In oil reservoirs, a significant amount of oil resides in small pores where nanoscale phenomena dominate wettability and drive the mobility of oil. Nanoscale phenomena hence control the quantity of oil to be recovered on the reservoir scale. However, there are significant scientific challenges in both experimental and computational quantification of wetting phenomena on the nanoscale. Experimentally, the challenge is controlling and characterizing extremely small amounts of liquids on sub-micron length scales. New measurement methods need to be developed in order to obtain high-quality data to be compared with simulation results. Computationally, the challenge is in the determination of adequate inter-molecular force fields, and accounting for multi-body effects requires molecular-level simulations including multiple fluids as well as surfaces. Such simulations strain computational resources. Nevertheless, an improved understanding of nanoscale phenomena to unlock trapped oil reserves demands combined experimental and computational investigation across multiple length scales. By investigating sub-micron oil droplets at an amorphous surface both theoretically and experimentally, we quantify local wetting properties at the nanoscale and probe the intrinsic wettability of the surface. The numerical simulations at the molecular level based on Classical Molecular Dynamics and Coarse-Grained Molecular Dynamics are compared with results obtained by means of high resolution microscopy. Our results demonstrate how the interactions between fluids and solids on the nanoscale determine the wetting behavior of the surface. The quantification of surface heterogeneities and chemical contaminants will enable the investigation of the effects of chemical additives such as polymers and nanoparticles on surface wettability. Ultimately, the results will be linked to mesoscale and macroscale enhanced oil recovery models.

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