Formation mechanisms of residual water in CO2-water-rock systems: Effects of the CO2 phase.

This study focused on the effects of the CO 2 phase on the formation mechanisms of residual water. Based on nine groups of core-flooding experiments, the order of residual water saturation was gaseous CO 2 > supercritical CO 2 > liquid CO 2 , and a quantitative power function relationship between residual water saturation and displacement time for different CO 2 phases was proposed. The experimental results show that when CO 2 transitions from the gaseous phase to the supercritical phase and then to the liquid phase, the decrease in the interfacial tension and cosine value of the contact angle in two-phase flow can lead to a decrease in residual water saturation. Meanwhile, an increase in the viscosity ratio of two-phase flow weakens the viscous fingering phenomenon and can also lead to a decrease in residual water saturation. However, the log Ca -log M stability phase diagram reveals that the viscous force is the primary factor influencing all core-flooding experiments. [Display omitted] • Effects of CO 2 phase on the formation mechanisms of residual water are studied. • Order of residual water saturation is gaseous CO 2 > supercritical CO 2 > liquid CO 2. • Viscous force is the main factor influencing CO 2 -water displacement in this study. [ABSTRACT FROM AUTHOR]