According to observation of cores and thin sections, as well as analyses of fluid pressure features and geochemieal indexes, the cause of fluid overpressure and the mechanism of shale oil enrichment in the Lucaogou Formation, Malang Sag, Santanghu Basin, were discussed. The results show that the shale oil of the Lucaogou Formation is generated in the low mature-premature stage of the source rocks and has the features of high density and high viscosity. The low-permeability and thick source rocks lead to high start-up resistance of fluid, which made it difficult for oil and gas to expel, so the retainment of oil and gas in source rocks is the major cause of formation overpressure. Excellent generation potential and well developed reservoir space are the basis for the oil retention; the pressure produced by hydrocarbon generation is not high enough to overcome the resistance of oil migration, which leads to the enrichment of shale oil. The enrichment degree of shale oil is controlled by hydrocarbon generation and storage capacity of lithofacies at various evolution stages.%通过岩心和薄片观察、流体压力特征和地球化学指标分析,探讨三塘湖盆地马朗凹陷芦草沟组泥页岩系统地层超压形成的原因以及页岩油富集机理.研究表明,芦草沟组页岩油是烃源岩在低成熟—成熟早期演化阶段生成的液态烃,具有高密度、高黏度的物性特点；烃源岩厚度大,渗透率低,造成流体启动阻力增大,油气不具备大规模向外排运的条件而滞留在源岩层中,其为超压形成的主要原因.芦草沟组泥页岩生烃潜力大,源内储集空间发育,是其生成的油气滞留其中的基础；生烃造成的地层压力不足以突破油气运移的阻力,是页岩油富集的直接原因.页岩油的富集程度受控于不同岩相在不同演化阶段的生烃、储烃能力.
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