超高压水力割缝穿层钻孔工艺参数优化及应用OA

Aiming at the problems of poor permeability,high gas content and inefficient gas drainage from in-seam boreholes in the No.3 coal seam of Zhaozhuang Coal Mine,ultra-high pressure hydraulic slotting combined with cross-measure boreholes was pro-posed to enhance the permeability of the coal seam.Through field tests,the reasonable technological parameters of ultra-high pres-sure hydraulic slotting for the No.3 coal seam were determined,and a comparative analysis was conducted on the gas drainage volume fraction,pure gas drainage volume,time to meet gas drainage standards and residual gas content in the coal mass after drain-age between the slotted zone and the unslotted zone.The results show that the optimal combination of technological parameters for ultra-high pressure hydraulic slotting in the No.3 coal seam of Zhaozhuang Coal Mine is as follows:slotting pressure of 80 MPa,slotting duration of 9 min,slotting rotational speed of 60 r/min and slot spacing of 1 m.Field application results indicate that the gas drainage volume fraction of ultra-high pressure hydraulic slotted cross-measure boreholes and ordinary cross-measure boreholes ranges from 17.21%to 51.86%and 12.48%to 34.12%,respectively,with the average single-borehole gas drainage volume fraction being 33.00%and 22.20%,respectively;the gas drainage volume fraction of ultra-high pressure hydraulic slotted cross-measure boreholes is 49%higher than that of ordinary cross-measure boreholes.The pure gas drainage volume of ultra-high pressure hydraul-ic slotted cross-measure boreholes and ordinary cross-measure boreholes ranges from 0.010 m3/min to 0.015 m3/min and 0.003 m3/min to 0.005 m3/min,respectively,with the average single-borehole pure gas drainage volume being 0.012 m3/min and 0.004 m3/min,respectively;the single-borehole pure gas drainage volume of ultra-high pressure hydraulic slotted cross-measure boreholes is 185%higher than that of ordinary cross-measure boreholes.The time required to meet gas drainage standards for the coal seam is 54 d and 154 d for ultra-high pressure hydraulic slotted cross-measure boreholes and ordinary cross-measure boreholes,respectively,representing a 65%reduction.After 54 days of drainage,at distances of 1.5,2.0 and 2.5 m from the gas drainage boreholes,the resid-ual gas content in coal around ultra-high pressure hydraulic slotted cross-measure boreholes is 6.886,7.538 and 7.952 m3/t,respect-ively,while that around ordinary cross-measure boreholes is 11.442,11.886 and 12.262 m3/t,respectively.The residual gas content in coal around boreholes decreases significantly after hydraulic slotting treatment.