New Hybrid Pore-Scale Simulation Method to Characterize Nanoparticle Transport, Aggregation, and Attachment Behaviors

Abstract

To facilitate the applications of nanoparticles (NPs) for enhancing hydrocarbon production, it is important to understand the transport and attachment behaviors of NPs on a microscopic scale. A novel, hybrid pore-scale simulation method using lattice-Boltzmann (LB) coupled with Langevin-dynamics (LD) is proposed to investigate the transport mechanism of nanoparticles in a microchannel. The LD method is developed to characterize the physics of Brownian motion, thermal fluctuation− dissipation, multi-body hydrodynamics, and particle−particle interactions. A discrete LB forcing source distribution is employed to couple with LD. The random force of NPs, friction force of NPs, van der Waals force, as well as the electrostatic force between NPs and the microchannel are quantified in this Euler−Lagrange method to more accurately simulate the transport and attachment of NPs. Various examples (i.e., single particle relaxation in viscous flow, Brownian motion in the dilute colloid system, and the attachment efficiency of NPs onto channel surface) are implemented to verify the LB−LD method. The controlling factors (i.e., ionic strength, particle diameter, and Reynolds number) are investigated in the attachment process of NPs. The NP with intense Brownian diffusion and weak hydrodynamic effect is prone to have better attachment efficiency. It is observed that a maximum value of attachment efficiency exists as the ionic strength increases to about 0.01 M. Moreover, the ionic strength of the aqueous phase exerts significant impact on the transport behavior of NPs: when the ionic strength is less than 0.005 M, an ordered structure of NP suspensions is formed due to the dominance of electrostatic repulsion force; varying structures of NP suspension are observed with the increase of ionic strength, and when the ionic strength is more than 0.01 M, a clustered structure of NP suspensions is formed by the dominance of van der Waals force. To quantitatively characterize the structure of NP suspensions under varying conditions, a general phase diagram including three flow patterns (isolated, transitional, and clustered regime) is first proposed for NP suspension with specified ionic strength and Reynolds number. The outcomes of this work provide valuable insights into the critical importance of particle size, ionic strength, and hydrodynamic effects on the attachment and transport of NPs in porous media.