Adsorption V. Nonequilibrium competitive adsorption of polydisperse ethoxylated sulfonates onto clay-containing cores and kaolinite

Austad, T., Fjelde, I. and Rolfsvag, T.A., 1992. Adsorption V. Nonequilibrium competitive adsorption of polydisperse ethoxylated sulfonates onto clay-containing cores and kaolinite. J. Pet. Sci. Eng., 6: 277-287. Nonequilibrium adsorption of a commercial polydisperse ethoxylated sulfonate, C-9-Ph-(EO)(x)SO3Na (x=3-10), onto precleaned and oil-containing reservoir cores has been studied at surfactant concentrations well above the CMC. An analytical HPLC method based on reversed-phase/ion-exchange has been worked out, which can be used to quantify and determine the relative cation affinity of the various EO-sulfonates. Chromatographic effects, which were related to increased adsorption of the low EO-number isomers, were observed for the precleaned core. No preferential adsorption of the different isomers was observed for the oil-containing core. Static equilibrium adsorption onto kaolinite at a surfactant concentration close to the onset of the adsorption plateau showed increased adsorption of the low EO-number isomers, while at very low surfactant concentration the larger EO-number isomers showed preferential adsorption. All experiments were carried out at 70 degrees C using synthetic seawater as the brine.