Research into technology for precision directional drilling of gas-drainage boreholes

Purpose. In order to solve the serious problem of borehole deflection in coal mine gas drainage, the precision directional drilling tool has been developed and improved, as well as the general borehole deflection laws have been studied. Methods. By using ordinary drilling pipes, one set of precision directional drilling tool and two sets of precision directional drilling tools, gas-drainage boreholes have been drilled in the mine and, subsequently, the borehole trajectory parameters have been measured using an inclinometer. Findings. The borehole inclination angle first tends to decrease and then to increase, while the azimuth angle generally increases. The precision directional drilling tool is effective, especially when using two sets of drilling tools. In this case, the average 100-meter final borehole deflection is reduced by 66.0%, the average inclination angle is reduced by 52.3%, and the average azimuth angle is reduced by 46.5%. Originality. A tool for precision directional drilling has been developed and improved, and its effectiveness has been confirmed; the general laws of borehole deflection have been summarized from the overall for subsection intervals. Practical implications. The research results are of great guiding significance for preventing the gas-drainage borehole deflections and further research on the tool for precision directional drilling.