Evolution of Poroelastic Characteristics and Permeability in Artificial Sandstones Undergoing Inelastic Deformation

Abstract

Abstract This study investigates saturated artificial sandstones' Poroelastic and permeability properties. Artificial sandstones were preferred because they were capable of manipulating porosity, particle size, and cement content. Various methods were developed to investigate drained jacketed Poroelastic parameter evolution in both elastic and inelastic domains, including Biot's coefficient, permeability, bulk, pore, and solid constituent moduli. Poroelastic characteristics are stress-dependent and nonlinear, up to 10 MPa effective stress. After the first stage, linear volumetric compaction and elastic moduli degradation continue until pore collapse. Porosity-stress graphs of some samples show inflection points that match the Hertzian fracture theory's prediction for grain crushing and pore collapse. The nonlinearity of Poroelastic moduli and permeability progression upon pore collapse has been demonstrated. Following the pore collapse, the primary factor influencing the bulk compressibility is the solid matrix deformation. Comparing Biot's coefficient values from two paths proves that solid components' jacketed bulk modulus is identical to the sample's unjacketed bulk modulus. Rock permeability is periodically measured based on effective stress, showing a greater drop at low effective stresses due to microcrack closure. Permeability sensitivity to effective stress (ɣ) and porosity (α) exponents were measured. The results show that effective stress affects permeability primarily through pore compressibility. The study found a numerical value of 0.67<γ×10-2<4.45 and 1.83<α<4.84 before pore collapse, and 3<γ×10-2<24 and 4.61<α<17.63 following pore collapse. Results show that GAMA is more stress-dependent than α post-pore collapse. This observation suggests that the permeability in high-stress conditions is predominantly influenced by cumulative damage rather than the compressibility of pores.