Abstract: Dark-colored strata within continental lacustrine sedimentary systems are primary target for shale oil exploration in China. Well Lutan1, deployed by the PetroChina Southwest Oil and Gasfield Company, recently achieved a notable breakthrough in shale oil exploration in the First Member of Lianggaoshan Formation. The well recorded an oil production of 45.7 t/d and a gas production of 5 900 m³/d, marking a significant advancement in shale oil exploration within the syncline area of eastern Sichuan Basin. Based on successful experience with Well Lutan1, this paper summarizes the accumulation patterns and primary controlling factors of shale oil in the First Member of Liangshan Formation in the syncline area of eastern Sichuan Basin. These are elucidated as below. (1) The Lianggaoshan Formation shale can be classified into three types, i.e., siliceous shale, argillaceous shale and mixed shale. Among them, siliceous shale is the most developed, followed by argillaceous shale, while mixed shale is extremely rare. The argillaceous shale formed in deep lacustrine basin, characterized by well-developed laminae and high organic matter content, represents the most favorable lithofacies for hydrocarbon exploration. (2) The reservoir spaces are predominantly intergranular pores of clay minerals and organic pores. These pores, along with shrinkage cracks generated during thermal evolution, contribute the majority of micropores and mesopores. In contrast, intergranular pores among brittle particles, intra- and inter-granular dissolution pores, and structural microfractures provide support for the formation of macropores, despite their limited occurrence. (3) A mechanism for high shale oil production and enrichment has been proposed, emphasizing that deep lacustrine basin environments control the development of high-quality shales, characterized by "rich laminae and abundant argillaceous minerals". Sustained favorable sealing conditions facilitate the achievement of "overpressure, hydrocarbon retention, and pore preservation". Both shale quality and continuous thickness are critical factors controlling the high production potential of lacustrine shale oil. The key factors for high-yield lacustrine shale oil are the continuous thickness of the shale, sealing conditions, and shale quality. In quiet, low-energy environments, the thicker the high-organic-matter, laminated argillaceous shale, and the wider and gentler the syncline structure, the stronger its hydrocarbon generation and storage capabilities. Thus, this configuration is more conducive to achieving high shale oil production. These findings provide theoretical insights and practical guidance for lacustrine shale oil exploration in eastern Sichuan Basin.

Key words: shale lithofacies, pore structure, continental shale oil, Sichuan Basin, Lianggaoshan Formation

摘要： 陆相淡水湖盆沉积体系中的暗色地层是中国页岩油勘探的重要领域。近期,中国石油西南油气田公司部署的禄探1井在凉高山组一段(凉一段)获得产油量为45.7 t/d、产气量为5 900 m³/d的突破,实现了四川盆地东部向斜区页岩油勘探的新进展。基于禄探1井的成功经验,总结了川东向斜区凉一段页岩油的成藏富集规律和主控因素:①1凉高山组页岩可划分为硅质页岩、黏土质页岩和混合质页岩3类,其中,硅质页岩最为发育,黏土质页岩次之,混合质页岩极少;形成于深水湖盆的黏土质页岩纹层丰富、有机质含量高,是最有利的勘探岩相类型。②黏土矿物晶间孔和有机孔是最主要的储集空间类型,其自身及热演化过程中形成的收缩缝贡献了微孔和介孔的主要部分;脆性颗粒粒间孔、粒内/粒间溶孔和构造微裂缝数量较少,是宏孔的主要来源。③提出页岩油高产富集机理,即深水湖盆环境控制着"富纹层、多黏土矿物"优质页岩的发育,持续良好的封闭条件有利于实现"超压、留烃、保孔",而页岩的品质和连续厚度则共同控制着湖相页岩油的高产。湖相页岩能否高产的关键取决于页岩层的连续厚度、封闭条件和页岩品质3方面:在安静低能环境下形成的高有机质纹层状黏土质页岩厚度越大、所处向斜构造越宽缓,其生烃/储烃功能越强,越有利于实现页岩油高产。上述成果可为川东地区湖相页岩油勘探提供理论参考和实践指导。

关键词: 页岩岩相, 孔隙结构, 陆相页岩油, 四川盆地, 凉高山组