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 lower concentration of the biomarkers

but higher concentration of aromatic hydrocarbons.It suggests that the depositional 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.