Pore scale study of amphiphilic fluids flow using the Lattice Boltzmann model

We study ternary amphiphilic fluid flow at pore scale using a bottom-up Lattice Boltzmann (LB) model. The model introduces a dipole to capture the amphiphilic structure of surfactant molecules, and characterizes microscopic fluid interactions at the kinetic level. We first verify the established model by three examples, i.e., interfacial tension test, phase separation, and droplet dynamics in shear flow. The numerical results show that surfactants reduce the interfacial tension (IFT), and are able to emulsify the amphiphilic fluids, and the contours of the droplets are quantitatively in agreement with the results of level set method. Then we study the droplet dynamics in a confined environment. The surfactants make the droplet easy to deform and break up in shear flow, but inhibit coalescence due to the Marangoni stress. Moreover, there are four typical patterns for droplet collisions, i.e. coalescence, breakup after coalescence, brushing past, and brushing back. Furthermore, we improve the model by considering the wettability reversal effect caused by surfactant adsorption onto walls, and find that surfactants can decrease the critical Bond number for oil detaching from walls by 90%. Finally, we simulate the surfactant-enhanced aquifer remediation (SEAR) or enhanced oil recovery (EOR) process in a 2D porous medium. Surfactants improve the oil recovery in all wetting conditions, but the surfactant loss due to adsorption onto walls diminishes the effect of IFT reduction. (C) 2019 Elsevier Ltd. All rights reserved.