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What is the best way to prevent scale in pipelines, wells, injection manifolds, etc?

asked Feb 26, 2014 in Subsea by ekwuemesam (3,660 points)
Scale in pipelines, wells, injection manifolds also greatly impacts the facility in a number of ways including deferred production, lost revenue and equipment failure.

4 Answers

+1 vote
answered Mar 23, 2014 by sabdullayev (5,290 points) | selected Mar 23, 2014 by Normandy
 
Best answer

There are two type of scales:

  • Calcium carbonate scale is usually located in the top of the wells from 2000ft and up. It looks similar to the scale you see around the heating element in your home water heater. The calcium carbonate scale has a white-creamy color.
  • Barium sulphate is typically located deep down in the horizontal part of the well below 6000ft. It has a more yellow to brown-ish color compared to calcium carbonate scale.

Possible methods of removing scales:

  • Acid washing is an effective removal method of calcium carbonate scale.
  • Coil tubing is used to where acid wash is not working. This method has so far been the most effective way to remove barium sulphate scale located deep in the well.

To prevent scale:

  • Gas lift scale inhibition is when a scale inhibitor is continuously injected into the lift gas which then is injected into the well in order to prevent calcium carbonate and iron sulphate scale from depositing on the tubing wall.
  • Scale Squeeze Treatment is when a scale inhibitor is bull headed down deep in the well in order to prevent barium scale from forming in the horizontal section of the well.
commented Apr 7, 2014 by karthikrg (1,090 points)
It cannot be categorically stated that calcite scale issues are seen in the top of wells at a certain depth. It depends greatly on fluid characteristics, P, T, bubble point, CO2 concentrations, pH, bicarbonate levels etc.
Scale colors are not always as described in your answer, as this depends on purity and if other scales co-precipitate alongside. Also, it is not possible to identify in general, the position of scale precipitation without detailed well information.
Acid washing will not remove barite scale.
Mechanical removal will be required for barite scale.
commented Apr 8, 2014 by Normandy (21,040 points)
Thanks karthikrg
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answered Mar 23, 2014 by Normandy (21,040 points)

The more mature the fields are, the more water you will need to squeeze the oil out of the reservoir. It is the water that contains ions such as calcium, barium and sulphates which form scale. The scale types that are experienced in the wells are calcium carbonate, iron sulphides and barium sulphates.

Acid wash, where acid is pumped into the well to remove the scale, is one of the oldest and most used methods. However, the acid only dissolves the calcium carbonate and iron sulphide scales; it does not prevent scale from forming. Acid wash is an expensive mitigation measure as production has to be shut in while the operation is being carried out plus the handling of the acid is a potential safety risk.

0 votes
answered Mar 23, 2014 by lampanda (2,450 points)
There is no single solution to the scale issue. In some places it might be best to wash the calcium carbonate and iron sulphide scale deposits away with acid, in other wells a scale inhibitor has to be applied.

Use scale inhibitor to prevent new scale being built up.

ClearWell Technology is a method where an electric current is created in the tubing and flowline of the well. This current is created by a device mounted externally at the surface. The current should prevent the ions from precipitating out as scale in the tubing – instead the ions are kept in solution and are produced with the well fluids.
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answered Apr 4, 2014 by Dan01 (1,560 points)
Pigging and scale inhibitor injection.
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