This study focused on the reactions between carbon dioxide (CO 2), porewater and host rock during geological CO 2 storage in deep reservoirs. The aim of this work was to provide a well-constrained laboratory experiment reacting known quantities of minerals with CO 2-rich fluids, to simulate situations where CO 2 is being injected into lithologies deep underground. The experiment was undertaken using a Ti-column, 100 cm long, held within a large pressure vessel. The column was packed with a simplified mineral assemblage. The reactant fluid was equilibrated with CO 2 at a temperature of 130°C and a pressure of 300 bar, before being pumped into the column held under the same conditions. Fluid was passed along the column at a constant flow rate for approximately 3.5 months. Fluids collected from the outlet end of the column were analysed to provide data on the fate of the dissolved species. 0n completion of the experiment, the column was then examined for mineralogical changes. The experimental results can be used as a test case for predictive geochemical computer modelling. Such models will help improve our ability to predict the long-term fate of CO 2 stored underground.