Effects of multiscale wave-induced fluid flow on seismic wave dispersion and attenuation in partially saturated porous rocks

Summary

Wave-induced fluid flow (WIFF) across multiple scales causes significant seismic wave dispersion and attenuation over a broad frequency range in partially saturated rocks. Accurately characterizing these effects is crucial for improving hydrocarbon reservoir detection. In this study, we develop a model that integrates mesoscopic Rayleigh bubble oscillation with an extended microscopic squirt-flow mechanism (with varying microcrack aspect ratios), including capillarity effects. Plane-wave analysis indicates that both P1 (fast P) and S waves are strongly influenced by multiscale fluid flow, with the extended squirt-flow mechanism producing a broader range of wave attenuation and dispersion at high-frequency. Numerical analysis shows that the pore structure controls wave-velocity dispersion and attenuation at different scales. The inclusion radius determines the mesoscopic relaxation characteristic frequency, and the microcrack porosity governs squirt flow. Furthermore, the model predictions agree reasonably well with two independent sets of experimental data, validating the applicability of the theory. This study provides valuable insights for understanding seismic wave dispersion and attenuation in partially saturated rocks.