Experimental Measurement of CO_2 Diffusion Coefficient in Porous Media using NMR Micro-Imaging

摘要

In the recent years, using CO_2 injection into oil reservoirs to enhanced oil recovery (CO_2-EOR) has attracted more and more attention from industry and laboratory experiment. The mass transfer and diffusion of CO_2 in oil is one of the key parameters of displacement process. In this study, by employing nuclear magnetic resonance (NMR) and a nonlinear fitting equation, the effective diffusion coefficient is calculated quantitatively. It proved that the experimental apparatus and mathematical procedure employed in this study were reliable to investigate and calculate the diffusion coefficient. Three main conclusions were obtained from this study: (i) the effective diffusion coefficient increases as the initial pressure increases; (ii) the relationship between CO_2 diffusion coefficient and pressure is nonlinear; (iii) the temperature effect on diffusion of CO_2 in oil is obvious because of the reduction in oil viscosity.