A VTI anisotropic media inversion method based on the exact reflection coefficient equation

Abstract

Anisotropy is widespread in the Earth’s crust, and VTI (vertical axis symmetry transverse isotropy) anisotropy is common due to stratigraphic pressure. Disregarding anisotropy leads to inaccurate inversion results in VTI media. To estimate accurate elastic parameters, the exact reflection coefficient equation of VTI media should be used. This equation is nonlinear and more accurate than the commonly used linear reflection coefficient equation. Although the inversion based on the VTI anisotropy exact reflection coefficient equation is a complex nonlinear inversion problem, it is still computable. Therefore, for VTI media, we derive the objective function combining Bayesian theory and use the iterative reweighted least squares method for a fast and stable solution. Adding Bayesian theory can improve the robustness of the algorithm. The accuracy and noise immunity of the method is tested with synthetic data. Finally, the method is applied on field data and obtains accurate elastic parameters. The results can provide an understanding of subsurface formations and serve as the base data for calculating fluid and fracture distribution.