Document Type : Original Article

Author

• Sadegh Sadeghzadeh

Associate Professor, Iran University of Science and Technology

Abstract

The integration of nanoparticles (NP) and surfactants is a highly promising strategy for Enhanced Oil Recovery (EOR), particularly in low-permeability reservoirs where conventional water flooding fails. In this work, we employ Molecular Dynamics (MD) simulations to investigate the synergistic role of silica (SiO2) nanoparticles and sodium dodecyl sulfate (SDS) in detaching ultrathin n-dodecane films from model quartz surfaces. Our simulation suite systematically assessed interfacial mechanisms using SiO2 NPs of three diameters (0.5, 1.0, and 2.0 nm) across varying SDS concentrations. The results demonstrate that SDS alone significantly reduces the oil-water Interfacial Tension (IFT). Crucially, the addition of 0.5 nm SiO2 NPs to the SDS system provides a powerful synergy, establishing a two-step detachment mechanism. Quantitatively, the optimal hybrid formulation achieved an ultralow IFT of 0.0004 ± 0.0001 mN/m, representing a >99.99% reduction from the pure water/oil system. Mechanistically, this synergy works by neutralizing attractive forces (reducing van der Waals oil-quartz interaction energy by 87%) while simultaneously amplifying repulsive forces (inducing a net positive electrostatic repulsion of +15.7 kJ/mol) via the formation of a dense, co-adsorbed NP-surfactant wedge-film. This concerted action drastically altered the rock wettability and increased oil mobility. The optimized hybrid system mobilized up to 40 % more n-dodecane molecules into the aqueous phase compared to pure water flooding, achieving a 25% improvement over SDS-only systems. Our findings provide molecular-level insights into the design of high-performance nanofluid formulations for maximizing oil displacement efficiency.

Graphical Abstract

Keywords

• Enhanced oil recovery
• silica nanoparticles
• SDS surfactant
• molecular dynamics
• wettability alteration
• oil detachment
• interfacial tension