Dissolution of CO2 in Aquifer Due to Natural Convection

Abstract

CO2 is the main compound identified as affecting the stability of the Earth’s climate of all greenhouse gases generated globally. It contributes significantly to climate warming and has risen from about 280ppm immediately prior to the industrial revolution to about 370ppm today. Geological storage of CO2 or the injection and stabilization of large volume of CO2 in the subsurface is one option being employed against rising CO2 emissions into atmosphere. It is important to have an overview of long-term fate of CO2 into the subsurface and know which scenarios can happen after injection and stabilization of CO2.

Convective mixing is a result of the density instability created by the diffusion near the interface. Due to diffusion, the upper part of the formation water is saturated in CO2. Plumes of CO2 move downwards after a characteristic time lapse and with a characteristic width. It is important to notice that the literature defines the first stated convection process as a density driven convection, though temperature driven convection is also a result of a density difference induced by temperature variation.

The black-oil simulator in a large scale has been used in this master’s thesis. In this study, several simulation models with different Cartesian grid sizes have been used on both two and three dimensional, to observe the onset of convection as CO2 dissolved in the aquifer.