Abstract: The features of Dongpu depression in Zhongyuan Oilfield include complex faults,many faulted blocks,multiple sets of source reservoir seal assemblages.It is difficult for post-stack migration to get perfect migration imaging effect in complex faulted blocks.However,pre-stack migration can improve the imaging effect.An effective Optimized Method for obtaining migration velocity field for pre-stack time migration is presented,which is based on velocity iteration and constrained by geological information.The method can improve accuracy of migration velocity.Through analyzing four key parameters of pre-stack time migration such as migration aperture,maximum migration angle,ray trace and anti-aliased,some parameter value is proposed,which is effective for the seismic data in Dongpu depression.Consequently,testing workload of processing procedure and blindness of parameter test are decreased so as to increase processing efficiency.Through pre-stack time migration,imaging accuracy in complex faulted blocks is improved,the positions of faults can be accurately ascertained, the relationships among faulted blocks are clarified,which are highly accorded with well data.

Key words: Dongpu depression, pre-stack migration, migration velocity, complex faulted blocks, migration parameters