Note: Descriptions are shown in the official language in which they were submitted.
CA 02385739 2003-08-12
1 "METHOD AND APPARATUS FOR REMOVING CUTTiNGS
2 FROM DRILLING FLUIDS"
3 fjELD OF INV~'iNIION
4 The present invention relates to a nuthod and apparatus for recycling
dnlling
fluids used in the dnlling of wells.
6 bACKGRO= OE THE 2MNT,IQN
7 The drilling of wells in the recovery of oil and gas typically compri.ses a
rig
8 dnlling the well with a hollow drill string. As the well is baing drilled,
drilling fluids
9 are pumped down the bore of r.he string. The drilling fluid passes through
openings in
the drill bit and returns to che surface through the annulus surrounding the
string,
l 1 carrying the cuttings produced by the drill bit. The drilling fluid is
then recycled to
12 remove the cuttings so that it may be used again.
13 Tradiuonal methods of recycling drilling fluid include using a centrifuge
to
14 separaie the liquid from the cuttings. In large drilling operations, to
keep up with the
volume of drilling fluid used, it is necessary to use either a very large
centrifuge or to
16 use a multiiude of centrifuges. In either case, the costs of operating such
a dti.lling
17 fluid recycling system are substantial.
18 lt is known to use a settling tAnk in combination with a cenrrifuge in a
fluid
19 recycling system_
The settling tank is used as a preliminary sTep to settle the cuttings from
the
21 fluid- The cuttings often renzain in suspension in the fluid and are often
referred to as
22 "solids". Flocculating agents may be introduced into the tank to assist in
the settling
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CA 02385739 2003-08-12
1 of solids. The drilling fluids are pumped into the receiving end of the
ta.nk. The tank
2 has a plurality of transverse walls or baffles that form a plurality of
comparunents
3 within the tank_ Each wall has an opening to penrut the flow of fluid from
an
4 upstream compartment to a downstreatn compartment_ The openings are
positioned
on the walls in sc;ch a manner that the fluid follows a sinuous path as it
flows fronz the
6 receiving end to the collecting end of the tank. As fluid flows from
compartrnent to
7 compartment, solids in the fluid settle to the bottonm of the tank.
8 Once fluid reaches the collecting end of the tank, it is withdrawn from the
tank
9 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
are
11 withdrawn from the tank and pumped through a centrifuge. Fluid recovered
from the
12 centrifuge is re-introduced into the r.ank at the receiving end.
13 While using the combination of settling tank and centrifuge is an
improvement
14 in comparison to using a centrifuge by irself, in practice, this circuit is
often unable to
keep up with the throughput of drilling fluid required in drilling a well. It
is often
16 necessary to temporarily halt drilling of the well until the settling tank
and centrifuge
17 can catch up and recover enough drilling fluid to commence drilling
opera.tions again.
18 The present inventaon addresses the shortconiings of the prior art and
provides
19 a medtod and appamtus that is better capable of recycling drilling fluid in
sufficient
quantity for typical dnUing operations.
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CA 02385739 2003-08-12
1 StTM&URY OF THE INVRNTION
2 The present invention is concerned with t- method and apparatus for
recycling
3 drilling fluids used in the drilling of wells_
4 The apparatus of the present invention coinprises a tank whose interior
space
is sub-divided into a plurality of compartments. Transverse walls are located
within
6 the tank, spaced approxuuately equidistant apart along the length of the
tank to define
7 the companments of the tank. At one end of the tank, there is a receiving
8 compartment. At the other end, there is a collecting compartment- A flow-
reversing
9 barrier locaied in the receiving compartment. The barrier compnses a venical
rec:tangular back panel with two vertical rectangular side panels extending
11 perpendicular from the back panel to form a U-shaped structure. A bottom
12 rectangular plate extends from the back panel partway along the bottom
edges of the
13 side panels, parnially enclosing the bottom of the barrier_
14 In each of the transverse walls, there is an opening in the upper end of
the wall
that enables fluid to flow from an upstream compartment into an adjacent
downstream
16 compartment. A flow-restricting baffle is mounted on the downsTream side of
each
17 transverse wall, aligned with the opening. The baffle comprises a vertical
rectangular
18 back plate with two vertical rectangular side walls that extend
perpendicular from the
19 back plate to form a U-shaped structure_ The baffle attaches to the wall on
either side
of ihe opening. The top edges of the plate and side walls are substanttally
aligned
21 with the Top of the transverse wall whereas the bottom edge of the plate
extends lower
22 into the cornpartment than the side walls. Each baffle side wall has a
plurality of
23 openings or slots.
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CA 02385739 2003-08-12
1 The bottom wall of the tank forms at least one trough that runs lengthwise
2 along the tank, passing through each of the compartments- There is a
conveyor in.
3 each trough for moving solids towards the collecting compartment. ln the
preferred
4 embodiment of the apparatus, there are four compattments and two troughs
running
along the bottom of the tank, each trough comprising an auger.
6 The method of the present invention comprises pumping drilling fluid
7 containing solids into the receiving compar[ment and directing the fluid
towards the
8 flow-reversing barrier. As the #ltud stYilces the barrier, the fluid stops
and reverses its
9 flqw in order to flow around the side panels of the barrier. Ttus causes
heavier ,olids
within the fluid settle to the boinom of the tank.
11 As fluid fills the receiving compantnent, the level of the fluid will rise
to ihe
12 opening in the transverse wall separating the receiving coxnparttnent from
the adjacent
13 downstrcam compartment. Fliud flowing through the opening encounters the
flow-
14 restrscting baffle where ir passes through the slots in the side walls and
the botrom
opening of the baffle. This causes solids in the fluid to settle to the bottom
of the
16 tank-
17 As fluid flows from compamnent to compartment, it passes through
18 subsequent baffles in each transverse wall opening until the fluid reaches
the
19 collecting compartznent. By the time the fluid reaches the collecting
eomparement,
substantially all of the solids in the fluid have settled to the bottom of the
tank_ Fluid
21 is then removed from the collecting departin.ent to be used again in the
drilling
22 operations.
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1 The serrled solids are moved towards the collecting comparanent by an auger
2 in each rrough. The augers expel a slurry of solids and fluid through
outlets on the
3 end wall of the tank. The slurry is then pumped through a centrifuge. The
residual
4 fluid in the slurry is removed by the centrifuge and introduced back into
the receiving
comparrment.
6 A flocculating chemical agent may also be used to assist in settling solids
from
7 the drilling fluid. In the apparatus as built, drilling fluid is skimmed
from the
8 coliecting compartment and mixed wiih a floccularing chemical_ The mixture
is
9 pumped into the receiving compartrAent and mixes with the received drilling
fluid.
Broadly stated, one aspecr of the present invention is a merhod for recycling
11 drilling fluid used in drilling operations comprising the steps of
directing a stream of
12 drilling fluid containing solids into a flow-reversing bdxrier located in a
receiving
13 com.partment of a setrhng tank, the settling tank further comprising a
collecting
14 compartment, rhe collecting compartment separated from the receiving
compartment
by a transverse wall, the wall defining an aperture with a flow-restricting
baffle
16 attached thereto, the flow-reversing barrier capable of causing the stream
ro reverse
17 direction and flow around the barrier thereby causing at least sorme of the
solids
18 contained in the fluid to settle to the bottom of the tank, allowing the
stream of fluid
19 to fiil the receiving compartment and pass ihrough the aperture and flow-
resrricting
baffle of the transverse wall as the fluid flows in a f'ust direcuon from the
receiving
21 comparpment to the collecting compartment, the flow-restricting baffle
capable of
22 causing at least some of the remaining solids contained in the fluid to
settle to the
23 bottom of the tank as the fluid flows through the aperture and baffle,
allowing the
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CA 02385739 2003-08-12
I fluid to flow in the first direction and fill the collecting compartment,
extracting fluid
2 from the collecting computment for re-use in drilling operations, moving the
settled
3 solids on the bottom of the tank in the first direction towards an outlet
locared in the
4 collecting compartment, and removing a mixture of fluid and solids from the
outlet.
Broadly stated, another aspect of the present invention is an apparatus for
6 recycling drilling fluid used in drilling operations comprising a setding
tank having
7 first and second end walls, two side walls extending between the end walls
and a
8 bottom enclosing the area defined by the bottom edges of the end walls and
the side
9 walls, the tank forming a receiving comparcmenc adjacent to the first end
wall and a
colleeting compartment ad.lacent to the second end wall, the second end wall
defining
11 an outlet, a flow-reversing barrier mounted in the receiving compartment,
the barrier
12 adapted to receive a stream of drilling fluid containing solids, the
barrier capable of
13 causing the stream to reverse direction and flow around the barrier thereby
causing at
14 least some of the solids contained in the fluid to settle to the bottom of
the tank, a wall
transversely mounted in the tank between the side walls, the wall separating
the
16 receiving and collecting compatcmenrs, the wall defining an apenure having
a flow-
17 restricting baffle, the baffle extending perpendicular from the wall
towards the
18 collecting compartment, the baffle capable of causing at least some of the
remaining
19 solids contained in the fluid to settle to the bottom of the tank as fluid
flows in a first
direction from the receiving comparunent to the collecting compartment and
passes
21 through the aperture and baffle, and a material conveyor for moving the
settled solids
22 at the bottom of the tank towards the outlet on the second end wall.
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CA 02385739 2003-08-12
1 aRiEE DF-SCIg>noN oFTHE DRw_ wn Gs
2 FIGURE 1 is a perspective view of the apparatus of che present invention.
3 FIGURE 2 is a top plan view of the apparatus of the present invention.
4 FIGURE 3 is a cross-sectional end view of Section III-III.
FIGURE 4 is a perspective view of the flow-reversing bairier of the apparatus
6 of the present invention-
7 FIGURE 5 is a front elevational view of ihe flow-reversing barner of the
8 apparatus of the present invention.
9 FIGURE 6 is a top plan view of the flow-reversing bamer of the apparatus of
IO the present invention.
11 FIGURE 7 is a side elevational view of the flow-restricring baffle of the
12 appar=atus of [he present invention-
13 FIGURE 8 is a perspective view of the flow-resmcting baffle of the
apparatus
14 of the present inveniion_
FIGURE 9 is a from elevational view of che flow-restricting baffle of the
16 apparatus of the present invention_
17 FIGLTRE 10 is a top plan view of the flow-restricting baffle of the
apparatus of
18 the preseni invention.
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1 F1GilRE 11 is a side elevational view of the flow-restricting baffle of the
2 apparatus of the present invention.
3 DETAILED E CRIP'I'1QN OF THE PJLEFE~tItED EMBOpIIVIEN''
4 The present invention is concerned with a method and apparatus for recycling
drilling fluids used in the drilling of wells. Illustrated in FIGURES 1 and 2
is the
6 preferred embodiment of the apparatus of the present invention. The
apparatus 10
7 includes settling tank 12 which comprises of end walls 8 and 9, side walls
13 and
8 bottom 19. Prefet~ably, the dimensions of tank 12 are 50 feet long by 5 feet
high by 10
9 feet wide. The preferred embodiinent has three uansverse walls 15 within
iank 12 to
lu form four compartments that are approximately 3,172 gallon.s in volume each
for a
i t tota] capacity of 12,688 gallons in tank 12. One comparr.ment defined by a
transverse
12 wall 15 is receiving compartment 14 located adjacent to end wall 8 of tank
12.
13 Another compartment defined by a transverse wall 15 is collecting
eompartnnent 14
14 located adjacent to end wal19 of tank 12_ The third transverse wall 15
defines the two
intermediate compartments 18 between receiving compartment 14 and collecting
16 compan.ment 16. Pump 34 is located in collecting cotnpartment 16 to
wirhdraw fluid
17 that has passed through tank 12 for re-use in drilling operations.
18 Bottom wall 19 of tank 12 in combination with inverted V-shaped rib 62 form
19 troughs 38 and 60 Ihat run lengthwise along tank 12 from end wal18 to end
wall 9. In
troet,ghs 38 and 60, respectively, augers 30 and 31 are used as material
conveyors to
21 move settled solids towards outlets 32 located on end wall 9. In the
preferred
22 embodiment, augers 30 and 31 are 10 inches in diameter and have a pitch of
10
23 inches. Augers 30 and 31 tum at approximately 9 revoluuons per minute and
are
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CA 02385739 2003-08-12
1 driven by drive mechmism 28. In the preferred embodiment, drive mechanism 28
2 comprises of an electric tnotor in the 2 to 3 horsepower range coupled to a
gearbox
3 (not shown). The output of the gearbox is coupled to one auger via a belt
and pulley
4 system (not shown)_ To synchronize the two augers to iutn at the same rate,
each
auger has a chain sprocket and are coupled to one another via a drive chain
(not
6 shown). It should be obvious to one skilled in the art that drive mechanism
28 may
7 also use an internal combustion engine or a hydraulic diive system as the
motive
8 power to turn uhe augen. It should also be obvious that the gear rario of
the gearbox
9 and the pulley sizes are dependent on the rype of motive power used in order
to oblaln
the desired turning raie of the augers.
11 A flow-reversing barrier 20 constructed from sheet steel is mounted
12 substalltially in the centre of receiving compartment 14 as shown in
FT.GIJRES 1 and
13 2. Referring to FIGURES 4, 5, 6;uld 7, barrier 20 has a vertical main back
panel 46
14 of approximately 34 inches high by 36 inches wide dnd two vertical side
panels 42
perpendicular to back panel 46, each side panel 42 being approximaiely 34
inches
16 high by 24 inches wide rhereby fornling a U-shaped structure. Balrier 20
also has a
17 bottom plate 44 between side panels 42 approximately 36 inches wide
extending 12
18 inches from back panel 46 along the bottom edge of side panels 42. The top
of
19 barrier 20 is supported by support bar 40 that runs transverse across the
top of lanlc
12. Bottom plate 44 sits on top of rib 62. Barrier 20 is further supported by
struts 41
21 that extend diagonally upward from rib 62 ro the bottom edge of back panel
46. This
22 results in the top of barrier 20 being approximately flush with the top of
tank 12_
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1 Within tank 12, transverse walls 15 define and separate receiving
2 compaztm~ent 14, intermediate compartments 18 and collecting compartment 16
3 within tank 12. On each transverse wail 15, there is an opening 23 located
near or at
= 4 the top of transverse wall 15. Preferably, opetung 23 is approximately 12
inches high
by 18 inches wide. A flow-resuicting baffle 22 is mounted on the downstream
side of
6 each transverse 15 wall, aligned with opening 23 as shown in FIGURES 1 and
2.
7 Referring to FIGURES 8, 9, 10 and 11, baffle 22 is constructed from sheet
steel and
8 has a vertical back plate 52 approximately 28 inches high by 18 inches wide
and two
9 vertical side walls 50 perpendicular to back plate 52, each side wall 50
being
approximately 24 inches high by 8 inches wide to form a U-shaped structure.
Each
11 side wall 50 of baffle 22 has five horizontal openings 54, each
approximately 6 inches
12 wide by 2 inches high, stacked vertically on side wall 50.
13 Refemng to FIGURES 1 and 2, the preferred embodiment of the apparatus
14 also includes mixsng tank 36 attached to end wall 9 of tank 12. Contained
in mixing
tank 36 is mixer 37. Mixer 37 is mechanically coupled to, auger 30 contained
in
16 trough 38 such that mixer 37 operates when auger 30 is dnven by drive
mechanism
17 28. Mixer 37 is used to prepare a flocculating cherrucal agent that assists
in settling
18 solids from the drilling fluid. In the apparatus as built, drilling fluid
is skimmed from
19 collecting compartment 16 and nuxed with the chemical in mixer 37 and is
pumped
into receiving comparunent 14 to mix with the received drilling fluid and
assist in the
21 settling of solids contained the drilling fluid. Another feature of the
preferred
22 embodiment of the apparatus of the present invention includes a walkway 64
is
23 mounted on a side wall 13 to permit an operator to inspect the fluid as
passes through
24 tank 12.
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CA 02385739 2003-08-12
1 In operation, drilling fluid cQntaining solids is pumped from holding tank
24
2 into receiving compaiment 14 and directed towards flow-reversing barrier 20
via
3 inlet 26. The flow of fluid is stopped by barrier 20 and reverses to flow
around side
4 panels 42. This causes heavier solids to settle to troughs 38 and 60 of tank
12. As the
fluid level rises in receiving compartment 14, the fluid will overflow into
the adjacent
6 downstream intermediate comparrment 18 rhrough opening 23 in transverse wall
15
7 separating the two compartments. Fluid flowing through opening 23 encounters
flow-
8 restricting baffle 22 where the fluid will strike back plate 52 and deflect
downwards to
9 boitom 19 of tank 12. FlLud also passes through slats 54 in side walls 50 of
baffle 22.
The flow of fluid through baffle 22 causes further solids in the fluid to
settle to the
11 bottom of tank 12. Fluid flows from compartment to compartment by passing
through
12 successive baffles 22 in each transverse wall 15 until the fluid reaches
eolleeting
13 compartment 16_ Fluid is withdrawn from collecting compartment 16 by pump
34 to
14 be used again in the drilling operations.
The solids that have settled to the bottom 19 of tank 12 are conveyed by
16 augers 30 and 31 along
troughs 38 and 60, respectively towards collectung
17 companrnent 16. Augers 30 and 31 expel a slurry of solids and fluid through
outlets
18 32 on end wall 9 of tank 12. In the preferred embodiment, outlets 32 are
coupled to
19 pipes 33 which are preferably 10 inches in diatneter. Pipes 33 extent to
intersect with
plenum 56, also made of 10 inch diameter pipe. Plenum 56 has end covers 57
that are
21 removable that allow for clean-out of plenum 56. Plenum. 56 receives the
slurry
22 discharged from ourlets 32 and directs the slurry to discharge ports 58.
Ports 58 are
23 typicaAy 4 inches in diameter and are connected via tubes, pipes or hoses
(not shown)
24 to a pump (not shown) to transfer the slurry to a centrifuge (not shown).
The
31 {P3077374 DOC; I }
CA 02385739 2007-01-11
1 centrifuge is used to separate the residual fluid from the solids in the
slurry. Fluid
2 recovered from the centrifuge may be re-introduced into the tank at the
receiving
3 compartment to remove further residual solids or it may be re-used directly
in the
4 drilling operations.
The apparatus as built can accommodate a flow rate of drilling fluid in the
6 range of 0 to 500 gallons per minute. It should be obvious to those skilled
in the art
7 that the size of tank 12 and the volume of each compartment is a function of
the
8 volume of drilling fluid to be recycled and the amount of solids that need
to be
9 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 drilling operation
the present
11 invention is being used with. While the preferred embodiment of the
apparatus of the
12 present invention incorporates three transverse walls to form four
compartments,
13 fewer or more transverse walls may be installed in the settling tank to
accommodate
14 the volume of drilling fluid required for the drilling operations.
Although a few preferred embodiments have been shown and described, it will
16 be appreciated by those skilled in the art that various changes and
modifications might
17 be made without departing from the scope of the invention. The terms and
18 expressions used in the preceding specification have been used herein as
terms of
19 description and not of limitation, and there is no intention in the use of
such terms and
expressions of excluding equivalents of the features shown and described or
portions
21 thereof, it being recognized that the scope of the invention is defined and
limited only
22 by the claims that follow.
23
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