The fifth panel discussion at GHGT-15 was held on Wednesday 17th March and was focussed around closure issues with CO2 storage projects, particularly looking at US regulations compared to policies in the EU. James Craig (IEAGHG) chaired this panel and welcomed six international panellists: Susan Hovorka (GCCC, The University of Texas at Austin), Marcella Dean (Shell Global Solutions International B.V), Matthias Raab (CO2CRC), Ziqiu Xue (Research Institute of Innovative Technology for the Earth (RITE)), Neeraj Gupta (Energy Division, Battelle) and David Riestenberg (Advanced Resources International, Inc.). The expert panel gave interesting insights into various applicable projects and discussed whether current policies and regulations are appropriate for determining site closure, how to verify stabilised CO2 plumes and the considerations for scale-up.
It seems clear that the US approach to site closure is rather cautious and prescriptive, whereas the EU approach is more performance and risk assessment-based. There was some concern that the US procedure is not targeted towards and intended purpose, and is vague so not required to be risk-based which is potentially a weakness. A more performance-based approach is better set up to deal with any problems within the project timescale so that success can be achieved. In the EU, a well-designed post-closure plan facilitates timely handover when it is a monitoring- and performance-based plan rather than time-based; this helps the regulator trust that when an operator sees changes in the risk profile of a project with the MMV, early corrective measures can be undertaken. Moreover a detailed risk assessment plan, for example based on a bow-tie evaluation, can be adapted throughout the life of a project from inception to closure.
The concept of scale-up is interesting as some of the projects have been small-scale pilots. The approaches to post-closure have been shown to be appropriate but this experience needs to be adapted to what is likely to be necessary at a larger size. Performance-based indicators will be important in scale-up and the definition is and will be project-specific; a pragmatic approach is required. The middle ground is to be clear on what is to be achieved and how to do it; key performance indicators (KPIs) can change and adapted over time but it is important to have an understanding of the risk and risk profile throughout.
Every project at different scales will have their unique challenges and it's important to define what is expected of a project. Anomalies which are not immediately evident should be expected and operators should be able to explain their origin. The fundamental knowledge to implement projects is already there, and now the confidence in subsurface models, and monitoring techniques, should be taken forward. As experience continues to grow, the storage and monitoring communities are gaining in experience and confidence – and they should not shy away from moving toward large scale CO2 storage.
Samantha Neades and James Craig