Based On The Complex Geological Structure Of The Wave Theory Of Seismic Data Imaging

The project of seismic data imaging under the complex geology structure is studied in this thesis. A generalized high order screen extrapolator of double square root (DSR) equation is derived from the non-stationary phase shift formula of wavefield continuation, thus a new prestack depth migration method in the cmp-offset domain is proposed. The migration results of the synthetic and ocean field datasets show that this method is correct and effective.Several prestack depth migration methods are proposed and unified to the synthetic source record migration method. These methods include plane wave migration with Fourier Finite Difference(FFD) extrapolator, maximum energy plane wave migration and prestack migration with phase encoding of areal shot records. The synthetic source is the generalization of plane wave source, controlled illumination source, piecewise plane wave source and areal sources with phase encoding etc. By migrating the synthetic source record, the computational cost of the conventional areal shot record migration can be reduced by several times without significantly degrading the image quality. The synthetic source record migration method is tested on Mamousi model, 3D SEG/EAEG salt model and field datasets. This migration method is proved to be correct, effective and practical.Undulate acquisition surface is one of the main properties of the seismic datasets from Western China. Based on the synthetic source record migration method and wave stack principle, a method of migrating directly from the undulate surface is presented and tested. A wave equation datuming method is also applied to redatuming the wavefield upward. This datuming method is derived from the Common Focus Point (CFP) concept.Estimating the macro velocity model is considered to be the key step of prestack imaging procedures. A migration velocity analysis method is proposed, in which the problem of velocity analysis is converted to the problem of determining the local maximums of the defined criterion function. The correctness and effectiveness of the method is proved by the numerical experiments on the theoretical model and field datasets.