Biological marks of the crude oil contain long lateral chain of tricyclic terpane, and the content of gammacerane is low.

原生物标志化合物分布,见长侧萜烷,但γ-蜡烷丰较低。

The crude oils of Chang 20 belong to typical immature oil which have odd even predominance and lower ratios of sterane and terpane maturity index.

长20井的原有正烷烃奇偶优势，又有较低甾萜烷异构体比值，属于典型的低熟原。