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Energies 2017, 10(5), 721; doi:10.3390/en10050721

The Role of Shearing Energy and Interfacial Gibbs Free Energy in the Emulsification Mechanism of Waxy Crude Oil

1
Key Laboratory for Enhanced Oil & Gas Recovery of the Ministry of Education, Northeast Petroleum University, Daqing 163318, China
2
Post-Doctoral Research Station of Daqing Oilfield, Daqing 163458, China
3
Independent Project Analysis, Inc., Ashburn, VA 20147, USA
4
School of Mechanical and Chemical Engineering, University of Western Australia, Perth, WA 6009, Australia
5
College of Chemistry, Jilin University, Changchun 130012, China
*
Authors to whom correspondence should be addressed.
Academic Editor: Alireza Bahadori
Received: 28 March 2017 / Revised: 6 May 2017 / Accepted: 16 May 2017 / Published: 19 May 2017
(This article belongs to the Special Issue Oil and Gas Engineering)
View Full-Text   |   Download PDF [4324 KB, uploaded 19 May 2017]   |  

Abstract

Crude oil is generally produced with water, and the water cut produced by oil wells is increasingly common over their lifetime, so it is inevitable to create emulsions during oil production. However, the formation of emulsions presents a costly problem in surface process particularly, both in terms of transportation energy consumption and separation efficiency. To deal with the production and operational problems which are related to crude oil emulsions, especially to ensure the separation and transportation of crude oil-water systems, it is necessary to better understand the emulsification mechanism of crude oil under different conditions from the aspects of bulk and interfacial properties. The concept of shearing energy was introduced in this study to reveal the driving force for emulsification. The relationship between shearing stress in the flow field and interfacial tension (IFT) was established, and the correlation between shearing energy and interfacial Gibbs free energy was developed. The potential of the developed correlation model was validated using the experimental and field data on emulsification behavior. It was also shown how droplet deformation could be predicted from a random deformation degree and orientation angle. The results indicated that shearing energy as the energy produced by shearing stress working in the flow field is the driving force activating the emulsification behavior. The deformation degree and orientation angle of dispersed phase droplet are associated with the interfacial properties, rheological properties and the experienced turbulence degree. The correlation between shearing stress and IFT can be quantified if droplet deformation degree vs. droplet orientation angle data is available. When the water cut is close to the inversion point of waxy crude oil emulsion, the interfacial Gibbs free energy change decreased and the shearing energy increased. This feature is also presented in the special regions where the suddenly changed flow field can be formed. Hence, the shearing energy is an effective form that can show the contribution of kinetic energy for the oil-water mixtures to interfacial Gibbs free energy in emulsification process, and the emulsification mechanism of waxy crude oil-water emulsions was further explained from the theoretical level. View Full-Text
Keywords: emulsification; Gibbs free energy; droplet deformation; shearing energy; shearing field emulsification; Gibbs free energy; droplet deformation; shearing energy; shearing field
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MDPI and ACS Style

Wang, Z.; Lin, X.; Rui, Z.; Xu, M.; Zhan, S. The Role of Shearing Energy and Interfacial Gibbs Free Energy in the Emulsification Mechanism of Waxy Crude Oil. Energies 2017, 10, 721.

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