Geosphere risk assessment conducted for the IEAGHG Weyburn-Midale CO2 Monitoring and Storage Project

This paper discusses the approach taken to the geosphere risk assessment conducted for the IEAGHG Weyburn-Midale CO2 Monitoring and Storage Project. The role of the geosphere risk assessment is to facilitate clear identification, analysis and communication of the often complex technical issues that could potentially reduce the ability of a CO2 storage project to store CO2 or to contain the bulk of the CO2 within the subsurface. It should provide sufficient information to enable the risks to the biosphere from potential CO2 releases from the storage project to be assessed so that stakeholders can come to a view about project acceptability.One of the main objectives of the Weyburn-Midale Project research was to test and demonstrate that around 30 Mt of CO2 is likely to remain safely stored underground for a very long period of time. The risk assessment concluded that, based on currently available data, this objective would be met. It also identified that although all identified risks met containment risk targets, well pathways pose by far the greatest risk to containment (approximately three and one half orders of magnitude higher than the risk posed by natural events and by EOR activities). Given the relative contribution of this risk to the overall containment risk for the project, it was identified that a review of well abandonment practices may be warranted to treat this risk.The risk assessment commenced early in the life of the Weyburn-Midale Project, thereby allowing knowledge gaps and areas of uncertainty to be identified. As a result, additional research was commissioned to address some of these gaps and uncertainties. The results of the research were incorporated into subsequent assessments of risk, thereby improving confidence in risk assessment outputs.