Stability of Thin Aqueous Films on Solid Surfaces

Gupta, Anuj
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The objective of this work is to gain insight into the influence of aqueous wetting films on reservoir wettability and on the transport and distribution of the wetting phase in porous media. Theoretical and experimental studies were conducted to identify the effect of factors such as brine composition, pH, oil composition, surfactant concentration and capillary pressure on the stability of thin films. A rigorous charge regulation model was developed to study how film thinning and destabilization is affected by electrostatic parameters. Ellipsometry was used to measure the thickness of thin aqueous films as a function of the applied capillary pressure. A comparison between theoretically computed and experimentally measured disjoining pressure isotherms shows reasonable agreement. It was found that electrostatic and structural forces play a key role in determining equilibrium film thicknesses. Additional work needs to be done for the theoretical calculation of hydration forces. Experiments were also designed to detect destabilization of such films. Such experiments allowed us to identify conditions under which wettability · alteration occurs due to the destabilization of the thin aqueous films.. In systems where films destabilize, these results allow determination of the time .scale over which this. occurs. Useful insight is provided into the. generation of mixed wettability states in hydrocarbon reservoirs.