  Electrokinetic in-situ recovery is an alternative to conventional mining,
relying on the application of an electric potential to enhance the subsurface
flow of ions. Understanding the pore-scale flow and ion transport under
electric potential is essential for petrophysical properties estimation and
flow behavior characterization. The governing physics of electrokinetic
transport is electromigration and electroosmotic flow, which depend on the
electric potential gradient, mineral occurrence, domain morphology, and
electrolyte properties. Herein, mineral occurrence and its associated zeta
potential are investigated for EK transport. The governing model includes three
coupled equations: (1) Poisson equation, (2) Nernst--Planck equation, and (3)
Navier--Stokes equation. These equations were solved using the lattice
Boltzmann method within X-ray computed microtomography images. The proposed
model is validated against COMSOL Multiphysics in a 2-dimensional microchannel
in terms of fluid flow behavior when the electrical double layer is both
resolvable and unresolvable. A more complex chalcopyrite-silica system is then
obtained by micro-CT scanning to evaluate the model performance. The effects of
mineral occurrence, zeta potential, and electric potential on the 3-dimensional
chalcopyrite-silica system were evaluated. Although the positive zeta potential
of chalcopyrite can induce a flow of ferric ion counter to the direction of
electromigration, the net effect is dependent on the occurrence of
chalcopyrite. However, the ion flux induced by electromigration was the
dominant transport mechanism, whereas advection induced by electroosmosis made
a lower contribution. Overall, a pore-scale EK model is proposed for direct
simulation on pore-scale images. The proposed model can be coupled with other
geochemical models for full physicochemical transport simulations.
