Practice of Directional Hydraulic Fracturing in Soft and Low-Permeability Coal Seam for Permeability Enhancement and Outburst Elimination
Aiming at the problems of high gas content and difficult extraction in soft and low-permeability outburst coal seams,as well as the risk of outburst during the coal mining process,directional hydraulic fracturing technology for permeability enhancement and outburst elimination was studied.Firstly,the mechanism of directional hydraulic fracturing for permeability enhancement and outburst elimination was elucidated.Through theoretical calculations,it was found that the initial fracturing pressure,flow rate,and injection volume of the coal seam were 22.8-30.5 MPa,130-200 L/min,and 216 m3,respectively.On this basis,4 hydraulic fracturing holes and 2 fracture guide holes were arranged in the pre-extraction roadway.During the fracturing process,the pump pressure,average water injection flow rate,and single hole water injection volume reached 28-31 MPa,140-177 L/min,and 260-330 m3,respectively,which were basically consistent with the theoretical calculation data.The experimental results show that the influence radius of directional hydraulic fracturing is greater than 30 meters,and the permeability coefficient of the coal seam reaches 0.840 m2/(MPa2·d),which is 60 times that of the original coal seam.The concentration of gas in a single hole has increased by 50％to 80％,and the pure amount of gas extracted from a hundred holes has reached 1.9 m3/min,resulting in a 90％increase in gas extraction capacity.After adopting directional fracturing,the amount of coal drilling work has been reduced by 64％,and the time for reaching the standard of extraction was 36 days ahead of the expected construction period.This technology can provide a reference for similar gas control projects.
Soft and low-permeability coal seamPermeability enhancementDirectional hydraulic fracturingGas extraction
万方数据
维普
