Geological sequestration of CO2 is internationally considered as a potential means of contributing to the planned reduction in anthropogenic emissions. Injecting CO2 at depth will involve the acidification of groundwater and the possible dissolution and precipitation of minerals in the reservoir and seal formations. Porosities may change as a consequence of these reactions, together with key flow and transport properties (permeability, diffusivity). These changes could possibly exceed the natural ranges of values in the geological formations. The injection and migration of CO2 could also be affected by these processes. The focus of this session will be to present experimental and modelling studies applied to the understanding and quantification of mineral reactions in the context of CO2 sequestration, together with the impact of these changes on fluid flow and solute transport.