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

原油生物标志化合物分布,见侧链三环萜,γ-丰较。

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.

20的原油既具有正烃奇偶优势，又具有较甾萜异构体比值，属于典型的熟原油。