Minimizing Dissolution Effects in CO₂-Water Interfacial Tension Measurements Using the Rising Pendant Drop Method

Area of Science:

• Geochemistry
• Physical Chemistry
• Chemical Engineering

Background:

• Accurate interfacial tension (IFT) measurements are crucial for carbon sequestration and gas hydrate research.
• Conventional pendant drop methods using water-in-gas configurations suffer from density inaccuracies due to CO2 dissolution.
• This leads to significant errors in calculated IFT values, hindering reliable subsurface CO2 storage assessments.

Purpose of the Study:

• To develop and validate a novel gas-in-water pendant drop technique for precise IFT measurements between CO2 and water.
• To overcome the limitations of conventional methods caused by CO2 dissolution and density changes.
• To establish a reliable method for determining CO2/CH4-water IFT under relevant reservoir conditions.

Main Methods:

• Developed a gas-in-water pendant drop technique with continuous injection to create stable CO2 bubbles.
• Minimized CO2 dissolution in the aqueous phase, allowing IFT calculation using pure-phase densities.
• Validated the method with CH4-water systems and systematically measured CO2/CH4-water IFTs from 0-80°C and up to 50 MPa.

Main Results:

• The gas-in-water pendant drop technique provides precise IFT measurements by avoiding density errors.
• IFT values were systematically measured for CO2/CH4-water systems across a wide range of temperatures and pressures.
• Results indicate that IFT stabilizes at lower temperatures with increasing pressure.

Conclusions:

• The developed gas-in-water pendant drop technique offers a significant improvement for accurate IFT determination in CO2-water systems.
• An empirical correlation based on density difference and temperature effectively models the observed IFT behavior.
• This research provides a critical foundation for advancing studies in CO2 storage and gas hydrate formation and dissociation.