A novel methodology for measurement of the diffusion coefficient between CO2 and oil based on quantification of the oil droplet swelling behavior

Accurate and fast determination of the diffusion coefficient of the CO2/oil system is essential in CO2 enhanced oil recovery (CO2-EOR) and CO2 geological sequestration practices. In this work, a novel methodology is proposed and demonstrated on measuring the diffusion coefficient of the immiscible CO2/oil binary systems based on quantification of the oil droplet swelling behavior. Five oil samples, including n-decane, n-dodecane, n-tetra-decane, n-hexadecane and liquid paraffin, are employed as the oil phase and the diffusion coefficient for each CO2/oil system were determined. After validation of the methodology based on good agreements between the measurement and the reported results for both the pure component oil and the synthetic oil, the diffusion characteristics of the CO2/oil systems are scrutinized in the pressure range 2-10 MPa and the temperature range 26.9-82.1 celcius. The measurement results clearly show the elevated system pressure could lead to stronger diffusion processes between the CO2 and the oil phase, while the temperature impacts on the diffusion process are more complex due to the synergistic effects of CO2 density and the oil viscosity. Performed in the state-of-the-art drop shape analyzer within a short measurement period, it is expected the proposed methodology could provide an efficient supplementary for diffusion coefficient measurements of the CO2/oil binary systems.