Enhanced Gas Recovery (EGR) involves CO2 injection into natural gas reservoirs to both increase gas recovery and trap CO2. EGR viability can be determined by reservoir simulations; however, these require a description of fluid dispersion (mixing) between the supercritical CO2 and natural gas. Here, this dispersivity (alpha) in sandstone rock plugs as a function of residual water fraction is quantified. To ensure the accuracy of such data, a novel core flooding experimental protocol that ensured an even spatial distribution of water was designed, minimized erroneous entry/exit contributions to mixing, and minimized dissolution of the CO2 into the water phase. Dispersivity was found to increase significantly with water content, although the differences in between sandstones were eliminated upon the inclusion of residual water. This enabled development of a correlation between and water content and, hence, between the dispersion coefficient and Peclet number that is readily incorporable into reservoir simulations. (c) 2017 American Institute of Chemical Engineers