What is a separator and what does it do? How to select oil separator?

A separator is used in the oil field, it is basically a pressure vessel that can separate the liquid from the well into oil and gas and the water content in the oil is separated or reduced by using a separator. Separators are used as the major components in petroleum production and in this, the separator will separate the fluids into oil, gas, and liquid. Separators are widely used in many petrochemical industries, oil refineries, power plants, etc. A separator is used to separate a lot of things such as gas, heavy and light oil, it is also used to separate oil from water, mud, or solid particles. The separator plays a major role in chemical industries for the separation of different chemicals.

What are the factors that should be considered for separation?

  • We must consider the operating pressure and temperature
  • Flow rate of the liquid must be considered
  • The ratio of gas and oil must be considered
  • The fluid properties must be considered like density, viscosity
  • We must also consider the impurities in the fluid

Why do we need separators?

Equipment such as pumps and compressors won’t handle gas-liquid mixtures, a pump needs gas-free liquid and a compressor would need liquid-free gas. The product specification would be limited because of the impurity such as the water content in oil. There will be inaccuracy for measurement devices if there is a presence of other phases.

What are the functions of a separator?

  • It separates vapor and liquid
  • It separates oil and water
  • It separates gas and oil from oil well fluids
  • It separates gas and solids
  • It separates liquid and solids
  • It can also do liquid-liquid separation
  • Optimum pressure maintenance
  • Maintenance of liquid seal

What are the components of a separator?

Every type of separators has four major sections and these sections are

Primary separation section

In this section, large liquid particles are removed such as slugs, so that the gas turbulence can be reduced and the liquid particles can be separated and this process is done by changing the velocity and flow direction.

Secondary separation section

In this section, the gravity settling of the liquid from gas is done after reducing the stream velocity and this process is completely dependent on particle size, gas and liquid properties, and the gas turbulence.

Liquid accumulation section

In this section the impurities are removed, this section doesn’t have stream turbulence and the solid particles in the fluid such as mud, would settle on the bottom of the separator and it would be removed. The separated liquid would flow out from the separator.

Mix extraction section

This section is to remove the small droplets of liquid in the last step of the separation.

Components of oil/gas separator

  • There is an inlet device that is used which is placed in the preliminary phase separation
  • Separation enhancement device is used in the primary section
  • A mist extraction device is used to reduce the liquid content from the gas
  • Many weirs are used to control the liquid level
  • Pressure relief devices are used
  • It has outlets for gas, oil, and water
  • Vortex breaker is used and a liquid level detector

What are the types of separators and how does a separator work?

The working of the separator is based on the principle that the fluid components have different densities and by this, we can divide the fluid as gas, oil, and water. Solid particles will be settled on the bottom of the separator and the oil can be separated.

Classification of separator

  • A two-phase separator would separate gas from the liquid stream
  • A three-phase separator is a separator that would separate the fluid into oil and water

Types of separators

Separators are divided according to their vessel configurations they are

Horizontal separators

This type of separator is used in oil wells that have high gas to oil ratios, it is commonly used for multiphase separation and for the liquid to liquid separation. This type is used in a place where headroom is less, it is also used if impurities or solid particles from the well fluid is high. This type of separator has a good wall thickness which is suited for its large diameter.


Vertical separators


This type of separator is used if we need to separate a huge amount of slug from the liquid. This separator vessel volume is small and these separators are used in oil wells that have a very low gas-oil ratio.

Spherical separators

This type of separator has a very compact vessel and it can do good gas separation and the surge space of this device is very low. This type of separator is not used to separate liquids that have a large amount of mud content and because of this it is not widely used as the other type of separator.

How to troubleshoot oil separator?

The life of the separator is depended upon certain things such as the package design of the compressor, the coolant in the compressor, the environment, and also the contaminants that enter through the compressor intake filter. If the pressure in the separator drops that means the separator is plugging with dirt, so in that case, we must check our compressor.

How to select oil separator?

  • It must be selected according to the flow rates
  • We must select a separator vessel according to the impurities such as dust, CO2, etc.
  • We must also consider the temperature and pressure range during the separation
  • The density difference between the gas and the liquids
  • Viscosity difference between the gas and the liquid must be considered
  • Particle size must be considered
  • The separator which is selected must match with the inlet rate of the fluid that is to be separated
  • A separator must be selected according to the retention time

What are the applications of separators?

  • Petroleum marketing facility
  • Oil refineries
  • Fueling process
  • Military purpose
  • Power plants
  • Water separation from oil
  • Gas and water separation
  • It is used for gas-solid separation
  • Petrochemical plants
  • Gas pipelines
  • It is used in natural gas processing plants
  • Chemical factories