北部湾盆地原油地球化学特征与成因类型

通过对北部湾盆地不同凹陷典型原油样品烃类组成特征的定量分析,发现盆地北部的涠西南凹陷所产原油中三环萜烷系列、藿烷系列和甾烷系列等生物标志物的浓度偏高,而芳烃浓度则明显偏低;但对于盆地南部的福山凹陷和迈陈凹陷的原油而言,则表现为三环萜烷系列、藿烷系列和甾烷系列等生物标志物的浓度偏低,而芳烃浓度则明显偏高的特征,表明该盆地北部和南部在沉积环境的性质和烃源岩的地球化学特征等方面存在显著差异.依据原油中甾、藿烷系列的浓度与芳烃浓度间的关系,可以确定不同凹陷所产原油的成因类型,结果表明,北部的涠西南凹陷和南部福山凹陷与迈陈凹陷的原油分属不同的成因类型,而乌石凹陷的原油则介于两者之间,显示过渡类型的特征.

Geochemical characteristics and genetic types of crude oils

Quantitative analyses on hydrocarbon components of typical crude samples from different depressions of Beibuwan basin indicate that the samples from the Weixinan depression in the northern part of the basin have higher concentrations of biomarkers in tricyclic terpanes, hopanes, and steranes, and that from the Fushan depression and Maichen depression in the southern part of the basin have relatively markers, but higher concentration of aromatic hydrocarbons. It suggests that the lower concentration of the biodepositional environment and geochemical characteristics of source rocks vary dramatically in the northern and southern parts of the basin. The distribution of hopanes, steranes and aromatic hydrocarbons can be used in the establishment of the genetic types of crude oils from different depressions of the basin. The results show that the genetic types of crude oils from the Weixinan depression and from the Fushan and Maichen depressions are different, and that the crude oils from the Wushi depression is a intermediate type with a transitional features.