Research On Wave Equation Prestack Depth Migration

Wave equation prestack depth migration is one of the important components of high precision and high resolution seismic exploration technology,which mainly solves the problem of geological imaging with complex geologic structure and strong transverse velocity variations variation.Compared with other migration methods(prestack time migration,poststack time or depth migration,etc.),the wave field extrapolation of prestack depth migration is deduced by solving the numerical solution of the wave equation directly,and then the imaging is superimposed in the depth domain.Therefore,the wave equation prestack depth migration is very suitable for the complex underground structure with strong lateral velocity variation,which can usually get better underground imaging.This paper introduces the development history and current situation of prestack depth migration technology,and expounds the basic theory of migration(migration principle,imaging principle and imaging condition).Based on the wave field extrapolation(phase shift extrapolation)of the frequency-wavenumber domain,the Split Step Fourier Operator,the Fourier Finite Difference Operator and the Generalized Screen Propagator Operator are derived according to wave field division principle and then realized separately in the shot domain.In the process of programming the migration algorithm,the key problems such as boundary condition,numerical dispersion and algorithm stability are analyzed and solved.Then the program is tested by various model(horizontal model,surface model,lens model,Marmousi model)and proved to be feasible.Finally I have summarized the advantages and disadvantages of the prestack depth migration and the key factors influencing the migration effect,which provides some reference for final quality control.