US20110236233A1

US20110236233A1 - Double Sealing Labyrinth Chamber for Use With a Downhole Electrical Submersible Pump

Info

Publication number: US20110236233A1
Application number: US12/730,950
Authority: US
Inventors: Dan Merill
Original assignee: Baker Hughes Inc
Current assignee: Baker Hughes Holdings LLC
Priority date: 2010-03-24
Filing date: 2010-03-24
Publication date: 2011-09-29
Also published as: AU2011232505A1; BR112012024210A2; WO2011119749A2; CA2793935A1; WO2011119749A3; NO20121094A1

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.

Description

BACKGROUND

1. Field of Invention
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.
2. Background of the Invention
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.
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.
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

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.
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.
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

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:

FIG. 1 is a side sectional view of an example of an electrical submersible pumping system disposed in a wellbore.

FIG. 2 is a side sectional view of an example of a labyrinth seal used in conjunction with an electrical submersible of the system.

FIG. 3A is an example of operation of the labyrinth seal of FIG. 2.

FIG. 3B is another example of operation of the labyrinth seal of FIG. 2.

FIG. 4 is a schematic example of an alternative embodiment of an electrical submersible pumping system.

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

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.
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.
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_Xof 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.
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.
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.
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.
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.
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_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.
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.
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.
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.
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.
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.

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;

an equalizing passage leading from the chamber to the motor;

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.