Center on Geo-processes in Mineral Carbon Storage (GMCS)
EFRC Director: Emmanuel Detournay
Lead Institution: University of Minnesota
Class: 2022 – 2026
Mission Statement: To develop the fundamental science and engineering capability that will lead to realizing the full potential for the large-scale subsurface sequestration of CO2 via mineralization
A promising strategy to reduce anthropogenic CO2 is to permanently mineralize carbon in mafic and ultramafic geologic reservoirs. These rock masses are advantageous due to their prevalence in the earth’s subsurface and their ability to rapidly store CO2 through mineralization. Recent successful pilot-scale mineral carbon storage projects in mafic rock, including CarbFix and CarbFix2 in Iceland and the Wallula basalt sequestration site in Washington State, have demonstrated storage via mineralization on a time scale of a few years [1-3]. However, storing the levels of CO2 needed to address the present climate crisis requires (i) a significant up-scaling of these operations and (ii) the ability to predict the impact of long-term, large-scale CO2 mineralization on the geologic reservoir. The mission of GMCS is to develop the fundamental science that will lead to realizing the potential for the large-scale subsurface storage of CO2 via mineralization [4-13].
For mafic and ultramafic rocks such as basalt and peridotite, efficient mineralization of the rock mass requires the existence or development of a penetrating fracture network that accommodates the flow and reaction of CO2-bearing fluids. This involves optimizing fully coupled thermal, hydrological, mechanical, and chemical processes that can sustain flow for long-term carbon mineralization. Complex feedbacks exist among fracture propagation, fluid flow, dissolution, precipitation, and fracture closure, including phenomena such as passivation of mineral surfaces that reduce reactive surface area [14]; carbonate precipitation that can clog pores and fractures [15]; subcritical fracture growth [16]; and reaction-driven cracking [17]. These questionsrequire a coupled understanding of fluid flow and transport in fractured media and the chemical and mechanical processes that occur during carbon mineralization. Such a coupled understanding does not currently exist, since the fields of fracture mechanics, fluid flow in fractures, and geochemistry are often studied separately for other subsurface applications such as hydrocarbon extraction, nuclear waste storage, or traditional carbon sequestration where caprocks and seals are used to prevent CO2 leakage [18]. However, carbon mineralization requires a coupled understanding of reaction rates, feedback between geomechanics and geochemical reactions, and the influence of flow and transport.
By expanding the frontiers of interdisciplinary research, GMCS aims to evaluate, for a given CO2 storage operation within a given reservoir, the evolution of the amount of carbon MM(tt) mineralized:
(1) where is the volume of the rock mass and mm(xx,tt) is the mineral carbon density (mass of carbon stored per unit volume of rock). All GMCS efforts are anchored by equation (1), with the aim to determine how different mechanisms affect the amount of CO2 mineralized with time so that the operation can be optimized and upscaled.
This is accomplished by pursuing research along three interconnecting thrusts, using laboratory experiments, analytical tools, and numerical simulations:
1. Reaction-driven cracking and fracture — aimed at elucidating the basic mechanisms affecting the process of carbon mineralization of mafic and ultramafic rock
2. Dissolution and precipitation regimes — aimed at understanding how mineral carbonation processes are affected by the interaction between flow and the surrounding rock matrix
3. Continuum and discrete modeling of fracture networks — aimed at developing capabilities to predict long-term capacity of a mafic or ultramafic reservoir for carbon storage and to design optimal solutions for reservoir stimulation
Examples of current research:
- Theory and Experiments on Micro-Poroelastic Models of Mafic and Ultramafic Rocks (Thrust 1)
- Modeling Mineral Dissolution and Precipitation in Fractured Media across Scales (Thrusts 2 & 3)
- Effects of Fluid Flow, Mixing, and Saturation Index on Mineral Dissolution and Precipitation (Thrust 2)
- Experimental Observations of Chemo-mechanical coupling during Carbon Mineralization in Fractures (Thrust 1)
- Identification of Time and Length Scales for Carbon Mineralization Processes (Thrusts 2 & 3)