Design Factors Relating To Properly Design The Right Size of Mud Gas Separator for Drilling Rig

A mud gas separator or poor boy degasser or gas buster is one of the most critical well control equipment on drilling rigs. It is used to separate gas kick from drilling mud while circulating kick out of wells or circulating gas while drilling or workover operations. The mud gas separator used on drilling rigs is typically a vertical cylindrical vessel with many baffle plates inside because vertical vessels have small footprints. The drilling mud from the well goes into the mud gas separator and hits baffles. Then gas will be removed due to hitting action. The gas will go up and exist to atmosphere via a vent line at the top of the vessel. The drilling fluid drops after colliding baffles and exists the mud gas separator through the line and return to a mud pit.

Many-factors-are-involved-to-properly-size-mud-gas-separator Continue reading

Blow Through Situation in Mud Gas Separator (Well Control Equipment)

Mud leg provides hydrostatic pressure in order to prevent mud going through the separator into the rig. If the pressure in the mud gas separator exceeds hydrostatic pressure provided by mud leg, gas blowing through situation will be happened. Once blow-through occurs with a mud gas separator, it is very difficult to stop this situation until the mud leg column is re-established.


Figure 1 illustrates mud-blow through. The pressure that will create blow-through can be calculated by determining hydrostatic pressure of mud leg. Continue reading

Mud Gas Separator (Poor Boy Degasser) Plays A Vital Role in Well Control Situation

Mud gas separator located at downstream of the choke manifold is one of the important well control equipment that you need to focus. It separates gas out of the mud after the gas comes out of hole. Gas will be vent to atmosphere via the vent line in derrick (offshore operation) or the line away from the rigs (land operation) and the mud will be returned back to the pit.

In the oilfield, people have several names for the mud gas separator as “poor boy degasser” or “gas buster”. While drilling, the mud gas separator should be lined up at all times and filled with the present mud weight currently used.


The concept of this equipment is density difference between liquid and gas. When the mud coming out from the choke manifold goes into the mud gas separator, mud will hit the baffle plates which are used to increase travelling time and allow gas to move out of the mud. Gas which has lower density than air will move up and mud will goes down due to gravity (see – Figure 1). Mud leg will provide hydrostatic pressure in order to prevent mud going through the separator into the rig. Continue reading