JOINT ANISOTROPIC AVO INVERSION OF PP AND PS WAVES USING THE EXACT ZOEPPRITZ EQUATIONS

Because the amplitude of seismic data highly depends on the reflection angle and the material properties, the amplitude variations with incidence angle or offset (AVA/AVO) inversion method, which can relate the subsurface structure’s properties with the seismic data effectively, is common tool nowadays in the petroleum industry.

Due to the solution of the exact Zoeppritz equations is difficult to calculate, which is the fundament of the AVO inversion, most conventional AVO inversions use the approximate expressions of the Zoeppritz equations to generate seismic wave reflection and refraction coefficients. However, those approximations do not work well for strong contrast and complex subsurface structures. Also, most conventional methods apply the AVO inversion in isotropic media, which are not working for anisotropic media.

To overcome these three shortages of conventional AVO methods, we use the exact Zoeppritz equations to compute the reflection coefficients and add an anisotropic perturbation term to compute the reflection coefficients more accurate in the anisotropic medium. We also combine the PS-wave reflection coefficients to the conventional PP-wave AVO inversion to reduce the local minimum problem. The truncated Taylor series expansion regarding the model parameter is used to generate the updating formula for the inversion, and the least-squares method is applied to implement the inversion. Based on the model test results, our new method can overcome the problems of conventional AVO inversions and extend the scope of application to the anisotropic medium.