Fluid identification and reservoir prediction based on frequency-dependent AVO inversion

Velocity dispersion and attenuation frequently occur in fluid-saturated reservoir rocks. However, most current reservoir prediction and fluid identification methods overlook the effects of seismic wave dispersion and attenuation. Instead, researchers primarily rely on frequency-independent elastic data and theoretical models. Frequency-dependent elastic parameters, in contrast, reveal more detailed information about reservoir fluids and significantly enhance the accuracy of fluid identification and reservoir prediction.Rock physics experiments and theoretical analyses have shown that rocks saturated with different fluids exhibit distinct velocity dispersion gradients. This finding underscores the potential of the velocity dispersion gradient as a reliable indicator for identifying target reservoirs. To extract the velocity dispersion gradient attribute, this study incorporates a frequency term into the Zoeppritz approximation and develops a frequency-dependent AVO  inversion equation. The study applies time-frequency analysis to seismic data, deriving the time-frequency spectrum. By integrating the time-frequency spectrum with the frequency-dependent AVO inversion equation, the method extracts the velocity dispersion gradient attribute.The study further analyzes how various factors influence the accuracy of dispersion gradient attribute inversion, using theoretical models and seismic physical analyses. It validates the reliability of the dispersion gradient inversion method and demonstrates its effectiveness in delineating reservoirs and identifying fluids.This research provides a robust approach for improving the precision of reservoir prediction and advancing fluid identification techniques.