Fluid-fluid displacement using spontaneous imbibition: effect of in-situ surfactants

This talk focuses on the displacement of a vegetable oil slug using an aqueous alkali solution within a capillary tube via spontaneous imbibition. The effect of surfactant formed in-situ due to a saponification chemical reaction between the carboxylic acids present in the vegetable oil and the aqueous alkali on the displacement process is studied by varying the alkali strength. The transient surface tension is measured using the pendant drop method and the rates of change in surface tension for different alkali strengths are used to estimate the Damkohler number. The final equilibrium surface tension is used to calculate the capillary number and the imbibition rate of displacement experiments with in-situ surfactants is compared to the previously reported surfactant-free case to quantify the effect of dynamic surface tension change. The energy dissipated in the bulk fluid due to viscous effects as well as the two contact likes is estimated as a function of dynamic contact angles at the aqueous-oil and oil-air menisci, respectively. The problem under study will be of significance to applications in microfluidics, hydrocarbon recovery, groundwater remediation, and wastewater treatment.