AVO inversion in V(x,z) media

Yalei Sun and Wenjie Dong

yalei@sep.stanford.edu, wenjie_dong@email.mobil.com

ABSTRACT

We implement a new Kirchhoff-typed AVO inversion scheme in V(x,z) media. The WKBJ Green's function is calculated using a finite-difference scheme. We propose a pair of Kirchhoff inversion operators which have more obvious physical meaning. By analyzing the Kirchhoff inversion operator, we find out an unique relationship between the weighting function and the kinematic equation, which is very important to recover the true amplitude of the reflection coefficient. Our scheme is a two-step AVO inversion approach. Common-image gathers (CIG) are generated in the first step. These common-image gathers can be used to update the velocity model and reduce the influence of velocity error in the final AVO inversion results. AVO intercepts and slopes are estimated in the second step using a least-squares procedure. Finally, a fluid-line section is generated to highlight the existence of V_p/V_s anomaly. One dipping-layered synthetic example demonstrates the accuracy of our scheme and the influence of NMO stretch on the estimated AVO coefficients. The result from a field data example, the Mobil AVO dataset, shows a strong V_p/V_s anomaly in the middle of the section that may be a potential hydrocarbon indicator.