Computing contact angles for oil-water-rock systems via thermodynamic integration

Area of Science:

• Materials Science
• Chemical Engineering
• Computational Chemistry

Background:

• Wettability, determined by contact angle, is crucial for enhanced oil recovery (EOR).
• Experimental contact angle measurements for oil-water-rock systems are costly and time-consuming due to slow adsorption equilibrium.
• Molecular simulations provide an efficient alternative for calculating contact angles.

Purpose of the Study:

• To compute oil-water contact angles on silica surfaces using molecular simulations.
• To investigate the influence of silica surface chemistry (Q2, Q3, Q4) on wettability.
• To demonstrate the utility of the cleaving wall technique for interfacial free energy calculations.

Main Methods:

• Utilized the cleaving wall technique to calculate solid-liquid interfacial free energy.
• Employed Young's equation to determine the oil-water contact angle.
• Modeled silica surfaces using the INTERFACE force field.
• Performed simulations using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS).

Main Results:

• Calculated contact angles for three silica surface chemistries: Q2, Q3, and Q4.
• Found that Q2 and Q3 silica surfaces exhibit complete wetting by water.
• Determined that the Q4 silica surface is partially non-wetted by water.

Conclusions:

• Molecular simulations, specifically the cleaving wall technique, accurately predict oil-water contact angles on silica.
• The INTERFACE force field and LAMMPS enable efficient computation of wettability for EOR applications.
• This approach facilitates broader use of molecular simulations for complex fluid-solid systems.