Oil-Water Transport in Clay-Hosted Nanopores: Effects of Long-Range
Electrostatic Forces
Abstract
Charged clay surfaces can impact the storage and mobility of hydrocarbon
and water mixtures. Here, we use equilibrium molecular dynamics (MD) and
nonequilibrium MD simulations to investigate hydrocarbon-water mixtures
and their transport in slit-shaped illite nanopores. We construct two
illite pore models with different surface chemistries:
potassium-hydroxyl (PH) and hydroxyl-hydroxyl (HH) structures. In HH
nanopore, we observe water adsorption on the clay surfaces. In PH
nanopores, however, we observe the formation of water bridges because of
the existence of a local, long-range electric field. Our NEMD
simulations demonstrate that the velocity profiles across the pore
depends strongly on water concentration, pore width and the presence or
absence of the water bridge. This fundamental study provides a
theoretical basis for understanding nanofluidics with charged surfaces
and can be applied in such as biological processes, chemical and
physical fields, and the oil and gas extraction in clay-rich formations.