Azimuthal Amplitude Difference-Based Multidomain Seismic Inversion for Fracture Weaknesses

Fracture weaknesses are two important parameters to describe the characteristics of reservoir fracture-induced anisotropy. Accurate estimation for fracture weaknesses is of great significance for seismic exploration and characterization of naturally fractured reservoirs, especially for gas-bearing reservoirs. Linear seismic inversion based on Bayesian theory can fuse prior information. And the inverse problem is solved in the form of the posterior probability density function (pdf) to obtain the maximum posterior solution. Based on the PP-wave reflection coefficient in a transversely isotropic medium with a horizontal symmetry axis (HTI), we first construct forward models in different domains by using the convolution model. Then, we select a relatively good initial model to realize the seismic inversion in the time domain, frequency domain, and joint time-frequency domain, respectively. Next, a relatively poor initial model is selected to estimate the low-frequency components in the Laplace-Fourier domain, and the final estimation is compared with the traditional approach. Finally, both synthetic and real data are used to verify the feasibility of inversion approaches in different domains. The anti-noise ability of estimated fracture weaknesses in the time domain is stronger than those of frequency-domain inversion. The joint time-frequency inversion inherits the advantages of the strong anti-noise ability of time-domain inversion and retains the excellent characteristics of high resolution of frequency-domain inversion, it balances between improving the resolution of seismic inversion and suppressing random noise. The estimation of low-frequency components for fracture weaknesses in the Laplace-Fourier domain can reduce the dependence of seismic inversion on the initial model and improve the estimated accuracy.