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井的原既有烷烃奇偶优势，又有较低甾萜烷构体比值，属于典型的低熟原。

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

原标志化合分布,见长侧链三环萜烷,但γ-蜡烷丰度较低。