Crude dehydration
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Crude oil heaters
A crude oil heater raises crude to the temperature at which water can be separated from it. In oilfield treatment this is usually an indirect fired heater: a burner heats a liquid…
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Emulsion (water-in-oil)
A water-in-oil emulsion is a dispersion of small water droplets in crude oil, held apart by natural surface-active films of asphaltenes, resins, waxes and fine solids. The droplets will not settle until…
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Electrostatic coalescer
An electrostatic coalescer is a pressure vessel with energised electrode grids, in which a high-voltage field coalesces water droplets in crude oil so they settle. Used without wash water it is a…
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Crude oil dehydrator
A crude oil dehydrator is an electrostatic coalescer that removes produced water from crude oil to meet a water specification, usually stated as basic sediment and water. No wash water is added.…
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Demulsifier
A demulsifier is a surface-active chemical injected into crude oil at parts-per-million levels to displace the natural films that stabilise water droplets. With the films weakened, droplets can merge and settle. It…
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Interface level
Interface level is the height of the boundary between settled water and the oil above it in a separator, dehydrator or desalter. Controlled by the water outlet valve, it must sit below…
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Rag layer
A rag layer is a band of emulsion and solids that collects at the oil-water interface in a separator or desalter. As it grows it reduces settling volume, confuses level instruments and…
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Indirect fired heater
An indirect fired heater warms a process fluid without exposing it to flame. A burner heats a bath of water or other liquid through a fire tube, and the process fluid flows…
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Stokes’ law
Stokes' law gives the settling speed of a small droplet in a liquid. Speed rises with the square of droplet diameter and with the density difference between the two liquids, and falls…
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A structured method for diagnosing high BS&W at a dehydrator or desalter outlet
High basic sediment and water (BS&W) at the outlet of an electrostatic dehydrator or desalter has a short list of possible causes. This paper sets out an order in which to check…