1. n. [Drilling]
A drilling mud filled open steel or earthen berm tank that is not stirred or circulated. By having mud slowly pass through such a container, most large drilling solids sink to the bottom, cleaning the mud somewhat. If the settling pit is small, as in the case of steel mud tanks, it must be cleaned out frequently as cuttings pile up on the bottom of the tank. In the early days of rotary drilling, some rigs had no more solids control than a large settling pit into which mud was discharged after coming back from the wellbore and suction for the mud pumps was taken at the other end of the pit. A major drawback to this type of "cleaning" is that solids intentionally put into the mud, such as barite, may settle to the bottom and be discarded rather than circulated back into the wellbore.