MODELING UNSTABLE ALCOHOL FLOODING OF DNAPL-CONTAMINATED COLUMNS

Abstract

Alcohol flooding, consisting of injection of a mixture of alcohol and water, is one source removal technology for dense non-aqueous phase liquids (DNAPLs) currently under investigation. An existing compositional multiphase flow simulator (UTCHEM) was adapted to accurately represent the equilibrium phase behavior of ternary and quaternary alcohol/DNAPL systems. Simulator predictions were compared to laboratory column experiments and the results are presented here. It was found that several experiments involved unstable displacements of the NAPL bank by the alcohol flood or of the alcohol flood by the following water flood. Unstable displacement led to additional mixing compared to ideal displacement. This mixing was approximated by a large dispersion in one-dimensional simulations and or by including permeability heterogeneities on a very small scale in three-dimensional simulations. Three-dimensional simulations provided the best match. Simulations of unstable displacements require either high-resolution grids, or need to consider the mixing of fluids in a different manner to capture the resulting effects on NAPL recovery.