Effects of temperature on salt precipitation due to formation dry-out during CO2 injection in saline aquifers

When CO2 is injected into saline aquifers, salt precipitation will occur near the injection well. To investigate the effects of temperature on salt precipitation, a series of non-isothermal numerical models were conducted by simulating the injection of cold CO2 into the aquifers with relatively high temperature. Some thermal processes, the evolution of CO2 plume, salt precipitation, the effects of gravity, and permeability reduction were analyzed. Furthermore, the deviance of the isothermal model was evaluated. The results show that the heat exchange between cold CO2 and hot rock significantly affects the formation temperature. The injection of colder CO2 can obviously decrease the extent of salt precipitation. A localized region with very large solid saturation occurs near the upper portion of the dry-out front. Furthermore, another localized region with larger solid saturation emerges near the lower portion of the dry-out front when the CO2 injection rate is low. This region seems to move upward because of dissolution and reprecipitation of salt caused by capillary-driven backflow of the aqueous phase. Salt precipitation can result in a significant decrease in permeability. Temperature-induced change of CO2 viscosity seems to have greater impact on the pressure evolution in the formation than precipitation-induced change of permeability. (C) 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.