In the unlikely event that CO2 were to leak from a carefully selected storage site, the leak would be fixed, and any environmental damage remediated to restore the site to a safe and secure state. This would be achieved by applying measures that have been successfully applied in the hydrocarbon industry for over 50 years, as well as new techniques developed specifically for CO2 geological storage. Measures include management of the injection process to reduce the pressure in the store that is driving the movement of CO2, and a range of methods to plug leaks, including the use of sealants (e.g. cements, gels, foams, nanoparticles) and hydraulic, gas and chemical barriers, some of which react with the CO2 to turn it into a stable mineral form. To date, such measures have not been required as, despite intensive monitoring, there have been no confirmed leaks from existing CO2 geological storage projects. Corrective measures covering potential leakage pathways, which can be broadly categorised as either manmade (e.g. related to the well and injection operations) or natural (e.g. caprock failure, faults or fractures), are a key part of storage risk management. Implications of leakage for adjacent environmental uses such as fishing, aquaculture and offshore renewables are likely minimal, though this requires further study.
Responsibility for corrective measures would lie with different parties at different stages over a site’s lifetime: the operator would likely be responsible during the operational phase and the post-closure period up until the point at which the operating licence expires; at this point, responsibility would likely transfer to the competent authority, i.e. Scottish or UK Government, depending on the location of the storage site. More work is required to establish this issue of transfer of liability more clearly, particularly given the regulatory transition associated with the UK’s exit from the EU.