U.S. patent application number 14/075656 was filed with the patent office on 2015-05-14 for electric submersible motor oil expansion compensator.
This patent application is currently assigned to GE Oil & Gas ESP, Inc.. The applicant listed for this patent is GE Oil & Gas ESP, Inc.. Invention is credited to Brian Paul Reeves.
Application Number | 20150132158 14/075656 |
Document ID | / |
Family ID | 51845536 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150132158 |
Kind Code |
A1 |
Reeves; Brian Paul |
May 14, 2015 |
ELECTRIC SUBMERSIBLE MOTOR OIL EXPANSION COMPENSATOR
Abstract
An electric submersible pumping system includes a motor that is
filled with motor lubricant fluid and a pump driven by the motor.
The electric submersible pumping system further includes a fluid
expansion module connected to the motor that is designed to
accommodate the expansion and contraction of the motor lubricant
fluid in the motor. The fluid expansion module preferably includes
a piston seal housing in fluid communication with the motor and a
bag seal housing in fluid communication with the piston seal
housing. The fluid expansion module further includes at least one
axially movable barrier in the piston seal housing and at least one
expansible barrier in the bag seal housing. The axially movable
barrier and the expansible barrier cooperate to permit the
expansion of the motor lubricant fluid without contaminating the
motor lubricant fluid with fluids or and solids from the
wellbore.
Inventors: |
Reeves; Brian Paul; (Edmond,
OK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GE Oil & Gas ESP, Inc. |
Oklahoma City |
OK |
US |
|
|
Assignee: |
GE Oil & Gas ESP, Inc.
Oklahoma City
OK
|
Family ID: |
51845536 |
Appl. No.: |
14/075656 |
Filed: |
November 8, 2013 |
Current U.S.
Class: |
417/410.1 |
Current CPC
Class: |
F04B 35/04 20130101;
H02K 5/132 20130101; E21B 43/128 20130101; F04D 13/0653 20130101;
F04D 13/10 20130101 |
Class at
Publication: |
417/410.1 |
International
Class: |
F04B 35/04 20060101
F04B035/04 |
Claims
1. An electric submersible pumping system for use in pumping fluids
from a wellbore, the electric submersible pumping system
comprising: a motor; a pump driven by the motor; and a fluid
expansion module connected to the motor, wherein the fluid
expansion module comprises: a piston seal housing; and a first
piston assembly contained within the piston seal housing, wherein
the first piston assembly is configured for sliding engagement
within the piston seal housing.
2. The electric submersible pumping system of claim 1, wherein the
fluid expansion module further comprises a second piston assembly
contained within the piston seal housing, wherein the second piston
assembly is configured for sliding engagement within the piston
seal housing.
3. The electric submersible pumping system of claim 2, wherein each
of the first and second piston assemblies comprises: a piston; and
at least one seal positioned around the outside of the piston.
4. The electric submersible pumping system of claim 3, wherein each
seal further comprises: a body; and an interior spring, wherein the
interior spring is configured to exert an outward radial force
against the body.
5. The electric submersible pumping system of claim 4, wherein the
piston seal housing includes a polymer liner.
6. The electric submersible pumping system of claim 1, wherein the
fluid expansion module further comprises: a bag seal housing; and a
bag seal assembly within the bag seal housing.
7. The electric submersible pumping system of claim 6, wherein the
bag seal assembly further comprises: a bag support; and a bladder
secured to the bag support.
8. The electric submersible pumping system of claim 7, wherein the
bag seal assembly further comprises one or more discharge ports and
wherein each of the one or more discharge ports is configured as a
one-way check valve that places the interior of the bladder in
fluid communication with the wellbore when opened.
9. The electric submersible pumping system of claim 1, wherein the
fluid expansion module further comprises a fluid exchange assembly
and wherein the fluid exchange assembly comprises: a solids screen;
exchange ports; and wherein the fluid exchange assembly is
configured to place the exterior of the bladder in fluid
communication with the wellbore.
10. The electric submersible pumping system of claim 1, further
comprising a seal section between the motor and the pump, wherein
the seal section comprises: a shaft; one or more mechanical seals;
and one or more relief valves.
11. The electric submersible pumping system of claim 10, wherein
each of the one or more mechanical seals comprises: a runner
connected to the seal section shaft; and a stationary ring in
contact with the runner.
12. A system for accommodating the expansion of motor lubricant in
a motor within an electric submersible pump used for removing
fluids from a wellbore, the system comprising: a seal section
connected to the motor; and a fluid expansion module connected to
the motor, wherein the fluid expansion module has a longitudinal
axis and wherein the fluid expansion module comprises: at least one
piston assembly, wherein the at least one piston assembly moves
along the longitudinal axis of the fluid expansion module in
response to an expansion of the motor lubricant; and a bag seal
assembly, wherein the bag seal assembly includes a bladder that
expands in response to movement of the at least one piston
assembly.
13. The system of claim 12, wherein the fluid expansion module
further comprises a fluid exchange assembly that places the
exterior of the bladder in fluid communication with the
wellbore.
14. The system of claim 12, wherein the seal section comprises: a
seal section shaft; and one or more mechanical seals connected to
the seal section shaft.
15. The system of claim 15, wherein the seal section further
comprises at least one relief valve that is configured to release
motor lubricant to the wellbore.
16. An electric submersible pumping system configured to pump
fluids from a wellbore, the electric submersible pumping system
comprising: a motor; wherein the motor is filled with motor
lubricant fluid; a pump driven by the motor; and a fluid expansion
module connected to the motor, wherein the fluid expansion module
comprises: a piston seal housing in fluid communication with the
motor; a bag seal housing in fluid communication with the piston
seal housing; at least one axially movable barrier in the piston
seal housing; and at least one expansible barrier in the bag seal
housing.
17. The electric submersible pumping system of claim 16, wherein
the at least one axially movable barrier in the piston seal housing
comprises a piston assembly.
18. The electric submersible pumping system of claim 17, wherein
the at least one expansible barrier in the bag seal housing
comprises a bladder.
19. The electric submersible pumping system of claim 18, wherein
the bladder has an interior that is in fluid communication with the
piston seal housing and an exterior that is in fluid communication
with the wellbore.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to the field of submersible
pumping systems, and more particularly, but not by way of
limitation, to a system for accommodating the expansion of motor
lubricants in high-temperature environments.
BACKGROUND
[0002] Submersible pumping systems are often deployed into wells to
recover petroleum fluids from subterranean reservoirs. Typically,
the submersible pumping system includes a number of components,
including one or more fluid filled electric motors coupled to one
or more high performance pumps located above the motor. When
energized, the motor provides torque to the pump, which pushes
wellbore fluids to the surface through production tubing. Each of
the components in a submersible pumping system must be engineered
to withstand the inhospitable downhole environment.
[0003] Components commonly referred to as "seal sections" protect
the electric motors and are typically positioned between the motor
and the pump. In this position, the seal section provide several
functions, including transmitting torque between the motor and
pump, restricting the flow of wellbore fluids into the motor,
protecting the motor from axial thrust imparted by the pump, and
accommodating the expansion and contraction of motor lubricant as
the motor moves through thermal cycles during operation. Prior art
seal sections typically include a "clean side" in fluid
communication with the electric motor and a "contaminated side" in
fluid communication with the wellbore. Bellows or bags have been
used to separate the clean side of the seal section from the
contaminated side.
[0004] Recently, manufacturers have employed polymer expansion bags
within the seal section to accommodate the expansion and
contraction of motor lubricants while isolating the lubricants from
contaminants in the wellbore fluid. Although generally effective at
lower temperatures, the currently available polymers become
somewhat permeable at extremely elevated temperatures and allow the
passage of moisture across the membrane. The moisture reduces the
insulating properties of polyimide and other films used to
electrically isolate components within the downhole pumping system.
Although piston-based systems may provide an alternative to the use
of polymer expansion bags, prior art piston-based seal assemblies
are susceptible to failure from sand, scale or other particulates.
There is, therefore, a need for improved designs that can be used
to accommodate expansion of motor fluids in elevated temperature
applications. It is to this and other needs that the preferred
embodiments are directed.
SUMMARY OF THE INVENTION
[0005] In preferred embodiments, the present invention includes an
electric submersible pumping system that is configured to pump
fluids from a wellbore. The electric submersible pumping system
includes a motor that is filled with motor lubricant fluid and a
pump driven by the motor. The electric submersible pumping system
further includes a fluid expansion module connected to the motor
that is designed to accommodate the expansion and contraction of
the motor lubricant fluid in the motor.
[0006] The fluid expansion module preferably includes a piston seal
housing in fluid communication with the motor and a bag seal
housing in fluid communication with the piston seal housing. The
fluid expansion module further includes at least one axially
movable barrier in the piston seal housing and at least one
expansible barrier in the bag seal housing. The axially movable
barrier and the expansible barrier cooperate to permit the
expansion of the motor lubricant fluid without contaminating the
motor lubricant fluid with fluids or and solids from the
wellbore.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 depicts a submersible pumping system constructed in
accordance with a preferred embodiment of the present
invention.
[0008] FIG. 2 provides a cross-sectional view of the motor, lower
fluid expansion module and seal section constructed in accordance
with a presently preferred embodiment.
[0009] FIG. 3 presents a cross-sectional representation of the
motor of the pumping system from FIG. 2.
[0010] FIG. 4 presents a cross-sectional representation of the
lower fluid expansion module of FIG. 2.
[0011] FIG. 5 presents a perspective view of a piston from the
lower fluid expansion module of FIG. 4.
[0012] FIG. 6 presents a cross-sectional view of the sealing ring
from the piston of FIG. 5.
[0013] FIG. 7 provides a cross-sectional view of the seal section
of the pumping system from FIG. 2.
[0014] FIG. 8 provides a cross-sectional view of a mechanical seal
from the seal section of FIG. 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] In accordance with a preferred embodiment of the present
invention, FIG. 1 shows an elevational view of a pumping system 100
attached to production tubing 102. The pumping system 100 and
production tubing 102 are disposed in a wellbore 104, which is
drilled for the production of a fluid such as water or petroleum.
As used herein, the term "petroleum" refers broadly to all mineral
hydrocarbons, such as crude oil, gas and combinations of oil and
gas.
[0016] The pumping system 100 preferably includes a pump 108, a
motor 110, a seal section 112 and a fluid expansion module 114. The
production tubing 102 connects the pumping system 100 to a wellhead
106 located on the surface. Although the pumping system 100 is
primarily designed to pump petroleum products, it will be
understood that the present invention can also be used to move
other fluids. It will also be understood that, although each of the
components of the pumping system are primarily disclosed in a
submersible application, some or all of these components can also
be used in surface pumping operations.
[0017] Generally, the motor 110 is configured to drive the pump
108. In a particularly preferred embodiment, the pump 108 is a
turbomachine that uses one or more impellers and diffusers to
convert mechanical energy into pressure head. In alternate
embodiments, the pump 108 is configured as a positive displacement
pump. The pump 108 includes a pump intake 118 that allows fluids
from the wellbore 104 to be drawn into the pump 108. The pump 108
forces the wellbore fluids to the surface through the production
tubing 102.
[0018] In the preferred embodiments, the seal section 112 is
positioned above the motor 110 and below the pump 108. The fluid
expansion module 114 is positioned below the motor 110. Although
only one of each component is shown, it will be understood that
more can be connected when appropriate, that other arrangements of
the components are desirable and that these additional
configurations are encompassed within the scope of preferred
embodiments. For example, in many applications, it is desirable to
use tandem-motor combinations, gas separators, multiple seal
sections, multiple pumps, sensor modules and other downhole
components.
[0019] It will be noted that although the pumping system 100 is
depicted in a vertical deployment in FIG. 1, the pumping system 100
can also be used in non-vertical applications, including in
horizontal and deviated wellbores 104. Accordingly, references to
"upper" and "lower" within this disclosure are merely used to
describe the relative positions of components within the pumping
system 100 and should not be construed as an indication that the
pumping system 100 must be deployed in a vertical orientation.
[0020] Referring now also to FIGS. 2 and 3, shown therein is a
cross-sectional view of the seal section 112, motor 110 and fluid
expansion module 114. As depicted in the close-up view of the motor
110 in FIG. 3, the motor 110 preferably includes a motor housing
120, stator assembly 122, rotor assembly 124, rotor bearings 126
and a motor shaft 128. The stator assembly 122 includes a series of
stator coils (not separately designated) that correspond to the
various phases of electricity supplied to the motor 110. The rotor
assembly 124 is keyed to the motor shaft 128 and configured for
rotation in close proximity to the stationary stator assembly 122.
The size and configuration of the stator assembly 122 and rotor
assembly 124 can be adjusted to accommodate application-specific
performance requirements of the motor 110.
[0021] Sequentially energizing the various series of coils within
the stator assembly 122 causes the rotor assembly 124 and motor
shaft 128 to rotate in accordance with well-known electromotive
principles. The motor bearings 126 maintain the central position of
the rotor assembly 124 within the stator assembly 122 and oppose
radial and axial forces generated by the motor 110 on the motor
shaft 128.
[0022] The motor 110 is filled with non-conductive lubricating oil
during manufacture that reduces frictional wear on the rotating
components within the motor 110. As the motor 110 cycles during use
and as the motor 110 is exposed to the elevated temperatures in the
wellbore 104, the lubricating oil expands and contracts. It is
desirable to prevent the clean motor oil from becoming contaminated
with fluids and solids in the wellbore. To permit the expansion and
contraction of the lubricating oil under elevated wellbore
temperatures, the seal section 112 and fluid expansion module 114
are connected to the motor 110 and placed in fluid communication
with the motor oil.
[0023] Continuing with FIG. 2 and referring now also to FIG. 4,
shown therein is a cross-sectional view of the fluid expansion
module 114. The fluid expansion module 114 includes a piston seal
housing 130, a bag seal housing 132, one or more piston assemblies
134, a bag seal assembly 136 and a fluid exchange assembly 138. In
a particularly preferred embodiment, the fluid expansion module 114
includes a pair of piston assemblies 134a, 134b. The piston
assemblies 134a, 134b are placed in the piston seal housing 130 and
are configured for axial movement within the fluid expansion module
114. The inside surface of the piston seal housing 130 includes a
polymer liner 140 that reduces friction and stiction. The polymer
liner 140 is preferably manufactured from PTFE, PFA, PEEK and other
high-temperature polymers. Alternatively, the inside surface of the
piston seal housing 130 can be manufactured from polished chrome,
stainless steel or other durable metal.
[0024] Turning to FIG. 5, shown therein is a perspective view of
one of the piston assemblies 134. The piston assembly 134
preferably includes a piston 142 and a pair of spring-energized
seals 144. The piston 142 is preferably manufactured from a
highly-polished metal, including chrome, stainless steel and
related alloys and has an outside diameter that is only slightly
smaller than the inside diameter of the piston seal housing 130.
Alternatively, the piston 142 can be manufactured from a
high-temperature rated elastomer or polymer. Preferred polymers of
the piston 142 include polytetrafluoroethylene (PTFE),
perfluoroalkoxy (PFA) and polyethether ketone (PEEK).
[0025] FIG. 6 presents a cross-sectional view of the seal 144. The
seal 144 includes an body 146 and an interior spring 148. The body
146 is preferably manufactured from a durable, high-temperature and
wear-resistant elastomer or polymer, such as
polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), polyethether
ketone (PEEK) and perfluoroelastomer. The interior spring 148 is
configured to exert force against the body 146 in an outward radial
direction. In this way, the spring 148 presses the body 146 against
the inside surface of the piston seal housing 130. The interior
spring 148 is preferably configured as a coiled ring or series of
connected Belleville washers.
[0026] Turning back to FIG. 4, the bag seal housing 132 includes
the bag seal assembly 136. The bag seal assembly 136 preferably
includes a bag support 150, a bladder 152, inlet ports 154 and
discharge valves 156. The bag support 152 is rigidly attached to
the inside surface of the bag seal housing 132. The bladder 152 is
secured to the bag support 150 with compression flanges 158.
Alternatively, the bladder 152 can be secured to the bag support
152 with grips or hose clamps. The inlet ports 154 provide a path
of fluid communication from the piston seal housing 130 into the
inside of the bladder 152 and bag support 150. Importantly, the bag
support 150 permits the passage of fluids between the piston seal
housing 130 and bag seal housing 132 only through the inlet ports
154. Fluids external to the bladder 152 are not allowed to pass
directly into the piston seal housing 130.
[0027] The discharge valves 156 are preferably one-way relief
valves that are configured to open at a predetermined threshold
pressure that exceeds the exterior wellbore pressure. In this way,
if the fluid pressure inside the bladder 152 exceeds the set-point
pressure, the discharge valves 156 open and relieve the pressure
inside the bladder 152 by discharging a small volume of fluid into
the wellbore 104. In a particularly preferred embodiment, the
bladder 152 is manufactured from a high-temperature polymer or
elastomer. Suitable polymers and elastomers include
polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA) and
polyethether ketone (PEEK).
[0028] The bag seal housing 132 also includes the fluid exchange
assembly 138. The fluid exchange assembly 138 includes a solids
screen 160 and a plurality of exchange ports 162. The exchange
ports 162 allow fluids to pass from the wellbore 104 through the
solids screen 160 into the bag seal housing 132 around the exterior
of the bladder 152. The solids screen 160 reduces the presence of
particulates in the bag seal housing 132. The solids screen 160 is
preferably manufactured from a metal or polymer fabric mesh.
[0029] During manufacture, the fluid expansion module 114 is filled
with clean motor lubricant. The piston assemblies 134a, 134b are
then placed into the piston seal housing 130. As the fluid in the
motor 110 expands during operation, the increased volume exerts
pressure on the upper side of the piston assembly 134a. In
response, piston assembly 134a moves downward toward piston
assembly 134b. When the volume between the piston assemblies 134a,
134b decreases, the increased pressure on piston assembly 134b
forces it downward toward the bag seal housing 132. As piston
assembly 134b moves downward it pushes clean motor lubricant
through the inlet ports 154, through the bag support 152 and into
the bladder 152. The bladder 152 expands to accommodate
introduction of fluid from the piston seal housing 130. As the
bladder 152 expands, fluid external to the bladder 152 is expelled
through the exchange ports 162 and solids screen 160. If the
pressure inside the bladder 152 exceeds the threshold pressure
limit of the discharge valves 156, the discharge valves 156 open
and vent a portion of fluid into the wellbore 104.
[0030] Conversely, during a cooling cycle, the fluid in the motor
110 contracts and the movement of the components within the fluid
expansion module 114 reverses. As the pistons 134a, 134b are drawn
upward, fluid is pulled out of the bladder 152. As the volume and
pressure inside the bladder 152 decreases, fluid from the wellbore
is pulled into the bag seal housing 132 through the solids screen
160 and exchange ports 162. The fluid expansion module 114 provides
a robust mechanism for allowing expansion and contraction of
lubricants from the motor 110 while maintaining an isolation
barrier between the clean motor lubricants and the contaminated
fluids from the wellbore 104. Notably, the use of piston assemblies
134a, 134b provide redundant barriers to the bladder 152 that are
not susceptible to the increased permeability found in even
high-temperature bladders. Accordingly, even if the bladder 152 is
exposed to extremely high temperatures and permits the passage of
some moisture from the wellbore 104 into the piston seal housing
130, the moisture is isolated from the motor 110 by the redundant
piston assemblies 134a, 134b.
[0031] In certain applications, it may be desirable to place the
pump 108 below the motor 110. In those applications, the fluid
expansion module 114 will be positioned above the motor 110 and the
seal section 112 will be placed between the motor 110 and the pump
108. In these alternative embodiments, the bag seal housing 132
will actually be positioned above the piston seal housing 130.
[0032] Turning to FIG. 7, shown therein is a cross-sectional view
of the motor 110 and seal section 112. The seal section 112 is
attached to the upper end of the motor 110 and provides a second
system for accommodating the sealing of the rotating shaft 128 to
the equipment and support the thrust load of the pump 108. The seal
section 112 includes a seal section shaft 164, a thrust bearing
assembly 166, one or more mechanical seals 168 and one or more
relief valves 170. During manufacture, the seal section 112 is
filled with clean motor lubricant oil.
[0033] The seal section shaft 164 is coupled to the motor shaft
128, or formed as a unitary shaft with the motor shaft 128, and
transfers torque from the motor 110 to the pump 108. The thrust
bearing assembly 166 includes a pair of stationary bearings 172 and
a thrust runner 174 attached to the seal section shaft 164. The
thrust runner 174 is captured between the stationary bearings 172,
which limit the axial displacement of the runner 174 and the motor
shaft 128 and seal section shaft 164.
[0034] In a particularly preferred embodiment, the seal section 112
includes a plurality of mechanical seals. Two mechanical seals
168a, 168b are depicted in FIG. 7. As best illustrated in the
close-up view of the mechanical seal 168 in FIG. 8, the mechanical
seals 168 each include bellows 176, a coiled spring 178, a runner
180 and a stationary ring 182. These components cooperate to
prevent the migration of fluid along the seal section shaft 164.
The stationary ring 182 has an internal diameter sized to permit
the free rotation of the seal section shaft 164. In contrast, the
bellows 176, springs 178 and runner 180 rotate with the seal
section shaft 164. The rotating runner 180 is held in place against
the stationary ring 182 by the spring-loaded bellows 176. The
bellows 176 preferably includes a series of folds that allow its
length to adjust to keep the runner 180 in contact with the
stationary ring 182 if the seal section shaft 164 should experience
axial displacement. The bellows 176 may be manufactured from thin
corrugated metal or from elastomers and polymers, including AFLAS,
perfluoroelastomer, polytetrafluoroethylene (PTFE), perfluoroalkoxy
(PFA) and polyethether ketone (PEEK).
[0035] Continuing with FIG. 7, the relief valves 170 are preferably
one-way check valves that are spring-biased in a closed position.
When a threshold pressure is exerted against the relief valves 170
by the internal pressure within the seal section 112, the relief
valves 170 temporarily open to release fluid from inside the seal
section 112 into the pump 108 or wellbore 104 to relieve the excess
internal pressure.
[0036] Thus, during thermal cycling of the motor 110, the motor
lubricant may expand from the motor 110 into the seal section 112
and the fluid expansion module 114. The fluid expansion module 114
provides the primary system for accommodating the expansion of
fluid from the motor 110 and the seal section 112 provides a
secondary system for accommodating the expansion of motor oil from
the motor 110. In the event that the fluid inside the seal section
112 exceeds a threshold pressure, the relief valves 170 temporarily
open to prevent damage to the motor 110 or mechanical seals 168.
The primary function of the seal section 112 is to prevent
migration of fluids along the shafts between the motor 110 and pump
108.
[0037] It is to be understood that even though numerous
characteristics and advantages of various embodiments of the
present invention have been set forth in the foregoing description,
together with details of the structure and functions of various
embodiments of the invention, this disclosure is illustrative only,
and changes may be made in detail, especially in matters of
structure and arrangement of parts within the principles of the
present invention to the full extent indicated by the broad general
meaning of the terms in which the appended claims are expressed. It
will be appreciated by those skilled in the art that the teachings
of the present invention can be applied to other systems without
departing from the scope and spirit of the present invention.
* * * * *