Seismic Anisotropic Fluid Identification in Fractured Carbonate Reservoirs

Seismic fluid identification plays an important role in reservoir exploration and development. Natural vertical fractures are common carbonate rocks, it is essential to consider fracture-induced anisotropy the of fractured reservoirs. We have developed a novel Bayesian elastic impedance variation with angle azimuth (EIVAZ) inversion approach for directly estimating fracture indicator (FFI), which can avoid cumulative errors produced indirect calculation process. Under assumption weak small incident angle, we first derive new approximate PP-wave coefficient horizontal transverse isotropic (HTI) media. Analysis shows that approximation has reasonable accuracy at angles incidence less than 30°. To estimate FFI from observed azimuthal P-wave seismic reflection data, further deduce EI equation establish two-step workflow. Finally, proposed demonstrated by tests on synthetic data example field set Sichuan Basin (China). Results show model parameters be reasonably estimated even moderate noise levels. The quasi-normal weakness relatively high values location reservoirs, reliably indicate gas-bearing reservoir.