Study On 3D Gaussian Beam Migration Method

Seismic imaging is an important component of modern seismic data processing.In recent years,with the increase of the difficulty of oil and gas exploration and the complexity of geological target,Seismic pre-stack migration technology has obtained the rapid development and has become the key technology of high-precision seismic data processing.Because of its flexibility and efficiency,Kirchhoff migration has been a widely used imaging method.Howerer,it has the disadvantages of caustic region,shadow region and multivalued traveltime in complex structures.Instead,the wave equation migration has superiority in the imaging accuracy,but the shortcoming in low efficiency in calculation.Therefore,as a kind of compromise of prestack Kirchhoff migration and wave equation migration,The Gaussian beam migration which keeps high computation efficiency and imaging accuracy simultaneously has been widely used in recent years.On one hand,Gaussian beam method adopts complex-valued dynamic ray-tracing parameters,which solves the problem of caustic region where the traditional ray method fails,improving the imaging result.On the other hand,Gaussian beam migration obtains the final wavefield by stacking the Gaussian beams contributing to imaging points without the time-consuming two-point(source-to-receiver)ray-tracing which can ensure the high calculation efficiency.With the widespread use of 3D seismic exploration,3D seismic migration imaging method research has become an important subject.This paper expands this method to 3D based on the previous two-dimensional gaussian beam migration method.This paper introduces the migration method mainly from the following several aspects:(1)According to the parabolic equation method,I calculate the solution of wave equation in ray neighborhood,also called the expression of 3-d gaussian beam.(2)According to the research of the predecessors' theory,I realize the three-dimensional common-source gathers gaussian beam migration method,and verify its validity with numerical tests.(3)According to the relationship between parameters of common-source gather and common-offset gather,I derive the expression of 3D common-offset gaussian beam migration and verify its validity with numerical tests.(4)To improve the efficiency of calculation,this paper adopts some optimization algorithms,such as the optimal algorithm of Hill,recently point searching,coarse grid and so on.In addition,I will analyze the influence of different parameters(such as angle range,initial beam width,ray parameters interval,etc.)on the result of imaging in this paper.