Kinetics of CO2 dissolution for underground applications

In the current energy transition context, underground storage of carbon dioxide (CO2) in salt caverns and aquifers has emerged as a promising solution for the Power-to-Gas process complications. However, mass exchange between the CO2 and the aqueous phase present in the storage site remains a major problem. This paper addresses the question of the kinetics of this mass exchange by performing both experimental and numerical investigations. A series of experiments under storage conditions were carried out in a PVT (Pressure-Volume-Temperature) cell, exposing a volume of CO2 to pure water or brine at low and high pressure values ranging between 10 and 16.8 MPa and at constant temperatures of 30 and 40 °C. In order to interpret the obtained experimental results and to characterize the transient mass exchange, two modeling approaches were developed: a simplified one based on pure diffusion, and a second combining pure diffusion with density-driven natural convection. Both modeling approaches have proven accurate in predicting the kinetics of CO2 dissolution. The scope of this study is limited to the laboratory scale but it can be used to quantify the CO2 dissolution on the storage site scale.