The importance of regional geological mapping in CO₂ storage site characterization : examples from the IEA Weyburn CO₂ monitoring and storage project

In the International Energy Agency (IEA) Greenhouse Gas Weyburn CO₂ Monitoring and Storage Project, carbon dioxide (CO₂) is being injected into a Mississippian-aged oil reservoir in the intracratonic Williston Basin, located in central North America. Assessing geological sites for long-term storage of CO₂ involves not only characterization of the reservoir, but also an understanding of the geological and tectonic framework of the region encompassing the containment unit. This paper presented the results of regional geological mapping that was conducted as part of the IEA Weyburn CO₂ Storage and Monitoring Project to determine the distribution of relationships between strata comprising the geological container, with particular emphasis on identifying and characterizing primary and secondary seals, mapping the distribution of aquifers and aquitards, and determining whether discontinuities were present in the system. In order to determine their impact on storage potential, subsurface processes and features affecting the containment system, such as locations of Devonian salt dissolution, were identified and assessed. A large region was mapped to reveal basin and tectonic trends that help define relationships among subsurface features and processes. Such regional stratigraphic data is needed for hydrogeological and structural investigations into site suitability, and for scaling and building a 3-dimensional geological model for numerical risk and performance assessment. This study provided new insights into the depositional history of the Williston Basin and the inter-relation among basement features, hydrogeological flow and depositional patterns. 10 refs., 7 figs