A vessel into which drilling mud is pumped to remove gas entrained in the drilling mud. Modern compact degassers use three commonly recognized methods of degassification; centrifugal force, turbulence, and vacuum.
An important part of well-drilling operations is keeping the drilling mud free of entrained gas, or bubbles that enter the mud as it circulates downhole through gaseous formations. One of the three functions of mud is to provide sufficient hydrostatic head to control a kick when high-pressure oil or gas is encountered.
When mud of a certain density is circulated, it can become infused with gas to an extent that, although the volume of mud may increase, the density is severely reduced at the surface. Several kinds of equipment remove the gas, but all have one aim in common; to make it possible for the gas bubbles to free themselves. One method flows the mud over wide sheets so the slurry is no more than 1/8-3/8 inch thick, and the bubbles may come to the surface and escape. Another method spray the mud against a baffle in a spray tank that squeezzes out the gas. A third method directs the mud through a vacuum tank where, under reduced atmospheris pressure, the bubbles of gas expand and break out of the slurry.