Direct pore scale numerical simulation of colloid transport and retention. Part I: Fluid flow velocity, colloid size, and pore structure effects

In this study, we have developed a combined lattice Boltzmann-smoothed profile method to explore coupled mechanisms governing transport of colloids and their retention in porous media. We have considered flow in a constricted tube and included hydrodynamic, gravity, buoyancy, van der Waals and electrostatic forces to simulate colloid transport and aggregation. A major advantage of this complete formulation is that it does not require any common assumptions which neglect the effects of inter-particle forces (e.g., dilute suspension, or clean bed filtration), and pore structure changes due to colloid retention. The results show an increase in colloid aggregation and surface coverage as pore velocity decreases. However, the pore void fraction and its conductivity show a reduction with decreased velocity. In the presence of a secondary energy minimum, rolling of colloids on the grain surface is demonstrated to be the major mechanism that prevents pore clogging. Details of these observations are provided and a comprehensive sensitivity analysis of model parameters is performed and discussed.