The development of ‘dry-run’ storage permit applications within SiteChar at two credible CO2 storage sites allowed development of effective approaches to site characterisation, which will enable robust and defensible permit applications to be developed by operators. The review of these applications and the lessons learnt will help regulatory authorities to identify the necessary levels of evidence required to assess the safety, containment and storage capacity of putative sites. This report presents the SiteChar recommendations which will enable operators to directly address key issues for cost efficient and effective storage permit applications.
Focused and risk-based site characterisation. The research conducted in SiteChar confirms that successful storage operations require site characterisation activities that are fit-for-purpose and focused on reducing uncertainty and risk for the specific site and specific CO2 storage project. This requires the Competent Authority and operator to share a common understanding of the site and the storage project. SiteChar recommends that site characterisation should be driven by risk and uncertainty assessment, aiming to anticipate, reduce and mitigate risks and identify objectives for subsequent storage performance monitoring.
Storage complex definition. Practical approaches to defining the storage complex are required and have been developed within SiteChar.
EC Storage Directive improvements. Recommendations are made to improve and clarify the EC Storage Directive on a number of topics including the benefits of establishing permit performance conditions, the circumstances under which permits might be revised, the role of Competent Authorities in evaluating the potential impacts of storage projects on other future uses of the underground and the challenges of planning all details of the operation prior to final investment decisions and subsequent site testing.
Demonstrating permanent safe storage. Firstly, establishing agreement during the permit process of the level of evidence required to demonstrate permanent safe containment will be a significant aspect of site characterisation activities. In addition to successfully obtaining a permit to store, this agreement will also enable the transfer of the site to the State at the end of the project. This transfer will be planned from the beginning and prepared for throughout the CCS project. Both operators and Competent Authorities will need certainty on the metrics by which the site performance will be assessed and by which safe, permanent containment will be demonstrated.
Secondly, managing uncertainty and conveying the level of confidence accurately without undermining the safety case require further attention. All predictions of site performance will carry a level of confidence and uncertainty. It will be important for Competent Authorities and operators to agree on the levels of acceptable uncertainty. Operators will need to develop a plan for uncertainty reduction during the process of operating the site, supported by an adequate baseline site characterisation and an appropriate program of site monitoring. Definition of acceptance criteria is the key to determine the level of required evidence to gain a storage permit, allowing both operator and regulator to demonstrate safe performance, both during the operational and closure phases and providing a basis for the design of the geological monitoring program and the corrective measures plan.
Recommendations for authorities. Governments set national policies and local authorities may contribute to their implementation through local policy development and the planning process. CO2 storage projects could therefore form a component of the discussions about the approaches to sustainable energy supply as well as use of the subsurface. Furthermore, assessing interactions with other users is a key consideration for regulators but this might be challenging for operators since such an assessment requires an overview of relevant future uses of the underground. Management of the pore space is also a strategic issue that requires both operators and relevant authorities to consider the efficient use of the pore space in the selection and operation of sites.