Injection of demulsifiers with LEWA packages in the oil and gas industry

Crude oil normally contains water in various percentages in an emulsion. Mainly the water is salty and the crude oil must be demulsified and desalinated with chemicals at the production site to get a higher price.

These chemicals can be added in various ways: By injection through a bore hole at high pressure, by injection at the collection point at low to medium pressure or by injection into the storage tank - intermittent metering at low pressure.

Demulsifying systems have been built by LEWA since the early 1960's; numerous installations have been in operation for over 40 years.


Advantages of LEWA packages for the injection of demulsifiers:

  • High metering accuracy
  • Leak-free, hermetically tight
  • Very good suction capability of the spring-loaded diaphragm return M900 pump head
  • Easy diaphragm replacement
  • All movable parts operate in protective and lubricating hydraulic fluid
  • Compact, modular design, which allows installation in the available space (e.g. on FPSOs)
  • Long service life (often more than 10,000 hours of continuous operation)
  • Avoidance of expensive production interruptions by using a sandwich diaphragm: Operation can be continued until the service team is on-site and the repair fits into the work flow


Process description

Demulsifiers are compounds that dispersed in very small amounts into the emulsion during injection that diffuse into the oil-water interface and function as stabilizers. They have a multitude of action mechanisms:

  • Reduction or prevention of electrostatic charges, which are responsible for the repulsion between the individual drops
  • Change of the wettability of the solids absorbed in the interface
  • Change of the viscoelasticity of the interface film

Description of the demulsification process:

The demulsifier concentrates on the surface of the small water drops and "collects" them. The drops form an increasing concentration of water. The water drops which refract the light, are removed. The visible effect is the brightening of the oil layer. The water droplets finally combine and are separated.

Why is the demulsifier a mixture?

Demulsifiers normally offer a combination of effects as:

  • Flocculent
  • Droplet separator
  • Wetting agents

A single substance cannot offer these combined properties, thus commercial demulsifier mixtures consist of several substances.

The most widely used methods are demulsifier injection systems at the bore hole and at collection points.

Bore hole injection is recommended:

  • The pumps used there are smaller and therefore less expensive.
  • The earlier in the process the water is removed, the less corrosion occurs (lower maintenance costs)

Considerable cost reduction due to demulsifying crude oil:

  • Easier transport and lower pressure loss due to viscosity reduction
  • Simple steel alloys can be used for pipelines and fittings instead of corrosion-resistant stainless steel, and in addition the cross-section can be reduced.
  • The corrosive portions in the crude oil are minimized and reduce corrosion in the production equipment
  • Longer operating times are possible


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