Comparative studies on quartz surface charge and brine ions interaction for oil detachment by sessile drop method and molecular dynamics simulation

Document Type : Research Article


China University of Petroleum


low salinity-surfactant brine on hydrophobic quartz surface for wettability alteration to mimic multiphase fluids flow in porous media was investigated using sessile drop experiments and molecular dynamics (MD) simulation. The surface-active components in crude oil shifted towards the oil-water interface leading to a reduction in interfacial tension γow and consequent reduction in contact angles for low brine concentrations. Further decreased brine concentrations resulted in dissolution of surface-active components into bulk brine. However, with increased brine concentrations, negative sites were induced on the quartz surface and boosted the adsorption of Ca2+ ions. The adsorbed cations bridged with the polar compounds in the crude oil resulting in the adherence of the organic molecules on the quartz surface. The monitoring and measurement of contact angles by sessile drop experiment was done. The initial and final contact angle readings were taken in ranges (77o-51o) to (18o- 05o) for NaCl brine while for CaCl2 brine, contact angles in ranges (70o-60o) to (19o - 06o). Intermolecular forces were found to play a key role, which resulted in electrostatic molecular attractions and oil shift from the surface as shown by relative concentration measurements in molecular dynamics simulation. Sodium chloride and Calcium chloride brines of varying concentrations (2,000 mg/L-50,000 mg/L) and sodium dodecyl sulfate (250 mg/L) as a surface-active agent was used.


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