Geochemical transformations induced by CO₂ injection in Lithuanian saline aquifers: implications for carbon sequestration

Carbon capture and storage (CCS) in subsurface reservoirs is a promising solution for mitigating carbon dioxide (CO₂) emissions. This study investigates the geochemical changes induced by CO₂ injection in Lithuanian saline aquifers through an experimental approach. Core flooding experiments were conducted on four outcrop sandstone core samples, involving cyclic brine and CO₂ injections to assess alterations in reservoir properties. One sample (BU1) was exposed to CO₂ for two days, whereas the remaining three samples (BL1, BS1, and BP1) underwent immediate CO₂ injection following brine injection. The findings showed that CO₂ injection reduces permeability, likely due to salt precipitation, as evidenced by scanning electron microscopy (SEM) imaging or due to possible mineral dissolution and precipitation. The sample BU1 showed the maximum decrease in permeability (23%) after being exposed to CO₂ for two days. The present work highlights the importance of understanding the geochemical interactions required for long-term stability and storage capability of CO₂ in a reservoir. Additionally, the study bridges a critical gap by presenting empirical data on Lithuanian saline aquifers, where such studies are sparse, and provides insights for future investigations on actual reservoir samples.