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Technical Paper: Effective Dehydration of Canadian Heavy Crude Oil and Dilbit

Society: SPE
Paper Number: 165464
Presentation Date: 2013
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Abstract

Heavy crude oils and diluted bitumen (dilbit) continue to be challenging to dehydrate for the oil and gas industry. The challenges include reduced density difference between crude oil and formation water, higher crude oil viscosity, and often smaller water droplets because of the techniques used for heavy crude oil production. 

Other challenges include higher crude oil conductivity and increased crude oil emulsion viscosity resulting from higher water cuts and increased solids content in the crude oil. Typically, crude oil dehydration vessels use heat, retention time, and AC type electrostatic dehydration technology. The AC technology produces limited voltage gradients and is not efficient for treating conductive crude oils, leading to the use of very large vessels and power units. 

The traditional remedy for the above challenges often leads to high operating temperatures, high dosage of demulsifier chemicals, equipment fouling, production upsets, and use of very large treaters. This means both higher operating expenditure (opex) as well as higher capital expenditure (capex). 

The use of combined AC and DC electrostatic technologies provides high bulk-water-removal efficiency in the weaker AC field, combined with higher removal efficiency of small water droplets in the stronger DC field. Further improvements include amplitude modulated electrostatic fields, high-frequency AC fields, improved electrode configurations, and improved fluid distribution inside the electrostatic treaters. 

More efficient dehydration and desalting processes provide potential for operating the treaters and desalters at lower operating temperatures and reduced dosage of demulsifier chemicals, in addition to the potential for using smaller treaters. 

This paper describes improved crude oil dehydration using advanced electrostatic dehydration technologies and an efficient test method for optimized use of production chemicals; case studies are included.

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