An Experimental Study of the Enhanced Mass Transfer Process by CO2 Absorption for Carbon Storage in Saline Aquifers
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- Studentoppgaver (TN-IEP) 
Diffusion of CO2 into water-based solutions generate an instability at the interface as a result of density differences. The rate of dissolution, the final saturation pressure and the mixing regime caused by convection dominated diffusion are important parameters when evaluating CO2 storage in geological formations. For this thesis, pressure decay experiments were conducted inside a low pressure (5-7 bar) transparent cylinder-cell with nonsaline and saline water-based solutions containing a pH indicator. In addition, a pressure decay model was derived to study the rate of diffusion and the corresponding final saturation pressure from the experiments conducted. The model was derived with suitable boundary conditions, to keep calculations simple while maintaining high accuracy regarding the measurements. Furthermore, visual interpretations of the mixing regime caused by the enhanced mass transfer mechanism were discussed. This was done in order to understand the contribution of the early and late time convection dominated diffusion of CO2 into the solutions. The experiment performed with saline water-based solution in a porous system had a noticeable reduction in the diffusion coefficient. A saturation pressure close to the ambient pressure is desirable to utilise the formation to its fullest potential without exceeding the storage capacity or fracture pressure of the cap rock. In addition, the convection flow showed a significant contribution to the enhanced mass transfer mechanism. The fingers propagated mainly downwards before merging or expanding in the horizontal direction. The observation is important regarding safe and protracted storage of CO2, where the risk of leakage is highly reduced.
Master's thesis in Petroleum engineering