Experimental mineral dissolution in Berea Sandstone reacted with CO2 or SO2 –CO2 in NaCl brine under CO2 sequestration conditions

• Greater mineral dissolution during SO2–CO2-brine experiments compared with CO2-brine
• Mineral behaviour shown via SEM images of identical spots pre- and post-experiment
• Geochemical modelling indicated that chlorite reacted during all experiments.

A comparison of the geochemical changes induced in sandstone by either pure or impure CO2 at geological CO2 storage conditions was investigated. Samples of Berea Sandstone were batch reacted in 1% w/v NaCl brine saturated with pure CO2 or mixed SO2–CO2 gas for 360 h at 50 °C and 10 MPa. Geochemical analysis of incremental water samples showed increases in the concentrations of elements such as calcium, magnesium, iron, manganese, and silicon throughout experiments, likely being the products of carbonate and reactive silicate dissolution. Scanning electron microscope images taken of specific points of interest before and after batch reactions confirmed dissolution of carbonates, but showed no reaction for minerals such as K-feldspar. The magnitude of apparent mineral reaction was higher for the mixed gas SO2–CO2-brine experiment, with geochemical modelling also indicating greater dissolution of reactive silicates such as chlorite, and potential precipitation of amorphous silica.