is implemented, and the maximum total footage of a single borehole reaches 1942 m, which lays the foundation for ensuring accurate drainage; the longest stable drainage The time exceeds 450 days, the cumulative amount of gas drainage in a single borehole exceeds 100,000 m3, and the borehole protection rate reaches a maximum of 92.6%, realizing the borehole protection of the entire borehole section, breaking through the inaccurate drainage area of soft coal seams, poor drainage effect and low efficiency and other difficult problems, realizing the precise, efficient and stable gas extraction from deep boreholes in soft coal seams.

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