关键词: 页岩岩相, 孔隙结构, 陆相页岩油, 四川盆地, 凉高山组

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