Labyrinth Chamber with Helical Blade for a Submersible Well Pump and Method of Use

Abstract

An electrical submersible pump assembly has a pump, a motor and a seal section with a labyrinth chamber. A guide tube surrounds a drive shaft in the seal section and contains lubricant in fluid communication with lubricant in the motor. The guide tube has a guide tube port adjacent the downstream end of the labyrinth chamber. A. labyrinth tube has an open inlet end in the downstream end of the labyrinth chamber and an open outlet end near the upstream end of the labyrinth chamber. The labyrinth communicates well fluid on the exterior of the seal section into the labyrinth chamber in contact with the lubricant in the labyrinth chamber. A non rotating helical blade in the labyrinth chamber encircles the guide tube, defining a helical flow path between the outlet end of the labyrinth tube and the guide tube port of the guide tube.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to provisional application 61/847,382, filed Jul. 17, 2013.

FIELD OF THE DISCLOSURE

This disclosure relates in general to electrical submersible pumps for wells and in particular to a pressure equalizing seal section between a pump and a motor that has a labyrinth chamber containing a non rotating helical blade.

BACKGROUND

Submersible well pump assemblies (ESP) are frequently used to pump well fluid. from hydrocarbon wells. A typical ESP has a pump driven by a motor. A seal section, normally located between the motor and the pump, has components to equalize pressure of lubricant contained in the motor with the hydrostatic pressure of the well fluid on the exterior of the ESP. Those components may be a flexible diaphragm, a bellows, or a labyrinth chamber.

A labyrinth chamber has a labyrinth tube extending downward from a connector or adapter on the upper end of the labyrinth chamber. The upper end of the labyrinth tube is open as well as the lower end, which is spaced a short distance above the lower end of the labyrinth chamber. A guide tube surrounds the drive shaft extending from the motor. The guide tube has a port near the upper end of the chamber. Lubricant from the motor flows up an annular clearance between the shaft and the guide tube and out the guide tube port into the labyrinth chamber. Well fluid flows down the labyrinth tube into the labyrinth chamber into contact with the lubricant. The well fluid applies the hydrostatic pressure on the exterior of the ESP to the lubricant in the labyrinth chamber, which communicates that pressure to lubricant in the motor. The well fluid has a higher specific gravity than the lubricant, thus is inhibited from flowing upward in the labyrinth chamber into the guide tube port to reach the guide tube port. It is important to keep the corrosive well fluid from flowing down the guide tube into the motor.

A labyrinth chamber works well in vertical wells and provides pressure compensation without any additional moving parts. However, if the pump is installed in a horizontal section of the well, the path from the outlet of the labyrinth tube to the guide tube port is approximately horizontal rather than being vertical. The well fluid entering the labyrinth chamber could more easily flow along the horizontal flow path than the labyrinth flow path that exists while the ESP is oriented vertically.

SUMMARY

The ESP assembly of this disclosure has a seal section with a labyrinth chamber between upstream and downstream ends of the seal section. A guide tube extends along the axis between the upstream and downstream ends. The guide tube contains lubricant in fluid communication with lubricant in the motor. The guide tube has an. inlet port adjacent the downstream end to communicate the lubricant within the guide tube into the labyrinth chamber. A labyrinth tube within the labyrinth chamber has an open inlet end in the downstream end and an open outlet end. within the labyrinth chamber adjacent the upstream end. The labyrinth tube communicates well fluid on the exterior of the seal section into the labyrinth chamber into contact with the lubricant in the labyrinth chamber to equalize a pressure of the lubricant with a pressure of the well fluid. A non rotating helical blade in the labyrinth chamber encircles the guide tube, defining a helical flow path between the outlet port of the labyrinth tube and the inlet port of the guide tube.

Preferably, the labyrinth tube extends sealingly through turns of the helical blade. In the preferred embodiment, an inner sleeve surrounds the guide tube. The helical blade has an inner edge joined to the inner sleeve. An optional outer sleeve surrounds the helical blade. The outer sleeve has an outer diameter in contact with an inner diameter of the housing. Alternately, rather than an outer sleeve, the helical blade may have an outer edge in contact with the inner diameter of the housing.

In the example disclosed, at least one baffle is placed along the helical flow path and mounted between adjacent turns of the blade. The baffle retards the flow of well fluid along the helical flow path. The baffle has a portion, such an inner edge, joined to the guide tube. Preferably, the baffle has upstream and downstream edges joined to adjacent turns of the helical blade. The baffle has an outer edge located inward from an outer diameter of the helical blade, defining a gap for well fluid to pass from an upstream side of the baffle to a downstream side of the baffle along the helical flow path.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an electrical submersible pump assembly in accordance with this disclosure.

FIG. 2 is a sectional view of part of the seal section of the pump assembly of FIG. 1.

FIG. 3 is a sectional view of the seal section of FIG. 2 taken along the line 3-3 of FIG. 2.

FIG. 4 is an isometric view, partly sectioned, of an alternate embodiment of the helical blade assembly of the seal section of FIG. 2 with the guide tube and shaft of the seal section not shown.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring to FIG. 1, electrical submersible pump assembly (ESP) 11 is illustrated as being supported on production tubing 13 extending into a cased inclined or horizontal section 12 of a well. ESP 11 could alternately be installed within a vertical portion of a well. ESP 11 could be supported by other structure instead of production tubing 13, such as coiled tubing.

ESP 11 includes several modules, one of which is a pump 15 that is illustrated as being a centrifugal pump. Pump 15 has an intake 16 for drawing in well fluid. Alternately, pump 15 could be other types, such as a progressing cavity pump. Another module comprises an electrical motor 17, which drives pump 15 and is normally a three-phase AC motor. A third module comprises a pressure equalizing or seal section 19 coupled between pump 15 and motor 17. Seal section 19 has components to reduce a pressure differential between dielectric lubricant contained in motor 17 and the pressure of the well fluid on the exterior of ESP 11. Intake 16 may be located in an upper portion of seal section 19 or on a lower end of pump 15. The terms “upper” and “lower” or used herein for convenience. While installed in a horizontal well section 12 as shown, “lower” refers to the upstream direction of well fluid flow, and “upper” refers to the downstream direction of well fluid flow. A thrust bearing unit 21 for motor 17 may be in a separate module or located in seal section 19 or motor 17.

ESP 11 may also include other modules, such as a gas separator for separating gas from the well fluid prior to the well fluid flowing into pump 15. The various modules may be shipped to a well site apart from each other, then assembled with bolts or other types of fasteners.

Referring to FIG. 2, seal section 19 has a cylindrical housing 23 secured by threads to upper and lower connectors 25, 27. Upper connector 25 normally bolts to pump 15 (FIG. 1), and lower connector 27 connects to thrust unit 21, Which may be located within a lower section (not shown) of seal section 19. One of the connectors 25 could alternately bolt to another seal section (not shown) in tandem, Which may have different components than seal section 19.

Each of the upper and lower connectors 25, 27 has a bore 29 extending along a longitudinal axis 31. A guide tube 33 extends along axis 31 from upper connector 25 to lower connector 27. The lower end of guide tube 33 inserts into and is sealed in bore 29 of lower connector 27. The upper end of guide tube 33 joins a seal 35 that seals guide tube 33 to upper connector 25. Seal 35 is fastened to a lower end of upper connector 25.

In this example, a shaft 37 extends from motor 17 (FIG. 1) through guide tube 33 of seal section 19 and into pump 15 (FIG. 1) to rotate pump 15. Normally, shaft 37 has several separate sections joined by splined couplings. Shaft 37 is radially supported in seal section 19 by bushings 39 in upper connector 25 and lower connector 27. If seal section 19 is located upstream from or below motor 17, there would be no shaft extending through it.

An inlet port 41 extends from the exterior of upper connector 25 to a lower end of upper connector 25. A labyrinth tube 43 is secured to the lower end of inlet port 41 and extends downward alongside and parallel to guide tube 33. Inlet port 41 admits well fluid to labyrinth tube 43 and has a check valve (not shown) to block any flow of fluid from labyrinth tube 43 back out of inlet port 41.

Upper and lower connectors 25, 27 and housing 23 define a labyrinth chamber 45 in seal section 19. Labyrinth tube 43 has a lower open end or outlet 44 that is a short distance above the lower end of chamber 45, the lower end 44 being above the upper end of lower connector 27. Chamber 45 will initially be filled with motor lubricant, but well fluid will be able to enter chamber 45 via labyrinth tube 43. Chamber 45 has an outlet port 47 extending through upper connector 25 to the exterior of upper connector 25, An optional pressure relief valve (not shown) in outlet port 47 allows fluid in chamber 45 to be vented in the event the pressure within chamber 45 exceeds the hydrostatic pressure of well fluid on the exterior of seal section 19. The pressure of the lubricant within motor 17 (FIG. 1) typically increases as the temperature of motor 17 increases due to operation.

Guide tube 33 has one or more guide tube ports 49 through its side wall near its upper end, which joins seal 35. Guide tube ports 49 communicate fluid in chamber 45 with an annular clearance or communication passage 51 located between the exterior of shaft 37 and the interior of guide tube 33. Annular clearance 51 is in fluid communication with lubricant in motor 17 so as to transmit the pressure in chamber 45 to the lubricant in motor 17. Bushings 39 that radially support shaft 37 do not form a seal, thus allowing lubricant in motor 19 to flow upward in annular clearance 51 during the filling procedure, explained below. A mechanical face seal (not shown) located in upper connector 25 seals around shaft 37 and retards well fluid from flowing down bore 29 of upper connector 37 into annular clearance 51.

A helical blade assembly 53 is shown inserted into chamber 45. In the embodiment of FIG. 2, helical blade assembly 53 has an optional outer cylindrical sleeve 55 that fits closely within the inner diameter of seal section housing 23. Optionally, seals (not shown) could seal between outer sleeve 55 and housing 23. Helical blade assembly 53 has an inner sleeve 57 that is concentric with outer sleeve 55 and has approximately the same axial length. Inner sleeve 57 has an inner diameter that slides over and closely receives the outer diameter of guide tube 33. Optionally, seals could be located between the inner diameter of inner sleeve 57 and the outer diameter of guide tube 33. The lower ends of outer sleeve 55 and inner sleeve 57 abut the upper end of lower connector 27 in this example. The upper end of outer sleeve 55 is spaced a short distance below the lower end of upper connector 25. A retainer ring (not shown) could fit into an annular profile 58 in the inner diameter of housing 23, if desired, to axially secure helical blade assembly 53 in housing 23 before securing upper connector 25 to housing 23. The upper end of inner sleeve 57 is illustrated as abutting the lower end of seal 35. Inner sleeve 57 has one or more ports 59 that register with guide tube ports 49.

A helical ramp, flight, or blade 61 is secured within helical blade assembly 53. Helical blade 61 extends around inner sleeve 57 in a spiral or helical pattern from the lower end to the upper end of inner sleeve 57. The angular degree of the helix is variable, and in the example shown, helical blade 61 makes several turns around inner sleeve 57. The thickness of helical blade 61 may also vary. The inner diameter of helical blade 61 is rigidly and sealingly joined to the outer diameter of inner sleeve 57. The outer diameter of helical blade 61 sealingly engages the inner diameter of outer sleeve 55. In this embodiment, helical blade 61 defines a sealed helical flow path 63 extending from lower connector 27 to guide tube and inner sleeve ports 49, 59.

Labyrinth tube 43 is preferably a part of the unitized helical blade assembly 53. Labyrinth tube 43 extends between outer sleeve 55 and inner sleeve 57 and sealingly through each turn of helical blade 61. Labyrinth tube 43 may be joined to a holes provided in each turn of helical blade 61. The upper end of labyrinth tube 43 protrudes above outer sleeve 55 and inner sleeve 57 and stabs sealingly into inlet port 41 at the lower end of upper connector 25.

In the embodiments shown, at least one baffle 65 is located within helical flow path 63 to impede the flow of well fluid from labyrinth tube outlet 44 to guide tube port 49. Several baffles 65 are shown in FIGS. 2-4, spaced along the helical length of flow path 63. Each baffle 65 comprises a plate with a portion 65a, which may be an inner edge, bonded or joined to inner sleeve 57. Each baffle 65 has an outer edge 65b that is spaced inward from outer sleeve 55, defining a gap 67 between baffle 65 and outer sleeve 55. Gap 67 allows well fluid to flow along helical path 63, but the flow rate of the well fluid will be impeded by baffle 65. Each baffle 65 has upper and lower edges 65c, 65d joined to adjacent turns of helical blade 61.

Referring to FIG. 3, baffles 65 are spaced at different angles relative to each other around axis. The angles between adjacent baffles 65 need not be the same. Baffles 65 are illustrated as being on radial lines of axis 31 in the embodiment of FIG. 3.

Referring to the alternate embodiment of FIG. 4, baffles 65′ may be oblique to axis 31, rather than on radial lines. Also, as shown in FIG. 4, outer sleeve 55 (FIG. 2) could be eliminated. The outer edge of helical blade 65′ would be in contact or closely spaced to the inner diameter of seal section housing 23. So as to facilitate fabrication, preferably, the outer edge of helical blade 65′ would not be bonded to the inner diameter of seal section housing 23. Although not shown, inner sleeve 57 could also be omitted; in that instance, the inner diameter of helical blade 65′ would be in contact with guide tube 33. Baffles 65 could be flat or curved. Whether or not inner and outer sleeves 57, 55 are employed, the inner diameter of helical blade 63 will be substantially the same as the inner diameter of labyrinth, chamber 45, and the outer diameter the same as the outer diameter of labyrinth chamber 45.

To retrofit a seal section 19 having a labyrinth chamber 45 and labyrinth tube 43, the operator removes one of the connectors 25, 27, then the existing labyrinth tube 43. The operator then inserts helical blade assembly 53 into chamber 45 and stabs labyrinth tube 43 into inlet port 41. If a retainer ring (not shown) is employed, the operator installs the retainer ring to secure helical blade assembly 53 to housing 23.

After securing seal section 19 to motor 17, the operator will pump lubricant into a till port near the lower end of motor 17 before installing the check valve in inlet port 41 and pressure relief valve in outlet port 47. The lubricant flows upward past bushings 39 in lower connector 27 and into annular clearance 51. Continuing to pump the lubricant causes the lubricant to flow out guide tube and inner sleeve ports 49, 59 and down helical flow path 63. The lubricant will flow up labyrinth tube 43 out inlet port 41. The lubricant will also flow out outlet port 47, indicating to the operator that motor 17 and chamber 45 have been completely filled.

The operator lowers ESP 11 into horizontal well section 12, which will contain a well fluid that is often a mixture of oil and water. Well fluid flows into labyrinth tube 43 and into chamber 45 in contact with motor lubricant. The hydrostatic pressure of the well fluid at inlet port 41 causes the pressure of the lubricant in chamber 45 and motor 17 to increase and equalize with the well fluid pressure.

As motor 17 begins to operate, it generates heat, which causes the lubricant to expand if the pressure within chamber 45 exceeds the pressure of the well fluid on the exterior of seal section 19 by a sufficient amount, the pressure relief valve in outlet port 47 allows some of the lubricant to be expelled. When motor 17 is shut down, the lubricant will cool, causing the pressure to drop and possibly some entry of well fluid down labyrinth tube 43 into chamber 45. Also, leakage of the seals of shaft 37 over time may tend to allow the encroachment of well fluid into chamber 45. Thus, eventually, well fluid will be in contact with the lubricant in chamber 45.

Normally, the well fluid has a greater specific gravity than the motor lubricant, resulting in the well fluid migrating downward. If installed within horizontal section 12 of a well, the migrating well fluid from labyrinth tube 43 has to flow upward to some extent along helical flow path 63 from the outlet of labyrinth tube 43 to guide tube and inner sleeve ports 49, 59. For example, if axis 31 is substantially horizontal, each time helical flow path 63 encircles axis 31, the well fluid would have to migrate upward, then downward. At each baffle 65 located above axis 31, the migrating well fluid has to build up to a sufficient height to flow over baffle 65 through gap 67. Well fluid can flow through gaps 67 more freely for the baffles 65 on the lower side of axis 31 than the baffles 65 located above axis 31. When installing ESP 11, the operator will not know which baffles 65 end up on the lower side of axis 31 and which on the upper side of axis 31. Without helical blade assembly 53, the flow path for encroaching well fluid would be horizontal if ESP 11 is oriented horizontally, thus much more direct when ESP 11 is inclined.

If ESP 11 is oriented vertically, in order for the well fluid to migrate down annular clearance 51 in lower connector 27, the well fluid must first pass upward through helical flow path 63 from the lower end of chamber 45 to guide tube and inner sleeve ports 49, 59. The well fluid collecting in the lower end of chamber 45 has to flow back upward in order to reach ports 49, 59 , which is more difficult because of the heavier gravity of the well fluid than the lubricant,

Helical blade assembly 53 may be formed of a variety of materials, such as carbon steel, stainless steel, Inconel, aluminum, or thermal plastic. The construction could vary from casting, machining, molding or other techniques. In addition, water absorbing materials could be inserted between the turns of helical blade 61 to remove water contamination from the clean motor lubricant.

While the disclosure has been shown in only one of its forms, it should be apparent to those skilled in the art that various modifications may be made. For example, having a unitized blade assembly 53 with an inner sleeve 57 allows a conventional seal section with a labyrinth chamber to be quickly converted, as discussed above. If desired, seal section 19 could have a bag or diaphragm type chamber in tandem with labyrinth chamber 45. Also, more than one labyrinth chambers 45 could be mounted in tandem.

Claims

1. An electrical submersible pump assembly, comprising:

a pump;

a motor cooperatively engaged with the pump for driving the pump;

a seal section having an axis and a labyrinth chamber between upstream and downstream ends of the seal section;

a guide tube extending along the axis between the upstream and downstream ends that contains lubricant in fluid communication with lubricant in the motor, the guide tube having an inlet port adjacent the downstream end to communicate the lubricant within the guide tube into the labyrinth chamber;

a labyrinth tube within the labyrinth chamber and having an open inlet end in the downstream end and an open outlet end within the labyrinth chamber adjacent the upstream end, the labyrinth tube adapted to communicate well fluid on the exterior of the seal section into the labyrinth chamber into contact with the lubricant in the labyrinth chamber to equalize a pressure of the lubricant with a pressure of the well fluid; and

a non rotating helical blade in the labyrinth chamber encircling the guide tube, defining a helical flow path between the outlet port of the labyrinth tube and the inlet port of the guide tube.

2. The assembly according to claim 1, Wherein the labyrinth tube extends sealingly through turns of the helical blade.

3. The assembly according to claim 1, further comprising:

an inner sleeve surrounding the guide tube; and

wherein the helical blade has an inner diameter edge joined to the inner sleeve.

4. The assembly according to claim 1, further comprising:

an outer sleeve surrounding the helical blade, the outer sleeve having an outer diameter in contact with an inner diameter of the housing, the helical blade; and wherein

the helical blade has an outer edge in contact with an inner diameter of the outer sleeve.

5. The assembly according to claim 1, wherein:

the seal section has a housing; and

the helical blade has an outer edge in contact with an inner diameter of the housing.

6. The assembly according to claim 1, further comprising:

at least one baffle along the helical flow path and mounted between adjacent turns of the blade for retarding flow of well fluid along the helical flow path,

8. The assembly according to claim 1, further comprising:

at least one baffle along the helical flow path;

the baffle having an inner edge joined, to the guide tube;

the baffle having upstream and downstream edges joined to adjacent turns of the helical blade; and

the baffle having an outer edge located inward from an outer diameter of the helical blade, defining a gap for well fluid to pass from an upstream side of the baffle to a downstream side of the baffle along the helical flow path.

9. An electrical submersible pump assembly, comprising:

a pump;

a motor;

a seal section housing, having upstream and downstream connectors that connect the seal section into the assembly between the motor and the pump, defining a labyrinth chamber between the upstream and downstream end connectors;

a shaft driven by the motor and extending through the seal section into cooperative engagement with the pump;

a guide tube surrounding the shaft and extending between the upstream and downstream connectors, the guide tube defining an annular clearance between the guide tube and the shaft that contains lubricant in fluid communication with lubricant in the motor, the guide tube having a guide tube port adjacent the downstream connector to communicate the lubricant within the annular clearance into the labyrinth chamber;

a labyrinth tube within the labyrinth chamber parallel to and spaced outward from the guide tube and having an open inlet end in the downstream connector and an open outlet end in the labyrinth chamber near the upstream end connector, the labyrinth tube adapted to communicate well fluid on the exterior of the seal section into the labyrinth chamber into contact with the lubricant in the labyrinth chamber to equalize a pressure of the lubricant with a pressure of the well fluid; and

a non rotating helical blade in the labyrinth chamber encircling the guide tube, defining a helical flow path between the outlet end of the labyrinth tube and the guide tube port of the guide tube.

10. The assembly according to claim 9, wherein the labyrinth tube extends sealingly through turns of the helical blade.

11. The assembly according to claim 9 further comprising:

an inner sleeve surrounding the guide tube;

an inner sleeve port in registry with the guide tube port; and

wherein the helical blade has an inner diameter edge joined to the inner sleeve.

12. The assembly according to claim 9, wherein:

the labyrinth chamber has an inner diameter and an outer diameter; and

the helical blade has inner diameter substantially the same as the inner diameter of the labyrinth chamber and an outer diameter substantially the same as the outer diameter of the labyrinth chamber.

13. The assembly according to claim 9, further comprising:

an outer sleeve surrounding the helical blade, the outer sleeve having an outer diameter in contact with an inner diameter of the housing.

14. The assembly according to claim 9, wherein the helical blade has an outer edge in contact with an inner diameter of the housing.

15. The assembly according to claim 9, further comprising:

at least one baffle along the flow path and mounted between adjacent turns of the blade for retarding flow of well fluid along the helical flow path.

16. The assembly according to claim 9, further comprising:

a plurality of baffles spaced along the helical flow path between adjacent turns of the blade for retarding flow of well fluid. along the helical flow path.

17. The assembly according to claim 9, further comprising:

at least one baffle along the helical flow path;

the baffle having an inner edge joined to the guide tube;

the baffle having upstream and downstream edges joined to adjacent turns of the helical blade; and

the baffle having an outer edge located inward from an outer diameter of the helical blade, defining a gap for well fluid to pass from an upstream side of the baffle to a downstream side of the baffle along the helical flow path.

18. A method of pumping well fluid from a well with a submersible pump assembly having a pump, a motor cooperatively engaged with the pump for driving the pump, and a seal section with a labyrinth chamber between upstream and downstream ends of the seal section, the seal section having a guide tube extending between the upstream and downstream ends that has an inlet port adjacent the downstream end, the seal section having a labyrinth tube within the labyrinth chamber and having an open inlet end in the downstream end and an open outlet end within the labyrinth chamber adjacent the upstream end, the method comprising:

mounting a non rotating helical blade in the labyrinth chamber around the guide tube, defining a helical flow path between the outlet port of the labyrinth tube and the inlet port of the guide tube;

flowing lubricant from the motor through the guide tube out the inlet port of the guide tube into the helical flow path in the labyrinth fluid chamber;

submersing the submersible pump assembly in well fluid in the well;

flowing well fluid through the labyrinth tube out the open outlet end into and along the helical flow path in contact with the lubricant to equalize a pressure of the lubricant within the motor with a pressure of well fluid exterior of the motor; and

driving the pump with the motor, causing the pump to pump well fluid from the well.

19. The method according to claim 18, wherein:

submersing the submersible pump assembly comprises installing the assembly within an inclined section of the well; and

flowing well fluid along the helical flow path requires the well fluid to flow upward above the guide tube, then back downward below the guide tube with each turn of the helical flow path.

20. The method according to claim 18, further comprising:

placing at least one baffle along the helical flow path; and

flowing well fluid along the helical flow path requires the well fluid to flow over the baffle.