The Application Of Pre-stack Depth Migration Under Density Constrained Velocity In Deep Exploration

The migration is an effective techniques to improve the lateral resolution of the image through converge and homing the cross-section wave,gyro wave,and diffraction wave.The pre-stack and stack time migration is the traditional migration method,and it is difficult to adapt the dramatic lateral velocity variation,can't solve the common reflection point stack problem of the inclined interface.However,deep reflection exploration often faces complex overlying structural.Therefore,we apply pre-stack depth migration to deep reflection seismic exploration,which can improve the SNR and resolution of the complex geological structure,multiple waves suppression and prominent deep reflections;not only that,compared to traditional time domain seismic profiles,depth domain imaging are more geological.Applying pre-stack depth migration to deep reflection seismic data processing mainly face pre-stack data preprocessing;establish the velocity-depth model;and flow problem of pre-stack depth migration imaging for deep reflection seismic.The most important problem of the pre-stack depth migration is establish an accurate velocity-depth model,and we know the density and velocity have a clear conversion relationship.Therefore,we can establish the corresponding density-depth model by sectioning the 3D gravity model of the work area,and use the density-velocity relationship to establish the corresponding speed-depth model.This article mainly includes the following aspects:(1)We introduced the major methods for pre-stack depth migration:Kirchhoff integration method(WJ Schneider,1979),wave equation method(Claerbout,1972),reverse time migration method(Baysal E,Kosolf D,1983),and analyzed the principle and characteristics of three prestack depth migration methods(2)Three-dimensional inversion of gravity,and build the density-depth profile;(3)Build the density-speed conversion relationship and establish a corresponding velocity-depth profile;(4)Data preprocessing;(5)Case study:Finally,using the model and the measured data in the Lu Zhong area,pre-stack depth migration imaging was performed by large-scale seismic processing software.The result of traditional pre-stack time migration and pre-stack depth migration are compared and analyzed.