Patent ID: 8287441

Claim:
A system for treating drilling fluid, the system comprising: a shale shaker comprising a vibrating screen located to receive drilling fluid containing cuttings retrieved from a well bore and to separate solids that do not pass through the vibrating screen; a horizontal decanter-type centrifuge connected to take in the separated solids from the shale shaker and to separate liquids from the separated solids; and a main centrifuge having an inlet connected to receive fluids that do pass through the vibrating screen of the shale shaker and a solids outlet wherein the solids outlet of the main centrifuge is connected to deliver solids to the inlet of the horizontal decanter-type centrifuge; wherein the horizontal decanter-type centrifuge comprises: a generally horizontal rotatable drum having a first tapered portion in which liquids are separated from the separated solids, the tapered portion having a wide end and a narrow end; and an infeed conveyor for delivering the separated solids to a main auger inside the drum, the main auger comprising a hollow shaft which supports a plurality of flights for sweeping the delivered separated solids toward a first set of openings near the narrow end, while permitting liquids which have separated from the separated solids to flow toward a second set of openings at an end of the drum opposing the narrow end.