Note: Descriptions are shown in the official language in which they were submitted.
CA 02328790 2000-12-19
SHROUD FOR USE WITH ELECTRIC SUBMERGIBLE PUMPING SYSTEM
FIELD OF THE INVENTION
The present invention relates generally to a system and
method for pumping a production fluid from a subterranean
well, and particularly to an electric submergible pumping
system having a shroud formed from a sheet material.
~ BACKGROUND OF THE INVENTION
Pumping systems, such as electric submergible pumping
systems are utilized in pumping oil and/or other production
fluids from producing wells. A typical submergible pumping
system includes components, such as a motor, motor
protector, submergible pump and pump intake. In certain
applications, a shroud is disposed about certain of the
submergible components. For example, a shroud may be
employed around the submergible motor to extend upwardly to
the pump intake, where it is fastened to the submergible
pumping system. Thus, the production fluid is drawn through
the shroud, past the motor and into the pump intake. The
produced fluid acts as a coolant when drawn past the
submerged electric motor. .
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Conventional shrouds are formed from tubing having an
inside diameter larger than the outside diameter of the
submergible pumping system components. However, when the
annular space between the well casing and the motor is
relatively small, much of that space is taken by the wall
thickness of the shroud tubing. In fact, in some situations
the diameter of the tubing must be reduced to a point that
the annular flow space becomes too small to provide
sufficient fluid to the pump. This can starve the pump and
ultimately damage the pump components. The narrow flow
passage is also susceptible to clogging due to deposits or
debris in the production fluid.
It would be advantageous to be able to utilize a
downhole shroud in a narrow', bore wellbore without undue
utilization of the cross-sectional wellbore space
potentially available as a fluid flow passage.
SUMMARY OF THE INVENTION
The present invention features a device for directing a
production fluid along a motor used in a submergible pumping
system deployable in a wellbore. The device includes a
motor shroud sized to fit within a wellbore. The motor
shroud includes a wall that defines an inner flow path of
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sufficient size to receive the motor therein. The wall of
the motor shroud is corrugated to form a plurality of
downflow and upflow passages, and a channel for the
electrical power cable.
According to another aspect of the present invention, a
submergible pumping system is provided for use in pumping a
production fluid from a subterranean well. The system
includes a submergible pump having a pump intake.
Additionally, the system includes a submergible motor
operably coupled to the submergible pump. A motor shroud is
disposed over at least the submergible motor and the pump
intake. The motor shroud is formed by a wall of sheet
material. Typically, the sheet material is a sheet metal
formed as a corrugated sheet.
According to another aspect of the invention, a method
is provided for cooling a downhole component of a
submergible pumping system disposed in a narrow wellbore.
The method includes placing a corrugated sheet material
around the downhole component to form an interior flow path
between the sheet material and the downhole component.
Additionally, an exterior flow path is formed between the
sheet material and the narrow wellbore. The method further
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s
includes drawing a wellbore fluid through the exterior flow
path in a first direction. Also, the method includes
drawing the wellbore fluid through the interior flow path in
a second direction.
According to another aspect of the present invention, a
method is provided for assembling and deploying a
submergible pumping system in a wellbore. The submergible
dumping system has a plurality of submergible components and
a shroud disposed about at least one of the submergible
components. The shroud includes a deformable sidewall and
an upper attachment end by which the shroud is coupled to at
least one of the submergible components. The method
includes assembling the shroud and those submergible
components that are at least partially contained within the
shroud. The method further includes mounting a first clamp
about the shroud and a second clamp about at least one of
the submergible components above the deformable sidewall.
The method further includes supporting the clamps proximate
an upper opening of the wellbore. Additionally, the method
includes assembling the remainder of the submergible pumping
system above the clamps.
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c
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will hereafter be described with
reference to the accompanying drawings, wherein like
reference numerals denote like elements, and:
Figure 1 is a front elevational view of a wellbore in
which an exemplary-submergible pumping system, according to
a preferred embodiment of the present invention, is
deployed;
Figure_2 is a cross-sectional view taken generally
along line 2-2 of Figure 1;
Figure 3 is a cross-sectional view taken generally
along 3-3 of Figure 1;
Figure 3A is an enlarged view of region 3A-3A of Figure
3;
Figure 4 is an expanded view of the portion encircled
by line 4-4 in Figure 1;
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Figure 5 is an expanded view of the portion encircled
by line 5-5 in Figure 1;
Figure 6 is a perspective view of an upper attachment
portion of the shroud illustrated in Figure 1;
' Figure 6A is a longitudinal cross-sectional view of a
power cable extending through the upper attachment portion
illustrated in Figure 6;
Figure 7 is a front elevational view of an alternate
embodiment of the system illustrated in Figure 1;
Figure 7A is an enlarged portion encircled by the line
7A-7A of Figure 7; and
Figure 8 is a front elevational view of the system
illustrated in Figure 1 suspended from an assembly clamp.
Figure 8A is a perspective view of a portion of a
multi-section shroud, according to an alternate embodiment
of the shroud illustrated in Figure 8; and
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Figure 9 is a perspective view of an alternate
embodiment of the system illustrated in Figure 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring generally to Figure 1, an exemplary pumping
system 10, such as an electric submergible pumping system,
is illustrated. Pumping system 10 may comprise a variety of
components depending on the particular application or
environment in which it is used. Typically, system 10
includes at least a submergible pump 12, a submergible motor
14, a motor protector 16 and a pump intake housing 18 having
an intake opening 20 through which a production fluid, such
as petroleum, is drawn into intake housing 18 by pump 12.
In the illustrated example, pumping system 10 is
designed for deployment in a well 22 within a geological
formation 24 containing desirable production fluids, e.g.
water or petroleum. In a typical application, a wellbore 26
is drilled and lined with a wellbore casing 28. Wellbore
casing 28 includes a plurality of openings or perforations
through which production fluids flow from geological
formation 24 into wellbore 26.
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Pumping system 10 is deployed in wellbore 26 by a
deployment system 32 that may have a variety of forms and
configurations. For example, deployment system 32 may
comprise tubing, e.g. production tubing 34, connected to
S submergible pump 12 by a connector/discharge head 36.
It should be noted that the illustrated submergible
pumping system 10 is merely an exemplary embodiment. Other
components can be added to the system, other configurations
of components can be utilized, and other deployment systems
may be implemented. Additionally, the production fluids may
be pumped to the surface through tubing 34 or through the
annulus formed between deployment system 32 and wellbore
casing 28.
Pumping system 10 further includes a shroud 38 disposed
about one or more of the submergible pumping system
components. For example, shroud 38 preferably is disposed
about submergible motor 14, motor protector 16 and fluid
intake 20.
Shroud 38 is disposed within wellbore 26 such that a
pair of fluid flow paths are formed. For example, an
external fluid flow path 40 is disposed between shroud 38
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and an interior surface 42 of wellbore casing 28.
Furthermore, an interior fluid flow path 44 is disposed
between shroud 38 and the enclosed submergible components,
e.g. motor 14 and motor protector 16. Thus, when pump 12 is
powered by motor 14, a low pressure area (suction) is
created at intake 20. This suction draws wellbore fluid
downwardly from perforations 30 through exterior fluid flow
path 40. The fluid is drawn around a bottom end 46 of
shroud 38 and upwardly through interior fluid flow path 44
to intake 20. The fluid is then discharged upwardly through
production tubing 34 via submergible pump 12. The flow of
fluid past,-for example, submergible motor 14 removes heat
created by motor 14 during operation.
Shroud 38 is formed from a sheet material 48 to occupy
a minimal amount of the cross-sectional annular space
between the submergible system components and interior
surface 42 of casing 28. Preferably, shroud 38 is formed
from sheet metal having a thickness less than approximately
1/8 of an inch. As illustrated best in Figures 2 and 3,
shroud 38 preferably is corrugated. In other words, sheet
material 48 forms a wall 50 about submergible motor 14,
motor protector 16 and intake 20 that has longitudinal
corrugations running from bottom end 46 to intake 20. The
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corrugations of wall 50 are formed as a series of
alternating ridges and grooves. For example, wall 50
includes an interior surface 52 that has a series of
alternating ridges 54 and grooves 56. Grooves 56 form
interior fluid flow path 44 that permit fluid to flow
upwardly past submergible motor 14 and motor protector 16 to
intake 20. Preferably, ridges 54 are disposed against the
submergible pumping system components, e.g. motor 14, to
further help dissipate heat as production fluid flows past
the exterior of shroud 38.
Similarly, wall 50 includes an exterior surface 58 that
has a series of alternating ridges 60 and grooves 62.
Grooves 62 are formed on an opposite side of wall 50 from
interior ridges 54, and ridges 60 are formed on an opposite
side of wall 50 from interior grooves 56. Effectively,
interior grooves 56 are separated from exterior grooves 62
by a plurality of sidewalls 63. The exterior grooves 62
form exterior fluid flow path 40 along which fluid flows
from perforations 30 downwardly to the bottom end 46 of
shroud 38.
In the illustrated embodiment, the grooves and ridges
are of varying size. For example, interior grooves 56
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become progressively larger in cross-sectional area moving
from one side of shroud 38 to the other. This design
permits the enclosure of a power cable 64 in one of the
larger or largest interior grooves 56, as illustrated best
in Figure 3. Power cable 64 may be a conventional power
cable utilized in providing power to submergible motor 14.
As illustrated in Figure 4, an end ring 66 is attached
to the interior of wall 50 proximate bottom end 46. End
ring 66 preferably is a metallic ring having an outer
profile that matingly engages and supports the interior
surface 52_of shroud 38, to which it is attached by, for
example, welding. End ring 66 has one or more axial
openings 68 to communicate the external flow path 40 with
the interior flow path 44. End ring 66 also includes a
central axial opening 69.
As illustrated in Figure 5, shroud 38 preferably is
attached to at least one of the submergible pumping system
components proximate an upper end 70 of shroud 38. For
example, shroud 38 may be affixed to intake housing 18 above
intake openings 20, as illustrated in Figures 1 and 5.
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In the preferred embodiment, a plurality of lugs 72 are
utilized to secure sheet material wall 50 to intake housing
18. As illustrated in Figure 6, each lug 72 includes a base
end 74 that matingly engages a corresponding interior groove
56 to block fluid flow therethrough. This ensures that the
fluid properly travels downwardly through the exterior
grooves of shroud 38 and then upwardly to intake opening 20
through the interior grooves of shroud 38. The lower end 74
o-f each lug 72 may be attached to wall 50 by, for instance,
welding. Several lugs 72 also include an upper tapered
portion 76 having an aperture 78 therethrough. Aperture 78
is designed.to receive a fastener 80 therethrough, as
illustrated best in Figure 5. An exemplary fastener is a
bolt designed for threaded engagement with corresponding
threaded apertures 82 disposed in intake housing 18, or in a
rotatable member attached to intake housing 18.
If power cable 64 is directed through one of the
interior grooves 56, one of the lugs 72 must be formed to
accommodate the power cable. Such a lug is illustrated in
Figure 6 and includes a truncated upper tapered portion 84
having an interior channel 86 for receiving power cable 64
therethrough. Upper portion 84 includes a pair of side tabs
or wings 88 having apertures 90 therethrough. Apertures 90
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are designed to receive corresponding fasteners 80 for
threaded engagement with intake housing 18. To prevent
fluid leakage past cable 64, a tapered packing 91 may be
inserted between cable 64 and interior channel 86 during
field installation, as illustrated in Figure 6A. Tapered
packing 91 may be either preformed or flexible, so that it
wraps around cable 64. Packing 91 preferably is formed of a
deformable material, such as lead, rubber or plastic.
As illustrated in Figures 7 and 7A, pumping system 10
may be modified by the addition of a lower scraper 92,
sometimes referred to as a bullnose scraper. Bullnose
scraper 92 includes a plurality of scraper ribs 94 designed
to scrape unwanted debris or materials from the interior of
casing 28 during deployment. of submergible pumping system
10. The removal of such debris and deposits helps prevent
damage to the sheet material forming shroud 38 and ensures
that external flow path 40 is not obstructed.
Scraper 92 also includes an axial opening 96. Axial
opening 96 is sized to receive a mounting stud 98 that is
mounted to and extends from a motor base 100 of submergible
motor 14. Stud 98 includes a shoulder 102 and a distal
threaded region 104 designed for threaded engagement with a
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retainer nut 106. Retainer nut 106 secures bullnose scraper
92 on stud 98 between shoulder 102 and retainer nut 106.
The opening 69 in end ring 66 is sized to receive stud 98
therethrough. The stud 98 transfers any resistance thrust
encountered during deployment to the motor rather than to
the sheet metal shroud 38, the motor being stronger than the
shroud. Also, should the sheet metal shroud 38 become
detached from the intake housing 18, as by corrosion, the
bullnose scraper 92 and stud 98 enable the shroud to be
retrieved from the well.
Submergible pumping system 10 may also include an upper
scraper 108 mounted above submergible pump 12 and shroud 38.
Upper scraper 108 includes a plurality of whole or partial
scraper rings 110. Scraper rings 110 are primarily designed
to scrape deposits and other collected material from the
interior of wellbore casing 28 when submergible pumping
system 10 is removed from a wellbore location. The scrapers
facilitate the removal of submergible pumping system 10
while limiting damage to shroud 38 and other submergible
pumping system components.
As illustrated in Figure 8, a special clamp 112 may be
used to facilitate deployment of the pumping system into the
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shroud. Clamp 112 mounts on the shroud by fasteners, such
as bolts, that pass engagingly through holes in the clamp
and thread into holes 113 (see Figure 6) in lugs 76. The
inside diameter of clamp 112 may be slightly larger than the
outside diameter of shroud 38, so that the fastener bolts
tend to expand the diameter of the shroud when tightened,
facilitating insertion of the submergible pumping system 10
into the shroud.
The clamp 112 may be formed of two separable
semicircular halves, as would be known to those of ordinary
skill in the art. Each half has two lugs 114 that allow
fasteners to join the two halves into a complete circle,
that encircles the shroud. Lugs 114 also serve to support
the clamp 112 and shroud 38.on a wellhead 115 during
deployment.
A preferred exemplary sequence of installation is as
follows
1. Clamp 112 is attached to the shroud
lugs 76.
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2. Clamp 112 is used to lift the shroud
38 and lower it into wellbore 26, so
that the clamp lugs 114 rest on the
wellhead 115.
3. Motor 14 with stud 98 attached to the
lower end, protector 16, and intake 18
are lowered into shroud 38, either
singly or as a subassembly. (If singly,
conventional submergible pumping system
to clamps may be utilized and placed on
shroud clamp 112 to support the
submergible pumping system components
without causing stress to the shroud
itself . )
4. During deployment of the submergible
pumping system components into the
shroud 38, the electrical power cable 64
is deployed into a sufficiently large
internal groove 56 of shroud 38 such
that it passes through channel 86 of the
special lug 72.
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5. When intake housing 18 is proximate
the top end of shroud 38, fasteners 80,
such as bolts, pass non-engagingly
through apertures (not shown) in shroud
clamp 112. These fasteners then pass
engagingly through holes 78 and 90 in
lugs 76 (see Figure 6) and thread into
holes 82 in the intake housing 18 or
holes in a rotatable ring mounted on
l0 intake housing 18.
6.. Fasteners attaching clamp 112 to
shroud 38 are then removed.
Subsequently, fasteners 80 may be fully
tightened, slightly reducing the
diameter of the shroud, so that it seals
effectively to the intake.
7. Clamp 112 is removed from shroud 38.
8. The submergible pumping system string
10 and shroud 38 are lifted clear of the
wellhead 115.
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9. Bullnose scraper 92 and retainer nut
106 are mounted on the lower end of stud
98, which protrudes from lower end ring
opening 69.
10. The submergible pumping system string
is then lowered into wellbore 26, and
the balance of the submergible pumping
system is deployed, as would be known to
those skilled in the art.
In some applications, it may be advantageous to divide
shroud 38 into multiple sections. For example, if the
required length of the shroud is greater than can be
transported or installed in.a single piece, the shroud may
be divided into multiple sections, as illustrated in Figure
8A. In the exemplary embodiment illustrated, shroud 38
includes a plurality of shroud sections 120 that are joined
together.
Multiple shroud sections 120 may be joined by
overlapping shroud section ends or by sheet metal splicing
channels that are attached to both sections. For example, a
joint member 122 or 151, in the form of a sheet metal
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splicing channel, may be sized for mating engagement with
the joined shroud sections 120 along either interior surface
52 or exterior surface 58. In the example illustrated,
joint member 122 is disposed on the exterior of shroud
sections 120 and matingly engages exterior grooves 62, while
joint member 151 is disposed on the interior and matingly
engages interior groove 44. The sheet metal splicing
channel may be joined to shroud sections 120 by appropriate
fasteners, such as screws, rivets or other fastening methods
or mechanisms. In the embodiment illustrated, a plurality
of fasteners 124, e.g. screws or rivets, are disposed
through sidewalls 63 of each shroud section 120. Typically,
the sheet metal channel 122 also includes corresponding
sidewalls 126 that each lie adjacent a sidewall 63, as best
illustrated in Figure 8A. Fasteners 124 are disposed
through adjacent sidewalls 63 and 126 to secure each shroud
section 120 to joint member 122 or 151.
During deployment of the overall pumping system 10,
each shroud section 120 is supported at the wellhead by an
appropriate clamp, similar to clamp 112 discussed above.
The clamp, however, preferably is designed for attachment to
a shroud section by fasteners, such as screws, that pass
through holes 128 formed in sidewalls 63, generally at the
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upper end of a given shroud section 120. The clamp is
designed to support a given shroud section, via fasteners
extending through sidewalls 63, to avoid interference with
pumping system components as they are inserted into the
shroud section 120. Once the supported shroud section 120
is attached to the next sequential shroud section, the clamp
may be removed, and holes 128 plugged. Holes 128 may be
plugged with, for example, short plugging screws that do not
extend beyond the maximum outer diameter of the shroud or
the minimum inner diameter of the shroud.
Another embodiment of a multi-section shroud is
illustrated in Figure 9. In this system, at least some of
the submergible pumping system components, e.g. motor 14 and
motor protector 16, are partially encased in sections of
shroud 38 before the submergible components are joined
together and installed in the well.
In this embodiment, shroud 38 includes a plurality of
shroud sections 140 that are fastened to each submergible
component. Each shroud section may be attached to a
corresponding submergible component by, for example, screws,
rivets, welding, adhesives, etc. In the embodiment
illustrated, each shroud section 140 includes a plurality of
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openings 142 disposed radially therethrough at the base of
each exterior groove 62. Holes 142 are located for
alignment with corresponding threaded openings 144 extending
radially inwardly into the outer wall of the submergible
component to which that particular shroud section 140 is
attached. Appropriate fasteners 146, such as screws, are
inserted through holes 142 and threadably engaged with
threaded openings 144 to secure each shroud section 140 to a
,corresponding submergible component, as illustrated in
Figure 9.
Attachment of shroud sections 140 directly to
submergible components facilitates attachment of the
bullnose scraper 92 when, for example, the required length
of a unitary shroud would be to great to lift the shroud
clear of the wellhead during installation. In this system,
the bullnose scraper 92 may be attached to the lowermost
submergible section before it is installed in the well.
Additionally, a sectional shroud of the type illustrated
permits access to certain areas of the submergible
components to permit joining of the submergible components
and to facilitate the overall installation procedure.
Exemplary access areas include clamp grooves, end flanges,
fluid ports, electrical connections, etc.
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When an access area is no longer needed, that area is
covered by a supplemental shroud section 148. In the
embodiment illustrated, each supplemental shroud section 148
is divided into a pair of components 150 that have ridges
and grooves corresponding to the ridges and grooves of the
sequential 'shroud sections 140. It should be noted that a
variety of single piece or multiple piece supplemental
shroud sections 148 can be designed.
The illustrated components 150 include a plurality of
holes 142 located for alignment with corresponding threaded
openings 144. As described above with respect to each
shroud section 140, fasteners, such as screws 146, may be
inserted through holes 142 in each component 150 and
threadably engaged with a corresponding threaded opening 144
formed in the enclosed, submergible components. Upon
installation of the supplemental shroud section 148, the
entire shroud 38 is completed to permit the appropriate flow
of fluid along external grooves 62 and internal grooves 56.
It will be understood that the foregoing description is
of preferred embodiments of this invention, and that the
invention is not limited to the specific fortes shown. For
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example, a variety of materials potentially may be used in
constructing the shroud; various other or additional
components can be contained within the shroud or mounted
above the shroud; varying numbers and sizes of corrugations
may be formed in the shroud; and the sequence and
arrangement of the pumping system components and
installation procedure can be changed to suit a specific
pumping application. These and other modifications may be
made in the design and arrangement of the elements without
departing from the scope of the invention as expressed in
the appended claims.
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