Mathematical modeling and multiscale simulation of carbon dioxide storage in saline aquifers

Carbon capture and storage (CCS) is a key technology to reduce CO 2 emissions from industrial processes, in particular from fossil-fuel based electricity generation. One important aspect of CCS is the safe long-term storage of the captured CO2 in geological formations, especially in deep regional saline aquifers. Predicting the long-term evolution of the injected CO2 requires an understanding of the basic physical mechanisms and the ability to capture them in field-scale numerical simulations. Simple mathematical models of trapping processes are developed to allow the identification of the dominant physical processes during CO2 storage and their associated length and time scales. First-order estimates of the duration of the active storage period and the migration distance are obtained as a function of the average properties of the aquifer. These estimates support the selection of storage sites, in particular at the early stages when limited data is available. They also show that the length scales associated with the physical processes in regional aquifers can span several orders of magnitude.;Multiscale simulation techniques are necessary to resolve physical processes and geological heterogeneity. In particular, robust multiscale methods of elliptic flow problems, must be developed. The multiscale finite volume method is analyzed in the context of multipoint flux approximations and shown to lose monotonicity for anisotropic problems. Strong anisotropy arises in the simulation of CO2 storage, because of the large aspect ratios of regional aquifers. A new compact coarse operator and new local fine-scale problems are introduced to obtain monotone coarse pressure solutions for anisotropic domains. This development presents a major step towards multiscale simulation of CO2 storage in large regional saline aquifers.