How surfactants mobilize oil trapped in a 3D porous medium

Surfactant solutions are promising candidates for enhancing oil recovery from subsurface reservoirs and promoting contaminant removal from groundwater aquifers. However, the mechanisms by which surfactants can mobilize a non-aqueous fluid trapped in a porous medium remain unknown. We use confocal microscopy to measure the flow field associated with oil mobilization by a surfactant solution in a transparent 3D porous medium. We find that the competition between surfactant adsorption, interfacial dilation/contraction, and the local Peclet number yields different forms of oil mobilization. These results could help better inform surfactant selection and design for flooding applications.