| This paper mainly study on pressure releasing technology to increase permeability of the LiZuizi coal mine hydraulic fracturing, using theoretical analysis, numerical simulation and field tests combined with A1coal seam floor roadway,32321regional field experimental study of the hydraulic fracturing pressure relief and permeability increasing effect. The results show that the hydraulic fracturing can improve Al coal seam permeability coefficient, strengthen the internal gas flow, wetting coal dust effect, and improve the extraction rate lower coal seam outburst danger.The mechanical characteristics of the hydraulic fracturing is analyzed, by drilling, large diameter can increase the pressure unloading drilling around the hydraulic fracturing of coal body, increase the drilling around the exposed surface area, strengthen the internal gas flow, to increase coal seam permeability effect. Analysis of the borehole initiation position and crack initiation required pressure, the critical value of fracture pressure.In the numerical experiment, the simulation of different initiation pressure buried depth of coal and rock mass, the initiation of the injection pressure increases with the depth of coal seam drilling, fracturing initiation pressure data to regression analysis and the buried depth of coal seam and the relation of fracture pressure:A1, calculation of the initial pressure for coal seam26.92MPa. The600m position of the fracture radius in the12.665～14.965m;500m the position of13.683～16.876m;400m location fracturing radius in16.011～18.846m; pressure relief area of the coal seam permeability coefficient is increased about2.5times.The field test, the fracture test of Al coal seam, safety measures before and after the fracturing process and fracturing of the detailed design, divided the strike and dip direction of scheme design. The tendency of50m to maximum influence radius, maximum influence radius70m, hydraulic fracturing on the concentration of gas extraction and extraction volume increase obviously, drainage in the concentration of36%-56%, the average drainage mixed flow concentration is0.31m3/min, the average drainage net flow is basically stable at0.16m/min, single hole net flow is about0.013m3/min pipe drainage, the average concentration of1.7times before the fracturing stem after fracturing; fracturing after single hole average extraction purity was3.5times of fracturing effect before fracturing, regional coal seam permeability coefficient of0.372m2/(MPa2·d) compared with the original0.062m2/(MPa2·d) increased6times.Research on the Lizuizi coal mine layer in the A1pressure relief and permeability increasing technology, based on field test, verify the simulation accuracy of the results of the analysis and numerical mechanics. |
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