Numerical simulation of surfactant-enhanced remediation of heterogeneous aquifer contaminated with nonaqueous phase liquids

Abstract

A three-dimensional, multiphase, multicomponent compositional simulator was employed to simulate nonaqueous phase liquid (NAPL) migration during surfactant-enhanced aquifer remediation (SEAR) in spatially correlated heterogeneous fields. Aquifer heterogeneity was accounted for by considering the permeability to be a spatially random variable, and a geostatistical method was used to generate random distributions of the permeability. Spatial distributions of saturations in the NAPL and temporal changes of organic recovery, effluent concentrations of organics and surfactant, and pressure drop at the injection well for heterogeneous aquifers were compared with those in a homogeneous aquifer to examine the effects of different levels of heterogeneity. Variations in permeability fields have a pronounced effect on the organic recovery efficiency due to the long-term persistence of nonaqueous phase liquid and additional dispersion. Permeability heterogeneity also leads to the tailing off of effluent organic concentrations and significant loss in injectivity over the remediation period. For a small slug of surfactant, surfactant-enhanced remediation resulted in a relatively small improvement in the recovery of NAPL, especially in highly heterogeneous aquifers. Migration of high-concentration organic plumes to other layers by crossflow was also found to have a significant influence on SEAR behavior.