Abstract:

Source rocks in E_s3 (the third member of Shahejie Formation) in Dongying depression are characterized by the predominance of pristane with a pristane/phytane ratio of 0.5～1.0 and small amount of gammacerane; while source rocks in E_s4 (the fourth member of Shahejie Formation) are characterized by the relative abundance of phytane with a pristane/phytane ratio of below 0.5 and rich in gammacerane.Based on this remarkable difference, the oil sources of oilfields in the central uplift belt of Dongying depression are classified into E_s3, E_s4 and mixing types,of which the E_s3 and mixing types are predominant. Sources of oil in different regions and different horizons vary greatly. Study on structural features and areal distribution of geochemical properties reveal that the hydrocarbons would migrate preferentially into the nearest reservoirs, thus the center of each sag consists of the center of oil source.The oil in the western area come mainly from the E_s3 source rocks in Lijin sag; small amount of oil in the southeastern area come from the E_s4 source rocks in Niuzhuang sag;while oil in the northeastern area have been generated by the source rocks in Minfeng sag. Oil of mixing type commonly occur in areas where faults are well developed, indicating that faults have large impacts on mixing type oil.

Key words: oil and source rock correlation, fault, central uplift belt, Dongying depression