南贝尔凹陷下白垩统油源分析及其成藏意义

南贝尔凹陷下白垩统发育3套暗色泥岩,通过对南贝尔凹陷下白垩统烃源岩和油砂进行地化分析,分析其生物标志化合物组成和分布特征,进行油源对比。综合分析认为,只有南屯组暗色泥岩是优质烃源岩,其烃源岩分布决定了油气藏的平面分布,在构造高部位已发现低成熟稠油。该组烃源岩发育于深水、弱还原淡水湖相的沉积环境,其烃源岩中五环三萜烷含量较高,以C30霍烷占优势,C29霍烷次之,C30重排霍烷和伽马蜡烷含量低,规则甾烷含量较高并以C29甾烷为主,含有少量的孕甾烷、升孕甾烷和重排甾烷。

Analysis of the Lower Cretaceous source rocks in Nanbeier depression and the implications for hydrocarbon accumulation

There are three sets of dark shale developed in Lower Cretaceous in Nanbeier depression.In this paper,the biomarkers and distribution features of the Lower Cretaceous source rocks and oil sands in Nanbeier depression were analyzed and the oil sources were compared with geochemical methods.Comprehensive analysis indicate that only the dark shale in Nantun formation is quality source rocks and its distribution determines the plane distribution of the hydrocarbon reservoirs with low maturity heavy oil discovered at the structural high.These source rocks were developed in a deep,weakly reduced light water lacustrine sedimentary environment.The source rocks are rich in pentacyclic triterpanes with C30 hopane being the dominant,followed by C29 hopane and small quantities of C30 diahopane and gammacerane.They also have relatively high contents of regular steranes with C29 sterane being the dominant and small quantities of pregnane,homopregnane and diasteranes.