Comprehensive molecular scale modeling of anionic surfactant-asphaltene interactions

Abstract

Asphaltene is the heaviest fraction of oil sands/bitumen, which is also the leading cause of these oil resources' high viscosity value. Nowadays, steam with additives is used to make oil sands/bitumen mobile through a reservoir by lowering their viscosity. Additives can be air, solvent, non-condensable gas (NCG), and surfactants. Surfactants can be used not only as a chemical additive in thermal oil recovery but also as an asphaltene inhibitor or dispersant. Formulating surfactants needs thorough and reliable knowledge about molecular interactions between asphaltene and surfactants. This paper has used molecular dynamics (MD) simulation to evaluate these interactions at thermodynamic conditions close to thermal-based oil recovery conditions. Three different asphaltene architectures observed in Athabasca oil-sands are used to examine the molecular interactions between asphaltenes and anionic surfactants.Moreover, the effect of a benzene ring on inter-molecular interactions at different temperatures is thoroughly investigated. Various analyses, including a radial distribution function (RDF), hydrogen bonds, and interaction energies, are employed to support the outcomes. Based on MD simulation results, the presence of a benzene ring in a surfactant structure can increase the interactions, especially van der Waals interactions. Moreover, the position and number of heteroatoms in asphaltene architecture play a vital role in asphaltene behavior in a solution. Results of this work give solid knowledge regarding asphaltene and surfactant interactions and provide helpful information for formulating surfactants, whether as an asphaltene inhibitor/dispersant or a steam additive for in-situ bitumen recovery.