Abstract: The slope zone in northern Biyang sag is characterized by complex structure, developed minor fault blocks, varied seismic vertical and horizontal velocities and difficult to get imaging, which result in that conventional imaging approaches are hard to meet the needs for exploration and development of this area. This paper presents the prestack time migration to curved rays for minor fault blocks, which is of more accurate migration, allowing the travel-time equation to be more close to the real pathway of layered media seismic wave propagation, the focused imaging to be more precise, the migrated results to be of good preserved amplitude processing property and the output trace gathers to be used for the lithologic analysis and inversion study. Case study shows that by this approach the imaging profiles with higher quality can be obtained, hence new recognitions of faults are gained, new traps are discovered and good oil shows in slope belt of northern Biyang sag have been encountered by drilling.

Key words: complex fault block, prestack time migration, seismic imaging, amplitude, trap