How to submit a CO2 storage permit: identifying appropriate geological site characterisation to meet European regulatory requirements

EU Member States are in the process of transposing European regulatory requirements that define the high-level conditions of a storage permit into their national laws. This regulatory framework defines a range of performance standards which recognise specific high-level uncertainties and long-term issues which storage developers will have to address. However, with one or two notable exceptions, the level of site characterisation required to obtain a storage permit has not been systematically evaluated. To determine the required geological site characterisation necessary to demonstrate adequate understanding of site performance, two storage case studies identify those issues that might remain challenging in the permitting process. These case studies, an onshore aquifer and an offshore multi-store site, produce credible dry-run storage permit applications from site geological characterisation activities, which are evaluated by a separate team, acting as a regulator. The applications, though necessarily reduced in scope from those anticipated for full storage projects, comprise the key elements of a permit. Issues identified during this process include: • Defining the storage complex boundaries, which for certain sites may be challenging, especially where expected pressure responses may extend for some distance or where lateral boundaries may not be clearly defined. We present examples of how these regulatory boundaries have been defined for the two case studies. • Key Performance Indicators (KPIs) include a range of metrics against which site performance can be measured, both during the operational and closure phases, providing a basis for the design of the geological monitoring program and the corrective measures plan. Defining qualitative terms such as ‘expected’ or ‘acceptable’ in appropriate quantitative metrics has been attempted for site ‘sufficient’ measured, both during the operational and closure phases, providing a basis for the design of the geological monitoring program and the corrective measures plan-specific KPIs in the case studies described. Whilst it might be relatively straightforward to define qualitative indicators, we conclude that KPIs will need to be defined quantitatively for them to be the most effective.