Assessing the Impact of Wettability and Heterogeneity on NAPL Dissolution Fingering

The emergence of preferential dissolution pathways, or fingers, in residual nonaqueous phase liquid (NAPL) zones can affect NAPL removal rates significantly. In such cases, standard mass-transfer models, which do not account for flow bypassing associated with these dissolution pathways, can result in predicted mass- transfer rates that are orders of magnitude too high. In previous work, an upscaled mass-transfer relationship based on dissolution front growth dynamics was shown to be capable of accounting for the impact of fingering on NAPL mass-transfer rates in water-wet, homogeneous systems. While promising, extending this approach requires better characterization of dissolution fingering under a wider range of conditions. To this end, we consider the influence of system wettability, spatial heterogeneity, and experimental boundary conditions on NAPL mass transfer and dissolution-fingering dynamics. Our investigation includes a series of two-dimensional laboratory experiments as well as computational modeling using modern, high-resolution numerical methods.