Study on collapsed borehole repair and permeability improved technology with borehole drilling along low permeability seam

In order to realize an effective reutilization of the collapsed borehole for the gas drainage borehole along the seam, the analysis from the space and time levels showed that in the gas drainage process, the plastic zone around the borehole, the rheclogy of the seam and the drainage negative pressure would have serious influences to the borehole collapsed. With the references of the collapsed borehole repair technology with crossing borehole, taking the water jet as the power, taking br eak through the borehole collapsed section, to shot down the coal in the plastic zone and to clean the falling coal in the borehole as the purpose, and the collapsed bor ehole repair and permeability improved technology with the borehole drilling along the seam was determined. The site test showed that after the repair and permeability improved technology with the borehole drilling along the seam, the gas drainage effect was obviously improved, the gas drainage concentration was increased by 1.4 ~ 5.0 times in average and the gas drainage mixed flow was increased by 1.2 ~ 3.5 times in average. The pure gas drainage flow was increased by 1.2 ~ 10.0 times in av erage. Beside the repair and permeability technique, the repair and permeability technology with the borehole drilling along the seam would also be affected by the bore hole inclination, borehole sealing and others.