Design of Carbon Dioxide Storage
We propose design strategies for CO2 injection to maximize storage in aquifers and to maximize both CO2 storage and enhanced oil recovery (EOR) in oil reservoirs. We propose a carbon storage strategy where CO2 and brine are injected into an aquifer together followed by brine injection alone. This renders 80-95% of the CO2 immobile in pore-scale droplets within the porous rock. The favorable mobility ratio between injected and displaced fluids leads to a more uniform sweep of the aquifer leading to a higher storage efficiency than injecting CO2 alone. This design was demonstrated through one-dimensional simulations that were verified through comparison with analytical solutions. We then performed simulations of CO2 storage in a North Sea aquifer. We then extended our study to oil fields. We propose to inject more water than the traditional optimum that maximizes only oil recovery. This causes the CO2 to remain in the reservoir, increases the field life and leads to improved storage of CO2 as a trapped phase. Again, a short period of chase brine injection at the end of the process traps most of the remaining CO2.
Martin Blunt, Imperial College London, United Kingdom