The Impact of Water Injection Simulation on CO₂ Storage Capacity in Offshore Saline Aquifers

Continuous or alternating water injection into saline aquifers can accelerate CO₂ dissolution and increase the safety of CO₂ storage. However, the hydrodynamic effect may interfere with the development of CO₂ plumes, affecting indirectly the actual storage capacity of the aquifer, to which available engineering solution remain very limited. We studied the potential water injection strategies and the influence of key operational parameters on the storage safety and capacity during CO₂ injection using a single well in an open saline aquifer. Results show that continuous water injection above the gas injection layer after a certain period could enhance significantly the storage intensity and increase the capacity. The early the water injection starts, the better the results. The storage capacity increases with the increase in water injection rate during gas injection. The temporal effect of water injection post gas injection on storage capacity needs to be evaluated case by case. Under a given total water injection volume, high-rate water injection during gas injection is more effective to enhance the storage capacity than low-rate and prolonged water injection. Reducing the spatial interval between the water injection layer and gas injection layer could enhance the actual storage capacity. Meanwhile, water injection could effectively reduce the CO₂ saturation near the injection well, and mitigate the risk of wellbore leakage.