In the borehole formation art, it is necessary to utilize drilling mud in order to circulate cuttings from the drill bit back up the borehole annulus to the surface of the ground.  Drilling mud is a mixture of water and bulk materials, such as clays, along with various other chemicals added to the mixture to modify the characteristics of the mud.  As the borehole penetrates deeper into the earth, pockets of gas are often encountered, whereupon the gas becomes entrapped within the drilling mud.  This reduces the apparent or effective specific gravity of the mud and therefore, it is desirable to be able to treat the drilling mud in a manner to remove as much of the gases from the mud as possible before the mud is returned to the borehole.  Otherwise, the mud may not effect the necessary hydrostatic head or pressure on the borehole wall to prevent a well blowout from occurring.  A well blowout is considered catastrophic in the art of wellbore formation. 
Method and apparatus which removes entrapped compressible fluids from drilling mud is the subject of the present invention.