A new image-based microfluidic method to test demulsifier enhancement of coalescence-rate, for water droplets in crude oil

The separation of water droplets from water-in-crude-oil emulsions is a vital process in the petroleum industry. Various components in crude oil, such as asphaltene, stabilize the water–oil interface, which inhibits the coalescence of water droplets. To enhance the oil–water separation, specific demulsifiers are often added to destabilize the emulsion and enhance the coalescence of the water droplets. In this work, we propose a new method to select an effective demulsifier and optimal concentration for a water-in-crude oil emulsion. This new experimental design involves an optical-access flow in a long 500 μm-square micro-fluidic channel, illuminated by a Near-Infrared laser and imaged with a B/W high-speed video camera. We can quantify the coalescence probability by using monodisperse droplets and identifying coalescence by their change in size. Coalescence probability is an indicator for selecting the optimal concentration and type of demulsifier.