Influence of carbonated brine and CO₂ nanobubbles on the rock-fluid interface of carbonate reservoir rocks

As concerns about climate change grow, conversations worldwide are shifting on how CO₂ emissions affect the atmosphere. As a result, solutions to lessen its effects are being explored. Among the numerous solutions currently in use are the utilization of CO₂ and sequestration by its injection into subsurface reservoirs. Within different industries, its application for field-related operations has also drawn increased interest; in this instance, the geochemical interactions between the injected gases and the rocks are crucial. With an emphasis on zeta potential variations as a measure of surface charge behavior, this study examines the effects of carbonated water and CO₂ nanobubbles (NBs) on the surface charge of carbonate rocks. Understanding these interactions is essential for field-scale applications, as carbonate rock surfaces can undergo charge alterations when exposed to CO₂-rich solutions. The study examined the surface charge of Indiana limestone, Guelph dolomite, Austin chalk and Desert pink samples under controlled settings to understand the dynamic effect of CO₂ on the chemistry of carbonate rocks, particularly when nanobubble technology is used. The findings show that carbonate rocks have different surface charges in seawater, formation water, and deionized water. Moreover, the temperature largely ignored in earlier studies was observed to play a critical role, especially when mineral dissolution serves as a governing mechanism. Interestingly, carbonated water showed greater mineral dissolution than CO₂ nanobubble solutions, suggesting that CO₂ speciation significantly impacts surface charge due to the higher dissolved CO₂. Additionally, the interaction of both fluids (carbonated water and CO₂ NBs) resulted in unstable surfaces. These results highlight the roles of temperature and water chemistry in determining the surface charge behavior of carbonate rocks at the solid–liquid interface, thus providing a fundamental understanding of their functions in interfacial phenomena.