Dynamic evolution of the CO2-brine interfacial area during brine imbibition in porous media

•The dissolution of brine injection into a CO2-filled packed bed was investigated.•An image analysis technique was developed to determine the interfacial area.•The effects of Re, gravity and heterogeneity on the interface were analysis. Explicit knowledge on the two-phase interface evolution during CO2 dissolving in brine provides accurate predictions on the subsurface behavior of long-term CO2 storage. In this research, the interfacial areas of CO2-unsaturated brine were dynamically measured during multiphase flow using 3D quantitative analyses. The two-phase interfaces during brine imbibition were divided into three terms based on their attributes, i.e., ganglia, cluster and singlet. The evolution terms of the interfaces were interesting, as their fates showed wide evolution patterns due to the diverging effects of the Reynolds number (fluid velocity × length scale/fluid viscosity) and gravity. The brine bypassed the CO2, and the interface evolved with the development of a priority path under a heterogeneity impact. Relying on the approach of the slice-averaged and volumetric measurement, the effects of forces and heterogeneity on the CO2-unsaturated brine interface were evaluated on different directions. Linear regression of the clouded data points exploited the validity of the power-law distribution from number of trapped cluster to frequency of interfacial area, and the max interfacial areas and variance decreased, while the mean interfacial area increased with brine saturation. Slice-averaged CO2-brine interfacial areas normalized by volume or geometric surface area decreased linearly with the brine saturation at different Reynolds numbers.