Abstract:

Based on the measured fluid pressure data，the origin of reservoir overpressure and its relation with hydrocarbon accumulation of the Paleogene of Dongying depression are systematically analyzed and the distribution model of overpressure hydrocarbon reservoirs is summarized.Mechanism for reservoir overpressure includes overpressure transference （divided into overpressure contact transference and overpressure connect transference）,uncompaction and oil cracking.The hydrocarbon reservoirs with high yield and overpressure formed due to the function of overpressure contact transference distribute in the third member and the fourth member of the Shahejie Formation and Kongdian Formation in the center of each sag，northern slope zone and the rim of the central uplift belt.The deep hydrocarbon is brought into the shallow strata and forms the shallow hydrocarbon reservoirs with high yield and medium overpressure by the effect of overpressure connecting transference,which distributes in the first member and second member of Shahejie Formation of the central uplift belt and Es3 and Es4 of the southern slope.the function of uncompaction develops in the strata of gypsum and salt rock of Es4 and Ek and is unfavorable to the formation of reservoirs.The process of crude oil cracking usually develops below the depth of 4000m and has not inevitable relation with the reservoir formation.

Key words: reservoir overpressure, origin, hydrocarbon accumulation, Dongying depression, Paleogene, Bohai Bay Basin