Surfactant-Enhanced Spontaneous Emulsification Near the Crude Oil-Water Interface

Spontaneous emulsification near the oil-water interface and destabilization of water-in-oil emulsions in the bulk oil phase may affect the efficiency of improved oil recovery. In this study, we investigate the effect of a demulsifier surfactant on spontaneous emulsification near the oil-aqueous phase interface and in the bulk oil phase through imaging. The results show that pronounced spontaneous emulsions may form near the oil-aqueous phase interfaces. The mechanism of diffusion and stranding is believed to dominate spontaneous emulsification. A demulsifier surfactant, which has been used for demulsification of water-in-oil emulsions in the bulk oil phase, is found to enhance spontaneous emulsification near the oil-water interface. The diffusive flux of water through the interface can be enhanced if the demulsifier is added into the aqueous phase, in which the demulsifier may act as a carrier. It can generate a region of local supersaturation combined with hydrated asphaltenes and result in faster and stronger spontaneous emulsification. We also investigate the effect of a viscosifier polymer on emulsion formation. The polymer is used to improve sweep efficiency in oil displacement. In this work, we show that it can inhibit emulsification in the bulk oil phase, but its effect on spontaneous emulsification near the interface is not pronounced.