Dynamic SV‐Wave Signatures of Fluid‐Saturated Porous Rocks Containing Intersecting Fractures

Abstract

Detecting fracture intersections is crucial for understanding rock hydraulic properties. For this purpose, we study the dynamic SV‐wave signatures of fluid‐saturated porous rocks containing intersecting fractures. A theoretical model is derived using the dynamic Biot's poroelasticity equations. Using this model, we analyze the features of SV‐waves and compare to those of previously studied P‐waves. The results show that the dispersion and attenuation of SV‐waves caused by elastic scattering and FF‐WIFF (Fracture‐Fracture Wave‐induced Fluid Flow) have a similar dependence on properties of intersecting fractures and fluid as those of P‐waves. However, the FB‐WIFF (Fracture‐Background Wave‐induced Fluid Flow) causes much smaller dispersion and attenuation for SV‐waves than for P‐waves. In particular, such dispersion and attenuation of SV‐waves are negligibly small for the orthogonally intersecting fractures regardless of wave incidence angles. In addition to the dispersion and attenuation, the WIFF and elastic scattering also greatly affect the anisotropy properties, which gives rise to frequency‐dependent velocity and attenuation anisotropies for both SV‐ and P‐ waves. Such anisotropy properties are sensitive to fracture intersection angles and are quite different between SV‐ and P‐ waves. These complementary features of SV‐ and P‐ waves provide the basis for fracture intersection detection using the combined features of these two waves. By comparing our model to the known results for the limiting cases, we validate our model.

Ultrasonic S‐wave indirectly detects the very narrow gap at contact of grains: Glass beads and Ottawa sands

“…The anisotropy was distinctly different and complementary between SV-wave and fast P-wave. Especially, in the extreme case of unconnected fractures, the theoretical model of Guo, Gurevich et al (2022) indicated that SVwave had a much smaller dispersion and attenuation than fast P-wave.…”

“…Furthermore, fast P‐wave presented anisotropy, as the factures were not randomly aligned and their network was not isotropic in the macroscopic sense. For SV‐wave, the intersections of fractures also played a crucial role on the acoustic responses of such a rock (Guo, Gurevich, et al., 2022). The anisotropy was distinctly different and complementary between SV‐wave and fast P‐wave.…”

“…Especially, in the extreme case of unconnected fractures, the theoretical model of Guo, Gurevich et al. (2022) indicated that SV‐wave had a much smaller dispersion and attenuation than fast P‐wave.…”

Effect of Multiscale Cracks on Seismic Wave Propagation in Tight Sandstones

“…Guo, Zhao, et al (2022) derived a theoretical model using the Biot's dynamic poroelasticity equations to analyze the dispersion and attenuation of P-waves caused by FF-WIFF (Fracture-Fracture Wave-induced Fluid Flow). Then, they (Guo, Gurevich, & Chen, 2022) further analyzed the SV-waves using the same approach. Their work can be helpful for us to further extend the multiscale fracture model.…”