Based on the stress-strain constitutive equation of porous media, a permeability model of the undersaturated coal reservoir is presented considering the effective stress, matrix shrinkage and slippage effect. Using the model and parameters from the coal seam of Qinshui basin, the permeability variations of this block in the process of reservoir pressure changing from the initial value to the depletion pressure are predicted. The model parameter sensitivity is analyzed. The results indicate that at the initial stage of the undersaturated coal reservoir, the coal reservoir permeability declines until the reservoir pressure drops to the critical desorption pressure, after that the permeability rises. The simulated results show that the coal reservoir permeability in the Qinshui basin reduces to 0.186×10-3μm2 when the pressure drops to the critical desorption pressure (3.80 MPa), then the permeability begins to rise with the pressure decline and rebounds to the initial value at 2.77 MPa, and finally at the depletion pressure 0.92 MPa, the permeability reaches to 3.182 times the initial value. Sensitivity analysis points out that the larger the value of Langmuir volume strain, Young's modulus and slippage coefficient, the better the improvement of the final permeability, while the Poisson ratio is just the reverse. The Langmuir volume strain is the most important influence parameter of the final permeability.
XUE Pei
,
WANG Yanbin
,
WANG Jin
,
ZHANG Xin
,
FAN Jingjing
. A Permeability Model of Undersaturated Coal Reservoir Considering Slippage Effect[J]. Science & Technology Review, 2014
, 32(27)
: 56
-59
.
DOI: 10.3981/j.issn.1000-7857.2014.27.009
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