Consequences of subsea CO2 blowouts in shallow water

Safety and risk assessment of the offshore geological storage of carbon dioxide (CO2) in the Carbon Capture, Utilization, and Storage (CCUS) value chain needs the evaluation of the consequences of possible accidental submarine CO2 leakages, including releases having high flow rate and very long duration, as blowouts. An innovative procedure for the estimation of the effects of submarine blowouts in shallow water was developed, based on the integration of specific sub -models. A model for blowout simulation is used to predict the features of the source term. The fate of the submarine plume is then assessed. Finally, the atmospheric dispersion of the surfacing gas is simulated, to estimate damage distances. The application of the methodology to a set of case studies evidences that in extremely shallow water the threshold distances of the gas cloud dispersing in the air can be higher for CO2 than for natural gas. However, when considering higher water depths, the release of CO2 to the atmosphere is strongly attenuated by the dissolution of CO2 in the water column.