Technology of drilling with casing protection hole for cross-layer drainageborehole in strong outburst coal seam

In order to solve the problem of jet orifice and short cross coal seam length during the process of cross-measure borehole, the technology of drilling with casing applied in strong outburst seam on the basis of the causes of borehole strong outburst was proposed in this paper, the structure of drilling tool, torque transmission device, casing shoe, casing and drill rig selection were introduced. The application showed that the technology of drilling with casing had a positive effect on controlling jet orifice and prevention of borehole outburst, and the intensity of borehole strong outburst was significantly weakened when the technology of drilling with casing was applied to cross outburst seam, the practical value and the calculation value of the drilling crumbs amount ratio was around 1, and the one-time success rate of crossing coal seam was increased by 30%，that was the technology was beneficial to drilling in outburst coal seam.