Risk Scenarios
CO2 capture and storage in geological formations is now establishing itself as a technical option that has the potential, when used in conjunction with other mitigation options (energy efficiency improvements, fuel switching and use of renewable energy), to make deep reductions in emissions of CO2. There are now several commercial scale projects, either underway or in the planning stage, that capture CO2 emitted from gas processing operations and store the CO2 in geological formations.
However, the commercial projects are only storing a small proportion of the CO2 that will be required to be removed from the atmospheric if the UNFCC (United Nations Framework Convention on Climate Change) goal of 'stabilisation of atmospheric concentrations of greenhouse gases' is to be achieved. To meet this goal, substantial deployment of mitigation options, including CO2 capture and storage, will be required across the globe. Widespread deployment of such technology will depend on gaining acceptance for the technology from policy makers and the general public.
Two key areas that will need to be demonstrated to gain public acceptance of CO2 capture and storage are: that the technology is safe, and that its environment impact is limited. Risk assessment will play a significant role in answering these questions. The risk assessment of CO2 capture and storage will allow a systematic evaluation of the potential impacts on humans or the environment from a release of the stored CO2. Risk assessment and risk management methods currently used by industry are both relevant to CO2 capture and storage and provide a valuable experience base. These tools can be adapted and further developed to be specific for the geological storage of CO2.
One tool for risk assessment of the geological storage of CO2 is the generic FEP database.
Generic FEP Database
Systems Analysis can be applied in assessing the performance of CO2 storage in geological formations. The first step in a systems analysis approach is to specify the boundaries of the system that is to be analysed (both in space and time) so that the System Domain is clearly identified. The system can then be described in terms of relevant Features, Events and Processes (FEPs - Features of the system, Processes that influence the evolution of the system, and the Events that can be viewed as processes that take place on comparatively short timescales).
Even for a well-characterised CO2 storage site, there will be unavoidable uncertainty regarding the future states or evolution of the system. Uncertainty in the long-term evolution of the system could be handled by carrying out calculations for a number of stylised conceptual descriptions of future states of the system or scenarios. Scenarios have become widely used in business and industry as planning and brainstorming tools.
The FEPs relevant to the geological storage of CO2 have been compiled in a generic database. Whilst not specific to any particular sequestration concept or location, the database has the capability to be cross-referenced to project-specific information. The FEPs contained in the database can describe the behaviour of CO2 in respect of the long-term safety and performance of the storage system following the completion of carbon dioxide injection and the sealing of the injection boreholes.
The database currently includes around 200 FEPs in a hierarchical structure, with individual FEPs grouped into eight categories. Each FEP has a text description and an associated discussion of its relevance to long-term performance and safety. Key references from the published literature are included to allow retrieval of more detailed information for each FEP. The database is internet-enabled incorporating hyperlinks to other relevant sources of information (reports, websites, maps, photographs, videos, etc.) and is searchable in a variety of ways.
The database provides a centralised source of information on relevant technical and scientific considerations relating to the long-term geographical storage of carbon dioxide. The use of FEPs to describe the CO2 storage concept to be evaluated should provide a powerful auditing tool to ensure that assessments incorporate all potentially significant factors.
The generic FEP database has been developed by Quintessa who have worked in close co-operation with safety assessment work carried out in North America for the Weyburn CO2 Monitoring and Storage Project. Quintessa's full report on the creation of the FEP database is available here - (2.86kb Adobe Acrobat PDF). To access the generic FEP database follow the link below.
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