Seismic Dispersion-Attenuation Analysis and Hydrocarbon Identification Within Fluid-Saturated Porous Orthorhombic Media

The wave-induced fluid flow (WIFF) between the pores in fluid-saturated porous orthorhombic (FSPOR) media inevitably leads to the wave energy attenuation and seismic dispersion. Yet the WIFF effect is seldom considered in the prevailing seismic inversion methods for FSPOR media. We developed a rock physics model for FSPOR media that incorporates the squirt-flow effect, jointly caused by the background matrix and fractures. We then analyzed the impacts of incidence angle and azimuth on wave dispersion and attenuation behaviors. We further derived a linearized PP-wave reflection coefficient equation in terms of P- and S-wave moduli, density, squirt-flow fluid indicator, Thomson’s anisotropic parameters, and weaknesses using the elastic inverse scattering theory. The proposed equation exhibits excellent consistency with two classic equations within moderate incidence angles. Incorporating the seismic wavelet effect, our reflection coefficient equation is incorporated into the Bayesian inversion framework to estimate model parameters. Synthetic tests demonstrate the feasibility and robustness of our method even with moderate noise. Field application shows that the inverted results are consistent with the drilling data near the well location and exhibit consistent lateral continuity with the seismic profiles. In addition, the inverted fluid indicator profile obviously discriminates the three oil-bearing reservoirs compared with the traditional fluid indicator, which demonstrates the potential of our method in hydrocarbon detection in fractured reservoirs.