关键词: 非平衡解吸, 煤系页岩气, 渗透率, 基质收缩, 气体解吸, 裂隙压缩系数

Abstract: In order to investigate the influence mechanism of reservoir pressure and gas desorption on permeability of coal measure shale gas reservoir, effective stress-permeability models of matrix and fracture for reservoir in non-equilibrium desorption state were proposed on the basis of the kinetic diffusion of gas in the matrix. Subsequently, the permeability models of reservoir in non-equilibrium desorption state and uniaxial strain condition were set up. The effectiveness of permeability models was discussed by analyzing results of the field and laboratory experiments on samples as well as permeability of reservoir. The permeability model in non-equilibrium desorption state can provide a better fit to the experimental values of permeability. A smaller pore volumetric modulus leads to a more rapid rebound in the matrix permeability; and a greater fracture compressibility yields a more drastic reduction in the fracture permeability. Afterwards, the influence mechanism of various parameters on reservoir permeability was studied. The results indicate that the matrix permeability first decreases and then rebounds, fracture permeability increases gradually with the decrease of matrix pressure when the fracture pressure decreases to a certain value. Matrix permeability increases and fracture permeability decreases gradually with the decrease of fracture pressure when the matrix pressure drops to a certain value.

Key words: non-equilibrium desorption, coal measure shale gas, permeability, matrix shrinkage, gas desorption, fracture compressibility