Mechanism of crude-oil/water interface destabilization by silicone demulsifiers

Oil exploitation is always accompanied by the nondesired formation of emulsions caused by the presence of naturally occurring surface-active molecules such as asphaltenes and resins. Because their presence stabilizes the oil/water interface, it is necessary to break the emulsions by adding other surface-active molecules. Formulations based on polysiloxane molecules were selected as effective nontoxic products to enhance the oil/water phase separation. Establishing the relation between the efficiency of formulations and the interfacial properties of silicone molecules is the objective of this study. Formulation selection is based on bottle tests using turbidimetric measurements and on dynamic tests using a "dispersion rig" setup that allows the formation of emulsions under pressure and temperature conditions and injection of additives into the formed emulsion online. Rapid kinetics of separation and high levels of separated water were observed. Dynamic interfacial measurements were performed using complementary techniques. The drop-volume technique allows the measurement of the evolution of crude-oil/water interfacial tension with time. The Langmuir trough technique is used to obtain 2D compression isotherms and to deduce the elastic properties of interfaces. The coalescence of water droplets leading to the destabilization of emulsions and consequently to the oil/water separation efficiency can be related to the rheological properties of water/crude-oil interface. Therefore, such comprehensive study based on a specific methodology can lead to a strict and effective selection of emulsion breaker additives in relation with the oil composition.