Experimental Verification of CO2 Dissolution Rate Due to Diffusion Induced Convection

Abstract

An experimental setup has been designed for measuring the dissolution rate of buoyant CO2 into the water phase below. Experiments were performed in a high-pressure cell, where the water phase was stabilized by a porous medium to mimic the situation of a gas cap in a storage reservoir. As many previous tests have been performed in 2D cells, this setup allows for 3D measurements of diffusion-induced convection. The tests are performed at high pressure where CO2 is at high density, similar to a real storage situation and the dissolved CO2 is measured by metering the pump that is automatically maintaining constant pressure. This allows rate measurements in a 3D environment. The basic interest was to determine the dissolution rate in the convective regime, but also the diffusion coefficient of CO2 in water was determined by this experimental setup. In addition, the onset time of convection was estimated. The result show that the dissolution rate measured during convection was one to two order of magnitude faster than predicted by semi-empirical correlations obtained by numerical simulations. The estimated onset time of convection was shorter than theoretical prediction. The overall results suggest that diffusion induced convection plays a more important role than previously assumed.