Poro-acoustoelasticity FD simulation of elastic wave propagation in prestressed porous media

Abstract

Insight into wave propagation in prestressed porous media is of importance to geophysical applications, such as monitoring changes in geopressure. This issue can be approached by the theory of poro-acoustoelasticity that extends the classical acoustoelasticity of solids to porous media. The relevant poro-acoustoelasticity equations can be formulated from anisotropic poroelasticity equations by replacing the poroelastic stiffness matrix with the acoustoelastic stiffness matrix containing both the second-order 2oeC and third-order 3oeC elastic constants. In this study, a rotated staggered-grid finite-difference (RSG-FD) method is used to solve a first-order velocity-stress formulation of poro-acoustoelasticity equations for elastic wave propagation in prestressed porous media. We perform numerical simulations of wave propagation for the model of poro-acoustoelastic homogenous space under three states of prestress-confining (hydrostatic), uniaxial, and pure shear. The resulting wavefield snapshots show fast P-, S-, and slow P-wave propagations in poro-acoustoelastic media under loading prestresses, which illustrates that the stress-induced velocity anisotropy is of orthotropy that is strongly related to the orientation of prestresses. These examples demonstrate the significant impact of prestress conditions on seismic responses in both velocity and anisotropy. Note: This paper was accepted into the Technical Program but was not presented at IMAGE 2022 in Houston, Texas.