OIL AND GAS MIGRATION MODEL "DOUBLE FAULTS-RELAY" AND ITS EXPLORATION PRACTICE ON THE EASTERN SLOPE OF SHIJIUTUO UPLIFT, BOHAI SEA

In order to reveal the regulations for oil and gas migration and accumulation in the eastern slope zone of Shijiutuo Uplift, Bohai Sea, so as to efficiently guide oil and gas exploration there, based on the comprehensive study of petroleum geological characteristics of the area, this paper puts forward a "double-fault-relay" model for hydrocarbon migration. It is proposed in the model that the vertical migration of hydrocarbon is mainly controlled by boundary faults, the shape of cross-section and the opening-closing rhythm of the faults, the lateral migration of hydrocarbon controlled by the distribution pattern of the Guantao Formation, while the accumulation of hydrocarbon in the final stage controlled by the secondary faults. Based on the statistics of 264 drilled sand bodies in the QHD33-1S Oilfield, the secondary faults (type A faults), which control hydrocarbon accumulation in sand bodies, all occurred along the dominant migration path, where the fault activity is over 50 m, and the distance cutting into the structural ridge of Guantao Formation is larger than 4 km. Exploration practice has proved that structural and structural-lithologic traps existed along the main migration path of oil and gas and controlled by type A faults are favorable areas for hydrocarbon accumulation.