The characteristics of turbidite reservoir and oil and gas distribution and enrichment pattern in the middle of third member Shahejie formation in Niuzhuang sub-sag have been investigated through core observation, thin section identification, property test and fluid inclusion analysis using drilling core, logging and oil testing data. The turbidite reservoirs in the study area are mainly lithic arkoses, containing fine sandstone, with middle-high porosity and low permeability. The space types in the reservoir are mainly primary pores, and secondary pores also develop, with moderate compaction dominated by carbonate cementation and siliceous cementation in the secondary place, and feldspar dissolution is the most common dissolution. The oil content has no apparent corresponding relationships with physical properties of the reservoir, but is controlled comprehensively by buried depth, formation pressure and physical properties of the reservoir. In plane, oil layers have a ring type distribution around hydrocarbon generation center and oil source fault, and areas with high formation pressure and oil source fault development are the favorable places for oil and gas enrichment. Oil and gas accumulation is determined by the spatial allocation relationship of hydrocarbon source rocks and reservoirs, and the timing allocation relationship of thermal evolution of hydrocarbon source rock and physical evolution of the reservoir. Reservoirs of shallow buried depth are oil-free, whereas those in deep areas tend to be oily. Reservoirs of similar buried depth tend to be oil-free in areas with poor physical properties and oil-rich in areas with good physical properties, and oil is likely to accumulate in fault-abundant and overpressured formation areas.

reservoir characteristics  /  oil and gas enrichment  /  turbidite  /  Niuzhuang sub-sag