Microscopic Mechanisms for the Dynamic Wetting of a Heavy Oil Mixture on a Rough Silica Surface

Molecular dynamics (MD) simulations and optical contact angle measurements were performed to shed light on the microscopic mechanisms for the dynamic wetting of heavy oil on rough silica surfaces. The surface wetting process was characterized by interaction energy, wettability transition, density profile, and penetration of each oil fraction, while competitive adsorption between oil and water droplets on rough surfaces was also investigated. Results highlighted the role of asphaltenes on the distribution and penetration of resins and aromatics, which might become either a driving force or mass transfer resistance for the wettability transition on rough surfaces. The competitive adsorption process was divided into three steps including water bridge formation, water penetration, and oil penetration. Water penetration promoted oil penetration by providing a channel for asphaltene invading. The overall tendency of simulation results agreed experimental observations. To our knowledge, this was the first attempt to gain atomistic insights into the heavy oil adsorption on rough mineral surfaces. Future works should focus on the interactions between heavy fractions of crude oil and a rough mineral surface, while oil mixture models involving asphaltenes should be encouraged in MD simulations for better interpreting the adsorption of oil contaminants in soils.