Note: Descriptions are shown in the official language in which they were submitted.
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SEPARATOR FOR REMOVING SOLIDS FROM DRILLING FLUID
FIELD OF THE INVENTION
This invention relates to a separator for removing particulate solids from
drilling fluid returning from a well.
BACKGROUND OF THE INVENTION
Wells have long been drilled using drilling fluid as the circulating medium.
Drilling fluid may be fresh water or, if finely divided clay has been added, drilling mud. One
purpose of drilling fluid is to provide a column of fluid that exerts hydrostatic pressure at the
bottom of the wellbore which prevents the entry of pressurized LylL~lI,a~ into the wellbore
from the formation being drilled. It also serves to carry solid cuttings up and out of the
wellbore. A primary dl~al~allla~ associated with the use of drilling fluid is the expense
associated with using large volumes of fluid. In view of the high cost of drilling fluid, it is
desirable to develop methods of recovering and reusing the drilling fluid.
The most common technique has been to use mud pits or settlement tanks
where the drilling fluid is stored and particulate matter allowed to settle out with the passage
of time. This technique has a major drawback in the length of time required and in many
instances, complete separation of solids from the fluid cannot be achieved in a reasonable
length of time. This is especially true with very fine solids.
A more recently developed techmique involves the use of centrifuge separators
to remove the solids. For example, a centrifugal separation system is described in U.S. Patent
5,344,570 issued to ~ h~ et.al. Although centrifugal separation accelerates the speed
of separation, there are drawbacks inherent in such techniques related primarily to the expense
and complexity of such systems.
It is also possible to physically filter drilling fluid to separate solids usingscreens or other filter means. In U.S. Patent 4,243,527 issued to Leonard, there is described
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an apparatus which treats drilling fluids by means of a screen and conveyor mounted screen
cleaning means which physically scrapes the screen and removes solids from the apparatus.
However, this system is unable to remove finer solids which pass through the screen. Also,
the screen may still clog despite the screen cleaning m~ nicm
The prior art also discloses the use of plate separators to remove solids that are
suspended in a liquid. In U.S. Patent 4,897,206 issued to Castelli discloses a bidirectionally
corrugated plate separator for fluid mixtures. The plate separator comprises a horizontal stack
of b;Ji~ ally corrugated plates with bleed holes in the crests and valleys to allow passage
10 of solids downward through the stack and the fluid upward through the stack.
Therefore, it is known to provide settlement as a method of separating solids
from drilling fluid. It is also known to use plate separators to remove solids in ~ p.~n~ion
These concepts are hlc~ nJI ' into the present invention which improves on the prior art by
15 providing a mobile, compact, self-contained solids separator for drilling fluid which quickly
and effectively removes virtually all solids.
SUMMARY OF THE INVENTION~0
In general terms, the invention provides a self contained apparatus for
separating solids from drilling fluid received from a drilling operation ~
(a) a separation tank having an internal wall which divides the separation tank into
first and second .;.~IlllJalllll.. ~ the first ~ulll~ ll being operative to receive
the drilling fluid from a drilling operation;
(b) first means to ~o .~ remove solids from the first l,OIll~ ll located at the bottom of the first ._olll~Jalllll~....~0
5 ~ 4
(c) means for skimming drilling fluid from the first ~Ulll,Uall~ and ll~l~f~,.flllg
the drilling fluid to the second culll,ua~
(d) second means to ~ y remove solids from the second ~,UIII,Ual ~11.~,.11
S located at the bottom of the second ~;UIll~
(e) means for separating the remaining solids from the drilling fluid from the
second ~ ,.l1, said separation means positioned above the second
~,ulll,u~llll~.ll such that solids removed by the separation means fall back into
the second ~,U.. I,Ual~ ,lll, and
(f) meams for collecting separated drilling fluid from the separation means.
Preferably, the skimming means is above the horizontal level of the separation
15 means such that the flow of drilling fluid from the first ~;ulll~ lll to the collection means
is driven by gravity alone.
In accordance with another feature of the invention, there may also be
screening meams associated with the separation tank for removing larger solid particles from
20 the drilling fluid prior to the drilling fluid entering the first CUIll~
It is a preferred feature of the invention that the first and second ~;UIIIIJa~llll..lll:i
have downwardly ,' ' ~ cross-sectional areas which ~,u~ u~ settling solids towards
the first and second solid removal means 1~ ,livt;ly. This may be ~cornrlieh~d by sloping
25 the lateral walls of the separation tank and the dividing wall such that each of the first and
second COIll~llll~,llb have a "V" shape in cross-section.
The separation means may comprise a plurality of horizontally stacked and
spaced corrugated plate separators having bleed holes in the crests and valleys of the plates.
30 Preferably, the plate separators are bidirectionally corrugated.
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- In another aspect of the invention, there is provided a method of removing
sllh~tS~ ly all of the solids from drilling fluid returning from a drilling operation, said
drilling fluid comprising a liquid, coarse solids, fine solids, finer solids and finest solids, the
method ~
s
(a) screening the drilling fluid to separate the coarse solids;
(b) providing a separation tank divided into first and second ~;u~ ,llL~ and
having fluid skimming and transfer means to skim and transfer drilling fluid
from the first ~U~IIAU~ to the second ~,olll~JalLIll~,lll,
(c) introducing the drilling fluid into the first ~;ulll~u~~ t and allowing fine solids
to settle downwardly and removing the fine solids collected at the bottom of
the first ~,UIIII)alLlll.,ll~,
(d) ~ .l,f~,llhlg the drilling fluid from the first ~ulll~JalLlllclll to a second
1~ and allowing the finer solids to settle duwllwaldly and removing
the finer solids collected at the bottom of the second ~,UIII~/alLIII.,Il~,
(e) filtering the drilling fluid from the second ~,UIIIIJalllll~,lll to remove the finest
solids, retaining the finest solids in the second CUIIIIJOILIII~.IIL, and
(f) removing and collecting the drilling fluid and returning the drilling fluid to the
drilling operation.
BRIEF DESCRIPTION OF THE DRAWINGS
The preferred emh-)~l of the invention will now be described in reference
30 to the accul~ illg drawings in which:
2 ~
Figure I is a schematic flow sheet of separation system.
Figure 2 is a partial cut-away view of the separator.
Figure 3 is a side cut-away view of the separator showing some internal
Figure 4 is a top cut-away view of the separator.
Figure 5 is view is an individual plate separator used in the plate separator
array.
Figure 6 is a schematic diagram of the electrical control system.
Figure 7 is a schematic diagram of the hydraulic motor and pump system.
Figure 8 is a view of a flow control valve and motor group.
Figure 9 is a view of the hydraulic tank pump and drive motor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention in its apparatus form is a separator (10) for treating drilling fluid
25 being returned from a well to remove substantially all of the solids suspended in the drilling
fluid so that the drilling fluid may be returned to the well to be reused.
The apparatus comprises a separation tank (12) which is divided into first (14)
and second (16) . . l~ lt~ by a dividing wall (18), a clean-out auger (20) in the first
30 ~ J~llllC;lll (14), a skimming trough (22) to transfer drilling fluid from the first
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~;u.~ ,llL (14) to the second CUIII~ lllClll (16), a clean-out conveyor (24) in the second
~;UIll,ualllll~,lll (16) and an array of plate separators (26).
The dimensions of the separator (10) are not essential to the invention.
S However, the preferred cilllb(nlilll~,lll of the separator (10) is small enough that it may be
cul~ tly transported from site to site on a flat bed truck or trailer. It is large enough to
handle the flow from most drilling operations. It is a,u,ul~ 'y 38 feet long, 8 feet wide
and 12 high. and has a total capacity of ~ JIU ' ' 1~/ 150 barrels: the first ~_Ulll,Uall
(14) has a capacity of ~llJ,UIU ' ' Iy 50 barrels while the second ~_UllI,Ual~ lll (16) has a
10 capacity of a~ 'y 100 barrels.
The separation tank (12) is generally rectangular when viewed from above and
is supported by a frame (28) of steel beams. The bottom portion (30) of the separation tank
(12) is formed by inclined first (32) and second (34) lateral walls which meet to form a "V".
15 The dividing wall (18) is also inclined generally parallel to the first lateral wall (32) and
attaches to the second lateral wall (34) to form the first UUIIIIJalllll~,.ll (14). Thus, both the
first amd second ~,UIII~JolLlll~,.lt:~ (14, 16) have a "V" shaped bottom portion when viewed in
cross-section (See Figure 2). The bottom of the first ~ulll,~ (14) is ~U~ y
midway down the separation tank (12).
The separator (10) does not require pumps to flow drilling fluid through the
separator (10). Because the first ~_Ulll,Ualllll~ (14) is higher than the second UUlll,Ualllll~,lll
(16), the plate separators (26) and the clean water tank (64) and skimmers (60), the force of
gravity causes the flow of drilling fluid through the separator (10). The rate of flow may be
25 controlled by the rate of addition of drilling fluid to the first CU..IIJalllll~,.ll (14).
A skimming trough (22) is provided at the top and to the side of the first
UUIIIIJalllll~.llt (14). The trough (22) has openings (23) in the trough bottom which connect to
transfer pipes (36) which lead to the second, , ~ ll1 (16). If the first CUIII~ (14)
30 is full, drilling fluid will spill into the trough (22) and the transfer pipes (36).
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A screw type auger (20) for cleaning out solids is positioned in the "V" of the
bottom portion of the first ~,u~ Jal~ (14). The clean-out auger (20) extends the length of
the first ~;wll,ualLlllwll (14). A first transfer auger (38) is placed at the output end (40) of the
clean-out auger (20) to lift the solids out of the first ~ullllJall~ ll (14). In turn, the first
5 transfer auger (38) leads to a drying auger (42) where the remaining drilling fluid is drained
from the solids. The solids are then deposited by the drying auger (42) into the mud tank
(not shown) while the fluid is returned to the first l,ullllJalllll~,lll (14) of the separation tank
(12).
A clean-out conveyor (44) is positioned in the "V" of the bottom portion (30)
of the second CUIII~ ;III (16). In the preferred nlllhO.~ l. .,1 the conveyor (44) is a belt
(46) with transverse members (48) to physically move solids which have settled to the bottom
of the second UUIII~ (16). The conveyor (44) leads to a second transfer auger (50)
which lifts solids out the second ~,Olll~alllll~lll (16) and into the drying auger (42) where the
solids mix with solids from the first transfer auger (38) and are eventually deposited into the
mud tank.
Rotary shale shakers (52) which are well known in the art are positioned above
the first l,Ulll~ ll. In the preferred rlllhO.I:.ll. .,l two shakers (52) are provided which are
elongated rotating drums. The drums include screening and flighting to separate larger
particles from the drilling fluid.
In operation, drilling fluid is taken directly from the flow nipple of the drilling
rig (not shown) and is pumped to the shale shakers (52). In the shale shakers, the screens
(53) separate solid particles about 500 microns in diameter or larger, which are then removed
by the flighting and deposited into the mud tank. Drilling fluid and smaller solids fall
through the screens and are deposited in the first ~;ulll~ (14) of the separation tank
(12).
Upon entering the first ~,ulll,uall~ lll (14), the fluid and solids are allowed to
settle. Settlement is aided by a vibrating bar (54) which is suspended in the first ~ulllAua~
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(14). Settlement is further aided by the slope of the second lateral wall (34) and the dividing
wall (18) which form the first uullluall~ lt (14). The sloping walls (34, 18) direct solids
which l.;UII~ ' in the bottom of the first ~ (14). The clean-out auger (20)
ly rotates to transfer the settled solids to one end of the ~,ulll,ualllll~,lll (14) and
5 deposits the solids into the first transfer auger (38) which removes the solids from the first
IUlC~ (14). A chemical floculant may be added to the drilling fluid in the first~,ulll,ualL~ (14) which causes à~ ;al;on of the solids to speed up the settlement process.
Drilling fluid at the top of the first ~,wll~ualllll~,lll (14) is skimmed by the trough
(22) and transferred to the second UUIII~Jalllll~,.ll (16) via the transfer pipes (36). There is no
need for a baffle or weir in the first ~;ulll,uall~ ,lll (14) to separate the incoming stream of
drilling fluid from the trough (22) as long as the incoming stream is diffuse amd is directed
away from the trough (22). The fluid is allowed to further settle in the second ~,UIII~Ual~lll~,lll
(16) and for a longer length of time than in the first culllualllll~,llt (14) due to the larger
capacity of the second ~ . 11.. ~.. 1(16). There is a second vibrating bar (56) suspended in
the second uullluali (16) which aids in the settling process. Settled solids arelr. ..l~ i by the sloping walls (32, 34) of the second cUlll,Ual~ ;lll (16). Solids which
settle out in the second l,Olll~alllll.,lll (16) accumulate at the bottom of the "V" and are
removed by the continuous conveyor (44) which leads to the second transfer auger (50).
Drilling fluid in the second ~,UllI,Ualilll~,lll (16) is pushed up through the plate
separators (26). The plate separators (26) are a plurality of horizontally stacked plate
separators (26) that cause the fluid to flow in a sinusoidal and laminar manner. In the
preferred rllll,o.l;~"r.,l bidirectionally corrugated plates of the type lllallll~al,lul~;l by Facet
25 Quantek, Inc. of Tulsa, Oklahoma are used. The drilling fluid is pushed upward into channel
A in between the two arrays of plate separators (26). The fluid then passes horizontally and
laterally in the direction of arrows B and C. The plate separatûrs (26) cause the drilling fluid
to migrate upwards through bleed holes in the crests while solids migrate downwards through
bleed holes in the valleys of the plates. Solids which are retained in the separator (10) by the
30 plate separators (26) fall back into the second uulll,ualL~ (16). Clean drilling fluid is
collected by the clean water skimmers which are elongated troughs (60) located lateral to the
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upper portion of the plate separators (26). Clean drilling fluid may then flow over the clean
water weir (62) and into the clean water ~,I~IIIIJol~IIICll~ (64). The drilling fluid in the clean
water ~ J~ i (64) may then be pumped back to the drilling rig for reuse.
S The separator (10) is electrically controlled and has an integral power supply.
A hydraulic pump is electrically driven to pressurize hydraulic fluid and operate an array of
hydraulic motors. The hydraulic motors drive the clean-out auger (20), the first transfer auger
(38), the drying auger (42), the clean-out conveyor (44), the second transfer auger (50) and
the shale shakers (52). The electrical and hydraulic systems of the preferred embodiment are
shown in Figures 6 to 9.
Variations and mo(lifil~ti~ns of the disclosed preferred rllllloll;lllrlll will be
apparent to skilled pr~titionPrs. All such variations and mn~lifi-~ti~ns are intended to be
rll~ d by the claims set forth herein.
