An Experimental Study on Efficient Demulsification for Produced Emulsion in Alkaline/Surfactant/Polymer Flooding

Tertiary oil recovery technologies, for example, alkaline/surfactant/polymer (ASP) flooding, can enhance oil recovery as an important oil displacement technology noteworthy in the present oilfields. However, it is the fact that the produced emulsion droplets have strong electronegativity, which will lead to the destabilization of electric field and affect the dehydration effect in the process of electric dehydration. This article innovatively proposed an efficient demulsification scheme, which uses polyaluminum chloride (PAC) as a chemical regulator to control electric field destabilization through the charge neutralization mechanism and then introduces demulsifier to promote oil–water separation. Furthermore, the dehydration temperature, power supply mode, and electric field parameters are optimized so as to achieve superior dehydration effect of ASP flooding produced liquid. The results indicate that PAC as a chemical regulator by exerting charge neutralization and electrostatic adsorption mechanism could reduce the electronegativity of the emulsified system, decrease the peak current of dehydration, shorten the duration of peak current of dehydration, improve the response performance of the electric field, and increase dehydration rate in the ASP flooding dehydration process. When the demulsifier dosage is 100–120 mg/l, using the composite separation process with the dehydration temperature of 45–50 °C for the thermochemical separation stage and 60 °C in the electrochemical dehydration stage and AC–DC composite electric field or pulse electric field can achieve better dehydration effect. The investigations in this study will provide support and basis for the efficient treatment of ASP flooding produced emulsion.