Abstract
Rock fracturing is widespread in the upper crust of the earth. Nearly all in situ rocks are subject to subsurface pressures. Understanding the influence of effective pressure (the difference between confining stress and pore pressure) on the elastic properties of fractured rocks is crucial for estimating in situ seismic properties. Wave-induced fluid flow (WIFF) and fracture elastic scattering (ES) attenuation mechanisms have been widely studied. However, the effects of effective pressure on WIFF and ES mechanisms in fractured rocks are relatively unexplored. To investigate the pressure influence on WIFF and ES in P- and SV-wave propagation, we develop a pressure-dependent dynamic model to incorporate multishaped microcracks’ squirt flow (MMSF), fracture-background WIFF (FB-WIFF), Biot flow, and ES mechanisms with nonlinear elastic and hyperelastic deformation stages. The results indicate that the WIFF and ES mechanisms are affected by effective pressure, except for the ES mechanism of normal incident SV waves. The WIFF is more susceptible to effective pressure than the ES mechanism. In addition, the closure of microcracks (soft pores) during effective pressure loading continuously decouples the MMSF mechanism from the FB-WIFF, Biot flow, and ES mechanisms, causing an increase in the velocity of P and SV waves and variations in the attenuation processes. These wave propagation characteristics help us understand the hydraulic properties of in situ fractured rocks. By comparing model predictions with ultrasonic laboratory velocity data under varying effective pressure loading, we validate our model.
Paper Information:
Wen-Hao Wang, Sheng-Qing Li*, Jun-Xin Guo, Cheng-Sen Zhang, Xing-Neng Wu, Yuan-Da Su, Xiao-Ming Tang, 2025, Pressure effect on wave propagation in saturated porous rocks with aligned fractures. Geophysics, 90(3), MR207–MR225, https://doi.org/10.1190/geo2024-0419.1
