渤海湾盆地梁家楼地区油气充注的分子示踪

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

梁家楼油田是发育在渤海湾盆地济阳坳陷东营凹陷沙三中亚段的一个深水浊积扇,精细油源对比表明,其油气主要来源于沙三下亚段和沙四上亚段2套不同沉积环境下形成的优质烃源层。运用分子成熟度梯度、含氮化合物等指标对不同原油族群的示踪研究结果表明,该油田油气有3个主要充注点,分别从西北、东北和南部3个方向沿断层和砂体向梁北、梁中和梁南块进行垂向和侧向运移,并充注成藏;尽管主要成藏期均发生在明化镇组沉积时期,包裹体分子记录结果仍然表明沙四段油气的充注早于沙三段。

Liangjialou Oilfield is a deep-water turbidite fan developed in the middle part of the 3rd member of Shahejie Formation （Es^3） in the Dongying Sag of the Jiyang Depression, the Bohai Bay Basin. The detailed oil-source correlation study shows that oil in this oilfield 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 [a]/[c] and the 4-/1-methyl dibenzothiophene （MDBT）, both indicate that oil in Liangjialou Oilfield 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 Oilfield. Biomarkers in oil inclusions suggest that oil originated from Es4 had filled into this oilfield earlier than that from Es3, although the filling events of both sources of oil occurred in the same Minghuazhen Formation of the Neocene period.