Azimuthal Seismic Attenuation and Anisotropy in Fractured Media: An Integrated VSP Study

Fracture-induced anisotropy and seismic attenuation strongly influence wave propagation in fluid-saturated reservoirs but are challenging to quantify jointly from seismic data. We present an integrated vertical seismic profiling (VSP) framework for estimating azimuthal anisotropy and attenuation in fractured media. A layer-stripping tomographic inversion of offset VSP first arrivals is used to derive azimuthally anisotropic P - and S -wave velocity models, while quality factors ( Q ) are estimated from VSP waveforms in the time–frequency domain. The resulting elastic and attenuation parameters are incorporated into a viscoelastic rock-physics model based on anisotropic Gassmann theory to generate azimuth-dependent synthetic VSP responses. Field data analysis reveals systematic azimuthal variations in both velocities and Q factors, indicating that fractures are the dominant source of anisotropy. Maximum velocities are aligned with the principal fracture orientation, whereas minimum velocities occur in fracture-normal directions. The lowest Q values are observed along fracture-parallel azimuths due to enhanced scattering and anelastic energy loss, while higher Q values correspond to mechanically stiffer directions. These trends are consistently observed across multiple depth intervals and are well reproduced by synthetic modeling. The results demonstrate that joint analysis of azimuthal anisotropy and attenuation from VSP data provides a robust tool for fracture characterization and reservoir development in fractured carbonate systems.