Research progress and prospects of characterization technology of shale oil occurrence states

The characterization of shale oil occurrence state is a hot topic of concern for many scholars and explorers, and it is also a challenging problem in the exploration and development evaluation of shale oil. This study systema-tically summarizes the current research progress on the visual and quantitative characterization of shale oil occurrence space, experimental techniques for the quantitative characterization of oil/hydrocarbon in different occurrence states, and characterization technology of molecular dynamics simulation. The advantages and limitations of the main characterization techniques are discussed, issues needing attention in the application process are highlighted, and the key research directions of shale oil occurrence characterization technology are explored. Based on the acquisition of sealed, pressure-preserved core samples and the use of liquid nitrogen freezing for sample preservation, future research on shale oil occurrence state characterization technology should focus on the following four aspects: (1) visualization characterization technologies for shale oil occurrence characteristics using ultra-low-temperature fluorescence spectroscopy, laser scanning confocal microscopy, and environmental scanning electron microscopy, as well as their combination technologies; (2) in-situ micro-zone online analysis technology for the occurrence state and components of retained oil in shale laminae; (3) quantitative characterization technology for fluid occurrence space and occurrence state under ultra-low-temperature and geological conditions using two-dimensional nuclear magnetic resonance; (4) molecular dynamics simulation technology for shale oil occurrence state within multi-scale pore-fracture systems under near-geological conditions. The improvement and development of shale oil occurrence state characterization technology should be advanced through multi-technology combination and technological innovation, so as to achieve near-in-situ, visual, and quantitative characterization of shale oil occurrence space, occurrence forms, occurrence states, and components. This will provide a reliable scientific basis for efficiently supporting the evaluation of oil content, occurrence state, and mobility, as well as the selection of shale oil sweet spot intervals, and the reasonable assessment and graded evaluation of resources in China's continental organic-rich shale series.