Note: Descriptions are shown in the official language in which they were submitted.
CA 02940395 2016-08-26
[001] ABRASION RESISTANCE IN WELL FLUID WETTED ASSEMBLIES
[002] BACKGROUND OF THE INVENTION
[003] 1. FIELD OF THE INVENTION
[004] Embodiments of the invention described herein pertain to the field of
well fluid wetted
assemblies.
[005] More particularly, but not by way of limitation, one or more embodiments
of the invention
enable abrasion resistance in well fluid wetted assemblies.
[006] 2. DESCRIPTION OF THE RELATED ART
[007] 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.
[008] 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.
[009] 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.
[0010] Currently available pump assemblies sometimes contain bearing surfaces.
Conventional
1
CA 02940395 2016-08-26
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.
[0011] 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.
[0012] 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.
[0013] Although tungsten carbide is a hard material, it is very brittle and
prone to breaking. Forming
2
CA 02940395 2016-08-26
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.
[0014] 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
[0015] 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.
[0016] 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
3
CA 02940395 2016-08-26
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.
[0017] 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.
[0018] 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.
4
CA 02940395 2016-08-26
[0019] BRIEF DESCRIPTION OF THE DRAWINGS
[0020] 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:
[0021] FIG. lA is a perspective view of a conventional sleeve of the prior
art.
[0022] FIG. 1B is an enlarged view of the surface of the conventional sleeve
of FIG. 1 A of the prior
art.
[0023] FIG. 2 is a perspective view of a conventional bushing of the prior
art.
[0024] FIG. 3A is a perspective view of a downhole electric submersible pump
(ESP) assembly of
illustrative embodiments.
[0025] FIG. 3B is a perspective view of a downhole ESP assembly of
illustrative embodiments.
[0026] FIG. 4 is a cross sectional view across line 4-4 of FIG. 3A of an
electric submersible pump
(ESP) of illustrative embodiments.
[0027] FIG. 5A is a perspective view of a polished sleeve of illustrative
embodiments.
[0028] FIG. 5B is an enlarged view of a polished surface of the sleeve of FIG.
5A of illustrative
embodiments.
[0029] FIG. 6 is a perspective view of a polished bushing of illustrative
embodiments.
[0030] FIG. 7A is a perspective view of a polished and coated sleeve of
illustrative embodiments.
[0031] FIG. 7B is an enlarged view of a surface of the polished and coated
sleeve of FIG. 7A of
illustrative embodiments.
[0032] FIG. 7C is a cross-sectional view across line 7C-7C of FIG. 7A of the
polished and coated
sleeve of illustrative embodiments.
[0033] FIG. 7D is an enlarged view of the polished and coated sleeve surface
of FIG. 7C.
[0034] FIG. 8 is a perspective view of a polished and coated bushing of
illustrating embodiments.
[0035] FIG 9. is a perspective view of a bearing set of an illustrative
embodiment.
[0036] FIG. 10 is a perspective view of a bearing set of an illustrative
embodiment.
[0037] 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.
CA 02940395 2016-08-26
DETAILED DESCRIPTION
[0038] 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.
[0039] 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.
[0040] "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.
[0041] "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.
[0042] "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.
[0043] 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.
[0044] 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
6
CA 02940395 2016-08-26
used equivalently. As used herein, the outer diameter is used to describe what
might otherwise be
called the outer circumference of a bearing.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] FIGs. 3A and 3B depict an exemplary ESP system arranged to pump natural
gas and/or oil
7
CA 02940395 2016-08-26
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.
100491 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.
8
CA 02940395 2016-08-26
[0050] 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.
[0051] 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.
[0052] 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. Patent
No. 8,684,679 that is assigned to the assignee of the present application,
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.
9
CA 02940395 2016-08-26
[0053] 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.
[0054] 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
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.
[0055] 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
CA 02940395 2016-08-26
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.
[0056] 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.
[0057] 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.
11
CA 02940395 2016-08-26
[0058] 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. FIG. 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 SP2 (graphite) and SP3 (diamond)
carbon bonding and
varying hydrogen content. Films with a higher SP3 bonding content may be
harder with a high level
of abrasion resistance, but may be less ductile than films with higher SP2
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.
[0059] 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.
[0060] 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
C. In another example,
layer 100 may be applied to substrate 705 using plasma-assisted chemical vapor
deposition at 180 C
with a plasma nitride surface layer that is then overlaid with physical vapor
deposition of DLC.
[0061] 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 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,
12
CA 02940395 2016-08-26
TSP may be utilized for layer 100. In layer 100 including TSP, the binder-
catalyzing material may be
removed from layer 100 by leaching.
[0062] 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 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.
[0063] 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.
[0064] 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.
[0065] 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.
13
CA 02940395 2016-08-26
[0066] 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 of the
following claims. In addition, it is to be understood that features described
herein independently may,
in certain embodiments, be combined.
14
