Emulsifying behavior between oil and water of flowback fluids from acidizing oil wells based on high-voltage electric field oil–water separation technology

Abstract

In this study, a high-speed emulsifier and electric dehydrator were used to study the main factors affecting the emulsifying stability of flowback fluids from acidizing oil wells in the DaQing oilfield of China. According to the variation laws of the chemical composition of the transition layer before and after the acid cleaning and descaling treatment, the effects of various components, including inorganic salts, solid nanoparticles, polymers, and surfactants, on the stability of emulsions were investigated. The results showed that sodium chloride (NaCl) had the best ability to maintain the stability of the emulsion. The effect of ferrous sulfide (FeS) nanoparticles on the emulsifying stability of the emulsion was higher than that of silica nanoparticles and calcium carbonate (CaCO₃) nanoparticles. The effect of the polymer on the stability of the emulsion was higher than that of the surfactant. When the mass fraction of asphaltene is higher than 0.67%, the stability of the emulsion would increase, creating a difficulty in demulsification. The mechanism of multi-factor synergistic emulsification is clarified in this study. The charges of NaCl itself were packed densely on the interface between oil and water to stabilize the number of charges on the interface, leading to the enhancement of the stability of the interfacial film. FeS nanoparticles, silica (SiO₂) nanoparticles, and CaCO₃ nanoparticles coalesced on the interface between oil and water to form a dense wrapping layer, which could effectively prevent flocculation, coalescence, or merger of the dispersed phase droplets caused by factors such as electrostatic attraction and interfacial energy changing the spatial structure. These results are of great significance to the efficient treatment of oilfield-produced fluids and environmental protection.