Cross-Scale Dispersion and Attenuation of Seismic Waves in VTI Media with Mixed Cracks

Abstract

Summary When seismic waves propagate in fractured media, pressure gradients are generated through porous rocks containing fluids and cause relative motion between the porous fluid and the solid skeleton, and this wave-induced flow effect causes velocity dispersion, attenuation, and frequency-dependent anisotropy of seismic waves. In this study, a cross-scale model of VTI medium containing mixed cracks is constructed based on anisotropic medium with the addition of Tang’s annular and penny-shaped cracks. Based on Biot theory, the constitutive relations and kinetic energy functions of wave-induced global fluid flow and two types of squirt flow are established, and the wave equations of WIFF in anisotropic media cross-scale are further derived. The velocity dispersion and attenuation, anisotropic frequency variation characteristics of seismic wave propagation in this model are analyzed, and compared with existing models and experimental data to verify the rationality of the theory in this paper. This theory enriches the research theory of multi-scale anisotropic wave-induced flow mechanism and builds a theoretical foundation for the subsequent work of fluid identification and reservoir prediction.