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井的既具有奇偶优势，又具有较低甾萜构体比值，属于典型的低熟。

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

生物标志化合物分布,见长侧链三环萜,但γ-蜡丰度较低。