Molecular insights into fluid-solid interfacial tensions in water + gas + solid systems at various temperatures and...

Area of Science:

• Geophysics
• Materials Science
• Chemical Engineering

Background:

• Fluid-solid interfacial tension is critical for geological storage of greenhouse gases and enhanced geo-resource recovery.
• Understanding these properties is essential for optimizing subsurface processes.
• However, fluid-solid interfacial behavior is not extensively studied.

Purpose of the Study:

• To investigate fluid-solid interfacial properties in multi-component systems.
• To determine the influence of temperature, pressure, and wettability on interfacial tension.
• To provide insights into interfacial phenomena relevant to geological applications.

Main Methods:

• Extensive molecular dynamics (MD) simulations were performed.
• Simulations covered three-phase systems: H2O + gas (H2, N2, CH4, CO2) + rigid solid.
• Conditions varied: temperature (298–403 K), pressure (0–100 MPa), and wettability (hydrophilic, neutral, hydrophobic).

Main Results:

• Vapor-solid interfacial tension is significant when fluid-solid interaction is strong or contact angle is near 90°.
• Increasing temperature decreases H2O liquid-solid interfacial tension but increases H2O vapor-solid interfacial tension.
• Pressure significantly affects H2O-solid interfacial tension in systems with CH4 or CO2, but not with H2 or N2.
• Gas-solid interfacial tension increases with pressure and gas-solid interaction, but decreases with higher temperatures.
• The impact of gases on contact angle follows the order: H2 < N2 < CH4 < CO2.

Conclusions:

• Interfacial tension behavior is complex and highly dependent on system composition, temperature, and pressure.
• The assumption of pressure-independent interfacial tension in Neumann's method requires careful consideration for non-hydrophilic surfaces with strong gas-solid interactions.
• Results offer crucial data for modeling and optimizing geological processes involving fluid-solid interfaces.