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

油生物标志化合物分布,见长侧链三环,γ-蜡丰较低。

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油既具有正烃奇偶优势，又具有较低甾异构体比值，属于典型低熟油。