Progress in research on drilling repair and protect technology for gas drainage in coal mine

Gas drainage drillings are prone to instability and blockage, resulting in shortened effective drainage time and sharp attenuation of drainage effects, which has become one of the bottlenecks restricting the accelerating development of coal mine methane. Based on the analysis of the instability mechanism of gas drainage drilling, and from the two aspects of drilling protection and blockage dredging, the four types of drilling repair and protect technology commonly used in coal mines, such as "grouting reinforcement", "protection with screen pipe", "mechanical dredging" and "water jet dredging" are systematically reviewed, and the application conditions, advantages and disadvantages are pointed out respectively. The research direction of drilling repair and protect technology for gas drainage in the future is discussed. The paper argues that evaluation system of drilling repair and protect technique, protection while drilling technique and dredging-protection integration technique are the development trend of drilling repair and protect technology.