Our results document that storage volume requirements are reduced by about 50% if CO2 is dissolved in the brine (solubility trapping),
rather than a separate supercritical fluid (structural or
stratigraphic trapping). In addition, CO2-bearing brine is
denser than CO2-free brine, so that CO2-saturated brine will
migrate downward within the formation, thus enhancing longterm
storage security. Although the present study does not
permit rigorous evaluation of the time scales required to
achieve these advantages, the results suggest that storage
volume requirements may be reduced by sequestration
protocols involving extraction of brine, dissolution of CO2
into the extracted brine at the surface, followed by reinjection
of the CO2-saturated brine into the formation.5,18 To fully
evaluate this alternative operational paradigm for geologic CO2
storage requires comprehensive reservoir simulations that
consider pressure evolution, fluid flow, and temporal changes
in CO2 trapping mechanisms. In addition, associated process requirements including characterization of life cycle energy,
emissions, and economic implications must be considered.