Research on gas extraction technology:hydraulic stamping and hydrofracture to pressure relief and permeability improvement

This paper is dedicated to improve efficiency of coal seam gas extraction,shorten engineering workload,and reduce gas extraction time through a new gas extraction technology which applies hydraulic stamping and pressure relief to increase permeability.The mechanism of hydraulic stamping and hydraulic pressure relief to increase permeability and the detailed description of the engineering implementation model are discussed.A case study of the gas extraction technology is explored,which was carried out in Xintian Coal Mine,Guizhou Province of China.Gas extraction parameters were monitored before and after the application of the technology.The results show that the maximum radius of the hydraulic punching hole is between 0.23 m and 0.72 m and the fracturing pressure of the coal seam is between 13 MPa and 26 MPa.It is also found that the average gas extraction concentration is increased by about 35% and the pure quantity of gas drainage is improved by 1.1 to 5.0 times after hydraulic stamping.Moreover,gas extraction concentration is increased by over 0.8 times and pure quantity of gas drainage is improved by 3 to 5 times after integrating pressure relief to hydraulic stamping,which is due to permeability increaseby pressure relief.These results demonstrate that efficient gas extraction can be realized by implementing hydraulic stamping and pressure relief technology to increase permeability of coal seam.This technology has engineering significance in increasing mine safety and productivity.