Functions of Nanoparticles and Surfactants in Enhanced Oil Recovery: Molecular Dynamics Studies

Abstract The roles of nanoparticles in enhanced oil recovery (EOR) are typically associated with stabilization of foams and emulsions (Fakoya et al. 2017) and with oil detachment due to creation of wedge effect in confined oil-water-rock contact region (Wasan et al. 2003). This publication focuses on these and other functions of nanoparticles in EOR applications, often performed in synergy with surfactant mixtures, e.g. abrasive removal of oil films from rock surfaces, wettability alteration, and improved transport of surfactant molecules through porous media. Conventional and non-equilibrium Molecular Dynamics (MD) techniques were applied to simulate behavior of nanoparticles and surfactant molecules on oil-water-rock interfaces in stationary and flow conditions and compute the energies of interactions between the components of the studied systems as well as interfacial tensions in them. Moving nanoparticles were found to be effective in detachment of oil film from rock surfaces. Increased temperature and addition of surface-active agent further enhance the oil-sweeping capability of colloidal nanosuspensions. Changes in interfacial tension as well as density profile computations showed that functionalized silica nanoparticles and related surfactant-nanoparticle compositions clearly exhibit surface active properties on oil-water interfaces that can be fine-tuned and utilized in EOR applications. The wettability-altering potential and surfactant-transporting capability of nanoparticles are also demonstrated. Oil-sweeping, wettability-altering, and surfactant-transporting capabilities of nanoparticles are demonstrated on the molecular level for the first time. Authors also believe that it is the first systematic numerical study of nanoparticle's and surfactant's contribution to the changes in interfacial tension on oil-water interface.