Effect of Temperature on the Geological Sequestration of CO₂ in a Layered Carbonate Formation

Geological sequestration of carbon dioxide (CO₂) in deep saline aquifers is one of the most promising technologies for large-scale CO₂ mitigation. Temperature can play a significant role in the ensuing geochemistry, affecting equilibria in a multicomponent system and impacting reactive transport processes. The objectives of this study are to quantify the effect of temperature on storage efficiency, solubility trapping of CO₂, pH of residual brine, and changes in the mineralogy and porosity. Using toughreact 3.3 (a reactive transport simulator), we have simulated the injection of CO₂ into a heterogeneous layered carbonate formation for a period of 50 years, followed by a 50-year equilibration period with no injection. Mineralogy and physical properties of the simulated aquifer are based on a dolomitic limestone aquifer located within the South Florida Basin. Simulations were conducted for seven values of temperature. Density of supercritical CO₂ decreases with an increase in temperature, which leads to higher buoyancy at elevated temperatures. Therefore, the storage efficiency of the aquifer decreases as temperature increases. Simulation results indicate that an increase in temperature from 35 °C to 95 °C results in a 35% decrease in storage efficiency. However, surprisingly, solubility trapping of CO₂ increases with an increase in temperature because the interfacial area increases with temperature. Temperature effects on pH and on porosity change (due to mineral dissolution and precipitation) are small. The study can be helpful in screening a reservoir for geological carbon storage based on the formation temperature.