Leaving CO2 safely in the ground
With CCS, CO2 is captured before it can be released into the atmosphere. After capture, it is stored in geological formations or reservoirs. It is a short- to mid-term solution before the long-term goal of a transition away from fossil fuel combustion to more sustainable forms of energy can be reached. The EU-funded 'CO2 site closure assessment research' (CO2CARE) project developed technologies and procedures to safely and securely abandon CO2 storage sites. It was launched to provide regulatory officials and stakeholders with the required knowledge to implement the EU Directive 2009/31/EC on CO2 Geological Storage. Project members produced pragmatic recommendations in the form of best practice guidelines for CCS management in the long term. Participation of partners from Australia, Canada, Japan and the United States, and data obtained from current and closed sites added to the field monitoring database and place the results of CO2CARE in a worldwide perspective. Research focused on well abandonment, reservoir management and risk mitigation to meet the requirements of no detectable leakage, a match between modelled and actual site characteristics, and long-term stability. Team members produced a report that covers risk management and decision-making procedures. They also designed software to compare modelled and measured data. A range of investigations into rock-sealing procedures was undertaken, as well as into chemical and physical mechanisms of CO2 trapping. Scientists modelled CO2 leakage and well behaviour over long timeframes — more than 10 000 years — to determine effects on the geology of the surrounding area. Main results of 'dry-runs' from three storage sites provide a template for site abandonment and transfer of responsibility for both site operators and regulators. Technical guidance on how to meet European Commission policy requirements and broader guidelines on reservoir management and, specifically, risk management are directly relevant to EU directives. They are also generally applicable to worldwide storage facilities. CCS is an extremely important part of climate change mitigation, but the procedures for long-term management are not well defined. The findings and publications of CO2CARE provide concrete guidelines for the future management of carbon storage.
Keywords
Carbon capture and storage, CO2, storage sites, geological formations, site closure
