The Effects Of Diffusion, Capillary Heterogeneity, And Porous Media Morphology On CO2 Migration In Porous Media

Abstract

The Modified Invasion Percolation (MIP) model was used to simulate the invasion of CO2 into a medium initially saturated with water and the style of capillary heterogeneity in combination with buoyancy and viscous forces were varied to yield 105 different simulation scenarios. Thereafter, the invasion of the CO2 gas is simulated using a finite difference model and the effective mass transfer coefficient is determined and linked to various styles of capillary heterogeneity. Results show that an increase in saturation does not result in an increase in mass transfer coefficient rather, the surface area, which in turn is controlled by the interplay of capillary heterogeneity effects and buoyancy forces, control the average mass transfer coefficient and the fractional mass left. We further correlated the mass transfer coefficient with the average surface area and saturation and we found that a very strong positive correlation coefficient exists between the surface area of the CO2 and mass transfer coefficient and a weak negative correlation coefficient exists between the average mass transfer coefficient and saturation exists, which improves with increasing stratification and increasing buoyancy forces. We also used a harmonic mean model to estimate the effective diffusivity in a Room Temperature Ionic Liquid (RTIL) membrane. A metallic porous membrane was thoroughly saturated with Emim(Tf2N) and placed in a diffusion chamber. CO2 gas was injected into the upper diffusion chamber and was alloto completely diffuse through the RTIL into the lower diffusion chamber. Lag-time technique was used to analyze the pressure-time data. Two different membrane configurations were used; 0.2-0.2&mgr; and 0.5-0.5&mgr;. Results show that the harmonic mean model reasonably predicts the effective diffusivity obtained from the experimental measurements