Injection strategies for large-scale CO2 storage sites

Abstract Existing pilot, demonstration and commercial storage projects have demonstrated that CO 2 geological storage is technically feasible. However, these projects do not operate at a scale that is necessary to make a significant reduction in greenhouse gas emissions into the atmosphere. The infrastructure for injecting carbon dioxide will need to be an order of magnitude larger than current CCS projects, at comparable size of existing petroleum installations. In most cases, the CO 2 injection scheme will consist of multiple wells, potentially including wells for monitoring and pressure control. Despite the advanced understanding of subsurface flow processes and development of modelling tools, there are still conflicting results in the literature on the estimation of pressure build-up, the resulting number of injection wells required for large-scale CO 2 geological storage and storage efficiency. For these issues, there do not appear to be any adequate analogues. As a result, studies on the regional impacts of CO 2 storage and the role of hydraulic properties of the sealing unit have been limited to more or less generic numerical modelling exercises. Since there are typically large uncertainties in model parameters, such as relative permeability, conclusions drawn from generic studies will have limited applicability until they can be tested against field data. Uncertainties in predicting reservoir properties and therefore in predicting injectivity will clearly affect the design and economics of the injection system. Potential trade-offs with respect to costs for transport and reservoir stimulation need consideration. Also, strategies and contingencies will need to be incorporated in development plans to allow for unforeseen changes in injection conditions during project life. Continuously updating reservoir models when new data become available and adapting injection strategies will be essential for the success of large-scale CO 2 geological storage.