Complex High Steep Structural Zone Prestack Depth Migration Technology Research

The area of complex and high dip structure is rich in oil and gas had become the current focus of seismic exploration. But these areas of poor seismic imaging caused by complex surface conditions, complex geological structure and strong horizontal velocity of variation, imaging technology in conventional seismic processing can not obtain the accurate form of underground structure. Because wave equation pre-stack depth migration had the characteristics of keeping fidelity and keeping amplitude, it is effective method to solve seismic imaging in the area of complex and high dip structure. Wave-filed extrapolation propagators are most important in wave equation prestack depth migration.Through to research and analysis wave-filed extrapolation propagators of wave equation prestack depth migration, found that usually wave-filed extrapolation propagators calculated by approaching single square root operator of frequency dispersion equation. But existing approximations of single square root operator of frequency dispersion equation don’t better approximate single square root operator of frequency dispersion equation and had bigger error between them. To solve the problems, on the basis of research the advantages of existing mathematical optimization algorithm, this thesis used more optimal mathematical optimization algorithm, such as rational Chebyshev approximation (this method is a optimization algrorithm that combines rational approximation and Chebyshev approximation), to improve wave-filed extrapolation propagator of wave equation pre-stack depth migration and to better approximate single square root operator of frequency dispersion equation. Which can reduce relative error between coefficients of wave-filed extrapolation propagator be optimized with single square root operator of frequency dispersion equation. And then improve the imaging effect of coefficients of wave-filed extrapolation propagator be optimized.Through to compare the optimization coefficient wave equation migration operators with the existing wave equation migration operators, find that the optimization coefficient wave equation migration operators are better than the existing migration operators, especially contrasted of the error and the imaging. In summary, through to research the theory and compare the seismic imaging profiles, found this thesis proposed coefficients of pre-stack depth migration wave-filed extrapolation propagator be optimized had better imaging result.