Micro‑migration of shale oil and its interaction mechanism with inorganic minerals

Recent studies have pointed to the significance of shale oil micro‑migration, yet visual evidence on this remains limited. In this study, atomic force microscope‑based nano‑infrared spectroscopy and field emission scanning electron microscopy were employed to compare the chemical structures of residual migrated shale oil and in‑situ organic matter and to further investigate their interaction mechanism with inorganic minerals. The results showed that, within the region of interest of residual migrated shale oil, the proxy for the hydrogen‑to‑carbon ratio‑ a signature of aliphatic methylene‑ exhibited an increase, while the proxy for the oxygen‑to‑carbon ratio‑ a characteristic signature of aromatic carbonyl‑ showed a decline. Quantitative analysis further revealed the differential attenuation of shale oil components during micro‑migration, with aromatic carbonyl exhibiting the strongest attenuation, followed by aromatic carbon‑carbon and aliphatic methylene. In contrast, the in‑situ organic matter exhibited sharp boundaries with adjacent minerals and showed no clear evidence of micro‑migration. Furthermore, atomic force microscope‑based nano‑infrared spectroscopy mapping indicated differential interactions between organic functional groups and inorganic minerals. Compared with aromatic components, aliphatic components showed a higher micro‑migration trend, mainly through relatively weak interactions with inorganic minerals. These findings provide nanoscale evidence for shale oil micro‑migration and offer valuable mechanistic insights into organic‑inorganic interactions, with implications for sweet spot prediction in unconventional shale oil reservoirs. Document Type: Original article Cited as: Jia, L., Gao, Z., Li, Z., Liu, Z., Oliva, R., Bai, L. Micro‑migration of shale oil and its interaction mechanism with inorganic minerals. Advances in Geo‑Energy Research, 2026, 21(2): 185‑197. https://doi.org/10.46690/ager.2026.08.08