CO2 Mineralization in Reactive Rocks

The safest long-term geologic storage of CO2 is its mineralization.  Such mineralization is most efficient via the injection of water-dissolved CO2 into mafic or ultramafic rocks. The injection of water dissolved CO2 is shown to be financially favorable. Notably the relative costs of the injection of pure CO2 is found to be similar to that of the dissolution of this CO2 into water as it is injected into the subsurface.    This is because the injection of pure CO2 requires higher injection pressures to get the CO2 into subsurface rock formations, owing to its low density, and these higher injection pressures require more robust and costly wells.  Such factors tend to balance out the cost of the larger number of wells required for the CO2-charged water injection and the water needed for the dissolution of this gas.  This latter cost is reduced if one used seawater rather than freshwater. Once injected into the subsurface this CO2-charged water will react with the subsurface rocks forming both carbonate minerals for the permanent storage of CO2, but also a suite of other secondary mineral products including clay minerals. The choice of target rock formation for CO2-charged water will affect greatly the rate and efficiency of this carbonation process.