U.S. patent application number 15/247302 was filed with the patent office on 2017-03-02 for abrasion resistance in well fluid wetted assemblies.
This patent application is currently assigned to Summit ESP, LLC. The applicant listed for this patent is Summit ESP, LLC. Invention is credited to Thomas John Gottschalk, Keith Leon Johnson, John Vanderstaay Kenner, David J. Lunk, Wesley John Nowitzki.
Application Number | 20170058616 15/247302 |
Document ID | / |
Family ID | 58103481 |
Filed Date | 2017-03-02 |
United States Patent
Application |
20170058616 |
Kind Code |
A1 |
Lunk; David J. ; et
al. |
March 2, 2017 |
ABRASION RESISTANCE IN WELL FLUID WETTED ASSEMBLIES
Abstract
Abrasion resistance in well fluid wetted assemblies is
described. A method of enhancing an abrasion resistance of
submersible assemblies includes polishing a first running surface
of a sleeve and a second running surface of a bushing until the
first running surface and the second running surface have a
roughness average of four micro-inches roughness average (Ra) or
less, coating the polished first running surface and the polished
second running surface with one of titanium nitride, titanium
aluminum nitride or a combination thereof, and placing the sleeve
and the bushing in an electric submersible pump (ESP) assembly
component such that the first running surface faces the second
running surface and the first running surface rotates with respect
to the second running surface, and pumping a fluid from an
underground formation to a surface location using the ESP
assembly.
Inventors: |
Lunk; David J.; (Big Cabin,
OK) ; Johnson; Keith Leon; (Claremore, OK) ;
Nowitzki; Wesley John; (Broken Arrow, OK) ;
Gottschalk; Thomas John; (Houston, TX) ; Kenner; John
Vanderstaay; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Summit ESP, LLC |
Tulsa |
OK |
US |
|
|
Assignee: |
Summit ESP, LLC
|
Family ID: |
58103481 |
Appl. No.: |
15/247302 |
Filed: |
August 25, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62210068 |
Aug 26, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/0473 20130101;
F04D 13/10 20130101; F04D 29/0413 20130101; E21B 43/128 20130101;
F04D 13/086 20130101 |
International
Class: |
E21B 17/10 20060101
E21B017/10; F04D 29/047 20060101 F04D029/047; F04D 13/08 20060101
F04D013/08; E21B 4/00 20060101 E21B004/00; E21B 43/12 20060101
E21B043/12 |
Claims
1. A submersible pump bearing set comprising: a rotatable sleeve
comprising a first polished running surface; a bushing surrounding
the rotatable sleeve, the bushing secured to a diffuser wall and
comprising a second polished running surface; wherein the second
polished running surface of the bushing faces the first running
surface of the rotatable sleeve.
2. The submersible pump bearing set of claim 1, wherein the
rotatable sleeve is a flanged sleeve comprising a tubular portion
and a flange extending radially from the tubular portion, and
wherein the flange comprises the first polished running
surface.
3. The submersible pump bearing set of claim 1, wherein the first
polished running surface and the second polished running surface
are made of a cemented carbide composite selected from the group
consisting of titanium carbide, tungsten carbide and tantalum
carbide.
4. The submersible pump bearing set of claim 3, wherein the first
polished running surface and the second polished running surface
comprise a coating of one of titanium nitride or titanium aluminum
nitride over each of the polished running surfaces.
5. The submersible pump bearing set of claim 3, wherein the first
polished running surface and the second polished running surface
comprise a layer of infused diamond-like carbon over each of the
polished running surfaces.
6. The submersible pump bearing set of claim 3, wherein the first
polished running surface and the second polished running surface
comprise a layer of one of polycrystalline diamond (PCD), thermally
stable PCD (TSP) or amorphous diamond over each of the polished
running surfaces.
7. The submersible pump bearing set of claim 1, wherein the first
polished running surface and the second polished running surface
have a roughness average of four micro-inches roughness average
(Ra) or less.
8. The submersible pump bearing set of claim 1, wherein the
rotatable sleeve is keyed to an electric submersible pump (ESP)
shaft.
9. The submersible pump bearing set of claim 1, wherein the
diffuser is in a stage of one of an ESP pump, ESP charge pump or
ESP gas separator.
10. A system for pumping a hydrocarbon from a downhole well, the
system comprising: a submersible pump that pumps a fluid
hydrocarbon from a well, the submersible pump further comprising: a
bearing set comprising a bushing and a flanged sleeve; each of the
bushing and the flanged sleeve comprising a polished running
surface; and the polished running surface of each of the bushing
and the flanged sleeve having a mirror finish.
11. The system of claim 10, wherein an inner diameter of the
bushing comprises the polished running surface of the bushing, and
an outer diameter of the flanged sleeve comprises the polished
running surface of the flanged sleeve.
12. The system of claim 10, wherein a bottom of a flange of the
flanged sleeve comprises the polished running surface of the
flanged sleeve, and a top of the bushing comprises the polished
running surface of the bushing.
13. The system of claim 10, further comprising a layer of
diamond-like carbon on the polished running surface of each of the
bushing and the flanged sleeve and the layer comprises a
diamond-like carbon film.
14. The system of claim 10, further comprising a coating of one of
titanium nitride or titanium aluminum nitride over each of the
polished running surfaces.
15. The system of claim 10, wherein a load bearing surface of each
of the polished running surfaces is at least 85% of a total surface
area of each of the polished running surfaces.
16. The system claim 10, wherein each of the polished running
surfaces has a roughness average of four micro-inches roughness
average (Ra) or less.
17. A method of enhancing an abrasion resistance of submersible
assemblies, the method comprising: polishing one of a first running
surface of a sleeve, a second running surface of a bushing, or a
combination thereof until the one of the first running surface, the
second running surface or the combination thereof has a roughness
average of four micro-inches roughness average (Ra) or less;
coating the one of the first polished running surface, the second
polished running surface or the combination thereof with one of
titanium nitride or titanium aluminum nitride; placing the sleeve
and the bushing in an electric submersible pump (ESP) assembly
component such that the first running surface faces the second
running surface and the first running surface rotates with respect
to the second running surface; and pumping a fluid from an
underground formation to a surface location using the ESP
assembly.
18. The method of claim 17, further comprising lapping the second
running surface of the bushing.
19. The method of claim 18, wherein the second running surface is a
top of the bushing.
20. The method of claim 17, wherein the polishing comprises wetting
the one of the first running surface of the sleeve, the second
running surface of the bushing or the combination thereof with a
water slurry.
21. The method of claim 17, wherein the one of the first polished
running surface, the second polished running surface, or the
combination thereof comprises silicon carbide.
22. The method of claim 17, wherein the one of the first polished
running surface, the second polished running surface, or the
combination thereof comprises Ni-resist austenitic cast iron.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/210,068 to Lunk et al., filed Aug. 26, 2015 and
entitled "ABRASION RESISTANCE IN WELL FLUID WETTED ASSEMBLIES,"
which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the invention described herein pertain to the
field of well fluid wetted assemblies. More particularly, but not
by way of limitation, one or more embodiments of the invention
enable abrasion resistance in well fluid wetted assemblies.
[0004] 2. Description of the Related Art
[0005] Fluid containing hydrocarbons, such as oil and natural gas,
are often located in underground formations. In such situations,
the oil or gas must be pumped to the surface so that it can be
collected, separated, refined and sold. Many of these underground
formations also contain well born solids, such as consolidated and
unconsolidated sand. The hydrocarbon laden fluid must pass through
the sand on their way to the pump intake, and ultimately to the
surface. When this occurs, the hydrocarbon fluid carries some of
that sand through pump components. Such well-born solids may have
severe abrasive effects on the submersible pump components and
increase the heat generated during use, since abrasive wear to the
pump causes inefficiency in its operation. As a result, careful
attention to fluid and pressure management in submersible pump
systems is needed in order to improve the production of hydrocarbon
laden fluids from subsurface formations.
[0006] Currently available submersible pump systems are not
appropriate for some well applications, such as high sand or
engineered sand environments. For example, pump components used in
oil or gas applications should be exceptionally resistant to
erosive wear. When a pump is used in an oil or gas well, equipment
failure is especially costly as this can impede well production and
replacing parts is undesirable since the equipment is deep in the
ground. Care must be taken in cooling the pump equipment and
avoiding the damage caused by abrasive materials in the produced
well fluid.
[0007] In the case of an electric submersible pump (ESP), a failure
of the pump or any support components in the pump assembly can be
catastrophic as it means a delay in well production and having to
remove the pump from the well for repairs. Downhole applications in
particular require that ESP pumps be able to survive constant
exposure to abrasive materials in the well fluid in addition to the
heat generated when the pump is in operation. A submersible pump
system with improved thrust handling and radial support
capabilities, such as an improved ability to withstand abrasion and
heat, would be an advantage in all types of submersible and
non-submersible assemblies.
[0008] Currently available pump assemblies sometimes contain
bearing surfaces. Conventional bearing surfaces include a
conventional sleeve and a conventional bushing. The conventional
sleeve is keyed to the shaft of a submersible pump and rotates with
the shaft as fluid is pumped to the surface of a well. The
conventional bushing is pressed into the wall of the diffuser of
the submersible pump, surrounding the outer diameter of the
conventional sleeve, and does not rotate. As the shaft rotates
along with the conventional sleeve, a thin layer of fluid forms in
between the rotating conventional sleeve and conventional
non-rotating bushing, providing hydrodynamic lift. The hydrodynamic
benefits of the bearing set depend upon a tight clearance between
the conventional bushing and conventional sleeve. A problem that
arises is that when the pump is in operation, abrasive material
passes between the outer diameter of the conventional sleeve and
the inner diameter of the conventional bushing. Abrasive wear may
cause loss of material between the rotating surfaces, enlarging the
clearance, which leads to low performance. Thus, these conventional
designs are not well suited to withstand excessive abrasion in
pumping systems or to keep the bearing surfaces cool. These
shortcomings decrease the longevity of the pump components.
[0009] Currently, in order to address abrasion and heat, grooves
are sometimes added to the bearing surfaces. The grooves assist the
flow of both fluids and solids through well fluid wetted assemblies
by creating channels in the radial or thrust support surfaces.
However, as wells include increased concentrations of sand, such as
in fracing applications that employ engineered sand or other high
sand conditions, the conventional grooves may not adequately combat
abrasion and heat, reducing the lifespan of the pump.
[0010] In addition, conventional sleeves and conventional bushings
are typically made of tungsten carbide. FIG. 1A illustrates a
conventional tungsten carbide sleeve of the prior art. FIG. 1B
illustrates an enlargement of the surface of a conventional sleeve
of the prior art at one-hundred times magnification. FIG. 2
illustrates a conventional bushing of the prior art, which also
includes a surface similar to that shown in FIG. 1B. The surface of
FIG. 1B demonstrates the roughness of conventional bearing
surfaces. The surface roughness is attributable to microscopic
peaks and valleys on the surface of the material that form as the
parts are ground during fabrication. The rough surfaces increase
friction and heat production as abrasive materials flow across the
bearing surfaces. As heat accumulates during operation of the pump
and temperatures rise, the material of the conventional sleeve and
conventional bushing tends to bind or weld together. Abrasive wear
may also be a precursor to this type of welding. This binding
between the bearing material increases friction and causes the pump
to seize. Separately, when producing fluid containing slugs or high
amounts of gas, pump stages can run dry further elevating
temperatures.
[0011] Although tungsten carbide is a hard material, it is very
brittle and prone to breaking. Forming the bearings from materials
harder than tungsten carbide is not considered practical, since the
brittleness would only increase and the bearings would break during
usage under the force of the pump.
[0012] Therefore, there is a need for better abrasion resistance in
well fluid wetted assemblies to more readily withstand the effects
of well-born solids, improve cooling characteristics, reduce
friction and surface defects and combat welding (seizing), thereby
improving the lifespan of the pump and pump components in
submersible pump applications.
BRIEF SUMMARY OF THE INVENTION
[0013] Abrasion resistance in well fluid wetted assemblies is
described. An illustrative embodiment of a submersible pump bearing
set includes a rotatable sleeve comprising a first polished running
surface, a bushing surrounding the rotatable sleeve, the bushing
secured to a diffuser wall and including a second polished running
surface, wherein the second polished running surface of the bushing
faces the first running surface of the rotatable sleeve. In some
embodiments, the rotatable sleeve is a flanged sleeve including a
tubular portion and a flange extending radially from the tubular
portion, and the flange includes the first polished running
surface. In certain embodiments, the first polished running surface
and the second polished running surface are made of a cemented
carbide composite selected from the group consisting of titanium
carbide, tungsten carbide and tantalum carbide. In some
embodiments, the first polished running surface and the second
polished running surface include a coating of one of titanium
nitride or titanium aluminum nitride over each of the polished
running surfaces. In some embodiments, the first polished running
surface and the second polished running surface include a layer of
infused diamond-like carbon over each of the polished running
surfaces. In certain embodiments, the first polished running
surface and the second polished running surface include a layer of
one of polycrystalline diamond (PCD), thermally stable PCD (TSP) or
amorphous diamond over each of the polished running surfaces. In
some embodiments, the first polished running surface and the second
polished running surface have a roughness average of four
micro-inches roughness average (Ra) or less. In some embodiments,
the rotatable sleeve is keyed to an electric submersible pump (ESP)
shaft. In certain embodiments, the diffuser is in a stage of one of
an ESP pump, ESP charge pump or ESP gas separator.
[0014] An illustrative embodiment of a system for pumping a
hydrocarbon from a downhole well includes a submersible pump that
pumps a fluid hydrocarbon from a well, the submersible pump further
including a bearing set comprising a bushing and a flanged sleeve,
each of the bushing and the flanged sleeve comprising a polished
running surface, and the polished running surface of each of the
bushing and the flanged sleeve having a mirror finish. In some
embodiments, an inner diameter of the bushing includes the polished
running surface of the bushing, and an outer diameter of the
flanged sleeve includes the polished running surface of the flanged
sleeve. In certain embodiments, a bottom of a flange of the flanged
sleeve includes the polished running surface of the flanged sleeve,
and a top of the bushing includes the polished running surface of
the bushing. In some embodiments, the system includes a layer of
diamond-like carbon on the polished running surface of each of the
bushing and the flanged sleeve and the layer comprises a
diamond-like carbon film. In certain embodiments the system further
includes a coating of one of titanium nitride or titanium aluminum
nitride over each of the polished running surfaces. In some
embodiments, a load bearing surface of each of the polished running
surfaces is at least 85% of a total surface area of each of the
polished running surfaces. In certain embodiments, each of the
polished running surfaces has a roughness average of four
micro-inches roughness average (Ra) or less.
[0015] An illustrative embodiment of a method of enhancing an
abrasion resistance of submersible assemblies includes polishing
one of a first running surface of a sleeve, a second running
surface of a bushing, or a combination thereof until the one of the
first running surface, the second running surface or the
combination thereof has a roughness average of four micro-inches
roughness average (Ra) or less, coating the one of the first
polished running surface, the second polished running surface or
the combination thereof with one of titanium nitride or titanium
aluminum nitride, placing the sleeve and the bushing in an electric
submersible pump (ESP) assembly component such that the first
running surface faces the second running surface and the first
running surface rotates with respect to the second running surface,
and pumping a fluid from an underground formation to a surface
location using the ESP assembly. In some embodiments, the method
further includes lapping the second running surface of the bushing
and the second running surface is a top of the bushing. In some
embodiments, the polishing includes wetting the one of the first
running surface of the sleeve, the second running surface of the
bushing or the combination thereof with a water slurry. In certain
embodiments, the one of the first polished running surface, the
second polished running surface or the combination thereof includes
silicon carbide. In some embodiments, the one of the first polished
running surface, the second polished running surface, or the
combination thereof includes nickel-resist austenitic cast
iron.
[0016] In further embodiments, features from specific embodiments
may be combined with features from other embodiments. For example,
features from one embodiment may be combined with features from any
of the other embodiments. In further embodiments, additional
features may be added to the specific embodiments described
herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Advantages of the present invention may become apparent to
those skilled in the art with the benefit of the following detailed
description and upon reference to the accompanying drawings in
which:
[0018] FIG. 1A is a perspective view of a conventional sleeve of
the prior art.
[0019] FIG. 1B is an enlarged view of the surface of the
conventional sleeve of FIG. 1A of the prior art.
[0020] FIG. 2 is a perspective view of a conventional bushing of
the prior art.
[0021] FIG. 3A is a perspective view of a downhole electric
submersible pump (ESP) assembly of illustrative embodiments.
[0022] FIG. 3B is a perspective view of a downhole ESP assembly of
illustrative embodiments.
[0023] FIG. 4 is a cross sectional view across line 4-4 of FIG. 3A
of an electric submersible pump (ESP) of illustrative
embodiments.
[0024] FIG. 5A is a perspective view of a polished sleeve of
illustrative embodiments.
[0025] FIG. 5B is an enlarged view of a polished surface of the
sleeve of FIG. 5A of illustrative embodiments.
[0026] FIG. 6 is a perspective view of a polished bushing of
illustrative embodiments.
[0027] FIG. 7A is a perspective view of a polished and coated
sleeve of illustrative embodiments.
[0028] FIG. 7B is an enlarged view of a surface of the polished and
coated sleeve of FIG. 7A of illustrative embodiments.
[0029] FIG. 7C is a cross-sectional view across line 7C-7C of FIG.
7A of the polished and coated sleeve of illustrative
embodiments.
[0030] FIG. 7D is an enlarged view of the polished and coated
sleeve surface of FIG. 7C.
[0031] FIG. 8 is a perspective view of a polished and coated
bushing of illustrating embodiments.
[0032] FIG. 9. is a perspective view of a bearing set of an
illustrative embodiment.
[0033] FIG. 10 is a perspective view of a bearing set of an
illustrative embodiment.
[0034] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof are shown by
way of example in the drawings and may herein be described in
detail. The drawings may not be to scale. It should be understood,
however, that the embodiments described herein and shown in the
drawings are not intended to limit the invention to the particular
form disclosed, but on the contrary, the intention is to cover all
modifications, equivalents and alternatives falling within the
scope of the present invention as defined by the appended
claims.
DETAILED DESCRIPTION
[0035] Abrasion resistance in well fluid wetted assemblies will now
be described. In the following exemplary description, numerous
specific details are set forth in order to provide a more thorough
understanding of embodiments of the invention. It will be apparent,
however, to an artisan of ordinary skill that the present invention
may be practiced without incorporating all aspects of the specific
details described herein. In other instances, specific features,
quantities, or measurements well known to those of ordinary skill
in the art have not been described in detail so as not to obscure
the invention. Readers should note that although examples of the
invention are set forth herein, the claims, and the full scope of
any equivalents, are what define the metes and bounds of the
invention.
[0036] As used in this specification and the appended claims, the
singular forms "a", "an" and "the" include plural referents unless
the context clearly dictates otherwise. Thus, for example,
reference to a running surface includes one or more running
surfaces.
[0037] "Coupled" refers to either a direct connection or an
indirect connection (e.g., at least one intervening connection)
between one or more objects or components. The phrase "directly
attached" means a direct connection between objects or
components.
[0038] "Downstream" refers to the direction substantially with the
primary flow of pumped fluid when the centrifugal pump is in
operation. Thus by way of example and without limitation, in a
vertical downhole submersible pump assembly, the downstream
direction may be towards the surface of the well.
[0039] "Upstream" refers to the direction substantially opposite
the primary flow of pumped fluid when the centrifugal pump is in
operation. Thus by way of example and without limitation, in a
vertical downhole submersible pump assembly, the upstream direction
may be towards the bottom of the assembly and/or deeper in the
ground.
[0040] As used in this specification and the appended claims, the
terms "inner" and "inwards" with respect to a bearing or other pump
assembly component refer to the radial direction towards the center
of the shaft of the pump assembly and/or the center of the aperture
of the component through which the shaft would extend. In the art,
"inner diameter" and "inner circumference" are sometimes used
equivalently. As used herein, the inner diameter is used to
describe what might otherwise be called the inner circumference of
a pump assembly component, such as a bearing.
[0041] As used in this specification and the appended claims, the
terms "outer" and "outwards" with respect to a bearing or other
pump assembly component refer to the radial direction away from the
center of the shaft of the pump assembly and/or the center of the
aperture of the component through which the shaft would extend. In
the art, "outer diameter" and "outer circumference" are sometimes
used equivalently. As used herein, the outer diameter is used to
describe what might otherwise be called the outer circumference of
a bearing.
[0042] As used in this specification and the appended claims, the
term "axial" and "axially" refers to the longitudinal direction
parallel to the length of the shaft of the pump.
[0043] Illustrative embodiments of the invention described herein
provide abrasion resistance in well fluid wetted assemblies. A
submersible pump of illustrative embodiments may include one or
more thrust and/or radial support bearing sets. The bearing set of
illustrative embodiments may include a polished surface, a thin
coating (microns in thickness) of titanium nitride or titanium
aluminum nitride, and/or a layer of diamond-like carbon. The
polishing may provide one or more running surfaces of the bearings
with a mirror finish. The coating or layer may be between one and
five microns thick or may be thicker, depending on the type of
layer employed. The polishing, coating and/or layer of illustrative
embodiments may decrease friction between running surfaces and/or
increase the surface hardness of the bearings, which may improve
abrasion resistance, improve heat handling capabilities, reduce
surface defects, improve lubrication and combat welding between the
rotating member and the stationary member of the bearing set. One
or more of these features may improve the lifespan of the pump.
Although bearing sets in submersible pump applications are
conventionally made of tungsten carbide, the polishing,
diamond-like carbon layer and/or coating of illustrative
embodiments may allow a softer, less expensive material such as
steel, aluminum or plastic to be employed as a substrate for the
coating while still maintaining or improving surface hardness,
abrasion resistance and heat handling capabilities and reducing
friction between the bearings. In addition, use of a softer
substrate such as steel or aluminum may reduce the brittleness of
the bearing as compared to bearings made of tungsten carbide or
other materials of similar hardness. The polishing, coating and/or
layering of illustrative embodiments, placed on the surface of a
soft substrate, may increase the surface hardness of the bearing
while avoiding the brittleness that may occur were the entire
bearing made of a harder substance such as tungsten carbide.
[0044] While for illustration purposes, illustrative embodiments
are described herein in terms of a thrust and/or radial support
bearing set of a submersible pump, such as a mixed flow or radial
flow centrifugal pump, nothing herein is intended to limit the
invention to those embodiments. Other components of electric
submersible pump (ESP) assemblies which may include stages and/or
thrust bearings, such as a charge pump or gas separator may also
make use of the improved bearing set of illustrative embodiments.
In addition, any centrifugal pump encountering abrasive materials,
such as horizontal surface pumps, may also make use of the improved
bearing set of illustrative embodiments.
[0045] FIGS. 3A and 3B depict an exemplary ESP system arranged to
pump natural gas and/or oil from underground formation 420 and
making use of the enhanced abrasion resistance of illustrative
embodiments. As illustrated, the system of ESP assembly 400 may
include well bore casing 445 with casing perforations 450 that
allows well fluid to enter casing 445. ESP motor 440 may be a two
pole, three phase squirrel cage induction motor that operates to
turn ESP pump 410. Motor lead extension 435 and the electrical
cable above it (not shown) may connect to a power source at the
surface of the well and provide power to ESP motor 440. ESP seal
430 may supply oil to the motor and provide pressure equalization
to allow for expansion of motor oil in the well bore. As shown in
FIG. 3A, in some embodiments ESP intake 425 may serve as the intake
for fluid into ESP pump 410. As shown in FIG. 3B, in certain
embodiments gas separator 455 may serve as the intake in gassy
wells. ESP charge pump 415, which maybe a lower tandem pump, may be
employed in gassy wells. ESP pump 410 may be a multistage
centrifugal pump including impeller and diffuser stages stacked
around a shaft to lift fluid to the surface of the well. Production
tubing 405 may carry pumped fluid to piping and/or storage tanks on
the surface, for example. One or more of these system components
may make use of the enhanced abrasion resistance of the invention.
In some embodiments, the bearings of illustrative embodiments may
be employed in ESP pump 410, ESP charge pump 415, gas separator 455
and/or ESP intake 425. For example, gas separator 455 may include
impeller and diffuser stages to increase the pressure of the fluid
during compression and separation of gases. Similarly, in gassy
wells charge pump 415 may be used in tandem with a primary
centrifugal pump, such as ESP pump 410, and may also employ
stages.
[0046] FIG. 4 illustrates a cross section of one embodiment of a
pump stage of ESP pump 410 of illustrative embodiments. The pump
stage of FIG. 4 may also be a stage of ESP charge pump 415 or ESP
gas separator 455. Diffuser 500 may be paired with impeller 505 and
remain stationary while impeller 505 rotates with shaft 510.
Bushing 200 may be pressed into and/or attached to the wall of
diffuser 500 and may remain stationary during operation of ESP pump
410, for example by interference fit. Sleeve 300 may be keyed to
shaft 510 and may rotate with shaft 510 when ESP pump 410 is in
operation. When ESP pump 410 is in operation and shaft 510 rotates
in a clockwise direction, pumped fluid and abrasive solids carried
therein may be guided between the outer diameter of sleeve 300 and
the inner diameter of bushing 200, as illustrated by axial arrow
530 and radial arrow 540. In grooved embodiments, axial groove (not
shown) and radial groove 230 may assist in guiding pumped fluid
between running surfaces 700 (shown in FIG. 9) of the bearings. As
illustrated in FIG. 4, pumped fluid is moving upward to a
successive stage of ESP pump 410 and/or production tubing 405.
Abrasives may be carried along with the flow of well fluid as shown
in FIG. 4 and/or may fall back to a previous stage in a direction
opposite arrows 530 and 540.
[0047] The surfaces of sleeve 300 and/or bushing 200 of
illustrative embodiments may be polished, infused with a layer of
diamond-like carbon and/or coated with titanium nitride or titanium
aluminum nitride, for example as illustrated by layer 100 shown in
FIG. 7B and/or polished surface 600 as shown in FIG. 5B. The
coating or layer of illustrative embodiments may permit softer,
less expensive materials (as compared to tungsten carbide) to be
used as the substrate material of the bearings of illustrative
embodiments. For example, steel, aluminum, plastic such as nylon or
polycarbonate, composites such as zirconia or Alumina, or
nickel-resist (Ni-resist) austenitic cast iron may be used as the
substrate underneath layer 100 of illustrative embodiments.
[0048] Running surfaces 700 may be sliding surfaces of bushing 200
and sleeve 300 that face each other and have different velocities
relative to one another. As shown in FIG. 9 and FIG. 10, running
surfaces 700 may include the inner diameter 910 of bushing 200, the
top 915 of bushing 200, the outer diameter 905 of sleeve 300 and/or
the bottom 900 of flange 105 of sleeve 300. In some embodiments,
bearing surfaces that are not running surfaces, such as the inner
diameter of sleeve 300 facing shaft 510 as well as the outer
diameter of bushing 200 pressed into diffuser 500, need not be
polished and/or need not include layer 100. However, in
illustrative embodiments it may be less labor intensive and
therefore more time and cost effective to polish, coat and/or
infuse all surfaces of the bearings. In some embodiments, it may
reduce fit-up issues to leave keyway 110 or inside diameter of
sleeve 300 facing shaft 510 (shown in FIG. 4) uncoated and/or
reserve coating or layering for running surfaces 700. FIGS. 9 and
10 illustrate running surfaces 700 of bushing 200 and sleeve 300
forming a bearing set and including layer 100 of illustrative
embodiments only on running surfaces 700. In FIGS. 9 and 10,
surfaces that are not running surfaces 700 do not include layer
100.
[0049] FIGS. 5A and 7A illustrate an exemplary sleeve 300 of
illustrative embodiments. FIGS. 6 and 8 illustrate an exemplary
bushing 200 of illustrative embodiments. Sleeve 300 may be tubular
in shape and may include flange 105, for example for thrust
support. The outer diameter 905 of sleeve 300 facing bushing 200
and/or the inner diameter 910 of bushing 200 facing sleeve 300, may
include intersecting grooves that may assist and/or guide the flow
of working fluid, and abrasive solids that may be contained
therein, across the surfaces of the bearings, for example as
described in U.S. Pat. No. 8,684,679 that is assigned to the
assignee of the present application and hereby incorporated by
reference in its entirety, and/or as illustrated by radial groove
230 (shown in FIG. 6). In grooved embodiments, axial, radial and/or
sector grooves may be applied to the running surfaces 700 of the
bearings during the casting process and/or ground in place prior to
polishing and prior to the application of layer 100.
[0050] The surface and/or running surfaces 700 of bushing 200
and/or sleeve 300 may be polished, as illustrated in FIGS. 5A-6.
Bushing 200 may be annular and/or cylindrical in shape. Similarly,
sleeve 300 may include a tubular portion and/or have a hollowed
cylindrical shape. The inventors have determined that the
cylindrical surfaces of bushing 200 and/or sleeve 300, including
inner diameters, may be polished using the methods of illustrative
embodiments described herein. The surface of bushing 200 and/or
sleeve 300 may be first polished and then coated or layered, may be
first coated or layered and then polished, may be polished without
the need for any coating or layer, or may be coated or layered
without the need for polishing. Polishing bearing surfaces may
improve surface finish, remove surface defects, increase
lubrication and/or provide a lower friction coefficient between the
bearings. FIG. 5B illustrates a polished surface of illustrative
embodiments at one-hundred times magnification. As shown in FIG.
5B, polished surface 600 may have peaks removed on the ground
surface to produce plateaus that increase the bearing surface area
that is load bearing. In one example, the load bearing surface area
of running surfaces 700 may be increased to 85%, 92% or 95%, as
compared to 50% or less in conventional bearings that are not
polished, since polishing may reduce the valley area on the surface
of the bearing. Although surface 600 of sleeve 300 is shown in FIG.
5B, the surface and/or running surfaces 700 of bushing 200 may be
similarly polished and appear similarly to the surface shown in
FIG. 5B.
[0051] In contrast to grinding, which produces a crude surface of
about 32 micro-inches roughness average (Ra) on a tungsten carbide
bearing, polishing may produce a much finer, smoother surface
and/or mirror finish. For example, polished surface 600 of
illustrative embodiments may have a roughness average of about 4.0
micro-inches Ra. In some embodiments, layer 100 applied to polished
surfaces 600 may further reduce the roughness average to about 3.0
micro-inches Ra. Polished surface(s) 600 may lower the coefficient
of friction between bushing 200 and sleeve 300, reducing the
horsepower (hp) needed to operate ESP pump 410. In one example, a
floater style pump may require 10 hp if no abrasion resistant (AR)
trim is present in the pump. Adding conventional AR components,
such as a conventional bushing and conventional sleeve, may
increase the necessary horsepower to 12 hp as a result of friction
between the convention bushing and conventional sleeve. Using the
polishing and/or coating of illustrative embodiments, the floater
style pump of this example may only require 10.5 hp making use of
polished and/or coated sleeve 300 and/or bushing 200 of
illustrative embodiments. Thus, polished surface 600 and/or layer
100 of illustrative embodiments may reduce the horsepower needed to
operate a pump employing AR trim.
[0052] Polishing may be accomplished by chemical, mechanical,
chemical-mechanical polishing or another polishing method known to
those of skill in the art. In some embodiments, surfaces may be
polished to a mirror finish. In one example, the bearing surfaces
may be wetted with a water slurry containing an abrasive material,
such as a colloidal silicon dioxide dispersed in water, aluminum
oxide and silicon carbide in an aqueous slurry, and/or pressure
against a firm surface. In some embodiments, diamond polishing
pads, a suspension of diamond paste and/or a spinning wheel may be
used to polish bearing surfaces. In another example, fluid-pressure
regulated wafer polishing may be employed. Lapping may be employed
in addition to polishing on bearing surfaces. For example, the top
of bushing 200 and/or bottom of sleeve 300 may be lapped to further
improve surface finish. Lapping of the bearing surfaces may use
progressively smaller diamond grit suspended in a glycol, glycerine
or other suitable carrier liquid. Polishing the bearings may remove
surface defects, improve surface finish and provide a lower
friction coefficient for the bearing. Polishing, lapping, layering
and/or coating the bearings may reduce the sliding coefficient of
friction between the bearings.
[0053] Illustrative embodiments may provide for a titanium nitride
coating, aluminum titanium nitride coating or infused diamond-like
carbon (DLC) layer on the surface of bushing 200 and/or sleeve 300.
Layer 100 may be applied to polished surfaces 600, unpolished
surfaces and/or surfaces may be polished after layer 100 has been
applied. In some embodiments, one of polishing or coating may not
be necessary. The layer or coating of illustrative embodiments may
increase the surface hardness of the bearings and/or allow the
bearing substrate to be of a softer, less expensive and/or more
ductile material as compared to tungsten carbide--without
sacrificing surface hardness, and in some embodiments, increasing
surface hardness. The hard layer or coating of illustrative
embodiments may assist in reducing surface defects increasing
lubrication and reducing welding between sleeve 300 and bushing
200. In diamond-like carbon film or infusion embodiments, the
diamond-like coating may expand with the substrate material during
temperature changes, thereby further increasing options for
substrate materials. Although polishing may be conducted after
layer 100 has been applied, the inventors currently prefer
polishing without the need for layer 100, or alternatively
polishing prior to application of layer 100 in order to obtain
polished surface 600 without losing a portion of layer 100 in the
polishing process.
[0054] Bushing 200 and/or sleeve 300 may be made of a cemented
carbide composite, such as titanium carbide, tungsten carbide or
tantalum carbide, another carbide such as silicon carbide, or
another material having similar hardness and abrasion resistant
properties. In some embodiments, bushing 200 and/or sleeve 300 may
include layer 100 of illustrative embodiments and be made of a
softer substrate 705 material such as plastic, steel, aluminum or
Ni-resist austenitic cast iron that would otherwise be too soft to
function as abrasion resistant trim in ESP applications.
[0055] FIGS. 7A-8 illustrate an exemplary coating or layer of
illustrative embodiments. Layer 100 may be a thin infusion, coating
and/or film of titanium nitride (TiN), aluminum titanium nitride
(AlTiN) or diamond-like carbon (DLC) between about one and five
microns in thickness. FIGS. 7C and 7D illustrate a cross section
view of an illustrative embodiment of layer 100. In FIG. 7D, layer
100 is shown on polished surface 600 of substrate 705. Layer 100
may provide a separation in surface hardness which may reduce
binding between sleeve 300 and bushing 200. DLC coating may be a
carbon compound having a combination of SP.sup.2 (graphite) and
SP.sup.3 (diamond) carbon bonding and varying hydrogen content.
Films with a higher SP.sup.3 bonding content may be harder with a
high level of abrasion resistance, but may be less ductile than
films with higher SP.sup.2 bonding content. DLC coating of
illustrative embodiments should have similar or slightly higher
hardness to titanium nitride at about 2500 on the Vickers scale,
and a friction coefficient of DLC against DLC of about 0.15.
Titanium nitride (TiN), on the other hand, may have a TiN on TiN
friction coefficient of about 0.4-0.9. In some embodiments, DLC may
be employed as layer 100 without modification to sleeve 300 and
bushing 200, due to the thinness of a DLC layer.
[0056] In certain embodiments, poly crystalline diamond (PCD),
thermally stable PCD (TSP) or amorphous diamond may be employed as
layer 100. PCD, TSP or amorphous diamond may be a coating of
between about 0.06 inches and 0.09 inches in thickness, and may be
brazed to keep layer 100 in place. Due to the thickness of PCD, TSP
and/or amorphous diamond coatings, sleeve 300 and bushing 200 may
need to be modified such as by removing material, to accommodate
the extra thickness added by layer 100.
[0057] Layer 100 may be applied using physical vapor deposition,
plasma-assisted chemical vapor deposition, or a similar process. In
one example, layer 100, whether DLC, AlTiN or TiN, may be applied
to substrate 705 using physical vapor deposition in a vacuum at
350.degree. C. In another example, layer 100 may be applied to
substrate 705 using plasma-assisted chemical vapor deposition at
180.degree. C. with a plasma nitride surface layer that is then
overlaid with physical vapor deposition of DLC.
[0058] In some embodiments layer 100 may be a PCD layer deposited
onto substrate 705 with the use of binder-catalyzing materials, for
example cobalt, nickel or iron. The catalyzing material may assist
in the formation of carbon-carbon bonds within layer 100 and
improve adherence of layer 100 to substrate 705. After deposition,
residual particles of binder-catalyzing materials may remain in
interstices and/or interstitial matrices interposed between PCD
particles. Above temperatures of about 750.degree. C., such as may
occur if the ESP assembly runs dry, layer 100 that includes a PCD
layer may suffer from differential thermal expansion between
catalyst and diamond particles in layer 100. In such instances
and/or in instances where the presence of binder-catalyzing
materials is undesirable, TSP may be utilized for layer 100. In
layer 100 including TSP, the binder-catalyzing material may be
removed from layer 100 by leaching.
[0059] PCD layer 100 having residual binder-catalyzing material
contained in the diamond structure's interstitial spaces may
undergo leaching to remove some, all, or about all, catalyst
impurities. A strong acid (like hydrofluoric acid or nitric acid)
or a combination of strong acids may be used as a leaching agent
that may remove binder-catalyzing material from PCD layer 100. Once
substantially free of such catalyst particles, layer 100 including
PCD becomes instead TSP. Layer 100 including TSP may withstand
operating temperatures of up to 1200.degree. C. In other
illustrative embodiments, the catalyst leaching process may be
performed with varying temperature and pressure conditions to
control the extent of catalyst removal and eventual physical
properties of the layer. In some illustrative embodiments, catalyst
particles may be leached from interstitial spaces and then replaced
with a similar, diamond-like material. In other illustrative
embodiments, the binder-catalyst may be removed by evaporation, or
galvanic means instead of acid etch leaching, as described
herein.
[0060] Leaching may also be applied to layer 100 including various
nitrides in order to remove other impurities that may have
accumulated during the deposition process. Removal of such
impurities may improve the homogeneity of layer 100, which may
prevent differential thermal expansion between different materials
contained in the layer.
[0061] FIG. 7B illustrates an enlarged view of layer 100 of
illustrative embodiments. In FIG. 7B, the enlarged surface of
sleeve 300 is shown, but the surface of bushing 200 may appear
similarly. Layer 100 of illustrative embodiments adhered to
substrate 705 may increase the operating life of the bearings in a
submersible pump in both benign and abrasive heavy environments.
The increased hardness that may be afforded by layer 100 may lower
the cost of the bearings since softer, cheaper materials such as
aluminum or steel may then be used as the base material for the
bearing, and then coated to increase surface hardness. The
substrate material may then be less fragile than conventional
bearing materials such as tungsten carbide, and as a result of the
coating of illustrative embodiments, still achieve surface hardness
to combat abrasion and increase the life of the pump.
[0062] The coating and/or polishing of illustrative embodiments may
reduce friction between the bearings, provide a lubrication barrier
that may prevent reduce friction and necessary horsepower, reduce
binding/welding, reduce surface defects and improve lubrication and
resistance to solids. The bonding shear strength of layer 100 may
be high and thus may not rub off during operation. The improved
features of illustrative embodiments may improve the lifespan of an
ESP pump making use of the bearings of illustrative
embodiments.
[0063] Thus, the invention described herein provides one or more
embodiments of abrasion resistance in well fluid wetted assemblies.
Further modifications and alternative embodiments of various
aspects of the invention may be apparent to those skilled in the
art in view of this description. Accordingly, this description is
to be construed as illustrative only and is for the purpose of
teaching those skilled in the art the general manner of carrying
out the invention. It is to be understood that the forms of the
invention shown and described herein are to be taken as the
presently preferred embodiments. Elements and materials may be
substituted for those illustrated and described herein, parts and
processes may be reversed, and certain features of the invention
may be utilized independently, all as would be apparent to one
skilled in the art after having the benefit of this description of
the invention. Changes may be made in the elements described herein
without departing from the scope and range of equivalents as
described in the following claims. In addition, it is to be
understood that features described herein independently may, in
certain embodiments, be combined.
* * * * *