Wave Equation Prestack Depth Migration And Its Application Study

Wave equation prestack depth migration is an ideal seismic data imaging technique for the area where there occur very complicated geologic structure and severe lateral velocity variation.The PSDM results allowed for high precise geologic and structural interpreation in complex regions.This thesis systemicly study the theory on the technique , develop an accurate efficient method on building velocity-depth model and image the seismic data by the technique with GeoDepth. Main contens as follows:A series of theories and methods involved in the paper on wave equation prestack depth migration are discussed,such as based sources, frequency-space domain finite-difference, split-step fourier and fourier finite-difference wave equation prestack depth migration. We also discuse all their keystones,migrationg processes,numerical tests and error analysises.A combining accurate and efficient method on interval velocity analysising and velocity-depth model building. First, we build accurate and reliable time model by picking time layers in time stack profile with drills and adopting drills control and tomography model inversion at near surface. Second, building initial velocity-depth model by coherency inversing interval velocities layer by layer. The last, by anisotropic wave equation interval velocity analysising method and residual velocity analysising way with visual tomography one after another, we obtain the final accurate reliable velocity-depth model set.To check up performance of above methods in processing actual seismic data, two seismic data in the West of Shi Chuan are utilized and this migration results are compared with those of prestack time migration and Kirchhoff prestack depth migration. As a result, the method awfully improves the quality of the imaging profiles: effective returning in middle-deep depth, and main aim layers'touches are apparent, waves relative energe is very good, characters more distinctness in order to trace and compare , all kinds of geological phenomena are very explicit. So the method provides reliable migration seismic data for geological interpreters.