Abstract: The Oulituozi area, an important resource replacement area for an annual light oil production of 500?04 t in the Liaohe oilfield, contains original oil in place (OOIP) of 3000?04 t. By the interpretation of newly acquired and processed 3D seismic data and drilling/logging data and the study of structural development history, the structural characteristics and genesis of the Cenozoic Paleogene formations in the Oulituozi area were analyzed, and their controlling effects on oil and gas migration and accumulation were investigated, in order to identify the favorable targets for future exploration. Following conclusions are drawn based on the study. First, the structural framework of the Oulituozi area was shaped in the Paleogene, when it sequentially evolved through four stages, i.e. arching, rifting, attenuating, and re-rifting, and underwent two major structural movements, i.e. extensional movement in the third member of Shahejie Formation (Es3) and strike-slip movement in the Dongying Formation (Ed). Second, the present structural framework in the study area is the superposition of the extensional system and the strike-slip system, and the structural evolution difference between the north and the south led to the unique flower structure with alternate normal and reverse faults and also the conversion of fault property. Third, major fault demonstrated a sealing performance during the oil and gas migration, and its barrier effect was unfavorable to the secondary migration of oil and gas. Fourth, intense structural movements significantly improved the reservoir physical properties. Fifth, the structural high in the flower structure and the fault-nose attached to the major fault are the most favorable zones for oil and gas accumulation, and stratigraphic oil reservoirs are developed within the overlap zones in the west.

Key words: Liaohe depression, Oulituozi, structural superposition, strike-slip fault, flower structure, oil and gas exploration