Research on Direct Pre-stack Depth Migration under the Undulating Topography Circumstance

摘要

Engineering seismic exploration aims at solving shallow and middle-layered problems.However the imaging precision will be severely confused by the usual static correction process if the records were taken from undulating topography areas.To a certain degree,the usual pre-stack migration helps to perfect the results,but it still can't be applied to complex topographic areas since the basic horizontal surface assumption.The direct pre-stack depth migration (DPDM) based on actual shot and receiver elevations,by which the static correction process is completely avoided before migration and surely the imaging precision will be remarkably improved.To obtain some artificial shot gathers for numerical experiments,we model the propagation of acoustic wave in undulating topography mediums with high-order staggered-grid finite-difference (FD) method.Since the large amount of regular interferences contained in the shot gathers,the static correction process must be performed to support the interference elimination through apparent velocity filtering method.Then every trace of these worked shot gathers should be removed back into their original positions by reverse static correction.Finally all the shot gathers will be migrated respectively by pre-stack reverse-time depth migration and then imaged.Obviously,in this case the static correction merely affects the regular interference decrease rather than pre-static migration.A group of model tests are presented to show that the DPDM can ideally turn away the mistakes caused by static correction and increase imaging precision of shallow and middle layers.