Investigating the Impact of Mineral Dissolution and Precipitation on Fluid Flow Characteristics in Basalt After CO2 Injection

Geological CO₂ sequestration in basalt formations represents a promising approach to mitigate climate change through secure carbon dioxide storage via mineral carbonation. This study investigates mineral dissolution, precipitation, and their influence on pore structure change during sequestration in basalt formations through batch experiments under controlled conditions (P: 8 MPa, T: 100 °C). The experiments were conducted in an autoclave system containing brine, where basalt sample (2 cm width and 9 cm height) was partially submerged to mimic a CO₂-brine boundary during CO₂ injection in basaltic formation.

CT imaging technique was employed to compare changes in pore structure in basalt before and after the experiment. To evaluate impact of basalt-brine-CO₂ reaction on pore structure, regions of interest (ROIs) were defined, focusing on the reacted zone and the transient zone, where mineral precipitation was most prominent. The reacted zone exhibited the formation of reddish minerals, likely iron oxide minerals, compared to unreacted zone. The transient zone, located at the CO₂-brine interface, displayed the deposition of white minerals. These findings demonstrated that mineral dissolution/precipitation varied spatially, leading to heterogeneous changes in pore structure and fluid flow characteristics. The significant precipitation observed in the transient zone caused pore connectivity reduction, potentially impacting permeability and flow pathways. This study would contribute to an understanding of fluid flow behavior during long-term CO₂ storage in basalt.