Carbon capture and storage in geological formations has been proposed in the last ten years to reduce the emissions of CO2 to the atmosphere. Geological storage consists in injecting supercritical CO2 into deep aquifers so that it remains trapped under a low permeability caprock. At the injection pressure, CO2 solubility is high and dissolution is controlled by diffusion and dispersion. CO2 saturated brine is highly acidic and will dissolve the rock, increasing its permeability, but also reducing its strength. Depending on chemical conditions, other minerals may precipitate, including carbonates, which effectively induce a mineralization of CO2. Eventually, after injection stops, a sizable amount of CO2 will remain trapped by capillary forces as residual CO2 bubbles. CO2 storage thus involves coupling of multiphase flow, solute transport, geochemical reactions and mechanical deformation. The outcome is non-obvious and requires modeling. Geological heterogeneity can both enhance and reduce the storage capacity. Enhancement can come from speeding up dissolution. Reduction may result from the chemical and mechanical weakening of the confining rock. More intrinsically, it has been recently established that heterogeneity modifies the expression of the processes across scales and may cause new processes to emerge. We propose in this project to improve our understanding of the influence of heterogeneity on the expression of the complex coupled processes involved in CO2 storage. Based on numerical simulations, we will build heuristic expressions of the emerging equations. These will be further analyzed with formal upscaling methodologies such as homogenization or renormalization. We expect to develop, first, a better understanding of the upscaled processes underlying site safety and, second, more accurate upscaled modeling tools. We will eventually determine how these tools can improve the design of injection strategies and the reliability of risk assessment predictions.
Call for proposal
See other projects for this call