This report consolidates the key findings of the application of the characterisation workflow conducted within the FP7 SiteChar project that has examined the entire site characterisation process, from the initial feasibility studies through to the final stage of application for a CO2 storage permit. The research is based on the characterisation at different levels of five sites representative of the various contexts and geology containing potential CO2 storage complexes in Europe. In addition to these technical issues, SiteChar has considered the economic challenges
of CO2 storage and addressed the important aspect of current public knowledge and perceptions regarding the storage of CO2 at both an onshore site and an offshore site.
SiteChar has extended and tested standard site characterisation workflows on the basis of criteria defined by the relevant European legislation. The methodology has been tested at a range of representative European storage sites where Carbon Capture and Storage is most likely to develop in the near term: a UK North Sea multi-store site offshore Scotland, an onshore saline aquifer in Denmark, an onshore gas field in Poland, an offshore aquifer in Norway and an aquifer in the Southern Adriatic Sea. At the Danish and Scottish sites, the characterisation has been conducted as far as possible in the framework of a research project so as to develop ‘dry-run’ storage permit applications that have been evaluated by a group of independent experts. The studies conducted at the other sites focused on specific barriers related to the site characterisation methodology, e.g. assessing the well integrity of a depleted hydrocarbon field with quite a number of abandoned wells, estimating the storage capacities in a multi-storage complex with structural traps and open saline aquifers, evaluating the geomechanical stability of a carbonate reservoir.
The research conducted on the sites clearly highlighted the need for a workflow independent of the site character, but the application of which has to be fit-for-purpose according to the project concept, the available data, the specific uncertainties and risks to be investigated. A key learning of the SiteChar project is that characterisation of a site for the purpose of obtaining a CO2 storage permit is a risk-based process with the objective of demonstrating safe and permanent storage. Risk analysis defines the scope of the site characterisation work that iteratively determines and constrains risks aiming to reduce their consequence and/or likelihood to agreed acceptable levels.
SiteChar experience has emphasized the need for a multidisciplinary expertise based on a close cooperation between disciplines sharing from the beginning of the project a common purpose for their activities, interdependencies, and, during the investigation progress, any changes to the project concept or site design so as to provide an adequate qualification of all aspects of the storage site in line with regulatory requirements.
The different steps of the characterisation workflow have been tested and outcomes illustrated at specific sites. They are related to the site characterisation activities as currently known for these sites; additional characterisation activities might be appropriate or might be developed in the future. It turned out that a very close interaction between the static geological modelling, fluid flow modelling and coupled fluid flow and geomechanical modelling should be planned for the site characterisation work schedule. For instance, hydrodynamic modelling is sensitive to geological attribution, geomechanical modelling requires specific extension of the model and specific description of faults, etc. Therefore, communication to discuss input data that are required and used in common between the activities as well as exchange of outputs from one modelling activity to another must be included in the plan of work. Similarly, all the software to be used for static
geological and fluid flow modelling of the storage site should be discussed at the outset of characterisation. Compatibility and interoperability should be tested before decisions are made of which modelling software is to be licensed for use and staff assigned with appropriate modelling skills.