Oil-in-water and water-in-oil emulsions formation and demulsification

In the petroleum industry, oil and water emulsions are frequent, not only in oilfield operations but also during the transportation and refining processes. Once depicting emulsion formation and stabilization, it is essential to analyse how it is possible to reverse the process, demulsifying the emulsion. Depending on operating conditions and fluid components, crude oils can form stable emulsions with water. In fact, some of the oil's compounds can act as natural surfactants, decreasing the interfacial tension between fluids, promoting emulsification. Several studies have been developed to analyse how the emulsification process occurs and how to demulsify them. However, the literature does not offer a systematic review of both methods. The current work is a critical review to highlight the energy input needed to promote the formation of an emulsion and the type of emulsifying agents necessary to enable the appearance of oil-in-water or water-in-oil emulsion. Secondly, this work also aims to review the state of the art of demulsification techniques applied in the oil industry. The result offers a robust background on this matter, discussing the demulsification methods, enabling a decision support perspective since it emphasizes their advantages and disadvantages.