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Microscopic Study of Oil Flocculation and Coalescence Processes for Understanding the Role of Surfactants in EOR Performance

Abstract A preliminary microscopic study of oil/oil droplet interactions in surfactant-added water is carried out to understand the oil/water interface changes with time and its effects on oil/oil droplet coalescence. This study is carried out on two oils (olive and crude oil) with varying concentrations of surfactant water ratios. The radii of curvature of the interface between coalescing oil droplets is used as a measure to reflect the change in surface energy. As oil droplets were placed in surfactant-added water, the radii of curvature were measured at three different states. Early state shows very little effect on oil/oil interfaces; in the later state, the effect is greater and interfacial tension decreases rapidly. At quasi-steady state, the state between the early and later, faster rate stage reduces with surfactant concentration in the case of olive oil. Increasing the surfactant concentration does not show the same effect on crude oil. The radii of curvature increase with time by increasing surfactant concentrations in olive oil; an inverse effect is found in crude oil. A natural surfactant prepared from the outer shell of pericarp of soapnut fruit was also used to study droplet formation and coalescence as well as to investigate the impact in interfacial tension and oil mobility.