Geo-processes in Mineral Carbon Storage - Fundamental Challenges

ABSTRACT: Mineral carbon storage presents a promising solution to mitigate anthropogenic CO2 emissions by taking advantage of mineralization reactions that occur when CO2 gets in contact with mafic and ultramafic rocks such as basalt and peridotite. Reaction with Mg, Fe, and Ca-rich minerals present in these rocks can transform CO2 into solid carbonates, thus making permanent subsurface storage feasible. Mafic and ultramafic rock masses are abundant in the Earth’s crust. Over the past decade, the concept of mineral carbon storage has been successfully pilot-tested in basalt formations, where reservoir permeability is relatively high and the presence of natural fractures expected. CarbFix and CarbFix2 in Iceland and the Wallula project in Washington state have both demonstrated carbon mineralization could occur on a time scale of months to years. However, the feasibility in low permeability ultramafic rocks such as peridotite is yet to be shown. Efficient mineralization of these rock masses requires the existence or development of a penetrating fracture network that accommodates the flow and reaction of CO2 bearing fluids. For both types of rocks, there are significant knowledge gaps in our current understanding of the relevant geochemistry, flow and transport processes, and the coupling between geomechanics and reactive transport for realistic engineering of largescale mineralization operations. In this talk, latest research conducted at the DOE/EFRC Center on Geo-processes in Mineral Carbon Storage (GMCS) will be presented, in particular, the efforts to address the fundamental questions on reaction induced cracking and the dissolution and precipitation regimes in a fractured porous medium, all of which are essential to realizing the potential of subsurface storage of CO2 via mineralization.