Abstract: Within the sedimentary basins, overpressure is occurred widespread and the generation mechanisms are various. The overpressure evolution has significant effects on the migration and accumulation of hydrocarbon. The oil test, logging data and effective stress characteristics are integrated to analyze the overpressure genetic mechanism. The research results show that the overpressure is influenced by both undercompaction and hydrocarbon generation in Dongying Formation and the hydrocarbon generation is the major factor in Shahejie Formation. The numerical modeling results of pressure evolution history prove that the combining action of fault opening controlled by tectonic activities and interbedded sandstones is the major factor of overpressure release explaining why normal pressure exists in some regions. The development and evolution of overpressure have controls over the current vertical distribution of different types of hydrocarbon reservoirs in the Huanghekou depression. Where the overpressure is well-developed, not influenced by fault activities and not released obviously, should be for searching for the Paleogene primary hydrocarbon reservoir, and where the Paleogene has been connected with the Neogene by faults, should be priority assigned to exploring the Neogene secondary hydrocarbon reservoirs.

Key words: overpressure, overpressure mechanism, basin modeling, Paleogene, Huanghekou depression, hydrocarbon