COLLOIDAL PROPERTIES AND EMULSION INVERSION: IMPACT OF ZWITTERIONIC SURFACTANTS ON CRUDE OIL EMULSION STABILITY

Surfactants have been used in Enhanced Oil Recovery (EOR) due to their ability to reduce interfacial tension, alter wettability, emulsify, and generate foam, which increases the oil recovery factor. However, back-production of surfactants during EOR could compromise water-oil (W/O) separation by stabilizing emulsions. Zwitterionic surfactants (ZWs) are commonly used in EOR thanks to their temperature and salt resistance, as well as high interfacial activity, which can significantly alter W/O separation kinetics, even at low concentrations. This study investigates W/O emulsions of Brazilian crude oil and brine formed in the presence of three ZWs at varying concentrations. The formation and stability of W/O emulsions and the produced water quality were evaluated and correlated with ZWs colloidal properties. Results indicate that ZWs can destabilize W/O emulsions at low concentrations (˜50 ppm) compared with traditional surfactants, due to faster adsorption at the interface. However, at high concentration (> 500 ppm), ZWs can invert interface curvature, leading to W/O/W emulsions and decreased water quality. These findings show that ZWs exhibit a distinct behavior relative to traditional surfactants used in the oil industry, accelerating phase separation of W/O emulsions at low concentrations while reducing produced water quality at high concentrations.