SURFACTANT ADSORPTION AT FLUID-FLUID INTERFACES WITH APPLICATIONS TO ALKALINE FLOODING (SURFACE TENSION, INTERFACIAL, DYNAMICS)

Adsorption of surfactants at fluid-fluid interfaces is studied with respect to equilibrium and dynamic behavior.;A consistent treatment of adsorption dynamics is formulated using a continuum approach. Surfactant transport in the bulk is assumed to consist of diffusion (and convection) with constant transport coefficients. Activation energy barriers to solute exchange between the bulk and the dividing surface are represented by means of kinetics of interphase reactions.;This treatment is used to develop diffusion-kinetic models for gas-liquid systems under stagnant batch conditions and for liquid-liquid systems under gyrostatic conditions of the spinning drop tensiometer. In the liquid-liquid case, the acidic oil/caustic system of alkaline flooding for enhanced oil recovery is investigated. This system is characterized by in situ generation of surfactants. By proposing a set of interfacial reactions, a chemical diffusion-kinetic model is developed. The resulting equations are solved with consideration to the changing geometry of the drop accompanying changes in interfacial tension in the spinning drop tensiometer.;Observations of dynamic interfacial tension minima in these systems are explained in terms of relative magnitudes of the adsorption and desorption barriers. Dynamic interfacial data for Wilmington Field (C-331) crude oil against caustic solution are correlated with the model. Being a chemical model, interfacial reaction rate constants so obtained are independent of the aqueous phase composition.;An equilibrium model is developed wherein the surface concentration of ionic surfactants is distinguished from their surface excess concentration by the contribution from the electrical double layer. Only surface concentrations are assigned to the dividing surface and the adsorption process is regarded as an interphase reaction. Adsorption isotherms are derived from considerations of interphase reaction equilibria.;A continuous flow model is developed to assess the role of dynamic effects in alkaline flooding processes. Axial dispersion of caustic and its uptake by the reservoir rock are taken into account. An unsteady state solution is obtained when a linear isotherm governs the caustic uptake by the reservoir rock while a steady state solution is obtained for a Langmuir isotherm. Predictions of interfacial tension behavior are made for Wilmington Field crude oil.