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Multicomponent Joint Elastic Reverse-time Migration For3D Multi-wave Seismic Data

Posted on:2014-06-27Degree:MasterType:Thesis
Country:ChinaCandidate:X F GongFull Text:PDF
GTID:2180330452462378Subject:Earth Exploration and Information Technology
Abstract/Summary:PDF Full Text Request
Multicomponent-joint reverse-time migration (ERTM) extrapolates wavefields basedon elastic wave equation using the recorded multicomponent data as boundary conditionsand produces images by applying the elastic imaging conditions, which are physicallymeaningful and will reduce the non-uniqueness of seismic interpretation effectively. Theconstruction of wavefields determines the efficiency and accuracy of the algorithm whilethe characteristics of amplitude and the pattern of the migrated images depend on theapplication of imaging conditions. Therefore, the key aspects of ERTM are theconstruction of wavefields and the application of imaging conditions. In order to get betterimages as well as to improve the efficiency and accuracy, a systemic research on ERTMhas been carried out in this paper.The theory of ERTM has been systemically presented in this paper. The fundamentaldifference of ERTM from the other migration methods is revealed by illustrating thewavefield construction method. Several imaging conditions have been analyzed to figureout the characteristics of each imaging condition in terms of the features of the images andthe efficiency. And polarity correction and the suppression of low-wavenummber noisehave been discussed as measures to enhance the amplitude of the migrated images.In this paper, an extended compact staggered-grid finite-difference scheme has beenpresented in this article. Compared with the staggered-grid finite-difference scheme andthe compact staggered-grid finite-difference scheme, the scheme proposed in this paperinvolves the least grids on both sides of the computed grid to achieve the same accuracy,which can raise the accuracy of wavefield construction and thereby improve the accuracyof ERTM. With the purpose of improving the efficiency of ERTM, this paper has carried out a research on how to reduce the disk storage and accelerate the computation boththeoretically and practically.Then a a special attention has been paid to the3D ERTM in this paper. It is pointed outthat the major problem of applying the current ERTM algorithm to3D cases lies in that theseparated S-wave is a vector inapplicable to the imaging condition. So, this paper suggeststo convert the vector S-wave of the receiver wavefield into a scalar prior to applying theimaging condition. Based on an analysis to the vectorial characteristic of S-wave, ascalarizing method for S-wave based on the propagation directions of source and receiverwavefields has been put forward. Then, the scalar PS is produced by crosscorrelating thescalar P-wave of the source wavefield and the scalar S-wave of the receiver wavefield.Finally, several numerical examples are presented in order to test the method involvedin this paper. The numerical results have confirmed the correctness and feasibility of themethods proposed in this paper..
Keywords/Search Tags:multicomponent-joint, elastic reverse-time migration, computationalstrategy, image amplitude, 3D PS imaging
PDF Full Text Request
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