Rates of mineral dissolution under CO2 storage conditions

• Geochemical models for CO2 storage benefit from a description of mineral dissolution rates based on available kinetic data.
• Uncertainty in kinetic model parameters leads to large uncertainty in some predicted mineral dissolution rates.
• An overview of modelling mineral dissolution kinetics is provided and ranges of uncertainty in kinetic parameters plotted.
• Variability in the reported parameters for iron-rich clay minerals leads to some of the least robust predictions.

Evaluating the potential of a sedimentary basin reservoir to securely store CO2 benefits from a comprehensive understanding of the geochemical reactions that take place once CO2 is injected into a formation. In particular, models that predict the transport and reaction of CO2 within a reservoir require a definition of the types of reactions affected by enhanced levels of CO2 and how the kinetics of these reactions will affect a heterogeneous mineralogy and formation waters within a reservoir over time. In this review we evaluate rate models used to describe mineral dissolution kinetics and compare the range in values reported for the kinetic parameters used to describe the reactivity of various minerals relevant to mainly siliciclastic reservoirs. Parameters that have a significant impact on model results include the reactive surface area of a mineral, the apparent activation energies used to extrapolate reaction rates to the temperatures of potential storage reservoirs (c. 50–125 °C) and the in-situ pH of formation waters with elevated concentrations of dissolved CO2. The variation in reported values for these parameters can lead to predicted rates that span many orders of magnitude for a given mineral. Despite these uncertainties recent success with geochemical models has been made by applying a Monte Carlo approach to optimise the kinetic parameters for minerals where robust thermodynamic and kinetic data do not exist.