Stress induced permeability changes in brittle fractured porous rock

Abstract

This paper aims at deriving an approximate model of stress-induced permeability enhancement for brittle cracked porous rock, based on the linear fracture mechanic theory. A recently proposed model of the effective permeability of a porous rock containing an anisotropic distribution of several crack families is used. In such a model, the fluid flow is modelled by Poiseuille's law within the crack and Darcy's law for the porous matrix. The presence of this effective permeability model coupled to an analytical expression of crack growth under shear loading enables the modelling of the permeability variation due to stress-induced cracking in a porous rock. The model is applicable for any initial crack density (i.e. lower, around or upper to percolation threshold). Comparisons with experimental results and existing models show the validation and the advantage of the present model. All stages of fluid flow through a cracked porous medium are also reproduced. The proposed model can be easily implemented in a hydromechanical formulation with application to fractured geological formations.