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

Abstract

AbstractDetecting 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.