Transport in Porous Media, Vol.134, No.3, 565-592, 2020
Shallow Subsurface Environmental Remediation by Using Tracer-Surfactant-Foam Processes: History-Matching and Performance Prediction
In situ subsurface remediation has been widely used as an efficient means of cleaning up non-aqueous phase liquid (NAPL) from contaminated soils and aquifer. The use of tracer, surfactant and foam is often considered to keep track of the propagation of injected fluids in the medium, dissolve and mobilize contaminants trapped by capillary forces, and overcome the level of heterogeneity and improve displacement and sweep efficiencies. This study shows an actual remediation process to reduce NAPL within a military base in South Korea, by injecting tracer and surfactant solutions together for a duration of 10 days. The site consists of 5 m-by-5 m area with 3 m depth under the existing structure of fuel-distribution facility. The results show that (a) computer simulations can be successfully performed to history-match the production of tracer and oil species from three extraction wells during field tracer and surfactant injection tests and (b) such a successful match can be combined with identification of the major pattern of the heterogeneity in the site. With estimated foam strengths from separate column tests, this study further extends the scope to the use of surfactant-foam remediation processes to examine how foam with a reduced gas mobility (causing higher apparent foam viscosity and pressure gradient) helps mobilizing and producing more oil, hence leading to improved displacement efficiency. Surfactant/foam processes are shown to have potential in overcoming subsurface heterogeneity and thus improving overall in situ remediation performance.