RELATIVE PERMEABILITY OF UNSATURATED POROUS MEDIA WITH STRESS BASED ON FRACTAL THEORY

The coupled behavior of fluid flow strain brings challenges to model the complex pore structures and relative permeability curve in porous media with stress. Therefore, based on fractal geometry and elastoplastic theory, a relative permeability model of porous media is developed. And the proposed model has been validated by comparing with stress sensitivity experiments on the relative permeability of gas–liquid phases and available experimental data on the relative permeability. The effects of stress, fractal parameters, pore structure, and capillary force on relative permeability are explored. It has been found that the relative permeability curves of the wetting and non-wetting phases with water saturation shift to the left and right as the stress increases, respectively. The physical meanings of each parameter in the proposed model are clear, it may provide comprehensive understanding on the fluid strain coupling behavior in porous media at different stresses (positive/negative).