Method Of AVA Multi-wave Pre-stack Inversion And Accuracy Analysis

Multi-wave pre-stack inversion is based on the multi-wave amplitude information and has provided intuitive lithology parameters for the reservoir prediction, which has played an important role in the current oil and gas prediction. Based on the transversely isotropic (VTI) medium amplitude characteristic equation, this thesis analyzes AVA features which are produced by four gas-bearing sandstone interface and synthesizes the multi-angle wave pre-stack AVA gathers with the geological model as the VTI medium. According to the above research, the method of multi-wave pre-stack AVA inversion and the factors which affects the accuracy of the AVA inversion of pre-stack have been analyzed, and the method which suits for multi-wave inversion of pr-stack AVA has been found. This method has also been used in the inversion of actual surface and VSP seismic data, which verifies its reliability and validity. The research of this thesis has been divided into the following aspects:1) After the reference of many related documents which studies AVA forward technology, this thesis has compiled the exact formula of VTI medium amplitude characteristic equation and has expressed the reflection coefficient with the plural forms which solves the problem of the adaptability of outside the transmission coefficient on the critical angle. Based on VTI media with amplitude characteristic equation, four gas-bearing sandstone interface of the AVA curve have been forwarded and their characteristics have been analyzed. All those have prepared basic data for the pre-stack inversion AVA.2) Based on VTI medium amplitude characteristic equation, this thesis adopts the method of generalized linear inversion to research the factors that affect the accuracy of AVA inversion of multi-wave stack. For example: the establishment of the method of inversion equation and the method of solving the inverse equation, AVA inversion of pre-stack multi-wave approach, pre-stack joint approach, the influence of noise, the selection of pre-stack data and pre-stack data processing, etc. Through analysis of various factors, this thesis has realized a more optimal method which suits to multi-wave inversion of pre-stack AVA.3)Aimed at earthquake ground wave inversion, this thesis has recorded the surface seismic model of forward order differential elastic wave and has used the joint inversion method to invert in order to verify its feasibility using for the surface seismic data. And also has tried to deal with the real multi-wave data.4) Aimed at VSP multi-wave inversion, this thesis has studied the methods suit to 3D VSP multi-wave inversion. Through the inversion of the model records of pre-VSP gathers by ray tracing method, this thesis has verified the applicability and reliability of this method to the VSP data and has applied it to the inversion of VSP real data.