奈曼凹陷烃源岩地球化学特征

Geochemical characteristics of hydrocarbon source rocks in Naiman sag

奈曼凹陷共发育下白垩统沙海组、九佛堂组上段、九佛堂组下段三套烃源岩,其中沙海组烃源岩有机质丰度较高,干酪根以Ⅰ型、Ⅱ_1型为主,处于未熟–低熟阶段,综合评价为中等烃源岩。九佛堂组上段烃源岩生油能力较差;九佛堂组下段烃源岩有机质丰度高,干酪根以Ⅰ-Ⅱ_1型为主,处于成熟阶段,综合评价为好烃源岩,是奈曼凹陷主力烃源岩层。该烃源岩发育于较强还原环境,有机质母质以藻类为主、高等植物为辅的混源类型。

There are three sets of source rocks developed in lower cretaceous Naimen sag, namely Shahai formation, upper part of Jiufotang formation and lower part of Jiufotang formation, among which the organic abundance of source rocks from Shasha formation is higher, the kerogen type is dominated by type Ⅰ and type Ⅱ1, which is in immature–under mature stage and believes to be the middle grading from comprehensive evaluation. The oil generation capacity of the upper Jiufotang formation is poor, while the organic abundance of source rocks in the lower part of Jiufotang formation is high, the kerogen type is dominated by type Ⅰ-Ⅱ1, which is in mature stage and believes to be good source rocks and the main source rock formation in Naiman sag. The source rock is developed in a strong oxygen-free environment, and the parent of organic matter is mixed with algae and supplemented by higher plants.