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Numerical Simulation And Reverse-time Migration Method Research Base On Acoustic Wave Equation

Posted on:2011-09-07Degree:MasterType:Thesis
Country:ChinaCandidate:H J ChenFull Text:PDF
GTID:2120360305455127Subject:Earth Exploration and Information Technology
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Seismic Numerical simulation is the important basis for Seismic exploration and Seismology, is a numerical simulation of the simulation of seismic wave propagation in the medium .As the seismic wave theory used in natural earthquake and seismic exploration, seismic simulation was produced, and with the development of seismic wave theory and computer technology, seismic numerical simulation technology has also been rapid development from 1960s,it has formed many modern seismic numerical simulation technology, such as the finite difference method, finite element method, virtual spectrum and the integral equation method and so on in present.This article describes the high accuracy finite difference numerical simulation of acoustic wave equation.Through the simulation results,we can see that the results of the high accuracy finite difference numerical simulation of acoustic wave equation is more precison, and it cansuppress the dispersion phenomenon effectively.Seismic migration is the core content of reflection seismology.Based on wave equation,Seismic migration put phase axis homing to its correct spatial location and focus energy to the scattering point diffraction in order to eliminate distortion in the reflection records.Seismic migration is closely related to the ultimate goal of seismic exploration,such as determine the distribution of subsurface structure,research the contact relationship between the straum and stratum,in order to find the favorable oil and gas accumulation zones.In addition, the article describes the method of reverse time migration in the seismic data processing. Reverse-time migration can be achieved, when we use wave equation to do reverse extrapolation for seismic data on the timeline. In the migration processing, wave field will exist as a vector instead of simple superposition of the scalar wave. Reverse-time migration can effectively suppress reflections and reduce the noise, has no dip limitation. So it can clearly and accurately imaging.Reverse-time migration (RTM) has not been used routinely until recently because of its computing expense,even though it offers a number of advantages over conventional depth-extrapolation migration methods such as handling evanescent energy and no dip limitation.Recently,RTM has spurred much interest because of the imaging challenges passed by increasingly complex subsurface targets and the availability of affordable computer resources such as Linux clusters.This article research the exact adjoint reverse-time migration and the least-squares reverse-time migration base on the conventional reverse-time migration.To reduce the migration artifacts arising from incomplete data or inaccurate instead of migrating data with the adjoint of the forward-modeling operator, a least-squares migration often is conside- red.Least-square migration requires a forward-modeling operator and its adjoint. In a derivation of the mathematically correct adjoint operator to given forward-time-extrapolation modeling operator, the exact adjoint of the derived operator is obtained by formulating an explicit matrix equation for the forward operation and transposing it.The programs that implement the exact adjoint operator pair are verified by the dot-product test.The derived exact adjoint operator turns out to differ from the conventional reverse-time-migration (RTM) operator,an implementation of wavefield extrapolation backward in time. And we use the three methods to migration the same modeled date. We can get the result that the exact adjoint reverse-time migration gives similar results for a conventional reverse-time migration, the least-squares reverse-time migration is quite successful in reducing most migration artifacts. The least-square solution using the exact adjoint pair produces a model that fits the data better than one using a conventional RTM operator pair.
Keywords/Search Tags:Seismic Numerical, Finite Difference, Exact Adjoint Reverse-Time Migration, Conventional Reverse-Time Migration, Least-squares Reverse-Time Migration
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