Prediction of Viscosity of the Oil-Surfactant-Brine Microemulsion Phase Using Molecular Dynamics Simulations

Estimation of the microemulsion dynamic viscosity under reservoir conditions is important as it is directly connected to the oil recovery predictions and optimization design. The dynamic viscosity of the microemulsion phase depends on not only the phase behavior but also the microstructure of the phase. Here, we aim to fundamentally understand and quantify the relevance of microemulsion phase viscosity to the surfactant concentration, water salinity, pressure, and temperature by conducting numerical design of experiments using molecular dynamics (MD) simulations. We use the Einstein relation, which is a reformulated Green-Kubo formula, to calculate and track the change in viscosity with the above-mentioned conditions. After our model is validated by comparing the simulated results with the available experimental data, the viscosity peaks or percolation thresholds are investigated for a specific range of salinity and surfactant concentrations. The outcome of this research results in achieving optimized rheological properties of oil-brine interfacial systems for oil recovery operations. © 2024 The Authors. Published by American Chemical Society.