Comparative Study of CO₂ Mineral Trapping: A Numerical Investigation

During CO₂ geo-storage, mineral dissolution is considered as the safest trapping technique but the longest and the most complicated as it includes different mechanisms: geo-chemical reactions, chemical reactions and physical mechanisms like diffusion and advection. Many factors also influence the mineral trapping capacity of the geological formation like mineralogy, temperature, pH, CO₂ fugacity, pressure of CO₂ and salinity of the brine. The scope of this study is to compare the mineral trapping of CO₂ of sandstone and carbonate formations using a numerical simulation approach as a function of temperature, salinity and mineralogy of the subsurface systems. Numerical simulation will be performed in this study using the geo-chemical, multi-component, non-isothermal, and multi-phase simulator CMG-GEM. 2D models will be used to study the mechanisms occurring during mineral trapping and how they affect its efficiency. Sensitivity analysis will be performed on the effect of temperature, mineralogy and brine salinity on CO₂ mineralization tendency for both geological formations at the same conditions. The mineral composition, porosity and storage capacity will also be evaluated. It was found that dissolution and precipitation of minerals occurred during and post CO₂ injection. The presence of small quantity of illite tends to decrease immensely the trapping capacity of CO₂. Moreover, temperature and salinity tends to promote the mineral activity during CO₂ storage. This paper thus provides new insights into the dynamics of CO₂ storage by mineral trapping pertinent to sandstones and carbonates. Furthermore, it will help in site selection evaluation for carbon geo-sequestration (CGS) projects. Extensive study of the parameters affecting the mineral trapping will be presented.