A model of shear dilation induced permeability evolution in the process of water injection in Karamay continental oil sand

Extra-super heavy oil reservoirs are generally developed by means of steam assisted gravity drainage (SAGD). In the early water injection stage, reservoir’s shear dilation generates shear fractures in the shear zone, which leads to the change of porosity and water/oil saturation. In order to study the dynamic evolution laws of the effective permeability in the process of water injection, this paper related absolute permeability with porosity through Kozeny-Poiseuille equation and Touhidi-Baghini equation and water effective permeability with water saturation through oil and water relative permeability curve equations, in view that porosity and water saturation vary with dilation volumetric strain. Then, three mathematical models of shear dilation induced permeability evolution were established. In addition, the prediction effects of each model were evaluated and analyzed based on experimental data. It is indicated that the traditional Kozeny-Carman equation is only applicable to porous granular media, but not to Karamay continental oil sand, which is the composite skeleton composed of bitumen basement type cementation, and neither to describe the permeability evolution induced by the shear fractures in the shear dilation zone. What’s more, the shear dilation induced permeability model established on the basis of Touhidi-Baghini equation can accurately predict the evolution laws of water effective permeability in the process of water injection, so as to provide reference and experience for the studies related to permeability.