A model study of enhanced oil recovery by flooding with aqueous surfactant solution and comparison with theory . Paul

With the aim of elucidating the details of enhanced oil recovery by surfactant solution flooding, we have determined the detailed behaviour of model systems consisting of a packed column of calcium carbonate particles as the porous rock, n-decane as the trapped oil and aqueous solutions of the anionic surfactant sodium bis-2-ethylhexyl sulfosuccinate (AOT). The AOT concentration was varied from zero to above the critical aggregation concentration (cac). The salt content of the aqueous solutions was varied to give systems of widely different, post-cac oil-water interfacial tensions. The systems were characterised in detail by measuring the permeability behaviour of the packed columns, the adsorption isotherms of AOT from the water to the oil-water interface and to the water-calcium carbonate interface and oil-water-calcium carbonate contact angles. Measurements of the %oil recovery by pumping surfactant solutions into calcium carbonate packed columns initially filled with oil were analysed in terms of the characterisation results. We show that the measured contact angles as a function of AOT concentration are in reasonable