MOLECULAR TRACING OF OIL FILLING IN LIANGJIALOU AREA, THE BOHAI BAY BASIN

Liangjialou Oil field is a deep-water turbidite fan developed in the middle part of the 3rd member of Shahejie Formation(Es3) in the Dongying Sag of the Jiyang Depression,the Bohai Bay Basin.The detailed oil-source correlation study shows that oil in this Oil field mainly sources from two sets of excellent source rocks formed under different depositional environments in the lower part of Es3 and the upper part of Es4.Two geochemical indicators,the molecular maturity and the nitrogen compound,are used to study the roles in tracing the crude oil families from different sources.The results show that two ratios of the molecular tracers,the benzocarbazole and the 4-/1-methyl dibenzothiophene(MDBT),both indicate that oil in Liangjialou Oil field has 3 main filling points,with oil migrating vertically and laterally from the northwest,the northeast and the south respectively along the existing faults and sand bodies into the northern,the middle and the southern Liangjialou Oil field.Biomarkers in oil inclusions suggest that oil originated from Es4 had filled into this Oil field earlier than that from Es3,although the filling events of both sources of oil occurred in the same Minghuazhen Formation of the Neocene period.