Dispersion of supercritical CO₂ and CH₄ in consolidated porous media for enhanced gas recovery simulations

Enhanced gas recovery (EGR) is a promising technology offering both CO₂ sequestration and enhanced recovery of natural gas when CO₂ is re-injected into producing natural gas reservoirs. Mixing of CO₂ and CH₄ is, however, potentially problematic and could lead to asset contamination. Essential for effective assessment of EGR are reservoir simulations that require accurate descriptions of dispersive mixing of the two supercritical fluids. Here we systematically measure this supercritical dispersion data in sandstone rock cores, accounting for erroneous gravitational and entry/exit contributions. Using the measured value of dispersivity (α) as the characteristic length scale for mixing, we are able to reconcile our dispersion data with literature values for unconsolidated media (packed beds). Furthermore, our measurements of supercritical dispersion in consolidated porous media have almost 50 times less scatter than the data available in the literature for packed beds. The consequential dispersion correlation as a function of medium Péclet number captures variations with temperature, pressure and dispersing species.