Parameterizing geochemical models: do kinetics of calcite matter?

Carbon capture and storage is considered one of the methods that can help reduce greenhouse gas emissions from point sources. The captured CO2 commonly contains impurities related to the fuel source. Critical to safely storing CO2 with impurities is an understanding of the chemical behavior of the CO2-impurity-water-rock system. Numerical modelling of storage scenarios provides one way of developing that understanding. In this study reactive transport modelling of CO2 with SO2 injection at a proposed storage site in Australia was conducted to evaluate the impact of incorporating calcite dissolution as either an equilibrium or kinetically controlled process. It was determined that proximal to the injector, there is an impact on model outcome for reactions that are strongly coupled like the calcite dissolution/gypsum precipitation reactions. The assumption of calcite equilibrium may lead to over estimating the extent of gypsum precipitation and pH buffering. That overestimation may have significant implications on site leakage risk assessments. (C) 2017 Published by Elsevier B.V.