The Importance of Mineral Surface Areas Exposed to Open Pores in Rotliegend Sandstones for Modelling CO2 Water-rock Interactions

Rotliegend reservoir rocks from the northern Netherlands were analysed in terms of mineralogical features, diagenetic mineral types and mineral surface areas which are exposed to open pores (effective mineralogy). The consideration of the effective mineralogy in comparison to the volumetric bulk rock composition of sandstones and the integration into CO2-water-rock simulation has shown that the mineral reactions are sensitive according to the initial data set. For the test scenario the results show that during CO2 storage especially long-term carbonate and silica reactions are affected. For the effective mineralogy data Mg-smectite stays in equilibrium with the solution which is caused by a higher initial amount of hematite and the release of iron for siderite precipitation. This reaction lowers the bicarbonate content in the solution and forces dolomite and ankerite to dissolve consequently. On the other hand Mg-smectite is unstable and carbonate minerals stay in equilibrium at the end of the simulation according to the volumetric mineralogy data.