Innovative Laboratory Techniques for Investigating Mineral Sequestration of Supercritical CO₂ in Sandstone Reservoirs

Carbon dioxide is the main greenhouse gas (GHG) due to its abundance in the atmosphere. CO2 capture and geological storage (CCS) technologies contribute to mitigating the effects of climate change by reducing its concentration. This requires suitable environments such as deep saline aquifers, which offer great potential on an industrial scale in Spain. These must guarantee the tightness of CO2 and the technical feasibility of injection, being key to the trap mechanisms developed at depth. Porous and permeable sedimentary units, such as sandstones, are ideal for this purpose, although mineralogical reaction rates in them tend to be slow. This study presents the development of an ATAP (High Temperature-High Pressure) assay device designed to reproduce the mineral sequestration of supercritical CO2 (SCCO2) in sandstone aquifers. Using computed tomography, changes in a rock saturated with brine and SCCO2 were observed for two months under controlled conditions (up to 120°C and 500 bar). Porosity variations were measured with helium pycnometry and compared with previous studies. The results highlight the need to reduce sample size, incorporate mineralogical, geomechanical and chemical analyses, and adjust test times according to rock characteristics. In addition, the use of catalysts to accelerate CO2 carbonation reactions is proposed.