Convective mixing fingers and chemistry interaction in carbon storage

•Convective mixing in carbon storage is simulated by a reactive transport model.•Geochemistry and fluid flow interaction is studied for various Ra and Da numbers.•A realistic carbonate-sulphate-rich aquifer from a potential CCS project is used.•Chemical reactions enhance convection and CO2 dissolution in this system.•Calcite buffers acidic fronts and fluid mixing drives porosity development.