Abstract: Reliable trap identification of complex structures depends on migration imaging precision of the seismic data, and the reliable migration imaging depends on the migration velocity field developed whether to be consistent with the geological interpretation model or not. Prestack time migrated is based on high-precision migration velocity which can constrain geological structure model. Taking the sedimentary evolution of complex structures in the study area into account, this paper presents a reasonable geological structure model and the corresponding migration velocity field. According to Snell's law, the prestack time migration processing to the 3-D seismic data is conducted, obtaining a more reliable migration imaging, finding out five fault stractigraphic traps among which one is a stratigraphic trap, describing 3 fan bodies of Xiazijie formation of the Permian. Good effects of seismology and geology are gained.

Key words: seismic interpretation model, migration velocity, reliable migration imaging, trap identification, sedimentary facies characterization