Evolution of poroelastic properties and permeability in damaged sandstone
Résumé
This paper is devoted to experimental investigation of mechanical behavior, poroelastic properties and permeability in saturated sandstone. The emphasis is to study the evolution of Biot's coefficients and permeability with the growth of microcracks. Basic mechanical responses are first investigated through triaxial compression tests, showing nonlinear stress–strain relations, volumetric dilatancy, pressure sensitivity, elastic modulus degradation and induced anisotropy. Original tests are then performed for the determination of Biot's coefficients in the axial and radial directions at different levels of stress. It is shown that the evolution of Biot's coefficient is clearly anisotropic in nature due to the oriented closure of initial microcracks and growth of induced microcracks. The rock permeability in axial direction is also measured for different values of stress; it decreases in the first stage with the closure of microcracks and then progressively increases due to the opening of induced microcracks. However, the permeability significantly increases only when the coalescence of microcracks occurs.