The Research On A Total Length Of Screen Guard And Hole Sealing Technology With Pressure In Soft Coal Seam

Coal and gas outburst affect the safe production of coal mining enterprises seriously, gas drainage is an effective mean to reduce the risk of gas outburst, achieve efficient gas extraction and utilization, of which extraction of gas drilling technology is the most widely used, however, due to soft coal seam’s characthers of highlights quality soft and pressure, etc, in the borehole construction, drilling holes collapse easily and change the shape quickly resulting in blocked gas drainage channels, shallow depth of screen decentralization which can’t even lower, and difficulty seal of hole sealing section. Gas drainage effect is often far from ideal. Therefore, it is necessary to sutudy the full-length screen hole and pressure sealing process,which has important practical and economic sense for improving the soft coal seam gas drainage prominent effect and reducing the incidence of accidents excavated coal and gas.This paper analyzes the soft prominent seam drilling hole collapse instability causes and characteristics,and studys the creep characteristics of the gas displacement drilling, on this basis, the drilling hole instability collapse of gas drainage effect influence is on the resesrch; secondly retaining hole and the full-length screen with pressure sealing technology is putted forward, the basic principles is introduced,retractable drill is designed to ensure the full-length screen decentralization, at the same time, corollary equipment are improved and designed such as screen tube, drill rodsand screen fixtures-, theory with pressure grouting is also studied to verify the feasibility of the process, the experiments of the plugging material characteristics are carried outto determine the appropriate sealing materials and ratio; and the means of numerical simulation and theoretical calculation are used for the relevant process parameters’ s simulation analysis and calculation to determine a reasonable scientific construction process parameters to provide a scientific basis for the field test; finally,the paper maks field test.Experimental results show that construction process parameters which combine the total length of the hole and pressure sealing screen protection technology reasonably could improve the effect of gas drainage, the feasibility of this technology is verified.