Fluid Identification Based on P-Wave Frequency-Dependent Azimuthal AVO Method in Fractured Media

Seismic anisotropy is relevant to frequency. When fractures in reservoirs are saturated with different fluid types (oil, gas and brine), the variation rates of anisotropy versus seismic frequency (which is called anisotropy dispersion) are different. Thus, anisotropy dispersion can be used to distinguish different fluid types in fracture. In this paper, P-wave frequency-dependent azimuthal AVO inversion algorithm is proposed and applied to real seismic data. The studies focus on the analysis of P-wave anisotropic dispersion response for different fluid saturation. Continuous wavelet transform is employed for spectral decomposition, aiming at well time-frequency localization. Real data application indicates that the magnitude of P-wave anisotropy dispersion of brine is far stronger than that of oil and gas in fractures. Our study firmly proves that the method aimed at calculating the P-wave anisotropic dispersion for different fluids saturation is valid and reliable, and this brings us the confidence to discriminate fluid by the calculated anisotropic dispersion values in fractured reservoir.