U.S. patent application number 13/398217 was filed with the patent office on 2012-09-06 for electric submersible pump floating ring bearing and method to assemble same.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. Invention is credited to Michael A. Forsberg.
Application Number | 20120224985 13/398217 |
Document ID | / |
Family ID | 46753418 |
Filed Date | 2012-09-06 |
United States Patent
Application |
20120224985 |
Kind Code |
A1 |
Forsberg; Michael A. |
September 6, 2012 |
ELECTRIC SUBMERSIBLE PUMP FLOATING RING BEARING AND METHOD TO
ASSEMBLE SAME
Abstract
A floating ring bearing for an electric submersible pump (ESP)
assembly disposable within a cased wellbore and a method to
assemble the same are disclosed. The ESP assembly includes a motor,
a pump, and a shaft coupling the pump to the pump motor. One or
more floating ring bearings are disposed within the motor and the
pump, each floating ring bearing circumscribing the shaft to
radially support the shaft. A floating ring is disposed within each
floating ring bearing. The floating ring circumscribes the shaft so
that the floating ring rotates about the shaft in response to
rotation of the shaft.
Inventors: |
Forsberg; Michael A.;
(Claremore, OK) |
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
46753418 |
Appl. No.: |
13/398217 |
Filed: |
February 16, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61448470 |
Mar 2, 2011 |
|
|
|
Current U.S.
Class: |
417/410.1 ;
29/898 |
Current CPC
Class: |
F16C 17/18 20130101;
E21B 43/128 20130101; Y10T 29/49636 20150115 |
Class at
Publication: |
417/410.1 ;
29/898 |
International
Class: |
F04B 35/04 20060101
F04B035/04; B21D 53/10 20060101 B21D053/10 |
Claims
1. An electric submersible pump (ESP) assembly disposable within a
cased wellbore, the ESP assembly comprising: a motor; a pump; a
shaft coupled between the pump and the motor; an outer bearing
surface circumscribing the shaft; fluid between the shaft and the
bearing surface; and an annular ring floating in the fluid and
rotatable with respect to the shaft and the outer bearing
surface.
2. The ESP assembly of claim 1, wherein the fluid comprises a
lubricant for transferring rotational inertia of the shaft to the
ring so that the ring rotates in response to rotation of the
shaft.
3. The ESP assembly of claim 1, wherein the outer bearing surface
comprises a portion of a housing of the pump.
4. The ESP assembly of claim 1, wherein the ring is disposed in the
pump and the fluid comprises wellbore fluid being pressurized by
the pump.
5. The ESP assembly of claim 1, wherein ring is disposed in the
motor and the fluid comprises dielectric fluid.
6. The ESP assembly of claim 1, wherein the ring rotates at a
slower rotation speed than the shaft.
7. The ESP assembly of claim 1, wherein the ring rotates at about
one-third to about one-fourth the rotation speed of the shaft.
8. An electric submersible pump (ESP) assembly disposable within a
cased wellbore, the ESP assembly comprising: a motor; a pump; a
shaft coupled between the pump and the motor; a stationary journal
defining a bore through which the shaft extends; fluid
circumscribing the shaft in the stationary journal; and an annular
ring floating in the fluid coaxial with an axis of the shaft and
rotatable with respect to the shaft to reduce the rotational
inertia of the fluid resulting from rotation of the shaft, the
annular ring rotating at a slower speed than the shaft so that
fluid between the ring and the shaft has a higher rotational
inertia than the fluid between the ring and the stationary
journal.
9. The ESP assembly of claim 8, wherein the fluid comprises a
lubricant for transferring rotational inertia of the shaft to the
ring so that the ring rotates in response to rotation of the
shaft.
10. The ESP assembly of claim 8, wherein the stationary journal
comprises a portion of a housing of the pump.
11. The ESP assembly of claim 8, wherein the ring is disposed in
the pump and the fluid comprises wellbore fluid being pressurized
by the pump.
12. The ESP assembly of claim 8, wherein ring is disposed in the
motor and the fluid comprises dielectric fluid.
13. The ESP assembly of claim 8, wherein the ring rotates at about
one-third to about one-fourth the speed of the shaft.
14. A method to assemble a floating ring bearing for use in an
electric submersible pump (ESP) to radially support one or more
rotating shafts coupling a motor of the ESP to a pump portion of
the ESP, the method comprising: (a) providing a stationary journal
defining a bore having an axis, the journal secured to a
non-rotating member of the electric submersible pump; (b)
positioning the shaft within the journal coaxial with the bore, the
shaft rotatable relative to the journal; (c) positioning a floating
ring coaxial with the bore between the journal and the shaft, the
floating ring defining an outer annular cavity between the floating
ring and the journal and an inner annular cavity between the
floating ring and the shaft; and (d) filling ESP with a fluid so
that the fluid flows through the ESP into the inner and outer
cavities, the fluid to transfer rotational inertia of the shaft to
the floating ring when the shaft rotates, thereby allowing the
floating ring to rotate within the journal.
15. The method of claim 14, further comprising providing the
stationary journal in the pump portion of the ESP and the fluid
comprising wellbore fluid pressurized by the pump portion.
16. The method of claim 14, further comprising providing the
stationary journal in the motor of the ESP and the fluid comprising
dielectric fluid filling the motor.
17. The method of claim 14, further comprising providing the
stationary journal in a seal section coupled between the motor and
the pump portion of the ESP and the fluid comprising dielectric
fluid filling the seal section.
Description
[0001] This application claims priority to and the benefit of
co-pending U.S. Provisional Application No. 61/448,470, by
Forsberg, filed on Mar. 2, 2011, entitled "ELECTRIC SUBMERSIBLE
PUMP FLOATING RING BEARING," which application is incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates in general to bearings supporting a
rotating member and, in particular, to bearings supporting rotating
shafts of an electric submersible pump and a method to assemble the
same.
BRIEF DESCRIPTION OF RELATED ART
[0003] Wells may use an artificial lift system, such as an electric
submersible pump (ESP) to lift well fluids to the surface. Where
ESPs are used, the ESP may be deployed by connecting the ESP to a
downhole end of a tubing string and then run into the well on the
end of the tubing string. The ESP may be connected to the tubing
string by any suitable manner. In some examples, the ESP connects
to the tubing string with a threaded connection so that an uphole
end or discharge of the ESP threads onto the downhole end of the
tubing string.
[0004] ESPs generally include a pump portion and a motor portion.
Generally, the motor portion is downhole from the pump portion, and
a rotatable shaft connects the motor and the pump. The rotatable
shaft is usually one or more shafts operationally coupled together.
The motor rotates the shaft that, in turn, rotates components
within the pump to lift fluid through a production tubing string to
the surface. ESP assemblies may also include one or more seal
sections coupled to the shaft between the motor and pump. In some
embodiments, the seal section connects the motor shaft to the pump
intake shaft. Some ESP assemblies include one or more gas
separators. The gas separators couple to the shaft at the pump
intake and separate gas from the wellbore fluid prior to the entry
of the fluid into the pump.
[0005] The pump portion includes a stack of impellers and
diffusers. The impellers and diffusers are alternatingly positioned
in the stack so that fluid leaving an impeller will flow into an
adjacent diffuser and so on. Generally, the diffusers direct fluid
from a radially outward location of the pump back toward the shaft,
while the impellers accelerate fluid from an area proximate to the
shaft to the radially outward location of the pump. Each impeller
and diffuser may be referred to as a pump stage. The shaft couples
to the impeller to rotate the impeller within the non-rotating
diffuser. In this manner, the stage may pressurize the fluid to
lift the fluid through the tubing string to the surface.
[0006] The rotating shaft of the ESP may be supported on rotary
bearings such as journal or plain bearings, sleeve bearings, or the
like. These bearing assemblies include a sleeve surrounding and
mounted to the rotating shaft, for example with a key, so that the
sleeve rotates with the shaft. The sleeve is supported by an
insert, for example a bushing, and a lubricant film between the
sleeve and the insert. The sleeve and shaft rotate within the
insert that is held in place by a race, in turn mounted to a pump
housing or pump body through a T-ring that prevents rotation of the
bearing relative to the pump housing or body. These types of
bearings face problems in environments where high vibration may
occur, for example in an eccentrically loaded shaft of an ESP or an
imbalanced rotating shaft of the ESP. In addition, due to the
relatively thin lubrication layer between the sleeve and the
insert, the bearing may be subject to a high degree of wear at the
high rotational operating speeds experienced by ESPs. This leads to
a significantly shorter life that may necessitate frequent
replacement of the bearings. Replacing rotary bearings in an ESP
may be extremely costly, particularly where the ESP is positioned
within increasingly deep wellbores. Therefore, there is a need for
a bearing that may accommodate high vibration of a rotating member
in an ESP while having increased wear resistance.
SUMMARY OF THE INVENTION
[0007] These and other problems are generally solved or
circumvented, and technical advantages are generally achieved, by
preferred embodiments of the present invention that provide an
electric submersible pump floating ring bearing and a method to
assemble the same.
[0008] In accordance with an embodiment of the present invention,
an electric submersible pump (ESP) assembly disposable within a
cased wellbore is disclosed. The ESP assembly includes a motor, a
pump, and a shaft coupled between the pump and the motor. The ESP
further includes an outer bearing surface circumscribing the shaft
and fluid between the shaft and the bearing surface. An annular
ring floats in the fluid and is rotatable with respect to the shaft
and the outer bearing surface.
[0009] In accordance with another embodiment of the present
invention, an electric submersible pump (ESP) assembly disposable
within a cased wellbore is disclosed. The ESP assembly includes a
motor, a pump, and a shaft coupled between the pump and the motor.
A stationary journal defines a bore through which the shaft extends
and fluid circumscribes the shaft in the stationary journal. An
annular ring floats in the fluid coaxial with an axis of the shaft
and rotatable with respect to the shaft to reduce the rotational
inertia of the fluid resulting from rotation of the shaft, the
annular ring rotating at a slower speed than the shaft so that
fluid between the ring and the shaft has a higher rotational
inertia than the fluid between the ring and the stationary
journal.
[0010] In accordance with yet another embodiment of the present
invention, a method to assemble a floating ring bearing for use in
an electric submersible pump (ESP) to radially support one or more
rotating shafts coupling a motor of the ESP to a pump portion of
the ESP is disclosed. The method provides providing a stationary
journal defining a bore having an axis. The journal is secured to a
non-rotating member of the electric submersible pump. The method
positions the shaft within the journal coaxial with the bore so
that the shaft is rotatable relative to the journal. The method
positions a floating ring coaxial with the bore between the journal
and the shaft. The floating ring defines an outer annular cavity
between the floating ring and the journal and an inner annular
cavity between the floating ring and the shaft. The method fills
the inner and outer cavities with a fluid freely flowing through
the ESP to transfer rotational inertia of the shaft to the floating
ring when the shaft rotates, thereby allowing the floating ring to
rotate within the journal.
[0011] The disclosed embodiments provide a bearing that can offer
improved damping and vibration characteristics. In addition, this
bearing type may be used in a system with high vibration to improve
the energy dissipation of the rotating shaft and, consequently, the
vibration characteristics. Furthermore, the disclosed embodiments
will experience reduced wear, such as abrasive wear, compared to
similarly situated bearings. This is because the effective velocity
between the shaft and the ring, and the ring and the journal is
lower.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] So that the manner in which the features, advantages and
objects of the invention, as well as others which will become
apparent, are attained, and can be understood in more detail, more
particular description of the invention briefly summarized above
may be had by reference to the embodiments thereof which are
illustrated in the appended drawings that form a part of this
specification. It is to be noted, however, that the drawings
illustrate only a preferred embodiment of the invention and are
therefore not to be considered limiting of its scope as the
invention may admit to other equally effective embodiments.
[0013] FIG. 1 is a schematic representation of an electric
submersible pump coupled inline to a tubing string and suspended
within a casing string in accordance with an embodiment of the
present invention.
[0014] FIG. 2 is a sectional view of a floating ring bearing of
FIG. 1, taken along line 2-2 in accordance with an embodiment of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings which
illustrate embodiments of the invention. 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 thorough and complete, and will fully convey the
scope of the invention to those skilled in the art. Like numbers
refer to like elements throughout, and the prime notation, if used,
indicates similar elements in alternative embodiments.
[0016] In the following discussion, numerous specific details are
set forth to provide a thorough understanding of the present
invention. However, it will be obvious to those skilled in the art
that the present invention may be practiced without such specific
details. Additionally, for the most part, details concerning
drilling rig operation, electric submersible pump construction and
operation, and the like have been omitted inasmuch as such details
are not considered necessary to obtain a complete understanding of
the present invention, and are considered to be within the skills
of persons skilled in the relevant art.
[0017] With reference now to FIG. 1 an example of an electrical
submersible pump (ESP) system 11 is shown in a side partial
sectional view. ESP 11 is disposed in a wellbore 29 that is lined
with casing 12. In the embodiment shown, ESP 11 includes a motor
15, a seal section 19 attached on the upper end of the motor 15,
and a pump 13 above seal 19. Fluid inlets 23 shown on the outer
housing of pump 13 provide an inlet for wellbore fluid 31 in
wellbore 29 to enter into pump section 13. A gas separator (not
shown) could be mounted between seal section 19 and pump section
13.
[0018] In an example of operation, pump motor 15 is energized via a
power cable 17 and rotates an attached shaft assembly 35 (shown in
dashed outline). Although shaft 35 is illustrated as a single
member, it should be pointed out that shaft 35 may comprise
multiple shaft segments. Shaft assembly 35 extends from motor 15
through seal section 19 to pump section 13. Impellers 25 (also
shown in dashed outline) within pump section 13 are coupled to an
upper end of shaft 35 and rotate in response to shaft 35 rotation.
Impellers 25 can be a vertical stack of individual members
alternatingly interspaced between static diffusers (not shown).
Wellbore fluid 31, which may include liquid hydrocarbon, gas
hydrocarbon, and/or water, enters wellbore 29 through perforations
33 formed through casing 12. Wellbore fluid 31 is drawn into pump
13 from inlets 23 and is pressurized as rotating impellers 25 urge
wellbore fluid 31 through a helical labyrinth upward through pump
13. The pressurized fluid is directed to the surface via production
tubing 27 attached to the upper end of pump 13.
[0019] Shaft 35 is radially supported within ESP 11 by bearings,
such as floating ring bearings 37. A person skilled in the art will
understand that any number of floating ring bearings 37 may be used
to support shaft 35 as necessary. Similarly, a person skilled in
the art will understand that floating ring bearings 37 may be
placed within any portion of ESP 11, such as motor 15, seal section
19, or pump 13 so that each component of ESP 11 may radially
support shaft 35 at one or more locations.
[0020] Referring to FIG. 2, shown is an example of a floating ring
bearing 37 that includes a journal 39, and a floating ring 41.
Journal 39 may be a stationary component. In the illustrated
embodiment, journal 39 may be an outer housing element of floating
ring bearing 37 suitably mounted to a pump housing, shaft support,
or shaft alignment member. A person skilled in the art will
recognize that journal 39 may mount to the appropriate member in
any suitable manner such that floating ring bearing 37 may support
shaft 39 as disclosed herein. In other embodiments, journal 39 may
be the pump housing, shaft support, or shaft alignment member
adapted to function as described herein with respect to journal 39.
In an example, journal 39 is a tubular member having a curved inner
surface that defines a bore 43 having an axis 45. An inner diameter
of bore 43 will be sufficient to accommodate placement of both
shaft 35 and floating ring 41 as described in more detail below.
Shaft 35 resides within bore 43 and is coaxial with axis 45.
Floating ring 41 also resides within bore 43 and is coaxial with
axis 45. Floating ring 41 has an outer diameter 42 smaller than the
inner diameter of journal 39 so that an outer annular cavity 47 is
formed between floating ring 41 and journal 39. Outer annular
cavity 47 extends radially outward from the outer diameter 42 of
floating ring 41 to the inner diameter of journal 39. Floating ring
41 has an inner diameter 44 larger than the outer diameter of shaft
35 to form an inner annular cavity 49 between shaft 35 and floating
ring 41. Inner annular cavity 49 extends from the outer diameter of
shaft 35 to inner diameter 44 of floating ring 41. Both outer and
inner annular cavities 47, 49 may be respectively filled with a
non-compressible fluid F.sub.1, F.sub.2, such as a lubricating oil,
grease, gas, or a fluid within ESP 11. Inner and outer annular
cavities 47, 49 allow shaft 35 and floating ring 41 to move
radially relative to one another, and relative to journal 39.
Floating ring 41 is not secured to shaft 35 for rotation
therewith.
[0021] A person skilled in the art will understand that floating
ring 41 has a length as needed to provide sufficient radial support
of shaft 35. Similarly, outer and inner annular cavities 47, 49 may
be defined in part by the length of floating ring 41. The length of
floating ring 41 may vary based on the dimensional and material
properties of shaft 35, the load carrying capacity of shaft 35 and
floating ring bearing 37, and they dynamic characteristics of the
rotation of shaft 35. A person skilled in the art will further
understand that floating ring 41 may move axially relative to shaft
35 and journal 39. However, axial movement of floating ring 41 may
be constrained by adjacent components of ESP 11. In some
embodiments, a limiter pin (not shown), annular shoulder on journal
39 (not shown), or similar feature may be used axially above and
axially below floating ring 41 to limit the overall axial movement
of floating ring 41, provided floating ring 41 may still rotate
relative to both journal 39 and shaft 35. Floating ring 41 may also
have a width sufficient to maintain the ring-like shape of floating
ring 41 when subjected to the pressure profile of the ESP 11
application of floating ring bearing 37 and the particular geometry
of the ESP 11 component, i.e. pump 13, motor 15, seal section 19,
etc., in which floating ring bearing 37 is used.
[0022] Shaft 35 may selectively rotate in response to operation of
motor 15 (FIG. 1). As shaft 35 rotates with a rotational velocity
w.sub.1, frictional forces between the exterior surface of shaft 35
and the surrounding fluid F.sub.2 in inner annular cavity 49 will
cause shaft 35 to impart rotational energy to the fluid F.sub.2 in
inner annular cavity 49 between shaft 35 and floating ring 41,
causing that fluid F.sub.2 to rotate in the same direction as shaft
35. In turn, the rotational motion of the fluid F.sub.2 in cavity
49 will impart rotational energy to floating ring 41 causing
floating ring 41 to rotate with a rotational velocity w.sub.2 in
the same direction as shaft 35. In the exemplary embodiment,
w.sub.2 is approximately 1/3w.sub.1 to 1/4w.sub.1. Similarly,
frictional forces between floating ring 41 and the fluid F.sub.1 in
cavity 47 impart rotational energy from floating ring 41 to the
fluid F.sub.1, causing the fluid F.sub.1 to rotate, although at a
lower velocity than floating ring 41, the fluid F.sub.2 in cavity
49, or shaft 35. Thus, shaft 35 may rotate within journal 39 with
reduced wear between shaft 35 and journal 39. In addition, the
reaction forces necessary to prevent rotation of journal 39 may be
significantly decreased as the total energy that may be exerted on
journal 39 is reduced through the successive energy transfers
between shaft 35, fluid F.sub.1, floating ring 41, and fluid
F.sub.2.
[0023] In the illustrated embodiment, the fluid F.sub.1, F.sub.2 in
cavities 47, 49 is not sealed from the working fluid that is pumped
up through pump 13 or the dielectric fluid that may fill seal
section 19 and motor 15. As shown, floating ring bearing 37 is a
hydrodynamic bearing lubricated with the working fluid or
dielectric fluid of the component in which floating ring bearing 37
is positioned. In an exemplary embodiment, shaft 35 may rotate at
slower rotational speeds during operation of ESP 11, for example at
approximately 3500 revolutions per minute. These operating speeds
permit use of the working fluid or dielectric fluid of ESP 11 to
lubricate floating ring bearing 37 and provide the fluid films
maintaining separation between shaft 35, floating ring 41, and
journal 39. In these exemplary embodiments, no additional
pressurization system or specialized sealing system is needed to
provide fluid F.sub.2 or Fluid F.sub.1 to outer and inner annular
cavities 47, 49, respectively. A person skilled in the art will
understand that alternative embodiments may seal the fluid in outer
and inner annular cavities 47, 49 from the working fluid or
dielectric fluid in use in ESP 11.
[0024] Outer annular cavity 47 has a width 51 between journal 39
and floating ring 41. Similarly, outer annular cavity 49 has a
width 53 between shaft 35 and floating ring 41. Widths 51, 53 are
selected based on the design parameters of the particular ESP 11
into which floating ring bearing 37 is placed. For example, to
decrease wear between shaft 35 and journal 39, widths 51, 53 may be
larger to allow for a larger decrease in the rotational velocity of
w.sub.2 relative to w.sub.1. However, a person skilled in the art
will understand that knowledge of the particular ESP 11 application
to which floating ring bearing 37 will be applied, including
knowledge of the load and operational speed requirements of ESP 11,
is necessary to accurately size widths 51, 53. A person skilled in
the art will further understand that widths 51, 53 will be limited
by the overall size of the ESP component.
[0025] A person skilled in the art will recognize that floating
ring bearing 37 may be used in any suitable component of ESP 11.
For example, floating ring bearings 37 may be used in pump 13,
motor 15, and seal section 19. In addition, floating ring bearings
37 may be used in optional equipment such as gas separators, sand
separators, and the like. A person skilled in the art will further
understand that each floating ring bearing 37 used in individual
components of ESP 11 may be sized according to the particular
component of ESP 11 in which floating ring bearing 37 is used,
provided that the particular floating ring bearing 37 may operate
as described herein.
[0026] Accordingly, the disclosed embodiments provide numerous
advantages. For example, the disclosed embodiments provide a
bearing that can offer improved damping and vibration
characteristics. In addition, this bearing type may be used in a
system with high vibration to improve the energy dissipation of the
rotating shaft and, consequently, the vibration characteristics.
Furthermore, the disclosed embodiments will experience reduced
wear, such as abrasive wear, compared to similarly situated
bearings. This is because the effective velocity between the shaft
and the ring, and the ring and the journal is lower.
[0027] This application claims priority to and the benefit of
co-pending U.S. Provisional Application No. 61/448,470, by
Forsberg, filed on Mar. 2, 2011, entitled "ELECTRIC SUBMERSIBLE
PUMP FLOATING RING BEARING," which application is incorporated
herein by reference.
[0028] It is understood that the present invention may take many
forms and embodiments. Accordingly, several variations may be made
in the foregoing without departing from the spirit or scope of the
invention. Having thus described the present invention by reference
to certain of its preferred embodiments, it is noted that the
embodiments disclosed are illustrative rather than limiting in
nature and that a wide range of variations, modifications, changes,
and substitutions are contemplated in the foregoing disclosure and,
in some instances, some features of the present invention may be
employed without a corresponding use of the other features. Many
such variations and modifications may be considered obvious and
desirable by those skilled in the art based upon a review of the
foregoing description of preferred embodiments. Accordingly, it is
appropriate that the appended claims be construed broadly and in a
manner consistent with the scope of the invention.
* * * * *