Natural mitigation of CO2 leakage accumulations

This study aims at investigating the role played by the overlying aquifer formation as a safety barrier in case of CO2 leakage accumulation (i.e. CO2 accumulated in an overlying aquifer after its leakage from the CO2 storage reservoir) by focusing on its natural capacity to prevent any further upward migration. Based on numerical simulations performed using TOUGH2/ECO2N incl. hysteretic module, we assess the processes influencing the quantity of mobile CO2 within the leaking plume and perform a sensitivity analysis to point out the key-parameters and conditions for an efficient natural trapping by dissolution and residual trapping. Additional simulations of a leak active remediation scenario on a complete system (storing reservoir connected to an overlying aquifer) show the importance of the natural trapping capacity of the overlying aquifer. This capacity could be integrated in the mitigation strategy, associating natural and engineered safety barriers. Gaining more knowledge on these formations can support first estimations of this natural capacity, and hence can help building the corrective measure plan and designing potential interventions during operations. (C) 2013 The Authors. Published by Elsevier Ltd.