Non-isothermal modeling of CO₂ injection into saline aquifers at a low temperature

To investigate the effects of temperature on the CO₂ storage in the deep saline aquifers, we set up a 2-D non-isothermal numerical model with simulating the CO₂ injection into the aquifers at a low temperature. The evolution of the CO₂ plume and the temperature in the aquifer were studied, and using temperature signal to monitor the arrival of CO₂ plume was also evaluated. In addition, the deviance of the isothermal model was analyzed. The results show when the cold CO₂ is injected into the aquifers, the aquifer can be divided into three zones in the direction away from the injection well during the injection period: temperature drop zone, temperature transition zone, and temperature rise zone. The temperature rise can reach approximately 1 °C in the temperature rise zone during the injection period, which should be enough for the temperature sensor to detect the arrival of the CO₂ plume. However, the value of the temperature rise reduces with distance from the injection well. Consequently, we indicate that it is not suitable to monitor the long-term migration of the CO₂ plume using temperature signal, especially after the injection stops. The initial formation temperature strongly affects the evolution of the CO₂ plume and the temperature distribution after the CO₂ injection. Not only the storage is safer, but also using temperature signal to monitor CO₂ plume is more feasible in the cold aquifer. The deviance of the isothermal model is small in the mass fraction of dissolved CO₂ and the arrival time of CO₂ plume throughout the simulation. However, the deviance of pressure buildup is great and increases with time (up to 15 %) during the injection period. The non-isothermal model is necessary to accurately assess the pressure buildup around the injection well during the CO₂ injection period.