Numerical Simulation of the Impact of High-Velocity Ocean Currents on CO<sub>2</sub> Leakage in Shallow Saline Aquifers

Offshore CO<sub>2</sub> storage in shallow saline aquifers presents significant potential due to its operational feasibility and large storage capacity. However, the natural or anthropogenic damage to the caprock integrity may trigger submarine CO<sub>2</sub> leakage. High-velocity ocean currents accelerate the dissolution and dispersion of leaked CO<sub>2</sub> in seawater, while current understanding in this field remains limited. This study establishes a seawater-CO<sub>2</sub> dissolution-dispersion numerical model based on shallow marine environments, in order to quantify how high-velocity currents affect CO<sub>2</sub> dispersion paths and the trend of concentration variations. Simulations reveal that at typical leakage rates (17.0-60.0 kg/day), high-velocity currents (0.20-0.405 m/s) expand the horizontal spread of dissolved CO<sub>2</sub> at different water depths by up to 45 m within 2 minutes, approximately 9 times wider than low-velocity situations (0.05 m/s). Simultaneously, rapid dilution occurs: while the peak concentration of CO<sub>2</sub> bubbles in high-velocity currents exhibit 1.37 times higher than low-velocity scenarios, dissolved CO<sub>2</sub> concentration stabilizes at merely 24.80% of the latter. The results indicate that high-velocity currents complicate the monitoring efforts of CO<sub>2</sub> leakage. These findings provide critical insights for predicting impacts of CO<sub>2</sub> leakage and optimizing monitoring strategies in shallow marine CO<sub>2</sub> storage projects.