Gas Seperators

Impact of Gas on an ESP :

When free gas is present in the first stage impeller (or first few stages), it takes up useable space and restricts the volumetric efficiency of the pump.  The result is a decline in expected production.  In fact, if the impeller eye fills completely with gas, the pump will "lock" or stop producing at all.

Gas Related Problems in an ESP :

• Vapor can tend to "Gas Lock" a pump leading to surging and 
• premature pump failure.  
• Vapor does not lubricate bearings well.
• Pumping efficiency is reduced.  
• Limits production

Gas locking can cause either current fluctuation or pump shut down on underload .

A device which handles more free gas will results in increased daily production .

There are two basic types of intake Sections:

1- Intakes

2- Gas Separators

     • Static 

     • Dynamic

Pump Intakes : 

A standard intake does not separate gas.  Some gas separation might occur with a standard intake, but it will only be Integral Intake Bolt-on Intake, but it will only be natural separation due to some of the gas not turning and going into the intake when the rest of the fluid does.

Gas Separators : 

A gas separator is still an intake, but with some special features designed to keep free gas from entering the pump.

Static Gas Separators :

Original gas separator designs were based on increasing gas separation by forcing the fluid flow to reverse in the wellbore.  This is where the name of this type of gas separator, REVERSE FLOW, comes from. Since this type of gas separator does no real "work" on the fluid, it is also called a "static" gas separator.

As well fluid enters the gas separator it is forced to change direction.  Some of the gas bubbles continue to rise instead of turn or rise inside of the gas separator, exit the housing and continue to rise.

Dynamic Gas Separators :

Dynamic gas separators actually impart energy to the fluid in order to get the vapor to separate from the liquid.  The original gas separator was called a KGS (short for either Kinetic Gas Separator or Kobylinski Gas Separator).  This design uses an inducer to increase the pressure of the fluid and a centrifuge to separate the vapor and liquid.  This design could likewise be called a centrifugal gas separator. 

The rotary gas separator design works in a similar fashion to a centrifuge.  The centrifuge "paddles" spinning at 3500 rpm cause the heavier fluids to be forced to the outside, through the crossover and up into outside, through the crossover and up into the pump, while the lighter fluid (gas) stays 

toward the center, and exits through the crossover and discharge ports back into the well.

Gas Separators Efficiency :

Normally we would use rule-of-thumb estimates like the following based on experience:

Testing conducted at Tulsa University actually showed that natural separation could be from 20% to  60 % and that with a rotary gas separator, total separation efficiencies could be as high as 99 %. The testing also indicated that gas separators (all types) do have definite flow ranges where they are effective and other flow ranges where they are not.