Study on gas-solid coupling mechanism of gas drainage from deep and low permeability seam

In order to reveal a gas percolation mechanism in the gas drainage from a deep seam, based on the low permeability, high ground stress and high gas pr essure features of the deep seam, in combination with Klinkenberg effect of the gas migration, a gas-solid coupling model of the seam gas drainage was established in consideration of the coal matrix and crack double porous medium. And according to the certain geological condition, a study was conducted on the numerical simulation of the coupling model. The results showed that the seam gas pressure would be in a decreasing tendency with the gas drainage time increased, a hopper phenomenon of the gas pressure drop was occurred around the borehole and the gas pressure more closed to the borehole would be decreased obviously. During the gas drainage p rocess of the deep and low permeability seam, the seam volume deformed and the gas desorption would be jointly affected to the variation of the seam permeability an d the gas drainage could make the seam gas pressure steadily reduced. The shrinkage and deformation occurred in the seam would cause the permeability increased. Meanwhile, the effective stress of the seam increased and the pressure deformation of the cracks and matrix in the seam would cause the permeability steadily reduce d.