The maturity of Chaochang region in Songliao basin is lower, and most of oils still keep odd even predominance of n alkanes.

• 松辽盆地朝长地区原油的成熟度普遍较低，大多数原油仍保留正烷烃奇偶优势，这主要与半咸水咸水环境中藻类母质生源输入有关。