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Understanding the capillary and wetting behavior of supercritical CO2 (scCO(2)) and brine in reservoir rocks is crucial for reliable predictions of geologic carbon storage, as it strongly impacts CO2 migration and residual trapping in the reservoir. The wetting state of such systems can be assessed through laboratory measurements of the capillary pressure characteristic curve. However, while some studies reported consistent scaling with strongly water wet systems, some others observed deviations from hydrophilic conditions. We present core-flooding drainage capillary pressure measurements using scCO(2)/water and N-2/water on a Berea sandstone, untreated, then fired, and then exposed to scCO(2) for 28 days. The purpose is to investigate the impact of firing and longer exposure to scCO(2), two potential sources for variability in experimental observations, on capillarity and wettability. The results show excellent agreement among all the core-flooding capillary pressure data, suggesting no change in wetting state due to firing or longer exposure.

Plain Language Summary Carbon capture and storage is a promising technology to limit anthropogenic greenhouse gas emissions responsible for global warming. It consists in capturing CO2 from large point source emitters and transporting it to a site where it will be injected in deep geological formations for storage. One important property of a rock in the presence of two nonmiscible fluids (here CO(2 )and formation brine) is the preference of one fluid over another to be in contact with the rock's surface, a property called wettability. Wettability directly impacts the way injected CO(2 )will flow in the subsurface and will stay trapped in the rock. However, although considerable effort has been made in the past decade to determine the wettability of storage rocks with respect to CO2 and brine, there is considerable variability in the reported data. This study focuses on two particular factors that could lead to the differences in experimental observations: the preparation of the rock sample used for measurements and the duration of exposure to CO2. We observed no change of wettability and general conditions favorable for CO2 trapping in the studied rock, a sandstone.