Oil migration in shale formations across multiple scales from nanometers to meters, a topic without receiving sufficient attention, is of great significance to the accumulation and production of shale oil. Compared with oil migration in conventional reservoirs usually with a long distance, shale oil migration is much shorter, which challenges the applicability of conventional characterization methods for shale formations. In addition, shale oil migration in different types of shale formations occurs at different scales, and their source-reservoir configuration, accumulation mechanism, and exploration plans are also different, greatly complicating a cost-effective and sustainable exploitation of shale oil resources. Accordingly, this review summarizes the experimental methods for characterizing the shale oil migration across multiple scales, and reveals the migration characteristics in three different types of shale oil formations of typical basins in China and USA. The shale oil migration distance in “pure shale-type” formation is the shortest and mainly in nanometer-microns scale. The migration characteristics of “pure shale-type” shale oil are difficult to reveal directly due to its ultra-short migration distance, which may be indicated by the microscale compositional changes at the surface of minerals being interacted with organic fluids and requires additional innovations on the shale oil migration characterization methods with a high accuracy. The shale oil migration distance in laminated-type shale oil formation is at the lamina (micron-millimeter) scale and the shale oil migrates from the organic matter-rich to -lean laminae. The lamina type (felsic, carbonate, or clayey) significantly affects the migration and enrichment of shale oil by providing different types of pore spaces and migration pathways. The shale oil “composition change” method effectively indicates the migration characteristics of shale oil among different laminae, while the “hydrocarbon expulsion efficiency” method is not accurate for the laminated-type shale oil. The migration distance of sandwich-type shale oil is at the millimeter-meter scale, which is the largest among three types of shale oil formations. The reservoir space is mainly intergranular pores and the shale oil migrates from the overlying or underlying organic matter-rich shale to the siltstone interlayer. Both “hydrocarbon expulsion efficiency” and “composition change” methods can be used to clarify the migration characteristics of sandwich-type shale oil. This review overall has a great significance for deeply understanding the characterization methods and migration characteristics of different types of shale oil formations at multiple scales.

中文翻译：

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多尺度页岩油运移：表征方法和不同模式的回顾


页岩地层中石油从纳米到米多个尺度的运移虽然尚未受到足够重视，但对页岩油的富集和生产具有重要意义。与常规油藏中石油运移通常距离较远相比，页岩油运移距离较短，这对页岩地层常规表征方法的适用性提出了挑战。此外，不同类型页岩地层中页岩油的运移规模不同，其源储结构、成藏机制和勘探方案也不同，使得页岩油资源的经济、可持续开采变得更加复杂。据此，本文总结了多尺度表征页岩油运移的实验方法，揭示了中美典型盆地3种不同类型页岩油的运移特征。 “纯页岩型”地层中页岩油运移距离最短，主要在纳米-微米尺度。 “纯页岩型”页岩油运移距离超短，难以直接揭示其运移特征，可能通过矿物表面与有机流体相互作用的微观成分变化来表征，需要额外的创新高精度的页岩油运移表征方法。层状页岩油地层中页岩油的运移距离为纹层（微米-毫米）尺度，页岩油从富含有机质的纹层向贫瘠的纹层运移。 纹层类型（长英质、碳酸盐质或粘土质）通过提供不同类型的孔隙空间和运移通道，显着影响页岩油的运移和富集。页岩油“成分变化”法能有效表征页岩油在不同纹层间的运移特征，而“排烃效率”法对于纹层型页岩油则不准确。夹层型页岩油的运移距离为毫米级，是三类页岩油层中运移距离最大的。储集空间主要为粒间孔，页岩油从上覆或下伏富有机质页岩运移至粉砂岩夹层。 “排烃效率”和“成分变化”方法均可用于明确夹层型页岩油的运移特征。总体而言，该综述对于深入认识不同类型页岩油地层多尺度表征方法和运移特征具有重要意义。