What is a Gun Barrel in Oil and Gas?

What is a Gun Barrel in Oil and Gas

A gun barrel is an atmospheric vessel that producers use to separate oil, water, and gas.

Gun barrels are also referred to as settling tanks and wash tanks.

How a Gun Barrel Works

  • Inside the barrel, the emulsion enters through an emulsion inlet and then enters a downward flume.
  • Gas is removed in the top of the flume.
  • The oil-and-water mixture enters the flume, flows downward and discharges under the water level.
  • The oil then rises through the water while the water remains in the bottom. This gives the oil-water mixture a very effective water wash.
  • Clean oil rises to the oil outlet nozzle, where it flows by gravity to the stock tank.

The control point in the gun barrel is that of the interface between the oil and the water.

Unfortunately, there are not layers of clean oil and free water in the vessel.

The top of the oil layer is clean oil, but further down the layer are more and more water droplets that have not had time to settle out.

The opposite is true of the water layer. Near the top, some oil droplets remain that have not had time to float out. The bottom is pure water.

Settling Time and Stream Purity

Although the basic purpose of treatment is to produce oil with less than 0.5% water, it is important not to lose a lot of oil in the outlet water. The goal is for both oil and water outlet streams to be pure.

The purity of each will depend upon the time that each spends in the settling tank.

In a gun barrel, the location of the interface will fix the settling time of each. If the interface level is high, the oil settling time will be less and the water settling time will be more, and vice versa.

The interface level should be set so that the oil purity is near 0.5% BS&W, or whatever the local limit is. This will allow the maximum settling time for the water phase, which means that the oil content of the water will be at a minimum.

In the gun barrel, as in many vertical treaters, the interface level is controlled with a water leg, which may be adjusted to change the height of the leg.

To speak with an expert about how we can help with controlling the levels in your gun barrel and other equipment, contact your local Kimray store or authorized distributor.


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