Reactive Transport Modeling and Sensitivity Analysis of CO₂–Rock–Brine Interactions at Ebeity Reservoir, West Kazakhstan

This study investigated the reactive transport modeling of CO2 injection into the Kazakhstan reservoir to identify mineralogical and porosity changes due to geochemical reactions. Additionally, sensitivity analysis was performed to test the effect of the surface area and gas impurity on the CO2 storage capability. Despite the current need to investigate carbon sequestration in Kazakhstan, a limited number of studies have been conducted in this field. The Ebeity oil reservoir sandstone formation in the Pre-Caspian Basin has been tested as a potential CO2 storage site. The 1D PHREEQC simulation results of 10,000 years suggest that reservoirs with a higher abundance of these secondary carbonates may be better suited for long-term CO2 sequestration. The concentration of Fe3+ fluctuated, influenced by magnetite and siderite dissolution, leading to ankerite precipitation at 20 and 40 m. The porosity increased from 15% to 18.2% at 1 m and 20 m, favoring a higher CO2 storage capacity, while at 40 m, it remained stable due to minor mineral alterations. A reduced surface area significantly limits the formation of dawsonite, a crucial secondary mineral for CO2 trapping. For instance, at λ = 0.001, dawsonite formation dropped to 6 mol/kgw compared to 24 mol/kgw at λ = 1. Overall, the results of this study can play an essential role in future geological analyses to develop CO2 storage in Kazakhstan for nearby reservoirs with similar geological characteristics.