Underground carbon dioxide storage in saline formations

This paper reviews key areas of carbon dioxide storage in saline aquifers. Among several potential geological carbon dioxide storage sites, saline aquifers offer the highest storage potential capacity and are relatively common worldwide. Geological storage of carbon dioxide in saline formations is achieved through various physical and chemical trapping mechanisms. When carbon dioxide is injected in the subsurface, it is first trapped by primary trapping mechanisms, which are static and hydrodynamic trapping below the cap rock. The secondary trapping mechanisms, solubility, mineral and residual trapping, are much slower and have a much longer timeframe for operating than primary trapping mechanisms. Knowledge regarding storage capacity in saline formations is highly uncertain due to their poor characterisation, heterogeneity and trapping mechanisms operating at different timeframe scales, which pose a huge challenge to establish a reliable methodology for storage capacity estimates. The potential cost of storage in saline aquifers is reasonably well known. However, the lack of any economic benefits makes this storage option less economically attractive than other geological sequestration strategies.