U.S. patent application number 13/801969 was filed with the patent office on 2014-01-30 for apparatus, system and method for pumping gaseous fluid.
This patent application is currently assigned to SUMMIT ESP, LLC. Invention is credited to Shiv Jayaram, Steven Keith Tetzlaff.
Application Number | 20140030055 13/801969 |
Document ID | / |
Family ID | 49995046 |
Filed Date | 2014-01-30 |
United States Patent
Application |
20140030055 |
Kind Code |
A1 |
Jayaram; Shiv ; et
al. |
January 30, 2014 |
APPARATUS, SYSTEM AND METHOD FOR PUMPING GASEOUS FLUID
Abstract
An apparatus, system and method for pumping gaseous fluid are
described. The centrifugal pump of the invention homogenizes at
least a portion of the gas and liquid contained in produced well
fluid thereby improving the efficiency of the pump in electric
submersible pump (ESP) applications and decreasing the downtime of
the ESP system. The impeller of the invention comprises an
increased inlet area. The centrifugal pump of the invention
comprises a single shroud located on the bottom side of an
impeller, an increased inlet area of the impeller and an increased
clearance gap between the impeller and a diffuser. One or more
truncated vanes extend substantially upstream from the single
shroud, wherein each truncated vane sits at a mid-pitch location
between untruncated vanes starting from the bottom side of the
impeller.
Inventors: |
Jayaram; Shiv; (Houston,
TX) ; Tetzlaff; Steven Keith; (Owasso, OK) |
Assignee: |
SUMMIT ESP, LLC
Tulsa
OK
|
Family ID: |
49995046 |
Appl. No.: |
13/801969 |
Filed: |
March 13, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61675578 |
Jul 25, 2012 |
|
|
|
Current U.S.
Class: |
415/1 ; 415/207;
416/223R |
Current CPC
Class: |
F04D 31/00 20130101;
F04D 1/04 20130101; F04D 1/00 20130101; F04D 29/2238 20130101; F04D
13/10 20130101; F04D 29/18 20130101 |
Class at
Publication: |
415/1 ;
416/223.R; 415/207 |
International
Class: |
F04D 1/00 20060101
F04D001/00 |
Claims
1. An impeller for an electric submersible pump assembly comprising
an increased inlet area.
2. The impeller of claim 1, wherein the increased inlet area is
between about 1.75 and about 2.5 times an inlet area of a
conventional inlet area.
3. The impeller of claim 1, further comprising a single shroud
located on a bottom side of an impeller.
4. The impeller of claim 3, wherein the single shroud extends
radially about a hub.
5. The impeller of claim 3, further comprising at least two
untruncated vanes extending substantially upstream from the single
shroud and at least two truncated vanes extending substantially
upstream from the single shroud, wherein each truncated vane sits
at a mid-pitch location between untruncated vanes starting from the
bottom side of the impeller.
6. The impeller of claim 5, wherein the truncated vanes are between
about 50% and about 75% of a chord length of the untruncated
vanes.
7. The impeller of claim 5, wherein the truncated vanes are
undivided.
8. The impeller of claim 5, comprising three truncated vanes and
three untruncated vanes.
9. The impeller of claim 5, comprising two truncated vanes and two
untruncated vanes.
10. The impeller of claim 5, comprising four truncated vanes and
four untruncated vanes.
11. The impeller of claim 1, further comprising an increased
clearance gap between an impeller and a diffuser.
12. The impeller of claim 11, wherein the increased clearance gap
is between about 0.060 inches and about 0.180 inches wide.
13. The impeller of claim 1, wherein an impeller is configured to
operate at about 8000 to about 12000 suction specific speed.
14. A centrifugal pump comprising: an impeller inward of a
diffuser, the impeller comprising a top side and a bottom side, the
top side open to the diffuser, and wherein the impeller further
comprises: a single shroud located on the bottom side of the
impeller and arranged radially about a hub; an untruncated vane
extending substantially upstream from the single shroud; and a
truncated vane extending substantially upstream from the single
shroud; and an increased clearance gap between the impeller and the
diffuser.
15. The centrifugal pump of claim 14, wherein there are at least
two untruncated vanes and wherein the truncated vane sits at a
mid-pitch location between the at least two untruncated vanes.
16. The centrifugal pump of claim 15, wherein there are three
untruncated vanes and three truncated vanes, and wherein each
truncated vane sits at a mid-pitch location between the untruncated
vanes.
17. The centrifugal pump of claim 14, wherein the increased
clearance gap is between about 0.060 inches and about 0.180 inches
wide.
18. The centrifugal pump of claim 14, wherein the truncated vane is
between about 50% and about 75% of a chord length of the
untruncated vane.
19. The centrifugal pump of claim 14, further comprising a bushing
and a flanged sleeve located directly upstream of the hub.
20. The centrifugal pump of claim 14, further comprising a bushing
and a flanged sleeve located directly downstream of the hub.
21. The centrifugal pump of claim 14, further comprising a first
bushing and a first flanged sleeve, wherein the first bushing and
the first flanged sleeve are located directly upstream of the hub,
and a second bushing and a second flanged sleeve, wherein the
second bushing and second flanged sleeve are located directly
downstream of the hub.
22. The centrifugal pump of claim 21, wherein the bushings and
flanged sleeves comprise tungsten carbide.
23. A method for pumping gaseous fluid comprising: placing a
centrifugal pump into a well containing gaseous fluid; operating
the pump to induce the fluid to flow towards the surface of the
well; causing at least a portion of the fluid to flow through an
increased clearance gap between an impeller and a diffuser; and
minimizing phase separation of the fluid by reducing a pressure
differential between a pressure side and a suction side of an
impeller vane.
24. The method of claim 23, wherein the pressure differential is
reduced by increasing an inlet area of the impeller.
25. The method of claim 24, wherein the inlet area is increased by
replacing the impeller vane with a truncated vane.
26. The method of claim 25, wherein the impeller comprises at least
two untruncated vanes, and wherein the truncated vane is placed at
a mid-pitch location between the at least two untruncated vanes
starting from a bottom side of the impeller.
27. The method of claim 23, further comprising the step of carrying
at least a portion of the axial thrust on the centrifugal pump with
a flanged sleeve and a bushing located directly upstream of the
impeller.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/675,578 to Jayaram et al., filed Jul. 25, 2012
and entitled "APPARATUS, SYSTEM AND METHOD FOR PUMPING GASEOUS
FLUID," 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 electric submersible pumps. More particularly, but not by
way of limitation, one or more embodiments of the invention enable
an apparatus, system and method for pumping gaseous fluid in
electric submersible pump down-hole applications.
[0004] 2. Description of the Related Art
[0005] Fluid, such as gas, oil or water, is often located in
underground formations. In such situations, the fluid must be
pumped to the surface so that it can be collected, separated,
refined, distributed and/or sold. Centrifugal pumps are typically
used in electric submersible pump applications for lifting well
fluid to the surface. Centrifugal pumps impart energy to a fluid by
accelerating the fluid through a rotating impeller paired with a
stationary diffuser. The rotation confers angular momentum to the
fluid passing through the pump. The angular momentum converts
kinetic energy into pressure, thereby raising the pressure on the
fluid and lifting it to the surface. Multiple stages of impeller
and diffuser pairs may be used to further increase the
pressure.
[0006] Conventional centrifugal pumps are designed to handle fluid
consisting mainly of liquids. However well fluid often contains gas
in addition to liquid. Currently available submersible pump systems
are not appropriate for pumping fluid with a high gas to liquid
ratio. Particularly, submersible pump systems need to be better
suited to manage gas contained in well fluid. When pumping gas
laden fluid, the gas may separate from the other fluid due to the
pressure differential created when the pump is in operation. If
there is a sufficiently high gas volume fraction, typically around
10% to 15%, the pump may experience a decrease in efficiency and
decrease in capacity or head (slipping). If gas continues to
accumulate on the suction side of the impeller it may entirely
block the passage of other fluid through the impeller. When this
occurs the pump is said to be "gas locked" since proper operation
of the pump is impeded by the accumulation of gas. As a result,
careful attention to gas management in submersible pump systems is
needed in order to improve the production of gas laden fluid from
subsurface formations.
[0007] A typical impeller of a centrifugal pump is shown in FIGS.
1A and 1B. In FIG. 1A, closed impeller 100 is shown with six evenly
spaced conventional vanes 105. For illustration purposes only,
upper conventional shroud 110 and lower conventional shroud 115 are
shown in FIG. 1B, but are not shown in FIG. 1A. FIG. 1B shows a
cross sectional view of closed impeller 100 with two conventional
shrouds, upper conventional shroud 110 and lower conventional
shroud 115. In FIG. 1B, conventional hub 125 is long and hollow and
connected to lower conventional shroud 115, upper conventional
shroud 110 and conventional vanes 105. Conventional hub 125 slides
over conventional shaft 130 and is keyed to conventional shaft 130,
which causes closed impeller 100 to rotate with conventional shaft
130. Closed impeller 100 rotates counterclockwise or clockwise with
shaft 130. Apertures 120 (shown in FIG. 1A) balance the pressure on
each side of closed impeller 100. Conventional closed impeller 100
has a suction specific speed of about 6000.
[0008] Closed impeller 100 is paired with a conventional stationary
diffuser, such as that shown in FIG. 2, such that each impeller
rotates within (inward of) the diffuser to which it is paired. The
diffuser does not rotate, but is mounted co-axially with the
impeller and nests on the diffuser of the previous stage. Typically
there is a clearance gap between the diffuser and impeller to which
it is paired. This conventional clearance gap is typically about
0.015 inches to about 0.02 inches in width for conventional
semi-open impellers.
[0009] Currently, gas separators are sometimes used in an attempt
to address the problems caused by gas in produced fluid. Gas
separators attempt to remove gas from produced fluid prior to the
fluid's entry into the pump. However it is often infeasible, costly
or too time consuming to ascertain the correct type of pump and
separator combination which might be effective for a particular
well, and even if the correct arrangement is ascertained, the
separator may not remove enough gas to prevent a loss in efficiency
and/or prevent gas locking.
[0010] 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. A submersible pump
system capable of homogenizing produced gaseous fluid would be an
advantage in all types of submersible assemblies.
[0011] Currently available pump assemblies do not contain
components to satisfactorily homogenize gas laden fluid and prevent
gas locking This shortcoming decreases the efficiency and overall
effectiveness of the pump assembly. Therefore, there is a need for
an apparatus, system and method for pumping gaseous fluid in
electric submersible pump applications.
BRIEF SUMMARY OF THE INVENTION
[0012] One or more embodiments of the invention enable an
apparatus, system and method for pumping gaseous fluid.
[0013] An apparatus, system and method for pumping gaseous fluid
are described. The impeller of an illustrative embodiment comprises
an increased inlet area. In some embodiments, the increased inlet
area is between about 1.75 and about 2.5 times the size of an inlet
area of a conventional impeller. In some embodiments, the impeller
comprises a single shroud located on a bottom side of the impeller.
In some embodiments, at least two untruncated vanes extend
substantially upstream from the single shroud, and at least two
truncated vanes extend substantially upstream from the single
shroud, wherein each truncated vane sits at a mid-pitch location
between untruncated vanes starting from the bottom side of the
impeller. In some embodiments, the truncated vanes are between
about 50% and about 75% of the chord length of the untruncated
vanes. In some embodiments, the single shroud extends radially
about a hub. In certain embodiments the suction specific speed of
the impeller is between about 8000 to about 12000.
[0014] The centrifugal pump of an illustrative embodiment comprises
an impeller inward of a diffuser and an increased clearance gap
between the impeller and the diffuser, the impeller comprising a
top side and a bottom side, wherein the top side is open to the
diffuser, and wherein the impeller further comprises a single
shroud located on the bottom side of the impeller and arranged
radially about a hub, an untruncated vane extending substantially
upstream from the single shroud, and a truncated vane extending
substantially upstream from the single shroud. In some embodiments
there are at least two untruncated vanes, wherein a truncated vane
sits at a mid-pitch location between the at least two untruncated
vanes starting from the bottom side of the impeller. In certain
embodiments, the increased clearance gap is between about 0.060
inches and about 0.180 inches wide.
[0015] The method of an illustrative embodiment may include a
method for pumping gaseous fluid comprising placing a centrifugal
pump into a well containing gaseous fluid, operating the pump to
induce the fluid to flow towards the surface of the well, causing
at least a portion of the fluid to flow through an increased
clearance gap between an impeller and a diffuser, and minimizing
phase separation of the fluid by reducing a pressure differential
between a pressure side and a suction side of an impeller vane. In
some embodiments the phase separation of the fluid is minimized by
an impeller with an increased inlet area. In some embodiments, the
inlet area is increased by replacing an impeller vane with a
truncated vane.
[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] The above and other aspects, features and advantages of the
illustrative embodiments will be more apparent from the following
more particular description thereof, presented in conjunction with
the following drawings wherein:
[0018] FIG. 1A illustrates a plan view of an impeller of the prior
art.
[0019] FIG. 1B illustrates a cross sectional view of an impeller of
the prior art.
[0020] FIG. 2 illustrates a perspective view of a diffuser of the
prior art.
[0021] FIG. 3 illustrates one embodiment of an exemplary electric
submersible pump (ESP) system.
[0022] FIG. 4A illustrates a perspective view of one embodiment of
a semi-open impeller.
[0023] FIG. 4B illustrates a perspective view of one embodiment of
a semi-open impeller.
[0024] FIG. 5 is a partial cross sectional view taken along line
5-5 of FIG. 3 of one embodiment of an impeller.
[0025] FIG. 6 is a cross sectional view taken along line 6-6 of
FIG. 3 of one embodiment of a centrifugal pump.
[0026] FIG. 6A is an enlarged view of one embodiment of the inlet
area of a centrifugal pump.
[0027] FIG. 7 is a flow chart illustrating an exemplary method of
pumping gaseous fluid.
[0028] 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 depicted 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
spirit and scope of the present invention as defined by the
appended claims.
DETAILED DESCRIPTION
[0029] An apparatus, system and method for pumping gaseous fluid
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.
[0030] 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 vane includes one or more vanes.
[0031] "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.
[0032] "Bottom" or "lower" side of an impeller refers to the
substantially downstream side of an impeller.
[0033] "Top" or "upper" side of an impeller refers to the
substantially upstream side of an impeller.
[0034] "Downstream" refers to the direction substantially with the
primary flow of fluid when the centrifugal pump is in
operation.
[0035] "Upstream" refers to the direction substantially opposite
the primary flow of fluid when the centrifugal pump is in
operation.
[0036] One or more embodiments of the invention provide an
apparatus, system and method for pumping gaseous fluid for use in
electric submersible pump applications. While the invention is
described in terms of an oil or water production embodiment,
nothing herein is intended to limit the invention to that
embodiment.
[0037] The invention disclosed herein includes an apparatus, system
and method for pumping gaseous fluid. In some embodiments, after
intake into the pump assembly, gas laden fluid may be rotated by a
centrifugal pump including a semi-open impeller. In some
embodiments, the semi-open impeller includes only a single shroud
arranged radially about a hub. In some embodiments, a truncated
vane and an untruncated vane, which may be arranged
circumferentially about the hub, may extend substantially upstream
from the single shroud. In some embodiments, the truncated vane may
be located at a mid-pitch location between two untruncated vanes
starting from the bottom side of the impeller. In certain
embodiments, the impeller may include two, three or four of each
truncated and untruncated vanes which alternate around the hub. In
some embodiments, the impeller may include an increased inlet area.
In some embodiments, there may be an increased clearance gap
between the impeller and a diffuser, through which the fluid may
flow. The features of the invention may minimize phase separation
of the fluid by reducing the pressure differential between the
pressure side and suction side of an impeller vane. This may
homogenize the liquid and gas in the fluid, increase the efficiency
and performance of the pump, prevent gas locking and reduce the
producing well's downtime.
[0038] In some embodiments, the vanes of the present disclosure are
arranged such that there is a larger inlet area of the impeller
than in conventional impeller designs. Specifically, the reduction
in the number of untruncated vanes and addition of one or more
truncated vanes of the present disclosure provide for additional
open space in the inlet region of the impeller. The impeller of an
illustrative embodiment may have between about 1.75 and 2.5 times
the size of the inlet area of a conventional impeller. The
additional open space may reduce the velocity of the fluid passing
through the impeller, which assists in maintaining high positive
pressure at the impeller inlet. The impeller of the present
disclosure is capable of operating with higher suction specific
speed as compared to conventional impellers. In some embodiments,
the impeller of the present disclosure may operate at about 8000 to
about 12000 suction specific speed.
[0039] The invention includes a centrifugal pump for electric
submersible pump (ESP) systems. FIG. 3 illustrates one embodiment
of an exemplary ESP assembly for use in the system of the
invention. This assembly may be located in an underground well
during operation. In FIG. 3, the centrifugal pump of an
illustrative embodiment comprises ESP charge pump 200, which is
located downstream of ESP intake 210. As shown in in FIG. 3, fluid
enters the ESP assembly through fluid intakes 215 on ESP intake
210. ESP charge pump 200 may homogenize fluid prior to the fluid
entering ESP primary pump 220.
[0040] In some embodiments, a gas separator (not shown) may be
located between ESP intake 210 and ESP charge pump 200 to reduce
the gas content of the fluid prior to the fluid entering ESP
primary pump 220. When used, the gas separator may be the intake
surface for the ESP pump system. In certain embodiments, the
centrifugal pump of the present disclosure eliminates the need for
a gas separator. In some embodiments, the centrifugal pump of an
illustrative embodiment may be used in conjunction with a gas
separator.
[0041] ESP primary pump 220 and production tubing string 225 are
downstream of ESP charge pump 200. In some embodiments, motor lead
extension 230 may plug into ESP motor 250 at one end and may be
spliced to another larger cable than runs the length of the well
bore to a junction box and/or a control panel on the surface of the
well site. Production tubing string 225 may be a conduit for the
produced well fluid to flow from the reservoir towards the surface.
ESP seal 240 sits between ESP motor 250 and ESP intake 210 and may
protect ESP motor 250 from well fluid.
[0042] FIGS. 4A and 4B illustrate perspective views of one
exemplary embodiment of a semi-open impeller of an illustrative
embodiment. Impeller 30 may include single shroud 300 arranged
radially about hub 310. Truncated vane 320 and untruncated vane 330
may extend substantially upstream from single shroud 300. In some
embodiments, truncated vane 320 sits at a mid-pitch location
between two untruncated vane 330 starting from the bottom side of
impeller 30. In certain embodiments, truncated vane 320 alternates
with untruncated vane 330, which vanes 320, 330 are
circumferentially disposed about hub 310. In some embodiments there
are two, three or four of each truncated vane 320 and untruncated
vane 330 disposed about hub 310. Greater or fewer number of vanes
320, 330 may also be used. In certain embodiments, the number of
truncated vane 320 varies from the number of untruncated vane 330
and/or the vanes 320, 330 may not strictly alternate. In FIG. 4B,
balance holes 340 are also shown on impeller 30 and assist in
equalizing the pressure on each side of impeller 30. In some
embodiments, impeller 30 may operate at about 8000 to about 12000
suction specific speed. In some embodiments, truncated vane 320 may
increase the performance of a pump's head flow and efficiency and
maintain high net positive suction pressure, without sacrificing
suction performance.
[0043] FIG. 5 is a partial cross sectional view taken along line
5-5 of FIG. 3 of one illustrative embodiment of an impeller for a
centrifugal pump. FIG. 5 illustrates one embodiment of single
shroud 300 and the arrangement of vanes 320, 330 disposed about hub
310 of impeller 30. In some embodiments, truncated vane 320 is
between about 50% and 75% the chord length of untruncated vane 330
(as judged from hub 310 and extending from the outer circumference
of single shroud 300). In certain embodiments, truncated vane 320
may be shorter or longer but always shorter in chord length than
untruncated vane 330. In some embodiments, a centrifugal pump of an
illustrative embodiment may include abrasion resistant trim, such
as busing 560 and flanged sleeve 570 (shown in FIG. 6) to increase
the lifespan of the centrifugal pump in the instance that solids
are also present in the produced well fluid.
[0044] In some embodiments the arrangement of vanes 320, 330 create
inlet area 610 of impeller 30 between about 1.75 and about 2.5
times the size of the inlet area of a conventional impeller. One
embodiment of inlet area 610 is illustrated in FIG. 6A. As shown in
FIG. 6A, the size of inlet area 610 may be calculated using the
formula:
Inlet Area=2.pi.RH-B
where R is mean inlet radius 620 as measured from centerline 640, H
is inlet vane height 630 and B is the vane blockage. The vane
blockage may be calculated as follows:
Vane Blockage = NH T sin .beta. ##EQU00001##
where N is the number of untruncated vane 330 in impeller 30, H is
inlet vane height 630, T is vane thickness 350 (shown in FIG. 5)
and .beta. is the inlet vane angle (shown in FIG. 5).
[0045] As truncated vane 320 do not contribute to vane blockage,
the arrangement of vanes 320, 330 of an illustrative embodiment
reduce the vane blockage and thereby increase inlet area 610.
[0046] FIG. 6 is a cross sectional view taken along line 6-6 of
FIG. 3 of one embodiment of a centrifugal pump of an illustrative
embodiment. Impeller 30 may be keyed to shaft 540 at hub 310, such
that impeller 30 rotates with shaft 540. Impeller 30 is paired with
diffuser 510. FIGS. 6, 6A show untruncated vane 330 for
illustration purposes, but truncated vane 320 may also be included
in impeller 30 in addition to or instead of untruncated vane 330,
for example as shown in FIGS. 4A, 4B and/or FIG. 5. In some
embodiments, no shroud is present on top side 550 of impeller 30.
Single shroud 300 is located on the bottom side of impeller 30.
[0047] Gap 530 is between untruncated vane 330 and/or truncated
vane 320 (shown in FIG. 5) of impeller 30 and diffuser 510. In some
embodiments, gap 530 is an increased clearance gap. The width of
gap 530 may be increased by machining the face of diffuser 510 that
sits parallel to the face of impeller 30. In some embodiments,
increased clearance gap 530 is between about 0.060 inches and about
0.180 inches wide, as required for various gas to liquid ratios. In
certain embodiments, increased clearance gap 530 may be wider or
narrower depending on the size of the pump and type of well and/or
fluid being pumped. In some embodiments, increased clearance gap
530 is at least wider than about 0.020 inches. Increased clearance
gap 530 allows the high pressure fluid to circulate and mix with
low pressure fluid. Balance holes 340 assist in equalizing the
pressure on each side of impeller 30.
[0048] In some embodiments, bushing 560 and flanged sleeve 570
located upstream and/or downstream of hub 310 assist in stabilizing
impeller 30 and/or holding impeller 30 in place during operation.
In some embodiments, bushing 560 and flanged sleeve 570 are located
directly upstream and downstream of hub 310. Bushing 560 and/or
flanged sleeve 570 may assist in carrying at least a portion of the
axial thrust load on impeller 30, such as upthrust and/or
downthrust. Bushing 560 and/or flanged sleeve 570 may be made of
tungsten carbide, silicon carbide or any other material having
similar properties. In some embodiments, bushing 560 and flanged
sleeve 570 comprise abrasion resistant trim.
[0049] As shown in FIG. 6, when impeller 30 is in operation, fluid
may flow downstream and/or upwards through passage 580 towards
successive stages of impeller 30 and diffuser 510 pairs and then to
ESP primary pump 220, eventually passing through production tubing
225 to a pipe, conduit, tank, collection container or other desired
location.
[0050] In some embodiments, ESP charge pump 200 comprises multiple
stages of impeller 30 and diffuser 510 pairs, which are stacked on
shaft 540. In certain embodiments, ESP charge pump 200 includes
between about 10 and about 100 stages of impeller 30 and diffuser
510 pairs. In some embodiments, impeller 30 may be employed in ESP
primary pump 220.
[0051] FIG. 7 is a flow chart illustrating an exemplary method of
pumping gaseous fluid of an illustrative embodiment. At step 710 a
centrifugal pump, such as ESP primary pump 220 and/or ESP charge
pump 200, is placed into a well containing gaseous fluid. The pump
may then be operated to induce the fluid to flow towards the
surface of the well at step 720. At least a portion of the fluid
may flow through increased clearance gap 530 between truncated vane
320 and/or untruncated vane 330, and a diffuser 510, at step 730.
At step 740, phase separation of the fluid may be minimized by
reducing the pressure differential between the pressure side and
suction side of truncated vane 320 and/or untruncated vane 330. In
some embodiments, the fluid flow may be caused by rotating an
impeller comprising truncated vane 320 and at least two untruncated
vane 330 extending substantially upstream from a single shroud 300,
wherein a truncated vane 320 sits at a mid-pitch location between
untruncated vane 330 starting from the bottom side of impeller 30.
In some embodiments, the pressure differential between the pressure
side and suction side of truncated vane 320 and/or untruncated vane
330 may be reduced by increasing impeller inlet area 610. Fluid may
then be lifted towards the surface, a transport conduit, pipe,
tank, collection container, or any other desired location at step
750.
[0052] The centrifugal pump of the invention may be suitable for a
variety of types of submersible stages known in the art for use in
submersible pumps. For example, mixed flow submersible pump stages,
as well as radial flow submersible pump stages, may make use of the
centrifugal pump of the invention. Both these and other submersible
stages suitable for use with an ESP system may benefit from the
centrifugal pump of the present disclosure.
[0053] Various embodiments of the invention may comprise various
numbers and spacing of truncated vane 320. ESP primary pump 220
and/or ESP charge pump 200 may benefit from the centrifugal pump of
the invention. One or more pump stages within ESP primary pump 220
and/or ESP charge pump 200 may benefit from the centrifugal pump of
the invention. In some embodiments the invention described herein
may be suitable for pumping fluid having a gas to liquid ratio of
up to about 50% by volume. The impeller of the invention may have
between about 1.75 and 2.5 times the size of the inlet area of a
convention impeller. In some embodiments, the impeller of the
invention may operate at about 8000 to about 12000 suction specific
speed.
[0054] While the invention herein disclosed has been described by
means of specific embodiments and applications thereof, numerous
modifications and variations could be made thereto by those skilled
in the art without departing from the scope of the invention set
forth in the claims. The embodiments described in the foregoing
description are therefore considered in all respects to be
illustrative and not restrictive. The scope of the invention is
indicated by the appended claims, and all changes that come within
the meaning and range of equivalents thereof are intended to be
embraced therein.
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