Application of comb directional long boreholes to regional gas control in complex formation

Abstract:

In view of the problems with gas drainage， such as short main holes， poor hole-making， frequent accidents in a coal mine of Bijie， Guizhou， a technique of using cross-floor comb-like directional long boreholes to control gas was put forward. The drilling pattern， drilling horizons and branch hole drilling processes were optimized to ensure the hole depth of the main hole and the coal intersection rate of the branch holes. During the trial， the drilling depth of the main holes was more than 600m， with the coal intersection rate of the branch holes up to 60%. The drilling hole completion quality has been obviously improved with the maximum gas drainage concentration per single hole up to 78%， the maximum gas extraction net volume 2.33m³/min， and less construction costs. It provides a new approach to gas control in the mining area of the Bijie city.