Dynamics of surfactant-enhanced oil mobilization and solubilization in porous media: Experiments and numerical modeling

• Multipoint resistivity is used to monitor oil mobilization and solubilization rates.
• Oil mobilization is evident at early times and oil solubilization at late times.
• A dispersion-like equation is used to model surfactant-driven oil mobilization.
• Kinetic parameters of both processes are estimated with inverse modeling.
• Solubilization rates of oil ganglia are estimated from tests on glass micromodels.

A fast and accurate technique based on multipoint electrical measurements is used to monitor the hydrocarbon mobilization and solubilization in a porous medium during the rate-controlled injection of a surfactant solution. The residual n-decane (n-C10) remaining in a soil column after one cycle of n-decane/NaCl solution drainage-imbibition is flushed by NaCl and sodium dodecyl sulfate (SDS) solution. The transient response of the water saturation averaged over five successive segments of the soil column is determined by monitoring the electrical resistance between successive ring electrodes, whereas the dissolved n-C10 concentration in effluent is measured with solid phase micro-extraction (SPME) and Gas Chromatography–Flame Ionization Detector (GC–FID). The oil ganglia mobilization and solubilization processes are modelled by using 1-dimensional mass balances coupled with a 2-parameter dispersion-like equation describing the rate of oil ganglia mobilization driven by the surfactant concentration gradient. The inverse modeling of experimental datasets allows the estimation of the parameters quantifying the rates of oil mobilization and solubilization. Visualization experiments of solitary n-C10 ganglia solubilization in flowing SDS/NaCl aqueous solution are employed to estimate approximately the local (pore-scale) mass-transfer coefficient of solubilization and assess the corresponding overall coefficient estimated from soil column test.