Gas extraction technology and application of near horizontal high directional drilling
Huijun Duan, Yi Wang, Qian Xiao, Jiale Wang, Peng Dong
Abstract
In order to solve the problem of gas accumulation in the upper corner caused by large gas emission due to high mining intensity in the fully mechanized top coal caving face of Wangjialing coal mine, we used numerical simulation method combined with the key stratum layer control theory to study the roof caving trend and development law of inclined mining fissure. Then we analyzed the evolution process of goaf fissure with the advance of the working face and the development height of roof fissure. Finally, we got the best hole layout position and drilling structure of near horizontal high-level directional long drilling. The practice indicates that we achieved nice gas extraction effect by setting near horizontal high-level directional long drilling borehole according to the above research results. The maximum net extraction volume of a single borehole is 2.10 m3/min, the maximum extraction volume fraction is 31.39%, and the total net amount of gas extracted from the four boreholes under construction is 289900 m3. The gas concentration in the upper corner of the working face decreased to 0.46% during extraction, and the problem of gas overrun in the upper corner was effectively solved.