Drilling experiment research on bedding directional drilling of soft—fragmentized coal seam of Qinglong Coal Mine

Abstract

For problems of shallow gas drainage hole depth, low control precision of drilling trajectory and poor gas drainage effect in soft—fragmentized coal seam of Qinglong Coal Mine, based on the analysis of mine gas geological conditions and existing pre—drainage modes, principle and key technologies of air compound directional drilling technology were introduced for bedding directional drilling construction, and a whole drilling experiment scheme was formulated including design of drilling field and borehole, selection of drilling equipment and assembly and summary of drilling technology requirements. A drilling experiment was carried out in 21608 roadway field. The experimental results show that bedding directional drilling construction in soft—fragmentized coal seam can be realized by the air compound directional drilling technology. 7 main boreholes and 2 main branch boreholes were completed, the total footage is 3 929 m, the maximum borehole depth reaches 406 m, and forming rate of borehole deeper than 300 m reaches 88.9%. Gas drainage volume fraction of experimental borehole is more than 68%, and the maximum gas drainage pure quantity of single borehole exceeds 2.55 m3/min with the average is more than 1 m3/min. Gas drainage pure quantity of the experimental borehole is more than 10 times of the one of conventional borehole, and gas drainage volume fraction increased about 50%, which verify the air compound directional drilling technology has good effect of borehole forming and gas drainage.

Keywords

• coal mine safety
• gas drainage
• soft—fragmentized coal seam
• bedding directional drilling
• air compound drilling technology