The Dongying Formation in Wenliu structure of Dongpu sag

Bohai Bay Basin

consists mainly of light brown sand-shale of alluvial fan depositional system.Saturated hydrocarbon chromatograms and Terpanes

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Ste-ranes mass chromatagrams reveal that the oil-bearing sandstone in the Dongying formation features in high gammacerane

low pristane/phytane ratio

and relatively low ratio of C

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aaa20S/(20S+20R) steranes and other mature indexes.Oil-source correlation indicates that oil from the Formation has a relatively close parentage relationship with the Es

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source rock.A comprehensive analysis of the homogenization temperature of organic inclusions

burial history and palaeogeothermal reconstruction

and geochemical characteristics of oil-bearing sands suggests that continuous oil charging lasted about 5.6Ma.During the middle and late periods of tectonic uplifting

about 1000 meters of the upper part of the Dongying Formation was denuded

causing the crude in the Formation biodegraded to different degrees

but leaving the normal alkanes distribution of inclusions basically intact.Since the Neogene

the burial depth of Dongying Formation has been increasing continuously

and the reservoirs has stepped into the stage of adjustment and preservation.