DEVELOPING A FRAMEWORK FOR MANAGING THE LONG TERM STORAGE OF CO_2 IN GEOLOGICAL FORMATIONS

摘要

Large-scale take up of capture and geological storage of CO_2 will require acceptance that geological storage can be a safe and effective greenhouse gas mitigation option. This will depend on the long-term storage performance and in particular, the duration of storage, the risk and consequences of leakage to the atmosphere and our ability to select, monitor and manage sites to mitigate the risk of leakage. The risks associated with release to atmosphere are twofold: local risks relating to health, safety and environmental impacts associated with localised high concentration CO_2 release and global risks that storage is not effective as a mitigation option. Safe and effective storage therefore requires the development of methodology and best practise for managing storage projects. This will need to integrate at all stages the risk-based approach that is being developed. Performance expectations, monitoring capability and storage management will strongly influence the social acceptability of this technology and its eligibility within commercial mechanisms that will be vital for large-scale deployment. Developing the framework for managing geological storage requires an understanding of the processes and risks, including the likely timescales and flux rates involved. The key subsurface processes are the migration of CO_2 after injection into the primary storage trap, potential further movement out of the trap, physical trapping, dissolution, residual gas trapping, mineralization and adsorption. The risk and consequences of leakage or release needs to be understood for all sites at all different stages in storage projects. In general the risks and mechanisms involved are now qualitatively understood and a structured approach to quantitative risk mitigation is being developed. The key risks are summarised and consideration is given to the main release mechanisms, including wells. Industry experience shows that remediation of wells is possible on a timescale of months. Given the processes, timescales and risks involved in geological storage, it will be necessary to develop the framework for managing storage projects. We discuss the key considerations resulting from the review of processes and leakage risks. These include active management of storage projects, continuous risk assessment, risk management, and remediation at all stages. A key aspect of the risk management activity is monitoring during the operational phase and the development of suitable monitoring strategies for the post-operational stage.