Influence of the Crude Oil and Water Compositions on the Quality of Synthetic Produced Water

Abstract

Produced water originates from the crude oil production. It is a mixture of organic and inorganic compounds and its composition is highly oilfield-dependent. The present study was carried out to increase the understanding of the relations between the crude oil properties and the composition of the aqueous phase on the produced water quality. Brines with different compositions and pH levels were mixed with five crude oils. Initially, the physicochemical properties and composition of the crude oils were determined, while the quality of the synthetic produced water samples were described by parameters such as the total oil concentration and organic carbon, pH, the drop size distribution and the Sauter mean diameter. The characterization part revealed that crude oils fell into two categories: light and heavier oils. 2 Most parameters like density, viscosity, total acid number (TAN) or composition reflected this division. A similar pattern was sustained for the water quality analyses. Water produced with heavier crude oils generally contained higher concentration of emulsified oil with the biggest and most polydispersed droplets. Light oils had a tendency to create water-in-oil emulsion between the oil and water phase, which impeded the phase separation, resulting in less free water. The Sauter mean drop diameters increased with pH of the water phase. However, the presence of calcium at the highest pH decreased the droplet size and the amount of free water, compared to the brine without divalent ions, which is in agreement with the interfacial role of the naphthenic acids in the crude oil emulsions. The results showed the significance of both the water and oil composition on the quality of the produced water. This can lead to improved fundamental perception of the produced water treatment process.

Microfluidic Investigation of Crude Oil Droplet Coalescence: Effect of Oil/Water Composition and Droplet Aging

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A microfluidic study of oil displacement in porous media at elevated temperature and pressure

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