How are geochemical reactions in aquifers connected to climate change mitigation?

The storage in deep saline aquifers of CO2 captured at point sources such as coal-fired power plants is a strategy that many regard as critical to limiting global warming to less than 2 degrees Celsius. But is Carbon Capture and Storage (CCS) safe? Might reactions between CO2, the native brine, and the host rocks modify the reservoir structure within ~10,000 years? Where does the injected CO2 go and what is its fate? Can CO2 escape to the overlying drinking water aquifers to cause unwanted reactions and degrade water quality? Our ability to understand and predict geochemical reactions in aquifers is critical for answering these questions.
This lecture will give an overview of geological carbon sequestration efforts and of the research advances in reaction kinetics and geochemical modeling necessary to predict the safety of CO2 storage. Recent innovative research by my students and collaborators on applying non-traditional stable isotope tracers in geochemical kinetics experiments has broken new ground in near-equilibrium reaction kinetics, which is critically relevant to CCS. The Mt. Simon Sandstone in the U.S. Midwest and the Sleipner Project in Norway represent planned and fully operational industrial-scale CO2 storage projects, respectively. I will present examples of numerical simulations of CO2 fate and geochemical reactions from both projects. The connections among the hydrosphere, lithosphere, and atmosphere as well as the overlap between basic science and pressing societal needs—the hallmark of groundwater sciences—become clear through a tour of the fascinating and intriguing CCS efforts around the world.

Further reading:
Zhu, C., Rimstidt, J.D., Zhang, Y.L., Kang, J.T., Schott, J. and Yuan, H.L. (2020) Decoupling feldspar dissolution and precipitation rates at near-equilibrium with Si isotope tracers: Implications for modeling silicate weathering. Geochim. Cosmochim. Acta 271, 132-153.
Zhang, G., Lu, P., Wei, X. and Zhu, C. (2016) Impacts of Mineral Reaction Kinetics and Regional Groundwater Flow on Long-Term CO2 Fate at Sleipner. Energy & Fuels 30, 4159-4180.