Kirchhoff Prestack Depth Migration In Anisotropic Media And Its Application Study

With the development of modernization, it is more and more demand for resources, resources where geological conditions is simple and easy exploitation can not satisfy people’s needs, people had to deep into geological conditions complex areas. In this case, the traditional post-stack time migration, and even pre-stack time migration has been unable to achieve satisfactory effect, especially for lager lateral velocity variation areas, often causes imaging position inaccurate and a false structure. Pre-stack depth migration based on velocity model can be a better solution to this problem. It can not only solve the speed of transverse and longitudinal change, but also solve the salt, piercing and other body imaging of complex geological anomalies and provide more accurate space-time position. But because the media have anisotropy, the depth of seismic physical model and the actual formation depth can not be closed. To solve this problem, people began to explore the anisotropic prestack depth migration, and have made great progress.This thesis study anisotropic Kirchhoff prestack depth migration theory and practical application, forming a complete set of anisotropic migration process, main content includes:(1) Anisotropic Kirchhoff prestack depth migration related to the basic theory: the classification of anisotropic media, parameters which determine the anisotropy media, the theory of Kirchhoff migration in anisotropic medium, calculation of travel time, building speed model.(2) Use Geodepth software process seismic data of a particular area with Anisotropic Kirchhoff prestack depth migration in order to get a complete set of anisotropic depth migration process, including: the initial model obtained using DIX velocity constrained inversion, then pick up residual velocity through human-computer interaction using chromatography methods for model optimization. We can calcute anisotropic parameters by Combining well material and seismic data , Anisotropic migration velocity model is obtained by using isotropic and anisotropic velocity relationships, and ultimately obtained the anisotropic migration velocity model; through testing to determine migration aperture, use Kirchhoff prestack depth migration methods to complete migration.Through this work, the closure error of the depth of geological layers between the seismic and drilling data is obtained. through the analysis, the following conclusions: Considering the effect of anisotropy, the section after an migration basically eliminate the seismic horizon and well horizon depth closed problem, closure error 7% after isotropic migration of reduced to 2% after anisotropic migration, structure more clear, tectonic clearer, fault surface imaging also has greatly improved.Concluded the anisotropic migration in production there are still some limitations: As many of anisotropic parameters, affected by the production efficiency, the anisotropic media are reduced to VTI media, and only considerδandε; geological conditions Complex areas, if make depth of seismic and geological horizon same completely, some false structures will appear, so after anisotropic depth migration, there are some errors between seismic and geological layers , but small enough to meet the imaging needs.