Nonlinear Prestack Elastic Parameters AVO Inversion

The technique of Amplitude Versus Offset (AVO) is becoming increasing important in hydrocarbon detection. As the basis of AVO theory, the Zoeppritz equation is based on several hypotheses such as the reflection and transmission on a single reflection interface in half of the infinite space. However, with the development of seismic exploration, oil-bearing strata are becoming thinner and thinner. Some layers are even only a few tens of meters thick. In this condition, the Zoeppritz equation is not suitable for elastic parameters AVO inversion. The difference of inversion results based on Zoeppritz equation will influence the oil and gas prediction negatively.This study focuses on using Brekhovski equation to substitute for Zoeppritz equation for higher precision of AVO inversion. Brekhovski equation does not need many assumptions and prerequisites and is expected to be suitable for thin-layer AVO inversion. Firstly, this study simplified the complicated Brekhovski equation and verified its correctness through comparing the reflection coefficients from forward modeling with the inversion results calculated by simplified Brekhovski equation.What's more, the simulated annealing algorithm is improved in several aspects and applied to elastic parameters AVO inversion based on Zoeppritz equation and simplified Brekhovski equation. Then, the errors of inversion results (elastic parameters) calculated by different equations are analyzed and discussed. It is proved that the errors of inversion results are too big and traditional AVO technology is not appropriate for thin-layer AVO effects analysis. While, the inversion results based on the simplified Brekhovski equation is more precise. Hence, it is believed that the simplified Brekhovski equation is suitable for thin-layer AVO analysis.