METHOD AND APPARATUS FOR REMOVING CUTTINGS FROM DRILLING FLUIDS

METHODE ET APPAREIL PERMETTANT D'ENLEVER LES DEBLAIS DES BOUES DE FORAGE

English Abstract

A method and apparatus for recycling drilling fluids used in the drilling
of wells is provided. The apparatus can comprise a tank having a plurality of
compartments. Drilling fluid containing solids pumped into a receiving
compartment of the tank is directed towards a flow-reversing barrier to cause
heavier solids to settle to the bottom of the tank. Fluid filling the
receiving
compartment flows downstream into an adjacent compartment by passing
through a flow-restricting baffle to cause more solids to settle. As fluid
flows
from compartment to compartment, it passes through successive flow-restricting

baffles to cause further solids to settle. Once fluid reaches a
collecting compartment, the fluid can be used again in drilling operations. A
conveyor extending along the bottom of the tank moves settled solids out
through an outlet in the collecting compartment. The settled solids can then
be passed through a centrifuge to recover residual fluids.

Claims

15

We claim:


1. An apparatus for removing solids from drilling fluid, comprising:

a) a settling tank having first and second end walls, two side walls
extending between the end walls and a bottom comprising at
least one v-shaped trough running lengthwise between the end
walls, the trough adapted to collect solids settled from the fluid,
the tank forming a receiving compartment adjacent to the first
end wall, a collecting compartment adjacent to the second end
wall, and an outlet;

b) barrier means for reversing the flow of a stream of drilling fluid
containing solids received in the receiving compartment, said
barrier means disposed in the receiving compartment and
adapted to cause said stream to reverse direction and flow
around said barrier means thereby causing at least some of the
solids contained in the fluid to settle to the bottom of the tank;

c) a wall transversely mounted in the tank between the side walls,
the transverse wall separating the receiving and collecting
compartments, the wall defining an aperture for allowing the fluid
to pass through as the fluid flows in a first direction from the
receiving compartment to the collecting compartment; and

d) a material conveyor for moving the settled solids at the bottom
of the tank towards the outlet.


2. The apparatus as set forth in claim 1 wherein said barrier means is
disposed substantially central in the receiving compartment.




16

3. The apparatus as set forth in any one of claims 1 to 2 wherein said
barrier means comprises:

a) a substantially vertical back panel;

b) two side panels extending from the side edges of the back panel
towards the first end wall; and

c) a bottom plate extending from the bottom edge of the back
panel towards the first end wall, the bottom plate extending
between the side panels.


4. The apparatus as set forth in any one of claims 1 to 3 further
comprising at least one additional wall transversely mounted between
the side walls thereby defining an at least one intermediate chamber
between the receiving and collecting compartments, the at least one
additional wall defining an aperture for allowing the fluid to pass
through as the fluid flows in the first direction.


5. The apparatus as set forth in any one of claims 1 to 4 wherein the
material conveyor is an auger running lengthwise along the bottom of
the trough, the auger driven by a drive mechanism, the auger capable
of moving settled solids towards the outlet.


6. The apparatus as set forth in any one of claims 1 to 5 wherein said
outlet is located on said second end wall.


7. The apparatus as set forth in claim 6 wherein the bottom of the tank
comprises two substantially parallel v-shaped troughs running
lengthwise along the tank from the first end wall to the second end wall,
the second end wall having two outlets, each outlet aligned with a




17

trough, each trough having an auger driven by the drive mechanism,
each auger capable of moving settled solids towards the second end
wall and through an outlet.


8. An apparatus for removing solids from drilling fluid, comprising:

a) a settling tank having first and second end walls, two side walls
extending between the end walls and a bottom enclosing the
area defined by the bottom edges of the end walls and the side
walls, the tank forming a receiving compartment adjacent to the
first end wall, a collecting compartment adjacent to the second
end wall, and an outlet;

b) a wall transversely mounted in the tank between the side walls,
the wall separating the receiving and collecting compartments,
the wall defining an aperture having a flow-restricting baffle, the
baffle extending perpendicular from the wall towards the
collecting compartment, the baffle capable of causing at least
some of the remaining solids contained in the fluid to settle to
the bottom of the tank as fluid flows in a first direction from the
receiving compartment to the collecting compartment and
passes through the aperture and baffle; and

c) a material conveyor for moving the settled solids at the bottom
of the tank towards the outlet.


9. The apparatus as set forth in claim 8 further comprising at least one
additional wall transversely mounted between the side walls thereby
defining an at least one intermediate compartment between the




18

receiving and collecting compartments, the at least one additional wall
defining an aperture having a flow-restricting baffle, the baffle
extending from the at least one additional wall towards the collecting
compartment, the baffle capable of causing at least some of the
remaining solids in the fluid to settle to the bottom of the tank as the
fluid flows in the first direction through the aperture and baffle.


10. The apparatus as set forth in any one of claims 8 to 9 wherein the
baffle comprises a rectangular back plate parallel to the wall, the back
plate spaced apart from the wall by two rectangular side walls
extending perpendicular from the side edges of the back plate towards
the wall and attached thereupon, each side wall defining a plurality of
slot-shaped openings.


11. The apparatus as set forth in any one of claims 8 to 10 wherein the
bottom of the tank comprises a v-shaped trough running lengthwise
along the tank from the first end wall to the second end wall, the trough
adapted to collect solids settled from the fluid, the trough aligned with
the outlet.


12. The apparatus as set forth in any one of claims 8 to 11 wherein the
material conveyor is an auger running lengthwise along the bottom of
the trough, the auger driven by a drive mechanism, the auger capable
of moving settled solids towards the outlet.


13. The apparatus as set forth in any one of claims 8 to 12 wherein said
outlet is located on said second end wall.




19

14. The apparatus as set forth in claim 13 wherein the bottom of the tank

comprises two parallel v-shaped troughs running lengthwise along the
tank from the first end wall to the second end wall, the second end wall
having two outlets, each outlet aligned with a trough, each trough
having an auger driven by the drive mechanism, each auger capable of
moving settled solids towards the second end wall and through an
outlet.


15. The apparatus as set forth in any one of claims 1 to 14 further
comprising a centrifuge.


16. A flow-reversing barrier for removing solids from drilling fluids in a
settling tank having first and second end walls, two side walls
extending therebetween and a bottom, said tank forming a receiving
compartment for receiving a stream of drilling fluid containing solids
adjacent to the first end wall and a collecting compartment adjacent to
the second end wall, the barrier comprising:

a) a substantially vertical back panel;

b) a pair of side panels extending from the side edges of the back
panel;

c) a bottom plate extending from the bottom edge of the back
panel, the bottom plate extending between the side panels; and
d) means for mounting said barrier in a receiving compartment of a

settling tank whereby said barrier is positioned to receive said
stream between said side panels towards said back panel
thereby causing said stream to reverse direction and flow




20

around said barrier thereby causing at least some of the solids
to settle to the bottom of the tank.


17. The barrier as set forth in claim 16 wherein said mounting means are
adapted to position said barrier substantially central in the receiving
compartment.


18. A flow restricting baffle for removing solids from drilling fluids in a
settling tank, said tank having at least one wall transversely mounted
between side walls of the said tank, the wall separating a receiving
compartment from a collecting compartment, the wall having an
aperture to allow drilling fluid to pass through as the fluid flows in a first

direction from the receiving compartment to the collecting
compartment, the baffle comprising:

a) a substantially vertical back plate; and

b) a pair of spaced-apart side walls extending from the side edges
of the back plate, said side walls adapted to be attached to the
transversely mounted wall of said settling tank and straddle said
aperture, said baffle adapted of causing at least some of the
solids contained in the drilling fluid to settle to the bottom of the
tank as the fluid flows in the first direction through said aperture.


19. The baffle as set forth in claim 18 wherein said side walls are adapted
to attach to the side of said transverse wall facing the collecting
compartment.


20. The baffle as set forth in any one of claims 18 to 19 wherein said walls
further comprise a plurality of slot-shaped openings.




21

21. A kit for a settling tank for removing solids from drilling fluids having

first and second end walls, two side walls extending therebetween and
a bottom, the tank forming a receiving compartment for receiving a
stream of drilling fluid containing solids adjacent to the first end wall
and a collecting compartment adjacent to the second end wall, the tank
having at least one wall transversely mounted between the side walls
separating the receiving and collecting compartments, the transverse
wall defining an aperture for allowing drilling fluid to pass through as
the drilling fluid flows in a first direction from the receiving compartment
to the collecting compartment, the kit comprising of one or more
components selected from the group consisting of:

a) a flow-reversing barrier comprising:

i) a substantially vertical back panel,

ii) a pair of side panels extending from the side edges of the
back panel,

iii) a bottom plate extending from the bottom edge of the
back panel, the bottom plate extending between the side
panels, and

iv) means for mounting said barrier in the receiving
compartment such that said barrier is positioned to
receive said stream directed between said side panels
towards said back panel thereby causing said stream to
reverse direction and flow around said barrier whereby at



22
least some of the solids contained in the drilling fluid
settle to the bottom of the tank; and

b) a flow-restricting baffle comprising:

i) a substantially vertical back plate, and

ii) a pair of spaced-apart walls extending from the side
edges of the back plate, said side walls adapted to be
attached to the transversely mounted wall straddling said
aperture, said baffle adapted to cause at least some of
the solids contained in the drilling fluid to settle to the
bottom of the tank as the fluid flows in the first direction
through said aperture.

22. The kit as set forth in claim 21 wherein said mounting means of the
flow-reversing barrier are adapted to position said barrier substantially
central in the receiving compartment.

23. The kit as set forth in any one of claims 21 to 22 wherein the side walls
of the flow-restricting baffle are adapted to be attached to the side of
the transverse wall facing the collecting compartment.

24. The kit as set forth in any one of claims 21 to 23 wherein the side walls
of the flow-restricting baffle further comprise a plurality of slot-shaped
openings.

25. A method for recycling drilling fluid containing solids, comprising:

a) directing a stream of drilling fluid containing solids into a flow-
reversing barrier located in a receiving compartment of a settling
tank, the settling tank further comprising a collecting


23
compartment, the collecting compartment separated from the
receiving compartment by a transverse wall, the wall defining an
aperture, the flow-reversing barrier capable of causing the
stream to reverse direction and flow around the barrier thereby
causing at least some of the solids contained in the fluid to settle
to the bottom of the tank;

b) allowing the stream of fluid to fill the receiving compartment and
pass through the aperture of the transverse wall as the fluid
flows in a first direction from the receiving compartment to the
collecting compartment;

c) allowing the fluid to flow in the first direction and fill the collecting
compartment;

d) extracting fluid from the collecting compartment for re-use in
drilling operations;

e) moving the settled solids on the bottom of the tank towards an
outlet; and

f) removing a mixture of fluid and solids from the outlet.

26. The method as set forth in claim 25 further comprising the step of
flowing the fluid in the first direction through an aperture of at least one
additional transverse wall, the at least one additional transverse wall
located between the receiving compartment and the collecting
compartment in the tank and defining at least one intermediate
compartment.


24
27. The method as set forth in any one of claims 25 to 26 further

comprising the step of introducing an effective amount of a flocculating
agent into the receiving compartment as the stream of drilling fluid
containing solids is directed towards the flow-reversing barrier.

28. The method as set forth in any one of claims 25 to 27 further
comprising the step of passing the mixture of fluid and solids removed
from the outlet through a centrifuge.

29. The method as set forth in any one of claims 25 to 28 wherein the
outlet is located on the second end wall and the settled solids are
moved in the first direction towards the outlet.

30. A method for recycling drilling fluid containing solids, comprising:

a) directing a stream of drilling fluid containing solids into a
receiving compartment of a settling tank, the settling tank further
comprising a collecting compartment, the collecting
compartment separated from the receiving compartment by a
transverse wall, the wall defining an aperture with a flow-
restricting baffle attached thereto;

b) allowing the stream of fluid to fill the receiving compartment and
pass through the aperture and flow-restricting baffle of the
transverse wall as the fluid flows in a first direction from the
receiving compartment to the collecting compartment, the flow-
restricting baffle capable of causing at least some of the solids
contained in the fluid to settle to the bottom of the tank as the
fluid flows through the aperture and baffle;


25
c) allowing the fluid to flow in the first direction and fill the collecting
compartment;

d) extracting fluid from the collecting compartment for re-use in
drilling operations;

e) moving the settled solids on the bottom of the tank towards an
outlet; and

f) removing a mixture of fluid and solids from the outlet.

31. The method as set forth in claim 30 further comprising the step of
flowing the fluid in the first direction through an aperture with a flow-
restricting baffle of at least one additional transverse wall, the at least
one additional transverse wall located between the receiving
compartment and the collecting compartment in the tank and defining
at least one intermediate compartment, the flow-restricting baffle
capable of causing at least some of the remaining solids contained in
the fluid to settle to the bottom of the tank as the fluid flows through the
aperture and baffle.

32. The method as set forth in any one of claims 30 to 31 further
comprising the step of introducing an effective amount of a flocculating
agent into the receiving compartment as the stream of drilling fluid
containing solids is directed into said receiving compartment.

33. The method as set forth in any one of claims 30 to 32 further
comprising the step of passing the mixture of fluid and solids removed
from the outlet through a centrifuge.


26
34. The method as set forth in any one of claims 30 to 33 wherein the

outlet is located on the second end wall and the settled solids are
moved in the first direction towards the outlet.

Description

CA 02596413 2007-08-20

"METHOD AND APPARATUS FOR REMOVING CUTTINGS FROM
DRILLING FLUIDS"

INVENTOR
Darin Merle Harding
TECHNICAL FIELD

The present disclosure relates to a method and apparatus for recycling
drilling fluids used in the drilling of wells.

BACKGROUND
The drilling of wells in the recovery of oil and gas typically comprises a
rig drilling the well with a hollow drill string. As the well is being
drilled, drilling

fluids are pumped down the bore of the string. The drilling fluid passes
through openings in the drill bit and returns to the surface through the
annulus
surrounding the string, carrying the cuttings produced by the drill bit. The
drilling fluid can then recycled to remove the cuttings so that it can be used
again.

Traditional methods of recycling drilling fluid can include the use of a
centrifuge to separate the liquid from the cuttings. In large drilling
operations,
it is necessary to use either a very large centrifuge or to use a multitude of
centrifuges to keep up with the volume of drilling fluid used in the drilling

operations. In either case, the costs of operating such a drilling fluid
recycling
system can be substantial.

It is known to use a settling tank in combination with a centrifuge in a
fluid recycling system or apparatus.

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2
The settling tank can be used in a preliminary step to settle the cuttings
from the fluid where drilling fluids are pumped into a receiving end of the
tank.
The cuttings are, initially, in suspension in the fluid and are often referred
to
as "solids". Flocculating agents can be introduced into the tank to assist in

the settling of solids. The tank can have a plurality of transverse walls or
baffles that form a plurality of compartments within the tank. Each wall can
have an opening to permit the flow of fluid from an upstream compartment to
a downstream compartment. The openings can be positioned on the walls in
such a manner that the fluid follows a sinuous path as it flows from the

receiving end to the collecting end of the tank. As fluid flows from
compartment to compartment, solids in the fluid settle to the bottom of the
tank.

Once fluid reaches a collecting end of the tank, the fluid can be
withdrawn from the tank to be used in the drilling operation. The settled
solids
are conveyed towards the receiving end of the tank using an auger. A slurry

of settled solids and fluid can be withdrawn from the tank and pumped
through a centrifuge. Fluid recovered from the centrifuge is re-introduced
into
the tank at the receiving end.

While using the combination of settling tank and centrifuge is an
improvement in comparison to using a centrifuge by itself, in practice, this
circuit is often unable to keep up with the throughput of drilling fluid
required in
drilling a well. It is often necessary to temporarily halt drilling of the
well until
the settling tank and centrifuge can catch up and recover enough drilling
fluid
to commence drilling operations again.

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3
It is, therefore, desirable to provide a method and apparatus that
addresses the shortcomings of the prior art and is better capable of recycling
drilling fluid in sufficient quantity for typical drilling operations.

SUMMARY
A method and apparatus for recycling drilling fluids used in the drilling
of wells is provided. The apparatus can comprise a settling tank whose
interior space can be sub-divided into a plurality of compartments.
Transverse walls can be located within the tank, spaced approximately
equidistant apart along the length of the tank to define the compartments of

the tank. At one end of the tank, there can be a receiving compartment. At
the other end, there can be a collecting compartment. A flow-reversing barrier
can be located in the receiving compartment. The barrier can comprise a
vertical rectangular back panel with two vertical rectangular side panels
extending perpendicular from the back panel to form a U-shaped structure. A

bottom rectangular plate can extend from the back panel partway along the
bottom edges of the side panels to partially enclose the bottom of the
barrier.
In each of the transverse walls, there can be an opening in the upper

end of the wall that enables fluid to flow from an upstream compartment into
an adjacent downstream compartment. A flow-restricting baffle can be
mounted on the downstream side of each transverse wall, aligned with the

opening. The baffle can comprise a vertical rectangular back plate with two
vertical rectangular side walls that extend perpendicular from the back plate
to
form a U-shaped structure. The baffle can attach to the wall on either side of
the opening. The top edges of the plate and side walls can be substantially

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CA 02596413 2007-08-20

4
aligned with the top of the transverse wall whereas the bottom edge of the
plate can extend lower into the compartment than the side walls. Each baffle
side wall can have a plurality of openings or slots.

The bottom wall of the tank can form at least one trough that runs
lengthwise along the tank, passing through each of the compartments. There
can be a conveyor in each trough for moving solids towards the collecting
compartment. In one embodiment, there can be four compartments and two
troughs running along the bottom of the tank, each trough comprising a
conveyor in the form of an auger.

The method of using the apparatus can comprise pumping drilling fluid
containing solids into the receiving compartment and directing the fluid
towards the flow-reversing barrier. As the fluid strikes the barrier, the
fluid can
stop and reverses its flow in order to flow around the side panels of the
barrier. This can cause heavier solids within the fluid settle to the bottom
of
the tank.

As fluid fills the receiving compartment, the level of the fluid can rise to
the opening in the transverse wall separating the receiving compartment from
the adjacent downstream compartment. Fluid flowing through the opening
encounters the flow-restricting baffle where it can pass through the slots in
the

side walls and the bottom opening of the baffle. This can cause further solids
in the fluid to settle to the bottom of the tank.

As fluid flows from compartment to compartment, it can pass through
subsequent baffles in each transverse wall opening until the fluid reaches the
collecting compartment. By the time the fluid reaches the collecting

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CA 02596413 2007-08-20

compartment, substantially all of the solids in the fluid will have settled to
the
bottom of the tank. Fluid can then be removed from the collecting department
to be used again in the drilling operations.

The settled solids can be moved towards the collecting compartment
5 by an auger in each trough. The augers can expel a slurry of solids and
fluid
through outlets on the end wall of the tank. The slurry can then be pumped
through a centrifuge. The residual fluid in the slurry can be removed by the
centrifuge and introduced back into the receiving compartment.

A flocculating chemical agent can also be used to assist in settling
solids from the drilling fluid. In a representative embodiment of the
apparatus,
drilling fluid can be skimmed from the collecting compartment and mixed with
a flocculating chemical. The mixture can then be pumped into the receiving
compartment to mix with the received drilling fluid.

Broadly stated, an apparatus for removing solids from drilling fluid is
provided, the apparatus comprising a settling tank having barrier means for
reversing the flow of a stream of drilling fluid containing solids to cause at
least some of the solids to settle to the bottom of the tank.

Broadly stated, an apparatus for removing solids from drilling fluid is
provided, the apparatus comprising a settling tank having at least one
transverse wall defining an aperture having a flow-restricting baffle to cause
at

least some solids in the drilling fluid to settle to the bottom of the tank as
the
fluid passes through the aperture and baffle.

Broadly stated, a flow-reversing barrier for removing solids from drilling
fluids in a receiving chamber of a settling tank is provided, the barrier
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6
reversing the flow of fluids into the receiving chamber to cause at least some
of the solids to settle to the bottom of the tank.

Broadly stated, a flow-restricting baffle for removing solids from drilling
fluids as they flow through apertures in transverse walls in a settling tank
is
provided, the baffle restricting the flow of the fluid to cause at least some
of
the solids to settle to the bottom of the tank.

Broadly stated, a kit for a settling tank for removing solids from drilling
fluids is provided, the kit comprising one or more components of the group
consisting of a flow-reversing barrier for mounting in a receiving chamber of
a

settling tank and a flow-restricting baffle for attaching to the downstream
side
of an aperture on a transverse wall in the settling tank.

Broadly stated, a method for recycling drilling fluid containing solids is
provided that comprises directing a stream of drilling fluid containing solids
into a flow-reversing barrier located in a receiving chamber in a settling
tank to

reverse the direction of the stream and cause at least some of the solids to
settle to the bottom of the tank.

Broadly stated, a method for recycling drilling fluid containing solids is
provided that comprises allowing a stream of drilling fluid to pass through
apertures in transverse walls in a settling tank, the apertures having flow-

restricting baffles to restrict the flow of the stream and cause at least some
of
the solids to settle to the bottom of the tank.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view depicting a settling tank.

Figure 2 is a top plan view depicting the settling tank of Figure 1.
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Figure 3 is a cross-sectional end view depicting section III-III of the
settling tank of Figure 2.

Figure 4 is a perspective view depicting the flow-reversing barrier of the
settling tank of Figure 1.

Figure 5 is a front elevational view depicting the flow-reversing barrier
of Figure 4.

Figure 6 is a top plan view depicting the flow-reversing barrier of Figure
4.

Figure 7 is a side elevational view depicting the flow-reversing barrier
of Figure 4.

Figure 8 is a perspective view depicting the flow-restricting baffle of the
settling tank of Figure 1.

Figure 9 is a front elevational view depicting the flow-restricting baffle
of Figure 8.

Figure 10 is a top plan view depicting the flow-restricting baffle of
Figure 8.

Figure 11 is a side elevational view depicting the flow-restricting baffle
of Figure 8.

DETAILED DESCRIPTION OF EMBODIMENTS

A method and apparatus for recycling drilling fluids used in the drilling
of wells is provided. Illustrated in Figures 1 and 2 is an embodiment of the
apparatus. Apparatus 10 can include settling tank 12 which can comprise end
walls 8 and 9, side walls 13 and bottom 19. In a representative embodiment,
the dimensions of tank 12 can be 50 feet long by 5 feet high by 10 feet wide.

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In this embodiment, tank 12 can have three transverse walls 15 to form four
compartments that are approximately 3,172 gallons in volume each for a total
capacity of 12,688 gallons in tank 12. One compartment defined by one
transverse wall 15 is receiving compartment 14 located adjacent to end wall 8

of tank 12. Another compartment defined by a transverse wall 15 is collecting
compartment 14 located adjacent to end wall 9 of tank 12. A third transverse
wall 15 can define two intermediate compartments 18 between receiving
compartment 14 and collecting compartment 16. Pump 34 can be located in
collecting compartment 16 to withdraw fluid that has passed through tank 12
for re-use in drilling operations.

Bottom wall 19 of tank 12 in combination with inverted V-shaped rib 62
can form troughs 38 and 60 that run lengthwise along tank 12 from end wall 8
to end wall 9. In troughs 38 and 60, respectively, augers 30 and 31 can be
used as material conveyors to move settled solids towards outlets 32 located

on end wall 9. In a representative embodiment, augers 30 and 31 can be 10
inches in diameter and can have a pitch of 10 inches. In operation, augers 30
and 31 can turn at approximately 9 revolutions per minute and can be driven
by drive mechanism 28. In one embodiment, drive mechanism 28 can
comprise an electric motor in the 2 to 3 horsepower range coupled to a

gearbox (not shown). The output of the gearbox can be coupled to one auger
via a belt and pulley system (not shown) although other coupling means can
be used as obvious to those skilled in the art. To synchronize the two augers
to turn at the same rate, each auger can have a chain sprocket and can be
coupled to one another via a drive chain (not shown). It is obvious to one

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9
skilled in the art that drive mechanism 28 can also comprise an internal
combustion engine or hydraulic drive system as the motive means to turn the
augers. It is also obvious that the gear ratio of the gearbox and the pulley
sizes are dependent on the type of motive means used in order to obtain the
desired turning rate of the augers.

In one embodiment, flow-reversing barrier 20 can be mounted
substantially in the centre of receiving compartment 14 as shown in Figures 1
and 2. In another embodiment, barrier 20 can be constructed from sheet
steel. Referring to Figures 4, 5, 6 and 7, barrier 20 can have, in a

representative embodiment, vertical main back panel 46 having dimensions of
approximately 34 inches high by 36 inches wide, and two vertical side panels
42 perpendicular to back panel 46, each side panel 42 being approximately
34 inches high by 24 inches wide thereby forming a U-shaped structure.
Barrier 20 can also comprise bottom plate 44 located between side panels 42

and can have dimensions of approximately 36 inches wide extending 12
inches from back panel 46 along the bottom edge of side panels 42. The top
of barrier 20 can be supported by support bar 40 that runs transverse across
the top of tank 12. In one embodiment, bottom plate 44 can sit on top of rib
62. In another embodiment, barrier 20 can further be supported by struts 41

that extend diagonally upward from rib 62 to the bottom edge of back panel
46. This can result with the top of barrier 20 being approximately flush with
the top of tank 12.

Within tank 12, transverse walls 15 can define and separate receiving
compartment 14, intermediate compartments 18 and collecting compartment
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16 within tank 12. On each transverse wall 15, there can be opening 23
located near or at the top of transverse wall 15. In a representative
embodiment, opening 23 can be approximately 12 inches high by 18 inches
wide. In further embodiments, a flow-restricting baffle 22 can be mounted on

5 the downstream side of each transverse 15 wall, aligned with opening 23 as
shown in Figures 1 and 2. Referring to Figures 8, 9, 10 and 11, baffle 22 is
shown. In a representative embodiment, baffle 22 can be constructed from
sheet steel and can have a vertical back plate 52 approximately 28 inches
high by 18 inches wide and two vertical side walls 50 perpendicular to back

10 plate 52, each side wall 50 being approximately 24 inches high by 8 inches
wide to form a U-shaped structure. Each side wall 50 of baffle 22 can have a
plurality of horizontal openings 54, each approximately 6 inches wide by 2
inches high, stacked vertically on side wall 50. In representative embodiment,
there can be four or five openings 54 on each side wall 50.

Referring to Figures 1 and 2, apparatus 10 can also include mixing
tank 36 attached to end wall 9 of tank 12. Contained in mixing tank 36 is
mixer 37. Mixer 37 can be mechanically coupled to auger 30 contained in
trough 38 such that mixer 37 operates when auger 30 is driven by drive
mechanism 28. Mixer 37 can be used to prepare a flocculating chemical

agent that assists in settling solids from the drilling fluid. In the
apparatus as
illustrated, drilling fluid can be skimmed from collecting compartment 16 and
mixed with the chemical agent in mixer 37. The resultant chemical mixture
can be pumped into receiving compartment 14 to mix with the received drilling
fluid and assist in the settling of solids contained the drilling fluid. In
another

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11
embodiment, apparatus 10 can further include walkway 64 mounted on side
wall 13 to permit an operator to inspect the fluid as passes through tank 12.

In one embodiment, drilling fluid containing solids can be pumped from
holding tank 24 into receiving compartment 14 and directed towards flow-
reversing barrier 20 via inlet 26. The flow of fluid is stopped by barrier 20
and

reverses to flow around side panels 42. This can cause heavier solids to
settle to troughs 38 and 60 of tank 12. As the fluid level rises in receiving
compartment 14, the fluid can overflow into the adjacent downstream
intermediate compartment 18 through opening 23 in transverse wall 15 that
separates the two compartments.

In another embodiment, fluid flowing through opening 23 can encounter
flow-restricting baffle 22 where the fluid can strike back plate 52 and
deflect
downwards to bottom 19 of tank 12. Fluid can also pass through slots 54 in
side walls 50 of baffle 22. The flow of fluid through baffle 22 can cause
further

solids in the fluid to settle to the bottom of tank 12. Fluid flows from
compartment to compartment by passing through successive baffles 22 in
each transverse wall 15 until the fluid reaches collecting compartment 16.
Fluid can then be withdrawn from collecting compartment 16 by pump 34 to
be used again in the drilling operations.

The solids that have settled to the bottom 19 of tank 12 can be
conveyed by augers 30 and 31 along troughs 38 and 60, respectively towards
collecting compartment 16. Augers 30 and 31 expel a slurry of solids and
fluid through outlets 32 on end wall 9 of tank 12. In one embodiment, outlets
32 are coupled to pipes 33, which can be 10 inches in diameter. Pipes 33 can

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extend to intersect with plenum 56, also made of 10 inch diameter pipe.
Plenum 56 can have end covers 57 that are removable that allow for clean-
out of plenum 56. Plenum 56 receives the slurry discharged from outlets 32
and directs the slurry to discharge ports 58. In a representative embodiment,

ports 58 can be 4 inches in diameter and be connected via tubes, pipes or
hoses (not shown) to a pump (not shown) to transfer the slurry to a centrifuge
(not shown). The centrifuge can then be used to separate the residual fluid
from the solids in the slurry as well known to those skilled in the art. Fluid
recovered from the centrifuge can then be re-introduced into the tank at the

receiving compartment to remove further residual solids or it may be re-used
directly in the drilling operations. In another embodiment, apparatus 10 can
further comprise a centrifuge that can be used in combination with tank 12 to
recycle drilling fluids.

In a representative embodiment, apparatus 10 can accommodate a
flow rate of drilling fluid in the range of 0 to 500 gallons per minute. It
should
be obvious to those skilled in the art that the size of tank 12 and the volume
of
each compartment is a function of the volume of drilling fluid to be recycled
and the amount of solids that need to be removed from the fluids to facilitate
their reuse. The size and dimensions of tank 12 can be scaled larger or

smaller, accordingly, to suit the requirements of the drilling operation.
While a
representative embodiment of apparatus 10 can incorporate three transverse
walls 15 in tank 12 to form four compartments, fewer or more transverse walls
15 can be installed in settling tank 12 to accommodate the volume of drilling
fluid required for the drilling operations.

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In other embodiments of apparatus 10, settling tank 12 can comprise
either one or the other of flow-reversing barrier 20 and flow-restricting
baffles
22. It is obvious to those skilled in the art that barrier 20 can be used with
any
settling tank that receives a stream of drilling fluid containing solids so as
to

cause at least some of the solids in the stream to settle to the bottom of
such
a tank. It is also obvious to those skilled in the art that baffles 22 can be
used
with any settling tank for removing solids from drilling fluids where the tank
comprises compartments defined by transverse walls and where the
transverse walls comprise apertures that allow the fluids to flow from

compartment to compartment whereby baffle 22 is attached to the
downstream side of such an aperture so as to cause at least some of the
solids to settle to the bottom of the tank as fluids flow through baffle 22.
In
other embodiments, the method described herein can be limited to using only
flow-reversing barrier 20 in tank 12 or to using only flow-restricting baffles
22
in tank 12 in addition to using both of barrier 20 and baffles 22 in tank 12.

In further embodiments, a kit can be provided for a settling tank used to
remove solids from drilling fluids, the kit comprising one or more components
selected from the group consisting of at least one flow-reversing barrier 20
and at least one flow-restricting baffle 22.

Although a few embodiments have been shown and described, it will
be appreciated by those skilled in the art that various changes and
modifications might be made without departing from the scope of the
invention. The terms and expressions used in the preceding specification
have been used herein as terms of description and not of limitation, and there

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14
is no intention in the use of such terms and expressions of excluding
equivalents of the features shown and described or portions thereof, it being
recognized that the scope of the invention is defined and limited only by the
claims that follow.

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Representative Drawing