Surfactant/Cosolvent Flushing of DNAPL Contamination

By the 1950s, petroleum engineers were using water-flooding to expand production from oil fields after in-situ pressures had decayed and production had greatly decreased (i.e., “pump and refine”). But water-flooding eventually left behind much by-passed oil because the injected water had lower viscosity than the oil, consequently the water would tend to flow through permeable pathways without displacing the by-passed oil. Mobility control was developed by petroleum engineers to improve recovery of oil by providing a high viscosity push to the injected aqueous solution. In NAPL remediation, an in-situ increase in viscosity can be attained by either injecting an aqueous polymer solution with (or without) surfactant or by injecting sequential slugs of surfactant then air to form a viscous foam in high-permeability units. The design and the field implementation of both surfactant-polymer and surfactant-foam floods is presented for two alluvial aquifers contaminated with coal tar and chlorinated solvents, respectively.