Quantitative Insights into Atomic Scale Oil–Clay Adhesion Governing Shale Oil Retention and Mobility

Nanoscale adhesion at oil–solid interfaces plays a central role in fluid retention, wettability regulation, and mass transport in energy and environmental systems. Yet the interfacial adhesion strength between complex hydrocarbons and individual clay minerals remains poorly quantified. Here, we combined atomic force microscopy (conducted in air at ~25 °C and ~40% relative humidity) with cryogenic scanning electron microscopy and surface wettability analysis to systematically probe oil–mineral adhesion on four representative clay minerals, that is, chlorite, illite, kaolinite, and montmorillonite. A clear adhesion hierarchy was established as montmorillonite (30.6 ± 7.3 nN) < kaolinite (41.3 ± 2.4 nN) < illite (52.1 ± 2.2 nN) < chlorite (70.9 ± 2.6 nN), significantly stronger than that of silica as a blank control (15.8 ± 0.7 nN). Mechanistic analysis revealed that the interfacial adhesion was likely governed by cooperative hydrogen bonding, dipole–dipole interactions, cation bridging (Mg 2+ , Fe 2+ , Ca 2+ , K + ), and local Lewis acid–base coordination arising from the intrinsic surface of clay minerals. Chlorite and illite exhibited abundant polar sites and exposed cations that generate strong binding to hydrocarbon molecules, whereas reduced interlayer hydration in montmorillonite suppresses effective interfacial coupling. This work established a quantitative framework linking surface functional groups and structural defects to nanoscale oil–solid adhesion, offering fundamental insights into interfacial mechanics relevant to fluid transport, separation, and hydrocarbon‐processing technologies.