Key technology and practice of deep borehole pneumatic directional drilling in broken-soft coal seam in Yangquan mining area
[Objective]In response to the need for precise,proactive,and regional management of gas in the broken-soft coal seam of the Yangquan Mining Area,a technical scheme utilizing pneumatic directional drilling for pre-drainage boreholes was proposed.[Methods]Based on the analysis of the technical challenges in pneumatic directional drilling,a series of technologies suitable for the broken-soft coal seam in the Yangquan Mining Area were developed.These in-clude stable operation technology for pneumatic downhole motors,precise control technology for drilling boreholes,ef-ficient deep-hole slag discharge technology,and pneumatic milling and salvage technology.The pneumatic directional drilling equipment was optimized,and field industrial trials were conducted in the broken-soft coal seam of the Yangquan Mining Area.[Results and Conclusions]The results indicate:(1)Through the optimization of the structure and technological process of the pneumatic downhole motor,as well as the design of low wind resistance pipelines,ab-normal braking of the pneumatic downhole motor was effectively resolved,achieving stable and efficient operation.(2)The optimization of borehole trajectory and technological parameters,the design of large-angle deflecting drilling tool combinations,and the development of pneumatic impact downhole motors ensured precise control of the borehole tra-jectory and improved the penetration rate of the coal seam.(3)The application of forced slag discharge with slide and rotary drilling and short-lifting drilling tools significantly enhanced slag discharge efficiency.(4)By adopting pneumat-ic milling and salvage technology,along with the specially designed retractable overshot,the complex downhole acci-dent handling requirements in the broken-soft coal seam of the Yangquan Mining Area were met,successfully resolving two severe sticking incidents.(5)In a certain mine in the Yangquan Mining Area,ten directional boreholes with a dia-meter of 120 mm were completed,each reaching depths of over 450 m,with the maximum borehole depth being 607 m and the maximum single-shift footage being 76 m.The directional boreholes in the broken-soft coal seam achieved signi-ficant gas drainage results,with the maximum pure gas drainage from a single borehole reaching 971.96 m³,thereby en-abling long-term stable gas drainage in the broken-soft coal seam of the Yangquan Mining Area.The research results provide a novel technical approach for the efficient management of gas in the broken-soft coal seam of the Yangquan Mining Area,demonstrating significant potential for practical application and widespread adoption.
Yangquan Mining Areabroken-soft coal seampneumatic screwdrilldirectional drillinggas drainageborehole trajectory control
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