Pore-scale assessment of alcohol-surfactant-biopolymer emulsions for oil-saturated media.

Remediating soils contaminated with light non-aqueous phase liquids (LNAPLs) and producing residual oil from reservoirs are governed by the same pore-scale limitations: capillary trapping, wettability-controlled connectivity, and inefficient displacement during conventional flooding. Here we evaluate alcohol-surfactant-biopolymer emulsions based on xanthan gum (XG), sodium dodecyl sulfate (SDS), and 1-pentanol as a single formulation intended to combine interfacial, partitioning, and mobility-control effects. The formulations were first assessed using FTIR spectroscopy, zeta potential, and dynamic light scattering (DLS) to verify chemical signatures, colloidal stability, and aggregate/droplet size trends relevant to emulsion stabilization. Flow behavior was quantified rheologically and showed shear-thinning, supporting injectability while providing viscosity-based mobility control. Pore-scale performance was then tested in micromodels to visualize and quantify diesel displacement in both homogeneous and heterogeneous porous networks. At high alcohol fraction (50% v/v), the emulsions promoted swelling of trapped diesel ganglia and improved displacement efficiency, consistent with alcohol partitioning coupled with surfactant-driven interfacial effects and polymer-stabilized fronts. Under these conditions, diesel removal reached ∼99% in homogeneous and ∼ 95% in heterogeneous micromodels within ∼1 pore volume of injection. In contrast, at lower alcohol fractions (6.25-12.5% v/v), displacement relied mainly on interfacial and rheological effects, and higher residual saturations remained. Overall, the results link physicochemical descriptors (stability/aggregation and rheology) to pore-scale mobilization outcomes and indicate that XG-SDS-1-pentanol emulsions can provide a tunable platform for hydrocarbon mobilization in porous media.