Saline Aquifers

Saline aquifers are geological formations consisting of water permeable rocks that are saturated with salt water, called brine.  Super-critical carbon dioxide (CO2), CO2 that has been pressurized to a phase between gas and liquid, may be injected into a saline aquifer where it may either dissolve in the brine, react with the dissolved minerals or the surrounding rock, or become trapped in the pore space of the aquifer due to its attraction to the walls of the aquifer (International Energy Agency (IEA), 2008).  An increase in the amount of trapped gas may decrease the relative permeability of CO2 into water in the region, forming a buffer zone that will slow the spread of the trapped CO2, called the plume, which could potentially escape if it travels too far. (MacMinn, 2008).  Ideal aquifers have layers of minimally porous rock, which prevent water flow and the escape of injected CO2 (IEA, 2008).  Cement is used to plug wells after injection is finished.


There are two types of saline aquifer sequestration: seabed aquifer sequestration and terrestrial saline aquifer sequestration.