The Research Of2-D Post-stack Depth Migration Method

Seismic exploration is a very important method in the increasing energy exploration allover the world. Seismic exploration can get underground geological structures conditions andsome valuable parameters of oil and gas, its reliability and accuracy are generally better thanthe other geophysical methods. However, in the actual data, because of the complexgeological structure, such as fluctuant stratum, faults, steep obliquity stratum, these alwaysmake seismic imaging results incorrect. Migration processing can move undergroundgeological structures’ reflectors into their ture position.This article start from the wave equation, on the basis of previous work, use upstreamwave-field extrapolation and principle of exploded reflector, achieved the phase-shiftpost-stack migration methods firstly. Phase-shift method is accurate and effective, upstreamwave equation can be solved exactly in f-k domain, it can process large inclination angleinterface, but can not process the lateral variation of stratum velocity. This paper, thenachieved the phase shift plus interpolation (PSPI) post-stack migration methods, it canprocess the lateral variation of stratum velocity, overcomed the shortcomings of thephase-shift method. This article introduced the Claerbout15degree and45-degree equationfinite-difference method. It also introduced splitting method of equation of higher order. Iachieved15degrees,45degrees,65degrees wave equation finite-difference post-stackmigration in spatial-frequency domain and gave the implementation process. Model testsshowed that, the biggest advantage of the finite-difference method is that it can adapt to anyvariation of stratum velocity, it can’t process large inclination angle interface, the higher-orderequation can improve this defect. For the geological models that have a slight change or nochange in lateral velocity, phase-shift method is an ideal post-stack migration algorithm.Phase shift plus interpolation method inherits the advantages of the phase-shift method andcan accommodate lateral velocity variations.Migration velocity error seriously affect seismic migration. Finally, this article comparedand analyzed the impact of velocity error and part velocity error on post-stack depth migrationresults. Speed error and migration depth is not equal, then are affected by many factors suchas stratum thickness and stratum velocity.