The Study On Gas Seepage Law Of Drilling Hydraulic

With the increase of depth and strength of coal under ground mining, underground geological conditions are becoming more complex. The frequent to currency of gas disasters is a serious threat to the life and safety of underground workers, and it is not only restricts the process of coal mining to a large extent, but also restricts the development of coal production, which are great losses to the our country and people's lives and property.Based on the comprehensive analysis of combed gas occurrence, seepage law and influence factors, the method of high pressure water jet is put forward to increase the permeability of the coal seam and reduce the gas pressure. Experimental studies on differences of coal body structure and the influence factors of the coal gas permeability before and after punching were conducted.Tests showed that:The role of hydraulic punching promotes the extension of crack and the production of new fractures. The effect is better especially in the coal seam which porosity is larger. At the same time, it is concluded that coal fracture has a great influence on the gas seepage law. Relative to the porosity, the fracture become more and more in the coal seam, the rate of gas permeability become larger and larger. The role of hydraulic punching promotes the production of fractures, adds rate of gas permeability. The coal metamorphic grade has less effect on the permeability of coal seam.With the increase of confining pressure, gas permeability in coal seam are getting smaller, under the condition of constant gas pressure. After punching, gas permeability of coal affected by the confining pressure becomes more and more obvious. the reduction of gas permeability is bigger than before punching, change speed. When the confining pressure increases to a certain range, the reduce speed of the gas permeability decrease sharply, and the variable range becomes small.When the confining pressure is constant, with the increase of gas pressure, gas permeability decreases gradually in the coal seam. When the gas pressure increases to a certain value, there is a turning point. In the coal seam gas permeability increases gradually. After punching, gas permeability range of variation is larger, amplitude of variation also increased, the turning point from decrease to increase also become larger in the coal seam.