Drilling mud gas buster also called a mud gas separator or poor boy degasser. It captures and separates large volume of free gas within the drilling fluid. If there is a “KICK” situation, this vessel separates the mud and the gas by allowing it to flow over baffle plates. –wiki
The purpose of a gas buster is to remove gas mixed with the drilling fluid before the drilling fluid goes over the shale shaker. A gas buster works well in fluid with large bubbles of free gas. (Often the gas is starting to break free in the flowline.) A problem with the basic gas buster is that the heavier gases will not rise and be dissipated in the air but settle around the rig.
Gas busters are a simple cylinder or baffle box at the flowline where
mixed drilling fluid and gas are roughly separated while flowing. The
drilling fluid goes to the shale shaker, and the gas is allowed to flow away or is sent to a flare line.
Drilling Mud Separators are holding tanks where mixed water, oil, and gas are allowed to separate by gravity. They have evolved in the last 50 years from simple open tanks to complex closed and pressurized tanks.
Separators can be informally divided into two groups: (1) atmospheric,
or unpressurized, and (2) pressurized, or closed
Degassers are somewhat different devices from the preceding two. The degasser is a tank in which a vacuum and/or spray removes entrained
gas from the mud system. Degassers handle much smaller gas volumes
than do gas busters or separators but do a more complete job of
removing the gas.
Shale shaker screening is dependent on a constant flow of drilling fluid
with cuttings. The fluid must pass through the screen, and the cuttings
must either pass through or be rejected by the screen. Gas cutting in the
drilling mud can have up to three different effects that upset the screening
1. Gas heading can cause volume surges in the mud flow that exceed the ability of the screen to handle fluid flow. This is usually from gas, intermixed in the mud, rapidly expanding at the surface and pushing large surges of drilling fluid out the flowline. Gas busters and gas separators are the solutions to this problem.