Published: 11/21/2016

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Electrostatic treater

A national oil company operating a remote gathering center needed to remove produced water containing salt from incoming crude oil in order to meet export specifications. This was being done by the center's process train, which included a free-water knockout drum, three-phase separator, heater, an electrostatic dehydrator, and a desalter. The crude had high inlet water content, and because of low operating temperature, the oil was very viscous. These operating conditions made the customer's AC electrostatic dehydrator struggle to handle the water content. The crude's high viscosity required extensive heating and higher demulsifier dosage for effective dehydration. These conditions, together with limited supply of freshwater, made the cost of running the gathering center very high for the operator. In response to these issues, Schlumberger evaluated the equipment and processing data. Based on the findings, it was proposed that the AC dehydrator and desalter undergo a retrofit to the NATCO DUAL FREQUENCY treater technology. This technology demonstrates advanced dehydration of high-water-cut emulsions through higher electrostatic forces and improved coalescence. It is capable of effectively reducing crude oil BS&W (basic sediment and water) at lower operating temperatures. The dual frequency provides a customizable electrostatic field, which when used with the NATCO LRC-II smart interface and three-phase, high-frequency power unit, permits the electrostatic field to be adjusted on-line to match the current operating conditions at the gathering center. The upgrade of the existing desalter and dehydrator was done through the manholes. The interior of the pressure vessel was thoroughly cleaned, inspected, and emptied of its internals. Next, the new inlet distributor and mud wash system were installed. The insulating hangers, support rails, and electrodes were hung. This was followed by the installation of the outlet collector pipe, new power unit, high-voltage assembly, and entrance bushings, after which the LRC-II smart interface was connected. When completed, the retrofit to the NATCO DUAL FREQUENCY treater technology reduced the operator's heat usage by 50% and provided a wider operating window despite the crude's high inlet water content. The operator used less washwater and demulsifier chemicals in the dehydration and desalting of incoming fluids, leading to a reduction in opex. Schlumberger can upgrade any dehydrator and desalter to the NATCO DUAL FREQUENCY electrostatic treater technology, and because it can be done much quicker than a new install, it enables a faster return on investment. From equipment diagnostics and process designs to customer training and maintenance programs, Schlumberger offers solutions that meet the toughest processing challenges while helping to protect our customers' operational viability. Contact us to learn more about our retrofit capabilities for your existing processing equipment.

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