1. Introduction
Because Wangjialing coal mine adopts sublevel caving mining method, most of the gas in the working face comes from the broken coal body in the mining layer. The gas was always concentrated in the tail of the support and the roof falling of the tail. During caving process, it is easy to cause gas overflow and high gas concentration at tailentry upper corner. Gas concentration at tailentry upper corner is often above 0.8% during mining process. In order to solve the problem, CCTEG Xi’an Research Institute undertake high position directional drilling and gas drainage in Wangjialing mine. Trajectories of directional drilling boreholes enter the target position in the middle and lower part of the coal seam roof fracture zone to ensure mining safety.
2. Solution
In order to achieve directional drilling to cover different sections and strata and to extract gas from fractured zones to the maximum extent, according to the geological information provided by the coal mine, a directional drilling field is arranged in the tailentry Lane of fully mechanized mining face. Directional long distance boreholes are arranged along the advancing direction of the working face, the spacing of the boreholes is 450~550m, each group of boreholes is constructed with 4~5 directional boreholes. Depth of the single borehole is 450~660m, and the effective overlap length between the two boreholes is 80m. The plane trajectory of the borehole is designed to extend 20~50 m from the middle of the working face to the side of the tailentry. The profile trajectory of the borehole is designed to extend in the sandstone of 30~50 m in the roof of No.2 coal seam.
3. Construction situation
145 directional drilling boreholes have been accomplished in 20101, 20102, 20103, 12106, 12109, 12301, 12309, 12311, 12318, 12322, working face. The maximum depth of the hole is 660m, the accumulative construction footage is 68808m, and the final borehole lies in the sandstone between 30 and 50m above the coal seam roof.
4. Achieved accomplishment
After drilling, the maximum gas drainage concentration of single hole is 25%. The maximum pure gas flow rate of single borehole is 1.5 m3/min, and the time of stable drainage is long. The concentration of gas in the upper corner of tailentry is reduced from 0.85% to less than 0.5%. High gas drainage efficiency from directional drilling has obvious advantage in gas control of the upper corner.
Hot Tags: high position directional drilling, China, manufacturers, suppliers, factory, wholesale, price list, buy, for sale,
