Abstract: Shengbei hydrocarbon-prone sub-sag is oil-gas enriched unit with the most potential of resources in Taibei sag. Shengbei structural belt is located at the central uplift area in Shengbei sub-sag. The late maturation of hydrocarbon source rocks and the oil-gas migration and accumulation feature depend on the distribution and charging degree of the reservoirs. By little impact of the orogeny's compression in Shengbei structural belt, the upward migration and accumulation of hydrocarbon from source rocks are generally conducted along the faults. It is the low potential energy and low amplitude uplift that allow oil and gas to be accumulated into the reservoirs. In addition, such factors as the reservoir rock development and the facies-belt and petrophysical property changes, etc. play important roles for petroleum distribution in the target zones. The vertical phase state changes during migration of condensate gas result in gradual precipitation of condensate oil, and forming the distributing pattern of upper oil and lower gas, with the decline of temperature and pressure. Under the action of compressed centrifugal-flow formed by asymmetric hydrodynamic field, the oil-gas amount migrated through the lateral leading-zone towards basin edge could be far more than the amount migrated upward vertically through the fault connecting the deep strata in the center of the basin. Hence, at the same time of enforcing oil-gas exploration of the low-range uplift area in Shengbei sub-sag, the sub-sag slope and transition region should be regard as the major targets for exploration.

Key words: late hydrocarbon accumulation, low-amplitude structure, lithologic boundary, condensate gas, hydrodynamic field