Mineralogical alterations of sandstone formations of Precaspian basin induced by the CO2 injection for permanent underground storage

Geological CO2 sequestration in the depleted oil wells could potentially provide a massive capacity for safe carbon fixation at depth. In the current study, we have performed hydrogeological and geochemical modeling to simulate the extent of subsurface gaswaterrock interactions after the injection of CO2 into sandstone formations of Precaspian Basin the leading candidate for the safe long-term geological carbon storage in Kazakhstan [1]. Using two-dimensional modeling in the TOUGHREACT simulation environment, we have thoroughly investigated mineralogical alterations, fluid composition changes, and variations in geophysical properties by supercritical CO2 injection. Ebeity reservoir, located on the northeastern side of the Caspian Sea, was chosen as a representative geological formation for the modeling of underground CO2 storage with the injection period of 100 years and subsequent monitoring for 10000 years. The reactive transport modeling results indicate that the injected CO2 could spread in 2000 m towards a radial direction from the injection point, and it could be solidified in the form of calcite, dawsonite, and dolomite as secondary mineral phases. The extensive dissolution of albite, kaolinite, and magnesite improved the porosity and permeability of the geological formation to promote its CO2 injectivity and storage capacity. According to the simulation results, the porosity could decrease up to 3% in locations near the injection point, a strongly acidified zone, which could also alter the possibility of the formation of carbonates. The simulation results suggest the huge potential of geological carbon dioxide storage in the depleted oil reservoirs of Kazakhstan, providing a relatively safe permanent CO2 fixation in the form of minerals. Keywords: CO2 injection, Mineralogical alteration, Radial transport, Toughreact. Acknowledgement: This study was supported by the NU Research Grant (091019CRP2106) and MES of the Republic of Kazakhstan (AP09260229). Reference: [1] Abuov, Y., Seisenbayev, N., & Lee, W. (2020). CO2 storage potential in sedimentary basins of Kazakhstan. International Journal of Greenhouse Gas Control, 103, 103186. doi:10.1016/j.ijggc.2020.103186