Definition - What does Possum Belly mean?
A possum belly is a metal container normally installed after the annulus or outlet pipe and before the mud tank or shale shaker on a drilling rig. Its main purpose is to slow the flow of drilling fluid as it returns from the point of drilling up through the annulus. Because the pressure of the mud as it enters the drill string can be as high as 7,500 pounds per square inch it is imperative to slow the flow before the drilling fluid is processed and recycled.
The possum belly may also be referred to as the distribution box or flowline trap.
Trenchlesspedia explains Possum Belly
Possum bellies are normally only used when the drilling fluid has additives such as bentonite, polymers, soda ash or surfactants. If the drilling fluid being used is brine water or freshwater then a possum belly is typically not used. Instead, the fluid flows directly into the mud tank. It is here that drilling fluid samples are taken in order to analyze the performance of the drilling system.
The possum belly gets its name because of the chambers' visual resemblance to the teat of a female possum.