Study Of Pre-stack Depth Migration Based On Kirchhoff Integral Method

Migration is one of the main seismic data processing technology, compared with the time migration, Pre-stack depth migration can solve the problem of complex geological structure better. Pre-stack depth migration is generally divided into two categories: The first category is based on the principle of superposition of Kirchhoff diffraction scan integration algorithm, the second is based on the theory of wave equation migration methods(such as finite difference migration method, Fourier migration, etc.). Kirchhoff integral method is the integral solution of the wave equation theory developed on the basis of pre-stack depth migration, by approximation, it is virtually identical to the ray theory, in line with Snell’s law, comply with the diffraction waves, reflection and refraction laws. Kirchhoff integral method pre-stack depth migration is composed of two parts: one is to calculate the travel time and the other part is Kirchhoff integration process. Migration of accuracy depends on the accuracy of travel time. In this paper, the calculation of travel time based on the shortest path ray tracing method, that is all possible paths between two points in the actual path underground corresponds to the minimum travel time.In this paper, the basic principle of Pre-stack depth migration from Kirchhoff integration algorithms based on the basis of previous work, study the Kirchhoff integral method Migration derivation and the shortest path ray tracing method to calculate travel time, using the Fortran programming language vertical spread converted wave pre-stack depth migration; analysis of the characteristics of converted wave, the establishment of the single scattering point model is verified Kirchhoff integral method P-SV converted wave pre-stack depth migration; describes the pre-stack time migration and pre-stack depth migration imaging results proved that pre-stack depth migration imaging position to avoid the occurrence of lateral deviation, has better lateral resolution; levels model and tilt model were established, verifying a too small or too large migration aperture makes migration section level with a false form of random noise phase axis, and the steep interface can not properly homing; the establishment of a series of theoretical models, such as fault combinations, combinations syncline, unconformity, intrusions, etc., through the Methods for each model P-SV converted-wave migration calculation to obtain a better imaging effects, the model can accurately homing basic interface, which laid the foundation for further research.