Effect of Stress on Wave Propagation in Fluid-Saturated Porous Thermoelastic Media

The effect of stress on wave propagation in fluid-saturated porous thermoelastic media is poorly understood. To fill this gap, we propose the dynamical equations for stressed fluid-saturated porous thermoelastic media based on the poroacoustoelasticity model and porothermoelasticity model to describe the effect of stress on the wave dispersion and attenuation. A plane-wave analysis for dynamical equations formulates stress-dependent velocities of five wave propagation modes, including three longitudinal (P) waves, namely fast P wave, slow P wave and thermal (T) wave, and two shear (S) waves, namely fast S wave and slow S wave. Additional slow P wave and T wave arise due to the Biot and thermal loss mechanisms in porothermoelastic media. The stress-induced rock anisotropy accounts for the S wave splitting phenomenon. Modelling results show that energy dissipations of fast P wave and T wave are induced by the coupling between Biot and thermal loss mechanisms, while the fast and slow S waves, slow P wave are only affected by Biot loss mechanism. The rock permeability and fluid viscosity are mainly related to Biot mechanism, while the thermal conductivity and thermal expansion coefficient for solid phase are related to Biot and thermal mechanisms. In addition, the triaxial stress and confining stress have remarkable effects on the wave velocities as well as attenuation peaks. The predicted wave velocities in water-saturated sandstone and granite behave a reasonable agreement with the laboratory measurements. Our results help to provide better understanding of wave propagation in high-stress high-temperature fields.