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Depth Domain Interval Velocity Modeling Research Of Seismic Wave Reverse-time Migration

Posted on:2016-10-06Degree:MasterType:Thesis
Country:ChinaCandidate:S WangFull Text:PDF
GTID:2180330473457678Subject:Mineral prospecting and exploration
Abstract/Summary:PDF Full Text Request
The technology of seismic wave reverse-time migration in depth domain is the most accurate imaging method in seismic wave migration imaging field nowadays. However, reverse-time migration is depended strongly on the interval velocity model. Reverse-time migration can achieve expected imaging effect depends on the accurate interval velocity model. In other words, interval velocity model determines the success or failure of seismic wave reverse-time migration. In this paper, we mainly study the key technology in seismic wave reverse-time migration and interval velocity modeling in depth domain. This paper mainly includes three parts:Detailed introduce the basic theory, principle of reverse-time migration and the key technology in the process of reverse-time migration imaging.We deduced in detail respectively suitable for 2d and 3d of staggered grid first-order rate-stress acoustic wave equation forward modeling and inverse high order accuracy finite difference method. Research is suitable for the 2d and 3d boundary condition of reverse-time migration, including best matched layer (PML) absorbing boundary and random boundary conditions, effective suppression of pseudo reflection noise. Besides, according to the zero delay normalized cross-correlation imaging conditions of migration imaging. Analysis the reasons of the low frequency noise in reverse-time migration, using Laplace filter operator to eliminate deteriorating effect of reverse-time migration imaging of low-frequency noise. We use two different examples to checking on the imaging effect of reverse-time migration.We research interval velocity model building in depth domain and subsequent modification method. Extracting CMP gathers from common-source, then, analysis stacking velocity, and, transform stacking velocity to root mean square velocity(RMS), besides, according to the DIX formula, we transform RMS into interval velocity in time domain. We use time-deep transformation to put the time domain interval velocity into interval velocity in depth domain. We put this model into reverse-time migration. Discusses the method of using wave vector calculation of seismic wave incident Angle, at the same time, using the method based on Hilbert transform, dip and application after modified sampling theorem of the normalized cross-correlation imaging condition of extracting Angle domain common imaging point gathers. Calculating angle gathers of residual curvature is derived in detail and gives the residual curvature, travel time residual, dip Angle, the quantitative relation Angle of incidence. Calculate the sensitivity matrix is given the required velocity model in the grid and calculation formula of travel path by walking Angle gathers the residuals and ray path and add regularization conditions build tomography velocity inversion equations. To solve the tomography velocity inversion equations was deduced in detail when using least-squares orthogonal decomposition method (LSQR) formula, to calculate the velocity update amount. According to the velocity update quantity of tomography inversion equations by initial velocity model of top to button correction step by step. When reverse-time migration Angle gathers are flattened, we would get the interval velocity model which is suitable for the reverse-time migration. We have one model data to prove the method of interval velocity modeling is right.Testing on three different parts of the interval velocity modeling and reverse-time migration, including two 2d data and a 3d data, to verify the study of the reverse-time migration and interval velocity modeling method in this paper is correct and practical in actual industrial production.
Keywords/Search Tags:reverse-time migration, interval velocity model in depth domain, migration velocity analysis, angle domain common image gather, interval velocity tomography velocity inversion
PDF Full Text Request
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