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 depend 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.

Green Fabrication of Porous Adsorbent with Structural Evolution of Mixed-Dimension Attapulgite Clay for Efficient Removal of Methylene Blue and Sustainable Utilization

“…The adsorption sites of porous adsorbents had two sources: one was the inorganic MDAPT clay, and the other was the sulfonic acid group of AMPS. Among them, MDAPT clay could interact with MB via nanopore structure and required no activation energy, whereas the sulfonic acid group for MB adsorption was driven by concentration mass transfer and required a large activation energy . When the MB concentration was low, MB only was absorbed by the porous adsorbent at the surface due to the lower mass transfer driving force.…”

Molecular Insights into the Salinity Effects on Movability of Oil–Brine in Shale Nanopore-Throat Systems

“…In this work, a slit-shaped Illite pore-throat model filled with oil–brine mixtures was constructed (Figure ). The mineral framework with 4 nm throat and 8 nm pore was built by replicating unit cells of Illite (space group: C 2/ m , a = 5.193 Å, b = 8.994 Å, c = 10.204 Å, α = 90°, β = 101.77° and γ = 90°) with chemical formula of K­[Si 7 Al]­(Al 4 )­O 20 (OH) 4 . , Illite was selected to construct pore walls since it is the typical representation of clay in shale. − The isomorphic substitutions in the tetrahedral sheets follow Loewenstein’s rule . The Illite framework was cleaved along the (010) plane to construct the pore-throat system.…”

“…In this work, a slit-shaped Illite porethroat model filled with oil−brine mixtures was constructed (Figure 1). The mineral framework with 4 nm throat and 8 nm pore was built by replicating unit cells of Illite 54 55,56 Illite was selected to construct pore walls since it is the typical representation of clay in shale. 57−59 The isomorphic substitutions in the tetrahedral sheets follow Loewenstein's rule.…”

Optimal nanocone geometry for water flow

“…Meanwhile, under the control of nanoconfined impact, water viscosity inside nanopores behaves differently, compared with that in bulk state 30,31,32 . Stemming from the fluid‐surface interactions, additional force, exerted by the surface as a form 33 of attraction or repulsion term, is imposed on nanoconfined water molecule, which depends on the distance between water molecules and surface. In the case of hydrophilic surface, water molecules, adjacent to the surface, tend to adsorb or stick on surface, and the adsorption thickness can reach up to 2–3 molecular diameter as reported 34–36 .…”