Mass transfer coefficient measurement during brine flush in a CO2-filled packed bed by X-ray CT scanning

A clear understanding of mass transfer properties during fluid injection in porous media is important for safe CO2 storage. In this study, dynamic experiments were conducted to elucidate transport during brine injection into a gaseous CO2-filled packed bed using X-ray CT technology. Homogenous glass beads were packed into the bed. Brine was injected downward at 0.005 and 0.03 mL/min. The CO2 distribution during brine injection was visualized along the flow direction, which reflected the mechanism transform between displacement and dissolution. The results showed that the distribution was related to the pore structure of the packed bed and flow rates. In addition, CO2 saturation and concentration profiles were obtained at various time points. CO2 concentrations predicted from saturation were orders of magnitude lower than equilibrium solubility. An image analysis technique was employed to determine the interfacial area, which was a function of saturation. Local and overall mass transfer coefficients which were correlated with local concentration and specific interfacial areas were calculated. This study provided a quantitative investigation of gas-liquid mass transfer in a packed bed, which contributed a calculated mass transfer rate during CO2 storage.