Simulated Fluid-Rock Interactions During Storage Of Temporally Varying Impure CO2 Streams

Impurities in CO2 streams influence the chemical reactivity in and mineral alterations of CO2 storage formations. Fluid-rock interactions have been investigated by means of reactive transport simulations using TOUGHREACT V3.0-OMG. A novel method has been established through which co-injection of SO2, NO2, O2 and H2 with temporally varying concentrations can be implemented in reactive transport model scenarios. The paper presents (i) model testing and validation against simulation results obtained by Xu et al. (2007), and (ii) results acquired from 1D-radial multiphase reactive transport simulations investigating two generic Bunter Sandstone reservoir formations. Results gained applying the novel hybrid approach show that modelling-based inaccuracies have largely been eliminated and inconsistencies are minimized. For the investigated generic Bunter Sandstone reservoir formations, two major geochemical processes are apparent. While the acidifying impurities SO2 and NO2 trigger carbonate dissolution coupled to anhydrite precipitation, presence of O2 leads to dissolution of iron-rich chlorite and subsequent goethite precipitation. Absolute changes of porosity for the two generic Bunter Sandstone formations are below 1 %. The total quantitative impact of SO2, NO2, O2 and H2 on mineral reactions is rather limited and their impacts on the petrophysical properties of the two investigated generic Bunter Sandstone formations are geotechnically negligible.