How a Gas Production Unit (GPU) Works

In this video, we follow the pipes on an oil and gas well site from the well head to a gas production unit. 

At the Well Head

At this well head, gas is being injected into the casing to pressurize the well, which is a process called gas lift. 

The pressure builds and lifts the production to the surface, and that fluid and gas in the well is sent over to the gas production unit to be processed.  

Gas Production Unit (GPU)

This flow line then goes into the gas production unit. A gas production unit is actually two pieces of equipment joined together inside a housing.  

At the inlet side, on the left is a line heater and on the right is a separator. Producers use a gas production unit to knock liquids out of their gas line.

Line Heater

The tag on the coil bundle tells us that this particular GPU has a coil made up of 3” 7,700-pound working pressure coils on the pre-heat side of the choke and 3,200-pound coils on the expansion side of the choke.

These coils are immersed in a water /antifreeze solution that acts as a heat transfer media. That solution is heated through the use of a firetube contained in that section of the GPU.  

All this is necessary because the pressure of the well bore is higher than that of the pipeline that the gas will be delivered to.

When you have a pressure drop, you will have a temperature drop as well. With that temperature drop, freezing can occur or hydrates will form, and both of those issues can cause problems for the producer.

The gas processing unit pre-heats the well stream before it comes to the choke, which is where the pressure drop and corresponding temperature drop takes place. The well stream is then heated and allowed to expand prior to entering the separator for further processing. 

Horizontal Separator

The separator in this video is a 1,440-pound vessel, approximately 10 feet long and 36 inches in diameter.  

There’s an inlet diverter inside, and that allows the well stream to hit against that diversion baffle. The baffle is then breaking up the well stream.  

Inside, liquids will start dropping out, and we will hold a level in the vessel. There are two styles of these vessels, one using a weir system and one using an interface system. This one uses an interface.    

This is a three-phase unit, with two level controllers. One is dumping water and one is dumping oil. The oil coming out of a gas production unit is very light oil.  

Gas to Instruments and Flame Arrestor

Horizontally, the separator is going to be half full of liquid. This means the top part of the separator will be full of gas.

The gas is going to go to sales and to power the various instruments controlling this unit.