Abstract
Due to overburden and tectonic stresses, many deep formation rocks contain vertically oriented fractures, resulting in significant seismic S-wave anisotropy and attenuation, as commonly observed from borehole acoustic anisotropy measurements in deep wells. Understanding the fracture-induced phenomena is of theoretical interest and practical importance. By applying a fracture scattering theory to a fluid-saturated rock containing vertical fractures, we investigate the fracture-induced effects on dynamic S-wave moduli, anisotropy, and attenuation anisotropy in the rock medium. This includes the effects of fracture-background wave-induced fluid flow and elastic scattering on the fractured rock's stiffness. The results indicate that fracture elastic scattering has a significant influence on the S-wave moduli and attenuation anisotropy. Compared with the velocity response of elastic scattering, Rayleigh scattering increases the S-wave anisotropy, whereas Mie scattering decreases it. The elastic scattering-dominated S-wave anisotropy and attenuation anisotropy are significantly affected by fracture size (diameter) and density. We use the theoretical results to interpret field acoustic anisotropy and attenuation anisotropy data acquired in a deep well, wherein the theory and measured data are in good agreement.
Paper Information：
Wen-Hao Wang, Sheng-Qing Li*, Chun-Xi Zhuang, Yuan-Da Su, Xiao-Ming Tang, 2025, Dynamic seismic S-wave anisotropy in vertically fractured rocks: Modeling and field application. Geophysics, 90(5), A31–A35, https://pubs.geoscienceworld.org/geophysics/article/doi/10.1190/geo2024-0908.1/660500/Dynamic-seismic-S-wave-anisotropy-in-vertically
