Minimizing Dissolution Effects in CO ₂ –Water Interfacial Tension Measurements Using the Rising Pendant Drop Method

Measuring the interfacial tension (IFT) between CO₂ and water is critical for understanding carbon sequestration in depleted oil reservoirs, saline aquifers, and shallow seabeds. In the commonly used pendant drop method, IFT is not measured directly but calculated from the drop's capillary length squared and the user-specified density difference (Δ<i>ρ</i>). However, in the conventional water-in-gas configuration, CO₂ dissolution continuously increases the aqueous-phase density, making the user-defined Δ<i>ρ</i> inaccurate and causing significant errors in the calculated IFT. To overcome this, we developed a gas-in-water pendant drop technique where continuous injection creates stable CO₂ bubbles with negligible dissolution in the aqueous phase, enabling precise IFT determination using pure-phase densities. Validated with CH₄-water systems, this method was used to systematically measure CO₂/CH₄-water IFTs from 0-80 °C and up to 50 MPa. Results show IFT stabilizes at low temperatures with increasing pressure, and an empirical correlation based on density difference and temperature effectively captures the behavior, providing a critical foundation for CO₂ storage and gas hydrate studies.