CO2 Sequestration through Deep Saline Injection and ...

although contribution to capacity estimates from mineralization must be considered, in addition
to hydrodynamic considerations that will govern the length of time CO2 may be safely stored as
the pure phase slowly diffuses into the system for solubility and mineral trapping.
Table 2
Average characteristics of Viking formation used in
solubility estimations (e.g. [14, 56, 60])
Parameter Assigned Value
Depth, m 2000
Temperature, deg C 55
Pressure, MPa 20
Salinity, g/l 70
Plan view area, km 2
400,000
Thickness, m 30
Porosity 0.2
5.2.3. Mineral Trapping and Capacity
Mineral trapping, as has been stated before, is a long term storage mechanism. The mechanism
as described by Ortoleva et al. [61] is that CO2 first dissolves in water to produce the weak
carbonic acid,
CO 2(g) + HO 2 � HCO 2 3
. (11)
This is followed by rapid dissolution of carbonic acid to for the bicarbonate ion which increases
the acidity of the solution,
HCO H + HCO −
� . (12)
+
2 3 3
This leads to the dissolution of many of the primary host rock minerals, which in turn causes
complexing of dissolved cations with the bicarbonate ions such as
Ca + HCO CaHCO
+
−
2 3 �
+
3
. (13)
These dissolved bicarbonate species react with divalent cations to precipitate carbonate minerals
and the formation of Ca, Mg, and Fe(II) carbonates are expected to be the primary means by
which the CO2 is immobilized [62] as is shown through the following equations:
48