Nanofluid-assisted enhanced sealing containment of caprocks for efficient geological CO₂ storage

Millions of tons of CO₂ are stored annually in geological formations in order to reduce greenhouse gas emissions, relying on caprock as a seal to prevent CO₂ leakage. The wettability of caprock is crucial for its effectiveness, and can be altered by organic acids present in the storage media. The present study investigates the impact of stearic acid on the CO₂ wettability of shale, along with the potential of alumina nanofluids to reverse this effect. Using contact angle measurements, X-ray diffraction, and other analytical methods, the study reveals that stearic acid increases the CO₂ wettability of shale, making it more difficult to contain CO₂ at higher pressures. Specifically, stearic acid-aged shale samples became CO₂-wet at 16 MPa, thus leading to lower capillary entry pressure and reduced containment capability. However, treatment with alumina nanofluids improves the wettability of shale to intermediate levels, with a 0.25 wt% concentration yielding optimal results. This adjustment also results in positive CO₂ column heights, thus suggesting better containment. The findings demonstrate that alumina nanofluids can enhance CO₂ storage in caprocks by improving the wettability, thus offering a promising approach to the optimization of geological storage solutions for sustainable energy transitions.