Rapid solubility and mineral storage of CO2 in basalt

The long-term security of geologic carbon storage is critical to its success and public acceptance. Much of the security risk associated with geological carbon storage stems from its buoyancy. Gaseous and supercritical CO2 are less dense than formation waters, providing a driving force for it to escape back to the surface. This buoyancy can be eliminated by the dissolution of CO2 into water prior to, or during its injection into the subsurface. The dissolution makes it possible to inject into fractured rocks and further enhance mineral storage of CO2 especially if injected into silicate rocks rich in divalent metal cations such as basalts and ultra-mafic rocks. We have demonstrated the dissolution of CO2 into water during its injection into basalt leading to its geologic solubility storage in less than five minutes and potential geologic mineral storage within few years after injection [1–3]. The storage potential of CO2 within basaltic rocks is enormous. All the carbon released from burning of all fossil fuel on Earth, 5000 GtC, can theoretically be stored in basaltic rocks [4]

Droplets evolution during ex situ dissolution technique for geological CO2 sequestration: experimental and mathematical modelling

CO2 can flow upward and leak through thief zones due to buoyancy effect during geological sequestration. To tackle this issue, the ex situ dissolution (ESD) concept was introduced aiming at full dissolution of CO2 at the surface, before it is injected into the ground, to increase the storage capacity and lower the risk of leakage. A mathematical model for CO2 droplets evolution in the ESD process is presented, followed by an experimental investigation to verify the proposed model. The developed model accounts for the droplet break-up process and transient mass transfer involved in the ESD. A number of mathematical correlations were developed to compute the average droplet size, break-up frequency, and droplet population in a turbulent dispersion regime. Experimental and mathematical results revealed that a minimum stable CO2droplet is achievable within a pipeline length of less than 50 m if the CO2 volume fraction is in the range of 5–15% and the brine flow rate varies between 0.25 and 2.0 Mt/yr. An acceptable agreement between the predicted and experimental droplet size distributions is observed. This study confirms that the ESD can reduce the leakage risk because of the formation of fine CO2 droplets