马朗凹陷芦草沟组页岩油形成机理与富集条件

三塘湖盆地马朗凹陷二叠系芦草沟组源内页岩油的发现对常规油藏勘探理论提出了巨大的挑战。在大量岩心观察、薄片鉴定的基础上，结合地质条件、分析化验、试油情况，深入研究了本区页岩油形成机制与富集条件。研究结果表明，芦草沟组页岩油主要是烃源岩在低熟-成熟早期演化阶段生成的原地滞留原油，页岩油具有高密度、高黏度的物性特点和低饱芳比、高非沥比的族组成特征。页岩油在源岩中的赋存形式主要有两种，即干酪根表面的吸附态及基质孔隙、纹层与水平层面间、微裂缝中的游离态。页岩油大面积连续分布在源岩层中，没有明显的油水界面，油水分异差，产油水比例取决于烃源岩的演化程度，需人工改造才能获得产能，单井产量小但稳产时间长。页岩油富集的控制因素为：①具有生成、储集大量石油的条件；②较好的保存条件，导致大量排烃的断裂不发育。

Formation mechanism and enrichment conditions of Lucaogou Formation shale oil from Malang sag, Santanghu Basin

Tight reservoirs were found in the Permian Lucaogou Formation of Malang sag in Santanghu Basin, which is a great challenge to the conventional oil-gas exploration theory. Based on the core observation and thin section identification, then combined with geological conditions, analytical data and testing for oil, we investigated in detail the formation mechanism and enrichment condition of Lucaogou Formation shale oil. The research result showed that Lucaogou Formation shale oil is a kind of low-maturity oil generated at the low-maturity to early-mature stage of source rocks and retained in-situ. The oil was characterized by high density, high viscosity, low saturated/aromatic hydrocarbon ratio and high non-hydrocarbon/asphalt ratio. There are two main forms for the occurrence of the shale oil in source rocks, one is an absorbed state on kerogen surface and the other is a free state in matrix pores, interlayers between laminae and flat seams, and microfissures. Besides, the shale oil is continuously distributed in a large scale in source rocks, with no obvious oil-water boundary and being poor in oil/water differentiation. The oil-water ratio in production depends on the thermal maturity of source rocks and wells cannot get the deliverability without artificial transformation. The yield of a single well is low but stable for a long time. There are two controlling factors for the shale oil enrichment, one is good conditions for generating and entrapping large amounts of oils, and the other is favorable preservation conditions of oils in source rocks due to undeveloped faults for oil expulsion.