Microfluidic Study of Oil Droplet Stability in Produced Water with Combinations of Production Chemicals

Discharged produced water contains traces of hydrocarbons after separation that might affect the eco-toxicity. These hydrocarbons can be oil droplets that are stabilized by added production chemicals and their combinations. The chemicals highly affect the treatment of the produced water before either reinjection or discharge to the sea. We apply microfluidic droplet generation for rapid evaluation of the synergistic effects of the combinations of production chemicals on the oil droplet stability. The coalescence frequency of dispersed droplets is calculated on the basis of high-speed camera video acquisition. The dispersed phase is either a model oil or a bottomhole crude oil sample, both in an aqueous medium. The individual and combined effects of a commercial demulsifier and a corrosion inhibitor are evaluated on the basis of the hydrophilic-lipophilic deviation theory. The presence of as low as 4 ppm of the water-in-oil demulsifier is demonstrated to stabilize oil-in-water droplets, while the corrosion inhibitor creates droplets in oil-water slug flow fashion. The presence of the corrosion inhibitor in conjunction with the demulsifier results in the droplet adherence to the channel surface. The importance of the right dosage and the right combination of production chemicals is demonstrated. The microfluidic droplet generation technique is a valuable tool for assessing the effects of production chemicals on oil droplet stability.

Automated summary

Produced water discharged after separation contains traces of hydrocarbons that can affect eco-toxicity. By using microfluidic droplet generation, we evaluated the effects of production chemical combinations on oil droplet stability. The presence of a water-in-oil demulsifier as low as 4 ppm was shown to stabilize oil-in-water droplets, while a corrosion inhibitor created droplets in oil-water slug flow. The right dosage and combination of production chemicals were demonstrated to be important for droplet stability.