Unconformity types and hydrocarbon accumulation models in the eastern depression of the North Yellow Sea basin

The eastern depression in the North Yellow Sea Basin is a typical superimposed basin,and stratigraphic unconformities are greatly developed in Mesozoic-Cenozoic formation with serious deficiencies.The unconformity interfaces of T1,T2,T4,T5 and Tg were identified on the basis of integrating well data and seismic data.We also analyzed the main unconformity type,planar distribution,lithologic features of the T5 interface and the hydrocarbon trap types in connection with T5.The research showed that parallel unconformity,truncation unconformity and overlap unconformity are the main unconformity types of T5,with the sand-sand,sand-mud and mud-clay being the main lithological combination types up and down the T5 interface.Hydrocarbon traps are mainly four kinds,including the stratigraphic overlap and underlying unconformity traps,truncated monoclinic traps,traps associated with stratigraphic overlap and buried hill,and traps associated with the faults and unconformity.Oil and gas exploration related to unconformity in this region should be concentrated in the vicinity of sags within the depression.