CO2 Wettability of Sandstones: Addressing Conflicting Capillary Behaviors

Abstract

Understanding the capillary and wetting behavior of supercritical CO₂ (scCO₂) 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 scCO₂/water and N₂/water on a Berea sandstone, untreated, then fired, and then exposed to scCO₂ for 28 days. The purpose is to investigate the impact of firing and longer exposure to scCO₂, 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.