An insight into the solar demulsification of highly emulsified water produced from oilfields by monitoring the viscosity, zeta potential, particle size and rheology

Facing increasing challenges to oil field production and energy utilization, tertiary oil recovery technologies, exemplified by alkali-surfactant-polymer (ASP) flooding, can significantly improve the oil recovery. However, it has produced an enormous amount of highly emulsified water to increase the tough water treatment in the oilfield. Currently, the dominated treatments have been focused on the traditional treatment methods, such as the thermal demulsification, electric demulsification and gas flotation demulsification. These technologies have high energy consumption and low efficiency, which blocks their wide applications in engineering. In this paper, we first performed a solar-driven sustainable demulsification by adopting the highly emulsified water produced from ASP flooding in the oilfield. The solar energy has three-fold effects, i.e. the photo, thermo and electrochemical action, on the demulsification. The solar thermal and electrochemical process serves as controlling domains for the thermo-aided electrochemical oxidation and separation to break the organic surfactants and polymers in the O/W interface. For an insight into solar demulsification, we monitored the variation of the viscosity, zeta potential, particle size, rheology and percent removal of the highly emulsified water in the real time. The results show the achievements of the solar O/W demulsification and separation via the five measurable parameters dominated by three solar based fields. The viscosity of the highly emulsified emulsion was decreased from 1.41 mPa s to 1.0 mPa s. The negative zeta potential was increased, which means that the repulsive electrostatic force among oil droplets was reduced. The viscoelasticity of the O/W interface was decreased, so the strength of the interface film was decreased. By monitoring the variation of the oil droplet size and distribution, it can be concluded that the mechanism of solar demulsification is a process in which the oil droplets conduct to continuously flocculate and coalesce, finally creaming or sedimentation. The percent removal reached 82.84% at a 60 °C temperature under the condition of 7 V potential driven by the light radiation. Further characterizations show that solar energy has a great effect on treating highly emulsified water produced from oilfields with low energy consumption and environmental protection.