Lithology Controls the Trade-Off Between CO2 Injectivity and Post-Injection Reaction Pathways in Geological Storage

Reservoir screening for geological CO2 storage must balance hydraulic performance against geochemical reactivity, but these attributes are rarely compared under a common numerical design. We used a unified two-dimensional radial TOUGHREACT v3.32/E CO2N benchmark to compare marble, granite, and sandstone at 75 and 100 °C. Six cases shared the same geometry, brine salinity, flow functions, boundary conditions, and nominal 12.5 kg/s injection schedule. Injection lasted 10 years, followed by post-injection evolution to approximately 100 years. At 10 years, a finite-domain component balance placed 86.51–87.66% of injected CO2 in the gas phase and 12.39–13.47% in incremental aqueous CO2. Closure errors were 0.0025–0.0836%, and SmCO2 remained zero within output precision. Sandstone produced the lowest overpressure (10.7–12.0 bar), marble provided the strongest carbonate buffering, and granite showed the largest pressure and acidification penalties. A G75 rerun with half the maximum time step reproduced the 10-year metrics but reduced the approximately 100-year local porosity extreme from 18.224% to 0.171%, showing that the original long-term extreme was not time-step robust. Sensitivity tests identify injection rate as the primary control on pressure and plume extent, whereas reactive surface area mainly controls carbonate-reaction magnitude. These results show that lithology does not rank along a single performance axis: robust screening must jointly evaluate injectivity, plume footprint, phase partitioning, and post-injection reaction pathways.