Gas Pre-Drainage Technology with Full Length Casing for Borehole Drilled Along Low Permeability Soft Seam

In order to improve the gas drainage effect of the soft and low permeability seam, according to the features of No.1252 (1) first coal mining face in the ea st block of Panyi Mine, the practices on the full length pre-drainage technology with the borehole along soft seam were conducted.After the measures conducted, the ga s drainage volume fraction of a single borehole increased from previous 20% ~40% to 90%, the pure gas drainage quantity was increased from previous 0.08 m3/min to 0.25 m3/min and the max pure quantity of a single borehole reached to 0.51 m3/min. The pure gas drainage quantity in per unit improved by 35% and the flow was stabl e.The gas drainage standard time per unit reduced from 93 days of the traditional pre-drainage technology to 26 days of the full casing pre-drainage technology with the borehole along seam. Thus the target for rapid outburst elimination and even outburst elimination was reached.