U.S. patent application number 13/608161 was filed with the patent office on 2014-03-13 for wellbore esp system with improved magnetic gear.
The applicant listed for this patent is Jamie Cochran, Richard McCann, Michael J. Rushby, Kenneth Smith. Invention is credited to Jamie Cochran, Richard McCann, Michael J. Rushby, Kenneth Smith.
Application Number | 20140069629 13/608161 |
Document ID | / |
Family ID | 49679551 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140069629 |
Kind Code |
A1 |
McCann; Richard ; et
al. |
March 13, 2014 |
WELLBORE ESP SYSTEM WITH IMPROVED MAGNETIC GEAR
Abstract
An electrical submersible pump system includes at least one
electric motor coupled to a mechanism for hanging the pump system
in a wellbore. At least one magnetic gear assembly is coupled at
its input to an output of the at least one electric motor. A
protector assembly is coupled at an input thereof to an output of
the at least one magnetic gear assembly. A pump is functionally
coupled at its input to a rotational output of the protector
assembly. The protector assembly includes a tortuous path assembly
having one end of each of a plurality of tortuous paths therein in
fluid communication with fluid in the wellbore. The tortuous paths
each have another end in fluid communication with dielectric fluid
disposed within the protector, the at least one magnetic gear and
the at least one electric motor.
Inventors: |
McCann; Richard; (Aberdeen,
GB) ; Smith; Kenneth; (Aberdeen, GB) ; Rushby;
Michael J.; (Aberdeen, GB) ; Cochran; Jamie;
(Kintore, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
McCann; Richard
Smith; Kenneth
Rushby; Michael J.
Cochran; Jamie |
Aberdeen
Aberdeen
Aberdeen
Kintore |
|
GB
GB
GB
GB |
|
|
Family ID: |
49679551 |
Appl. No.: |
13/608161 |
Filed: |
September 10, 2012 |
Current U.S.
Class: |
166/66.4 |
Current CPC
Class: |
E21B 43/128
20130101 |
Class at
Publication: |
166/66.4 |
International
Class: |
E21B 43/12 20060101
E21B043/12 |
Claims
1. An electrical submersible pump system, comprising: at least one
electric motor coupled to a mechanism for hanging the pump system
in a wellbore; at least one magnetic gear assembly coupled at its
input to an output of the motor; a protector assembly coupled at an
input thereof to an output of the at least one magnetic gear
assembly; and a pump functionally coupled at its input to a
rotational output of the protector assembly; wherein the protector
assembly comprises a tortuous path assembly having one end of each
of a plurality of tortuous paths therein in fluid communication
with fluid in the wellbore, the tortuous paths each having another
end in fluid communication with dielectric fluid disposed within
the protector, the at least one magnetic gear and the at least one
electric motor.
2. The pump system of claim 1 wherein the pump comprises a
progressive cavity pump.
3. The pump system of claim 1 further comprising a flexible torque
transmission shaft disposed between a rotational output of the
protector assembly and a rotational input of the pump.
4. The pump system of claim 3 wherein the protector assembly
comprises a jointed coupling engaged at one end with the bottom of
a drive shaft extending through a housing disposed below the
magnetic gear assembly, the jointed coupling engaged at its other
end to the flexible torque transmission shaft.
5. The pump system of claim 4 wherein the drive shaft is rotatably
supported in its housing at both its longitudinal ends by bearings,
at least one of the bearings configured to accept thrust loading
from the drive shaft to isolate the thrust loading from the at
least one magnetic gear assembly.
6. The pump system of claim 5 wherein the tortuous path assembly is
disposed at a lower end of the drive shaft housing.
7. The pump system of claim 1 wherein the hanging mechanism
comprises a coupling to join to a lower end of a coiled tubing, and
wherein an electrical cable coupled to the pump system is disposed
within the coiled tubing.
8. The pump system of claim 1 further comprising an electrical
connector sub including a connector ring in contact with a first
contact pin extending from the at least one electric motor and at
least one contact slot in contact with at least a second, longer
contact pin extending from the motor.
9. The pump system of claim 1 wherein synchronization is
mechanically maintained between each of a plurality of magnetic
gear assemblies, and of each of a plurality of electric motors.
10. The pump system of claim 1 further comprising a variable volume
reservoir disposed within the protector assembly and in fluid
communication with the dielectric fluid end of the tortuous path
assembly.
11. The pump system of claim 1 wherein the pump is the furthest
downhole rotating part of the pump system.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND
[0003] This disclosure relates generally to the field of electrical
submersible pumps (ESP) used to lift fluids out of wellbores
drilled through permeable formations. More specifically, the
disclosure relates to ESP systems having magnetic gears to provide
a torque transmission connection between the motor and the pump
used.
[0004] U.S. Pat. No. 7,549,467 issued to McDonald et al. describes
a wellbore pump which includes a motor disposed in the wellbore.
The motor is supplied by power from a source external to the
wellbore. The pump includes a magnetic gear member rotationally
coupled at an input thereof to an output of the motor, and a pump
coupled at its input to an output of the magnetic gear member.
[0005] Electrical connection to the ESP system, transfer of torque
from the motor to the pump and sealing the pump against wellbore
fluid pressure while maintaining dielectric fluid in the motor and
gear assembly are all considerations in the design of an ESP
system. Accordingly, there is a need for improved ESP systems
taking into account such considerations.
SUMMARY
[0006] An electrical submersible pump system includes at least one
electric motor coupled to a mechanism for hanging the pump system
in a wellbore. At least one magnetic gear assembly is coupled at
its input to an output of the motor. A protector assembly is
coupled at an input thereof to an output of the at least one
magnetic gear assembly. A pump is functionally coupled at its input
to a rotational output of the protector assembly. The protector
assembly includes a tortuous path assembly having one end of each
of a plurality of tortuous paths therein in fluid communication
with fluid in the wellbore. The tortuous paths each have another
end in fluid communication with dielectric fluid disposed within
the protector, the at least one magnetic gear and the at least one
electric motor.
[0007] Other aspects and advantages of the invention will be
apparent from the description and claims which follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is an overview of an example ESP system.
[0009] FIG. 2A shows an example implementation of the ESP system of
FIG. 1 wherein data transmission from the ESP system and control
thereof may be remotely performed over a network, such as the
Internet.
[0010] FIG. 2B shows an example wellbore hanger/outlet.
[0011] FIG. 2C shows an example of coiled tubing conveyance of an
ESP system.
[0012] FIG. 3 shows an example upper portion of the ESP system of
FIG. 1.
[0013] FIG. 4 shows an example electric motor of the example ESP
system.
[0014] FIG. 5 shows an example connection between a magnetic gear
and a flow section including pressure compensation.
[0015] FIG. 6 shows the example connection in more detail.
[0016] FIGS. 7 and 8 show cut away views of an electrical contact
(starpoint) sub.
[0017] FIG. 9 shows an example of a flexible shaft assembly.
[0018] FIG. 10 shows an example of a torque through connector.
[0019] FIG. 11 shows internal details of an example protector with
a tortuous path assembly.
[0020] FIG. 12 shows an example segment of the tortuous path
assembly in more detail.
DETAILED DESCRIPTION
[0021] An example ESP system 10 that may be conveyed into a well
using jointed tubing, wireline, slickline or coiled tubing, for
example, is shown generally in FIG. 1. The ESP system 10 may
include an upper or "top" sub 12 that is configured to make
connection to an end of one of the foregoing conveyance devices for
movement into and out of the wellbore. A lower end of the ESP
system 10 may include a "muleshoe" sub 28. The muleshoe sub 28 may
be added below a pump 26 to provide protection while running into
the wellbore during deployment, and to provide a mounting location
for a pump intake memory gauge. In addition, the muleshoe sub 28
may provide a suitable location for inner bore sealing as part of a
well barrier control mechanism. Both a single-shot sealing option,
and a pressure responsive valve with multiple stable positions may
be considered as suitable example options for wellbore sealing
below the muleshoe sub 28. For purposes of this disclosure, the
term "up" is intended to mean in a direction toward the outlet of a
wellbore, while "down" is intended to mean in the opposite
direction. Corresponding terms may include "upper end" and "lower
end" with reference to various modules or sections that make up the
ESP system 10.
[0022] The top sub 12 may be followed successively by a "star point
sub" 13 and a motor 14, which in the present example may be an
electric motor. The star point sub 13 may include one or more
sensors and control devices related to operation of the ESP system
and the motor 14. The star point sub 13 may also be used to make
electrical connection between a cable (see FIG. 2). The motor 14
may be coupled at its lower end to a magnetic gear assembly 16. In
the present example, the magnetic gear assembly 16 accepts as
rotational input from the motor 14 high rotational speed and low
torque, and converts such rotation therein into low rotational
speed at correspondingly (inversely) proportional high torque. A
protector 18 may be similar in operating principle to the protector
ordinarily used in ESP systems and may be configured to exclude
wellbore fluid at existing wellbore pressure and temperature from
entering the magnetic gear assembly 16 and the motor 14. The
protector 18 may also axially decouple the magnetic gear assembly
16 and the motor 14 from axial and lateral loading generated by the
pump 26. Not shown in FIG. 1 for clarity is a flow shroud that
diverts wellbore fluid flow from the pump outlet (122 in FIG. 11)
so that it can travel in an annular space outside the ESP system 10
and be sealingly diverted into a tubing or coiled tubing and thence
flow upwardly in the wellbore.
[0023] The present example of ESP system 10 may be of modular
design, and enable first lowering the pump 26, including the
muleshoe sub 28, a flex sub 27 to enable relative axial deflection
between the upper components (terminating at field coupling sub
coupled to the upper end of a pump discharge sub 20, and thence
coupled to a lower end of the protector 18 and the components
described above. The pump 26, flex sub 27, pump discharge sub 20
and a field coupling sub 22 may be inserted into the well first, to
be followed by the foregoing described components beginning with
the field coupling sub 22. The entire ESP system 10 may also be
lowered into the wellbore as an assembled unit. The pump 26, flex
sub 27, protector 18, magnetic gear assembly 16, motor 14 and star
point sub may each be enclosed in a respective pressure resistant
housing and may be coupled by threads, locking rings or any other
device known in the art for joining housing segments together, end
to end.
[0024] FIG. 2A shows the example ESP assembly 10 of FIG. 1 as it
may be deployed in an example wellbore. The pump 10 assembly may be
deployed at the end of threaded, jointed tubing 42, extending from
the pump 10 to a wellhead 40. Selective length adjustments of the
jointed tubing to ensure proper axial positioning of the ESP system
10 may be made using one or more selected short length "pup" joints
48 of threaded tubing. Electrical and/or optical signal cable 46
may extend from top sub (12 in FIG. 1) along the exterior of the
jointed tubing 42, retained thereon by bands 44 up to a dual
orifice hanger disposed in the wellhead 40. An example of such a
hanger is shown in cross section at 41 in FIG. 2B. Tubing and fluid
flow exit from the wellhead 40 may extend to a flow tee 38 and to
fluid processing devices (not shown) proximate the surface.
Electrical connections from the wellhead 40 may extend to a
junction box 36 wherein a power supply (not shown) may be provided
to supply electrical power to operate the motor (14 in FIG. 1) and
to strip off sensor signals from the cable 46 and conduct them to a
signal communication subsystem 34 so that data signals from the ESP
assembly 10 and control signals communicated thereto may be
transferred to and from a remote control station 30 such as may
communicate over a secure network such as a secure server 32
connected to the Internet.
[0025] In other examples, the pump system 10 may be inserted into
and removed from the wellbore using a coiled tubing unit. An
example of the foregoing is shown in FIG. 2C and may include a
storage reel 150, a coiled tubing 152 thereon, a roller assembly
154 and a tubing injector 156 coupled to the wellhead 40. The cable
(46 in FIG. 2B) may be disposed inside the coiled tubing 154 in
such examples. See, as a non-limiting example, U.S. Pat. No.
5,285,008 issued to Sas-Jaworsky.
[0026] FIG. 3 shows an example connection between the star point
sub 13 and the motor 14. The star point sub 13 may include various
forms of sensors 54, for example pressure, temperature and flow
sensors. The star point sub 13 may include electrical feedthroughs
130 to enable external electrical connection to the cable (46 in
FIG. 2A) to be transposed to internal electrical connections
between the various "subs" or components of the ESP system. In FIG.
3 connection 56 to the motor (14 in FIG. 1 is shown) wherein the
feedthroughs 130 are visible. In some examples, the feedthroughs 13
may not extend past the motor. FIG. 3 also shows an example
connection between the star point sub (14 in FIG. 1) and the top
sub (12 in FIG. 1). The motor housing and star point sub housing
may be coupled by threads 8 as shown in FIG. 3.
[0027] FIG. 4 shows an example connection 56 between the motor 14
and the magnetic gear assembly (16 in FIG. 1). The motor 14 output
shaft may be rotationally connected by splines or other connection
to an input shaft of the magnetic gear assembly (16 in FIG. 1). The
motor housing and the magnetic gear housing may be directly
connected, such as by threads, or may include a double-male
threaded coupling 8A threadedly coupled to female threads at
adjacent longitudinal ends of the motor housing and the magnetic
gear assembly housing.
[0028] FIG. 5 shows connection between the lower end of the
magnetic gear assembly 16 and an upper portion of the protector 18.
The protector 18 may consist of a thrust section, a pressure
compensation section and a tortuous path section, shown in FIG. 5
at 62, 64, and 68, respectively. A drive shaft 99 may be
rotationally coupled to the output of the magnetic gear assembly 16
using splines or any other torque transmitting fitting. The
tortuous path section 68 will be further explained with reference
to FIGS. 11 and 12.
[0029] The thrust section 62 is shown in more detailed view in FIG.
6. The thrust section 62 may include bearings 62A to isolate thrust
loading and lateral loading in the drive shaft 99 from the magnetic
gear assembly (16 in FIG. 1), while freely transmitting rotation
therethrough. The pressure compensation section 63 may include a
flexible bladder or reservoir 64 to maintain pressure of hydraulic
or other dielectric fluid filling the interior of the protector 18
at pump discharge pressure so that no wellbore fluid will enter the
interior of such components and may compensate the system volume
for temperature changes. The components located above the protector
18 may include provision for communication of hydraulic pressure
from the bladder or reservoir 64 to the interior of such components
so that wellbore fluid will be less likely to enter any or all of
them by reason of differential fluid pressure.
[0030] FIG. 7 shows a cut away view of an example star point sub
13A. The star point sub 13 may include a pressure resistant, high
strength housing 13A that may be connected at one end to the top
sub (12 in FIG. 1). O-rings 13J may sealingly engage the lower end
of the star point sub 13 to the motor (14 in FIG. 1) housing, in an
end section 13B sized to fit within a corresponding opening in the
motor housing. A suitable opening 13C may be provided in the
housing 13A wall to enable passage of an electrical contact (see
FIG. 3) between contact pins and the motor (14 in FIG. 1).
[0031] Electrical connection to one of the electrical conductors in
the cable (46 in FIG. 2A) may be made to a bus bar ring 13F
disposed in an annular space in the upper part of the housing 13A.
The bus bar ring 13F may be supported at the end of a conductor pin
13E insulatingly supported in an appropriately sized annular space
to limit movement of the conductor pin 13E. A lower electrical
contact 13D makes mechanical and electrical contact with conductor
pins (see FIG. 3) to provide an electrical conductor path to the
motor (14 in FIG. 1). The conductor pin 13E in FIG. 7 may be the
"neutral" conductor in a two pole, single phase electrical power
system, or may be one of three conductors in a three phase, delta
connected system. Conductor pin 13E may also be the neutral
conductor in a four-wire, wye connected three-phase power system.
In the present example, the conductor pin 13E may be shorter than
the other conductor pins in the starpoint sub 13. In the present
example, the conductor pin 13E may terminate at its upper end in a
bus bar ring 13F. FIG. 8 shows a similar cut away view of the star
point sub 13, wherein a long conductor pin 13G may make electrical
contact with a cable conductor other than the neutral conductor.
The bus bar ring 13F may have an opening for each long conductor
pin 13G to enable passage therethrough. The long electrical
conductor pin 13G may make electrical contact with the electrical
cable (46 in FIG. 1) through a surface cable contact 13H.
[0032] FIG. 9 shows a cut away view of the lower end of the
protector 18 coupled to the flex sub 27. The upper end of a flex
shaft 104 may be coupled to one end of a torque through connector
102. The torque through connector 102 may be connected at its other
end to the driveshaft (99 in FIG. 5) The flex shaft 104 may be
sufficiently flexible to absorb any bending loads occurring between
the torque through connector 102 and the pump rotor 26B, which is
connected at its upper end to the bottom of the flex shaft 104.
[0033] FIG. 10 shows an example of the torque through coupling 102.
An opening may be formed in the bottom of the drive shaft 99 to
slidingly receive an input mandrel 102B. When the mandrel 102B is
inserted into the opening in the drive shaft 99, it may be locked
in place with a locking pin 102C. An output mandrel 102A may be
rotationally and axially locked into the input mandrel 102B by
rotating the output mandrel 102A one quarter turn so that a keyed
coupling 102C, 102D is engaged. The flex shaft (104 in FIG. 9) may
be coupled to the output mandrel 102A by a threaded connection
102AA.
[0034] FIGS. 11 and 12 show, respectively, a seal section and a
tortouous path assembly disposed in the seal section. The torturous
path in the seal assembly for the ESP system communicates ambient
pressure to dielectric fluid filling the motor, while sealing
wellbore fluids from the motor. The torturous path includes a
series of tubes and chambers circumscribing the pump drive shaft
(99 in FIG. 10). Communication tubes, upper and lower shaft seals
provide additional defense from wellbore fluid ingress into the
seal section. One communication tube has an end in fluid
communication with the wellbore fluid and another has an end in
fluid communication with the motor dielectric fluid. The
communication tubes extend into the seal section from opposite
directions and each has an opening opposite from where the
respective tube enter the chamber. A port is provided in the intake
tube, most remote from the upper shaft seal, and a port in the
discharge tube is provided adjoining the upper shaft seal. Thus a
torturous path is provided between the lower and upper shaft seal's
thereby minimizing pressure differential, leading to deterioration
in shaft seal integrity.
[0035] FIG. 11 shows the relevant section of the protector 18 and
the location of the tortuous path assembly therein. An upper
portion of the protector may include a shaft seal 110 and a thrust
bearing assembly 114 (also shown in FIG. 6 at 62). Thermal
expansion of the dielectric fluid for the motor may be compensated
by a compensating reservoir 116 (also shown in FIG. 6 at 64).
Another shaft seal 118 may be disposed at a selected position along
the drive shaft 99, generally at the upper end of the tortuous path
section 112. The tortuous path section 112 may have a lower shaft
seal 120 at its lower end. The pump discharge 122 is shown just
below the tortuous path section.
[0036] FIG. 12 shows an example of a segment of the tortuous path
assembly 112. Wellbore fluid may be applied to an intake tube 112B
at one end of the assembly 112. A discharge tube 112A may be
disposed at the same end of the assembly 112 as the intake tube
112B inlet. Wellbore fluid pressure may be forced to return through
the discharge tube 112A by suitable arrangement of another,
similarly configured segment disposed above the one shown in FIG.
12. By having fluid flow through such tubes and have the flow
direction reversed in each section, a sufficiently tortuous path
may be provided such that intrusion of wellbore fluid into the
dielectric fluid may be minimized, while maintaining a U-tube
effect in all inclinations.
[0037] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
* * * * *