Classifying – separating – and assorting solids – Precedent preparation of items or materials to facilitate... – Selective differentiation
Reexamination Certificate
1999-09-21
2001-02-27
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Precedent preparation of items or materials to facilitate...
Selective differentiation
C209S003000, C209S004000, C209S208000, C209S210000, C209S724000, C209S725000, C210S521000, C210S206000, C210S205000
Reexamination Certificate
active
06193070
ABSTRACT:
TECHNICAL FIELD
This invention relates to separators for removing solids from fluids. The methods and apparatus of the invention have particular application in removing solids from drilling fluids used in well drilling operations.
BACKGROUND
Wells for recovering oil, gas and the like are typically drilled by a drilling rig which includes a hollow drill string with a bit at its lower end. As the drill string is rotated, drilling fluids are pumped down through a channel in the drill string. The drilling fluids pass through the bit and return to the surface on the outside of the drill string. The fluids carry cuttings from the drilling operation to the surface. The drilling fluids are recovered at the surface and then recycled. Water may be used as drilling fluid in shallow drilling. In deeper wells the drilling fluids are denser drilling muds of various compositions as is known to those skilled at drilling wells.
Various apparatus and methods are known for removing cuttings and other undesired solids from drilling fluids so that the drilling fluids may be reused. A widely used method for removing solids from drilling fluid is to pass the recovered drilling fluid through a centrifuge. The centrifuge separates the undesirable solids from the drilling fluid. The drilling fluid output from the centrifuge may then be reused. Because of the volume of drilling fluid used in a typical well drilling operation, it is necessary to either have a very large centrifuge system or to provide multiple centrifuges. The costs of having a centrifuge system on site and operating the centrifuge system are significant. There is a need for a solids separation system capable of removing solids from drilling fluids which can be provided and operated at reduced cost relative to prior art systems.
SUMMARY OF THE INVENTION
It is an object of this invention to provide methods and apparatus for removing solids from drilling fluids which are more cost effective than prior art systems.
One aspect of the invention provides a method for recycling fluid in a drilling operation. The method comprises the steps of: receiving a stream of fluid containing solids; introducing the fluid and a flocculating agent into a settling tank, the tank comprising a plurality of compartments and a material conveyor extending through the compartments in a lower portion of the tank; allowing the fluid to flow along the settling tank in a first direction to a collection area while allowing solids to settle to the bottom of the tank and operating the material conveyor to carry settled solids in a second direction opposite to the first direction toward an output port in the tank; withdrawing fluid from the collection area; and, withdrawing a mixture of solids and fluid from the outlet port.
Another aspect of the invention provides apparatus for removing solids from fluids. The apparatus comprises a settling tank and a centrifuge having an inlet in fluid communication with an output port on the settling tank. The settling tank comprises a fluid receiving chamber at a first end of the tank; a fluid output chamber at a second end of the tank; a plurality of transverse apertured baffles extending across the tank between the fluid receiving chamber and the fluid output chamber, the baffles defining one or more intermediate chambers between the fluid receiving chamber and the fluid output chamber; a material conveyor extending along a lower side of the tank to an outlet port at the first end of the tank, the material conveyor comprising a motor driving the material-conveyor to carry materials in a direction toward the outlet port; and, a fluid outlet at the second end of the tank.
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King David
Rowney Brian Raymond
Grand Tank (International) Inc.
Jones David
Oyen Wiggs Green & Mutala
Walsh Donald P.
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