Abstract:

Abstract:Complexity of hydrocarbon accumulation process is a major factor influencing petroleum exploration in a multicyclical superimposed basin.Modeling of hydrocarbon generation in the PermoCarboniferoussource rocks in the Linqing Depression,the Bohai Bay Basin reveals that four stages of hydrocarbon generation occurred in the middlelate Triassic,the late Cretaceous,the Paleogene,and the NeogeneQuaternary,respectively.The volume of hydrocarbons generated in the first stage was very small and that generated in the second stage is insignificant too.The peak hydrocarbon generation occurred in the Cenozoic.Systematic analyses of fluid inclusions from 76 samples of six wells show that three stages of hydrocarbon accumulations dominated by gas charging events occurred in the late Jurassicearlier Cretaceous (141.9-95.7Ma),the Paleogene (51.0-33.1Ma),and the NeogeneQuaternary (19.7-0Ma),respectively.All the hydrocarbon charging events initiated during the depression of the superimposed basin and terminated during its uplifting.The hydrocarbons charged in the first stage were almost completely destroyed and turned into bitumen,while the hydrocarbons charged in the second and third stages might accumulate in the Upper Paleozoic stratigraphicstructural traps in the central sags compartmentalized by the NWtrending faults.These traps might be favorable exploration targets.

Key words:  Key words： hydrocarbon accumulation stage,fluid inclusion,Paleozoic,superimposed basin,Linqing Depression, the Bohai Bay Basin