The electrocoalescers' technology: Advances, strengths and limitations for crude oil separation

Water-in-oil emulsions are encountered in production, processing and transportation of crude oils. Their stability is an issue of great concern and economic relevance, impacting operations at several Saudi Aramco gas-oil separation plants (GOSPs). A number of technologies can be applied to destabilize emulsions, to meet the export specifications of maximum 0.3% water-in-oil and 10 lbs per thousand barrels (PTB) of total dissolved salts in the crude oil. Among those technologies, electrocoalescence has the potential to reduce heating which is energy intensive. Electrocoalescence also limits the use of chemicals, which may contaminate the produced water. This paper summarizes some theoretical aspects and recent developments on electrocoalescence; experimental data are also provided to demonstrate strengths and limitations of this technology. Tests carried out in a laboratory flow loop equipped with an electrocoalescer package show that separation performances are poor when the emulsions' Reynolds number in the electric field zone is low and when the water droplet size distribution in the emulsion is centered at small diameters. As a consequence, the engineering studies for integrating an electrocoalescer package inside an existing separation facility should promote moderately turbulent emulsion flow condition to ensure that the technology will work efficiently. (C) 2011 Elsevier B.V. All rights reserved.