U.S. patent application number 12/730950 was filed with the patent office on 2011-09-29 for double sealing labyrinth chamber for use with a downhole electrical submersible pump.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. Invention is credited to Dan Merill.
Application Number | 20110236233 12/730950 |
Document ID | / |
Family ID | 44656730 |
Filed Date | 2011-09-29 |
United States Patent
Application |
20110236233 |
Kind Code |
A1 |
Merill; Dan |
September 29, 2011 |
Double Sealing Labyrinth Chamber for Use With a Downhole Electrical
Submersible Pump
Abstract
A labyrinth seal assembly for an electrical submersible pumping
system that communicates downhole pressure to a pump motor while
sealing wellbore fluids from the motor. The labyrinth seal assembly
includes a chamber circumscribing a pump shaft, labyrinth tubes,
upper and lower shaft seals, and inner and outer guide tubes
coaxially circumscribing the shaft. One labyrinth tube has an end
in fluid communication with the wellbore fluid and another has an
end in fluid communication with the pump motor. The labyrinth tubes
extend into the chamber from opposite directions and each have an
opening distal from where they enter the chamber. A port is
provided in the inner guide tube distal from the upper shaft seal,
and a port in the outer guide tube is provided proximate the upper
shaft seal. Thus a labyrinth path is provided between the upper
shaft seal and the chamber.
Inventors: |
Merill; Dan; (Claremore,
OK) |
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
44656730 |
Appl. No.: |
12/730950 |
Filed: |
March 24, 2010 |
Current U.S.
Class: |
417/410.1 |
Current CPC
Class: |
F04B 17/03 20130101 |
Class at
Publication: |
417/410.1 |
International
Class: |
F04B 17/03 20060101
F04B017/03 |
Claims
1. An electrical submersible pump assembly disposable within a
wellbore comprising: a motor; a pump coupled to the motor; a seal
section housing between the pump and the motor; upper and lower
guide members in the seal section housing, each having a central
passage therethrough, defining a chamber in the seal section
housing; an equalizing passage leading from the chamber to the
motor; a shaft extending between the pump and the motor and through
the central passages in the upper and lower guide members in the
seal section housing; an upper seal between the passage of the
upper guide member that seals around the shaft and seals well fluid
from the chamber; and an inner labyrinth seal assembly
circumscribing the shaft between the upper and lower guide members
and comprising a looping flow path with an upper end in fluid
communication with fluid in the central passage between the upper
seal and an upper port in fluid communication with the chamber, so
as to prevent well fluid that may leak past the upper seal from
entering the pressure equalizing passage.
2. The electrical submersible pump assembly of claim 1, further
comprising an outer labyrinth seal assembly comprising a looping
flow path in the chamber having a first end in fluid communication
with well fluid ambient to the pump assembly and a second end in
fluid communication with the pressure equalizing passage for
equalizing pressure of lubricant in the motor with well fluid.
3. The electrical submersible pump assembly of claim 2, wherein the
second end of the inner labyrinth is above the second end of the
outer labyrinth.
4. The electrical submersible pump assembly of claim 1, further
comprising a lower seal that seals around the shaft and between the
chamber and the motor.
5. The electrical submersible pump assembly of claim 1, wherein the
inner labyrinth seal comprises a tubular outer guide tube
circumscribing the shaft, a tubular inner guide tube disposed
between the shaft and the outer guide tube and coaxial with the
outer guide tube, a lower port formed through a side of the inner
guide tube, and the upper port being formed through the outer guide
tube between the lower port and the upper seal.
6. The electrical submersible pump assembly of claim 2, wherein the
outer labyrinth seal assembly comprises, an upper communication
tube in pressure communication ambient to the pump assembly and
having an open end open to the chamber, and a lower communication
tube in pressure communication with the pressure equalizing passage
leading to the motor and having an open end open to the chamber and
that above the open end of the upper communication tube.
7. The electrical submersible pump assembly of claim 1, wherein an
upper end of the inner labyrinth seal assembly is coupled to the
upper guide member and a lower end of the inner labyrinth seal
assembly is coupled to the lower guide member.
8. An electrical submersible pump assembly disposable within a
wellbore comprising: a motor; a pump coupled to the motor; a seal
section housing between the pump and the motor; a chamber defined
in the seal section housing; upper and lower guide members in
opposing ends of the seal section housing, each having a central
passage therethrough; an equalizing passage leading from the
chamber to the motor; a shaft extending between the pump and the
motor and through the central passages in the upper and lower guide
members; an inner labyrinth seal assembly comprising an upper end
in fluid communication with fluid in the central passage between
the upper seal, an upper port in fluid communication with the
chamber, and a looping flow path that extends axially along the
shaft and radially between the upper end and upper port; and an
outer labyrinth seal assembly comprising a looping flow path in the
chamber having a first end in fluid communication with well fluid
ambient to the pump assembly and a second end in fluid
communication with the pressure equalizing passage for equalizing
pressure of lubricant in the motor with well fluid.
9. The electrical submersible pump assembly of claim 8, wherein the
second end of the inner labyrinth is above the second end of the
outer labyrinth.
10. The electrical submersible pump assembly of claim 8, further
comprising a lower seal that seals around the shaft and between the
chamber and the motor.
11. The electrical submersible pump assembly of claim 8, wherein
the inner labyrinth seal comprises a tubular outer guide tube
circumscribing the shaft, a tubular inner guide tube disposed
between the shaft and the outer guide tube and coaxial with the
outer guide tube, a lower port formed through a side of the inner
guide tube, and the upper port being formed through the outer guide
tube between the lower port and the upper seal.
12. The electrical submersible pump assembly of claim 8, wherein
the outer labyrinth seal assembly comprises, an upper communication
tube in pressure communication ambient to the pump assembly and
having an open end open to the chamber, and a lower communication
tube in pressure communication with the pressure equalizing passage
leading to the motor and having an open end open to the chamber and
that above the open end of the upper communication tube.
13. The electrical submersible pump assembly of claim 8, wherein an
upper end of the inner labyrinth seal assembly is coupled to the
upper guide member and a lower end of the inner labyrinth seal
assembly is coupled to the lower guide member.
14. The electrical submersible pump assembly of claim 8, further
comprising a bag seal having a bladder with a side in pressure
communication with the labyrinth seal assembly.
15. An electrical submersible pump assembly disposable within a
wellbore comprising: a motor; a pump coupled to the motor; a seal
section housing between the pump and the motor; upper and lower
guide members in the seal section housing, each having a central
passage therethrough, defining a chamber in the seal section
housing; an equalizing passage leading from the chamber to the
motor; a shaft extending between the pump and the motor and through
the central passages in the upper and lower guide members in the
seal section housing; an upper seal between the passage of the
upper guide member that seals around the shaft and seals well fluid
from the chamber; and an inner labyrinth seal assembly comprising:
an upper end coupled to the upper guide member and in fluid
communication with fluid in the central passage between the upper
seal, a lower end coupled to the lower guide member, an inner guide
tube extending between the upper and lower guide members and
circumscribing the shaft to define an annulus therebetween, a port
formed through a side wall of the inner guide tube proximate the
lower guide member, an outer guide tube extending between the upper
and lower guide members and circumscribing the inner guide tube to
define an annulus therebetween, and a port formed through a side
wall of the outer guide tube proximate the upper guide member.
16. The electrical submersible pump assembly of claim 15, further
comprising an outer labyrinth seal assembly comprising a looping
flow path in the chamber having a first end in fluid communication
with well fluid ambient to the pump assembly and a second end in
fluid communication with the pressure equalizing passage for
equalizing pressure of lubricant in the motor with well fluid.
17. The electrical submersible pump assembly of claim 15, wherein
the outer labyrinth seal assembly comprises, an upper communication
tube in pressure communication ambient to the pump assembly and
having an open end open to the chamber, and a lower communication
tube in pressure communication with the pressure equalizing passage
leading to the motor and having an open end open to the chamber and
that above the open end of the upper communication tube.
18. The electrical submersible pump assembly of claim 15, further
comprising a bag seal having a bladder.
19. The electrical submersible pump assembly of claim 18, wherein
the bag seal circumscribes the inner labyrinth seal assembly.
20. The electrical submersible pump assembly of claim 18, further
comprising an outer labyrinth seal assembly comprising a looping
flow path in the chamber having a first end in fluid communication
with well fluid ambient to the pump assembly and a second end in
fluid communication with the pressure equalizing passage, wherein
the bag seal has a side in pressure communication with the outer
labyrinth seal assembly.
Description
BACKGROUND
[0001] 1. Field of Invention
[0002] The present disclosure relates in general to submersible
well pumps, and in particular to seal assemblies used in
combination with the motors that drive submersible well pumps.
[0003] 2. Background of the Invention
[0004] In oil wells and other similar applications in which the
production of fluids is desired, a variety of fluid lifting systems
have been used to pump the fluids to surface holding and processing
facilities. It is common to employ various types of downhole
pumping systems to pump the subterranean formation fluids to
surface collection equipment for transport to processing locations.
One such conventional pumping system is a submersible pumping
assembly which is supported immersed in the fluids in the wellbore.
The submersible pumping assembly includes a pump and a motor to
drive the pump to pressurize and pass the fluid through production
tubing to a surface location. A typical electrical submersible pump
assembly ("ESP") includes a submersible pump, an electric motor and
a seal section interdisposed between the pump and the motor.
[0005] Pressure within the ESP is generally at about atmospheric
prior to being inserted into a wellbore. Since wellbore pressure
often significantly exceeds atmospheric pressure, the pressure
within the ESP is equalized to wellbore pressure, thereby reducing
pressure differential across the ESP housing. One hazard of high
ESP housing pressure differentials is the wellbore fluid could
breach seals and leak into the motor of the ESP. This is of special
concern with regard to the motor, where the conducting fluids
within the wellbore could create electrical shorts to damage the
motor. The seal section communicates wellbore fluid pressure to the
motor fluid pressure thereby minimizing pressure differentials and
prolong seal life. The seal section can also protect the motor from
contamination as the wellbore fluid usually contains deleterious
substances such as particulate solids and other debris from the
formation. Conventional seal sections have not proved completely
effective in preventing environmental contamination of the
motor.
[0006] Thus, there is a need for a seal section capable of
effectively preventing deleterious substances, such as particulate
solids and other matter contained in formation fluids, from
entering the motor where such contaminants can interfere with the
efficient operation of the motor and can reduce the operational
life of the motor.
SUMMARY OF INVENTION
[0007] Disclosed herein is an electrical submersible pump assembly
disposable within a wellbore. In one example, the electrical
submersible pump assembly includes a motor, a pump coupled to the
motor, a seal section housing between the pump and the motor, upper
and lower guide members in the seal section housing, each having a
central passage therethrough, defining a chamber in the seal
section housing, an equalizing passage leading from the chamber to
the motor, a shaft extending between the pump and the motor and
through the central passages in the upper and lower guide members
in the seal section housing, an upper seal between the passage of
the upper guide member that seals around the shaft and seals well
fluid from the chamber, and an inner labyrinth seal assembly
circumscribing the shaft between the upper and lower guide members
and comprising a looping flow path with an upper end in fluid
communication with fluid in the central passage between the upper
seal and an upper port in fluid communication with the chamber, so
as to prevent well fluid that may leak past the upper seal from
entering the pressure equalizing passage. An outer labyrinth seal
assembly may be included with the electrical submersible pump
assembly, where the outer labyrinth seal assembly has a looping
flow path in the chamber with a first end in fluid communication
with well fluid ambient to the pump assembly and a second end in
fluid communication with the pressure equalizing passage for
equalizing pressure of lubricant in the motor with well fluid. In
one example, the second end of the inner labyrinth is above the
second end of the outer labyrinth. A lower seal may be included
that seals around the shaft and between the chamber and the motor.
An example inner labyrinth seal may include a tubular outer guide
tube circumscribing the shaft, a tubular inner guide tube disposed
between the shaft and the outer guide tube and coaxial with the
outer guide tube, a lower port formed through a side of the inner
guide tube, and the upper port being formed through the outer guide
tube between the lower port and the upper seal. An outer labyrinth
seal assembly may include, an upper communication tube in pressure
communication ambient to the pump assembly and having an open end
open to the chamber, and a lower communication tube in pressure
communication with the pressure equalizing passage leading to the
motor and having an open end open to the chamber and that above the
open end of the upper communication tube. An upper end of the inner
labyrinth seal assembly may be coupled to the upper guide member
and optionally with a lower end of the inner labyrinth seal
assembly coupled to the lower guide member.
[0008] Also disclosed herein is an alternative embodiment of an
electrical submersible pump assembly, which too may be disposable
within a wellbore, the alternate electrical submersible pump
assembly with a motor, a pump coupled to the motor, a seal section
housing between the pump and the motor, a chamber defined in the
seal section housing, upper and lower guide members in opposing
ends of the seal section housing, each having a central passage
therethrough, an equalizing passage leading from the chamber to the
motor, a shaft extending between the pump and the motor and through
the central passages in the upper and lower guide members, an inner
labyrinth seal assembly comprising an upper end in fluid
communication with fluid in the central passage between the upper
seal, an upper port in fluid communication with the chamber, and a
looping flow path that extends axially along the shaft and radially
between the upper end and upper port, and an outer labyrinth seal
assembly comprising a looping flow path in the chamber having a
first end in fluid communication with well fluid ambient to the
pump assembly and a second end in fluid communication with the
pressure equalizing passage for equalizing pressure of lubricant in
the motor with well fluid. The second end of the inner labyrinth
can be above the second end of the outer labyrinth. A lower seal
can be included in the alternate embodiment that seals around the
shaft and between the chamber and the motor. An example embodiment
of an inner labyrinth seal has a tubular outer guide tube
circumscribing the shaft, a tubular inner guide tube disposed
between the shaft and the outer guide tube and coaxial with the
outer guide tube, a lower port formed through a side of the inner
guide tube, and the upper port being formed through the outer guide
tube between the lower port and the upper seal. An example outer
labyrinth seal assembly includes an upper communication tube in
pressure communication ambient to the pump assembly and having an
open end open to the chamber, and a lower communication tube in
pressure communication with the pressure equalizing passage leading
to the motor and having an open end open to the chamber and that
above the open end of the upper communication tube. An upper end of
the inner labyrinth seal assembly may be coupled to the upper guide
member with a lower end of the inner labyrinth seal assembly
optionally coupled to the lower guide member. A bag seal may be
included with the embodiment of the electrical submersible pump
assembly, the bag seal having a bladder with a side in pressure
communication with the labyrinth seal assembly.
[0009] Another embodiment of an electrical submersible pump
assembly is disclosed herein that includes a motor, a pump coupled
to the motor, a seal section housing between the pump and the
motor, upper and lower guide members in the seal section housing,
each having a central passage therethrough, defining a chamber in
the seal section housing, an equalizing passage leading from the
chamber to the motor, a shaft extending between the pump and the
motor and through the central passages in the upper and lower guide
members in the seal section housing, an upper seal between the
passage of the upper guide member that seals around the shaft and
seals well fluid from the chamber, and an inner labyrinth seal
assembly. In an embodiment, the inner labyrinth seal assembly has
an upper end coupled to the upper guide member and in fluid
communication with fluid in the central passage between the upper
seal, a lower end coupled to the lower guide member, an inner guide
tube extending between the upper and lower guide members and
circumscribing the shaft to define an annulus therebetween, a port
formed through a side wall of the inner guide tube proximate the
lower guide member, an outer guide tube extending between the upper
and lower guide members and circumscribing the inner guide tube to
define an annulus therebetween, and a port formed through a side
wall of the outer guide tube proximate the upper guide member. An
outer labyrinth seal assembly may be included that includes a
looping flow path in the chamber having a first end in fluid
communication with well fluid ambient to the pump assembly and a
second end in fluid communication with the pressure equalizing
passage for equalizing pressure of lubricant in the motor with well
fluid. In a specific example, an outer labyrinth seal assembly may
have, an upper communication tube in pressure communication ambient
to the pump assembly and having an open end open to the chamber,
and a lower communication tube in pressure communication with the
pressure equalizing passage leading to the motor and having an open
end open to the chamber and that above the open end of the upper
communication tube. Optionally, the electrical submersible pump
assembly may include a bag seal having a bladder. In one example,
the bag seal circumscribes the inner labyrinth seal assembly. One
example embodiment includes an outer labyrinth seal assembly with a
looping flow path in the chamber having a first end in fluid
communication with well fluid ambient to the pump assembly and a
second end in fluid communication with the pressure equalizing
passage and the bag seal with a side in pressure communication with
the outer labyrinth seal assembly.
BRIEF DESCRIPTION OF DRAWINGS
[0010] Some of the features and benefits of the present invention
having been stated, others will become apparent as the description
proceeds when taken in conjunction with the accompanying drawings,
in which:
[0011] FIG. 1 is a side sectional view of an example of an
electrical submersible pumping system disposed in a wellbore.
[0012] FIG. 2 is a side sectional view of an example of a labyrinth
seal used in conjunction with an electrical submersible of the
system.
[0013] FIG. 3A is an example of operation of the labyrinth seal of
FIG. 2.
[0014] FIG. 3B is another example of operation of the labyrinth
seal of FIG. 2.
[0015] FIG. 4 is a schematic example of an alternative embodiment
of an electrical submersible pumping system.
[0016] While the subject device and method will be described in
connection with the preferred embodiments but not limited thereto.
On the contrary, it is intended to cover all alternatives,
modifications, and equivalents, as may be included within the
spirit and scope of the present disclosure as defined by the
appended claims.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0017] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings in which
exemplary embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
construed as limited to the illustrated embodiments set forth
herein; rather, these embodiments are provided so that this
disclosure will be through and complete, and will fully convey the
scope of the invention to those skilled in the art. Like numbers
refer to like elements throughout.
[0018] Referring now to FIG. 1 an example of an electrical
submersible pumping system 20 (ESP) is shown in side view disposed
in a sectional view of a wellbore 22. In this example the wellbore
22 intersects a subterranean formation 24. The ESP 20 of FIG. 1
includes on its lower end a motor 26, a seal section 28 attached to
an upper end of the motor 26, and stacked above the seal section 28
is an optional separator 30. The ESP 20 further includes a pump 32
on the end of the separator 30 opposite this seal section 28.
Wellbore fluids, shown illustrated by the arrows, enter the ESP 20
via a fluid inlet 34 shown on the separator 30. After entering the
fluid inlet 34, the wellbore fluids may be directed through the
separator 30 and onto the pump 32. The separator 30 can be used to
remove or separate any vapor that may be mixed within the wellbore
fluid and then forward the liquid within the fluid to the pump 32
and direct the separated gas on vapor to a bypass around the pump
32. The fluid inlet 34 can be positioned on the pump 32 in ESP 20
embodiments not including a separator 30. A shaft 33, shown in
dashed line, is coupled between the motor 26 and pump 32 for
driving the pump 32. The pump 32 pressurizes the wellbore fluid and
directs it into production tubing 36 shown attached to one end of
the pump 32. The production tubing 36 extends within the wellbore
22 and terminates at an upper end at a wellbore assembly 38. From
the wellbore assembly 38, the produced wellbore fluid can be
transmitted for subsequent processing.
[0019] One example of a seal section 28 is shown in a side
sectional view in FIG. 2. In this example the seal section 28
includes an annular housing 50 shown circumscribing an axis A.sub.X
of the ESP 20 and defining a chamber 52 therein. A generally
cylindrically shaped lower guide 54 is illustrated coaxially
coupled with a lower end of the housing 50 that includes a cavity
55 on a side facing the chamber 52. An annular adapter plate 72 is
illustrated coupled to the lower guide 54 on the side facing the
chamber 52 and having a contoured side profiled to match a
corresponding profile of the cavity 55. A generally cylindrically
shaped upper guide 56 is shown mounted on an end of the housing 50
opposite where it couples with the lower guide 54. The example of
the upper guide 56 shown in FIG. 2 is generally coaxial with the
housing 50 and lower guide 54. The upper guide 56 is shown having a
cavity 57 formed on a side facing away from the chamber 54. The
shaft 33 passes through both the lower guide 54 and upper guide 56
in a bore 58 in the lower guide 54 and a corresponding bore 59
coaxially formed within the upper guide 56.
[0020] A tubular outer guide tube 60 is shown circumscribing the
shaft 33 and coaxially within the housing 50. On a side of the
adapter plate 72 opposite the cavity 55 is an upwardly projecting
annular flange 63; the lower end of the outer guide tube 60 is
shown sealingly engaged around the flange 63. A bore 67 extending
through the adapter plate 72 provides a passage for the shaft 33.
The end of the outer guide tube 60 opposite the adapter plate 72 is
in sealing engagement with a lower surface of the upper guide
56.
[0021] An annular space is formed between the outer guide tube 60
and shaft 33 and disposed within this annular space is an inner
guide tube 62. The inner guide tube 62 is shown having a lower end
inserted within the bore 67 formed through the adapter plate 72 and
thus coupled to the adapter plate 72. The upper end of the inner
guide tube 62 terminates proximate the lower surface of the upper
guide 56 and is coaxially coupled within the outer guide tube 60 by
an annular sealing ring 65. The sealing ring 65 extends in the
annular space between the outer diameter of the inner guide tube 62
and inner surface of the outer guide tube 60 thereby providing a
sealing interface between these opposing surfaces of the inner and
guide tubes 62, 60 and serves to secure the upper end of the inner
guide tube 62 within the ESP 20.
[0022] A port 70 is shown formed through the side wall of the inner
guide tube 62 proximate the connection of the inner guide tube 62
with the flange 63. The port 70 provides pressure and fluid
communication between the annular space between the shaft 33 and
inner guide tube 62 and the annular space between the inner guide
tube 62 and outer guide tube 60. The outer guide tube 60 also
includes a port 64 shown formed through a side wall in the outer
guide tube 60 and proximate the connection of the outer guide tube
60 with the upper guide 56. The port 64 provides pressure and fluid
communication between the chamber 52 and the annular space between
the inner guide tube 62 and outer guide tube 60.
[0023] Still referring to FIG. 2, a bushing assembly 74 is shown
inserted within the cavity 58 and disposed between the lower guide
54 and shaft 33. Also inserted within the bore 58 is an annular
seal member 76 that fills the annular space between the bore 58 and
shaft 33 and provides a liquid seal in this space. In this example,
the seal member 76 remains stationary with the lower guide 54 and
does not rotate with shaft 33 rotation. An annular disk like seal
face 78 is shown on a side of the seal member 76 opposite the
bushing assembly 74. A spring 80, illustrated coaxial about the
shaft 33, provides a force against the seal face 78 to urge the
seal member 76 onto a radial ledge formed within the bore 58.
[0024] As noted above, the seal section 28 can provide fluid
pressure communication to the motor 26 (FIG. 1). Although not shown
in FIG. 2, a motor may be included with this embodiment coupled to
the ESP 20 on the side of the lower guide 54 opposite the adapter
plate 72. Pressure communication with the motor 26 may be provided
via a passage 82 shown formed lengthwise through the lower guide 54
and extending also through the adapter plate 72. A tubular lower
communication pipe 84 is illustrated having an end inserted into
where the passage 82 opens into the cavity 52. The lower
communication pipe 84 is shown projecting into the cavity 54 and
substantially parallel with the axis A.sub.X. The upper end of the
lower communication pipe 84 is open and in fluid and pressure
communication with the cavity 52. Pressure communication between
the cavity 52 and ambient to the ESP 20 may be provided through an
upper communication pipe 86 shown inserted within a passage 88. In
this embodiment, the upper communication pipe 86 is a tubular
member having an open lower end within the chamber 52 at a location
below the open upper end of the lower communication pipe 84. The
base of the upper communication pipe 86 inserts into where the
passage 88 opens to the chamber 52. The passage 88 is shown
extending lengthwise through the upper guide 56 and through the
cavity 57 within the upper guide 56. The passage 88 continues
lengthwise through an adapter plate 90 shown sealingly coupled
within the opening of the cavity 57. The passage 88 extends through
the adapter plate 90 and terminates at a port 91 formed on the
outer surface of the ESP 20.
[0025] Still referring to, the embodiment in FIG. 2, a bushing
assembly 92 is provided within the bore 59 of the upper guide 56
that circumscribes the shaft 33. A seal member 94 is also shown
disposed in the bore 59 and is similar to the seal member 76. A
seal face 96 and associated spring 98 are further illustrated for
urging the seal member 94 into a radial ledge formed within the
bore 59 of the upper guide 56.
[0026] One example of operation of the seal section 28 is
illustrated in a side sectional view in FIG. 3A. In this example,
an embodiment of an ESP 20 is disposed within a wellbore 22 so that
wellbore fluid 100 may enter the ESP via the port 91. After
entering the port 91, the wellbore fluid 100 flows through the
passage 88 and the upper communication pipe 86; and then settles
within the chamber 52 proximate the opening of the upper
communication pipe 86 within the chamber 52. In this example, the
motor 26 and the cavity 52 were filled with a motor fluid 102, such
as a dielectric fluid or lubricant, prior to insertion into the
wellbore 22. The higher pressure and higher density well fluid 100
urges the motor fluid 102 out of the upper communication pipe 86.
Since the motor fluid 102 has a density lower than the wellbore
fluid 100, the wellbore fluid 100 settles within the lower end of
the cavity 52. The fluids 100, 102 then stratify to define a fluid
interface 104 therebetween. The pressure within the wellbore fluid
100 is communicated to the motor 26 through the motor fluid 102 in
the cavity 52, the lower communication pipe 84, and the passage 82.
It should be pointed out that the seal section 28 may be directly
adjacent the motor 26, or separate with modular segments between.
Moreover, by positioning the opening of the lower communication
pipe 84 above the opening of the upper communication pipe 86, the
higher density wellbore fluid 100 deposits below any ingress to the
lower communication pipe 84 where it settles within the cavity 52.
While below the opening of the lower communication pipe 84, the
wellbore fluid 100 is blocked from communication with the motor 26
where it might damage some motor components.
[0027] Referring now to FIG. 3B, a scenario is illustrated where
the seal member 94A has become damaged, thereby allowing wellbore
fluid 106 to pass between the upper guide 56 and shaft 33. The
wellbore fluid 106 can then enter the space between the shaft 33
and inner guide tube 62, where it flows through a looping downward
and then upward path similar to the flow path through labyrinth
assembly provided by the upper and lower communication pipes 86,
84. More specifically, wellbore fluid 106 entering the space
between the shaft and inner guide tube 33, 62 gravitates downward
and through the port 70. Exiting the port 70 the wellbore fluid 106
is within the space between the inner guide tube 62 and outer guide
tube 60 and the higher pressure from the wellbore 22 and the
hydrostatic pressure of the higher density wellbore fluid 106
pushes the wellbore fluid 106 upward within the space and in the
direction of the upper guide 56. When reaching the port 64 formed
in the outer guide tube 60, the wellbore fluid 106 enters the
chamber 52 and stratifies therein. An interface 108 is provided to
illustrate addition of the wellbore fluid 106 that enters the
chamber 52 via the failed seal member 94A and not to imply
differences in fluid properties between the wellbore fluid 106 and
wellbore fluid 100 that entered the chamber 52 via the upper
communication pipe 86. In the example shown in FIG. 3A, the
interface 104A is between the wellbore fluid 106 and motor fluid
102 and moved upward from its position shown in FIG. 3A.
[0028] An alternative example of an ESP 20A is illustrated in
schematic view in FIG. 4 and having a seal section 28A adjacent a
second seal section 110 shown stacked above the seal section 28A.
In this example, the second seal section 110 is a bag or bladder
type seal having a flexible membrane 112 within the second seal
section 110. A port (not shown) may communicate fluid to one side
of the membrane 112 wherein the opposing side of the membrane 112
is in fluid communication with the passage 88 (FIG. 2). Yet further
optionally, the second seal section 110 may comprise multiple
bladder type seal sections as well as one or more additional
labyrinth type seal sections as described in FIGS. 2 through 3B. In
another embodiment, the inner and outer guide tubes 60, 62 could be
employed in a seal section that included a bladder.
[0029] It is understood that variations may be made in the above
without departing from the scope of the invention. While specific
embodiments have been shown and described, modifications can be
made by one skilled in the art without departing from the spirit or
teaching of this invention. The embodiments as described are
exemplary only and are not limiting. Many variations and
modifications are possible and are within the scope of the
invention. Accordingly, the scope of protection is not limited to
the embodiments described, but is only limited by the claims that
follow, the scope of which shall include all equivalents of the
subject matter of the claims.
* * * * *