Note: Descriptions are shown in the official language in which they were submitted.
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
HIGH TEMPERATURE DOWNHOLE MOTORS WITH
ADVANCED POLYIMIDE INSULATION MATERIALS
RELATED APPLICATIONS
[001] This application is a continuation-in-part of United States Patent
Application Serial No.
13/706,322 filed December 5, 2012, entitled "High Temperature Downhole Motors
with Advanced
Polyimide Insulation Materials," the disclosure of which is herein
incorporated by reference.
FIELD OF THE INVENTION
[002] This invention relates generally to the field of electric motors, and
more particularly, but not
by way of limitation, to improved magnet wire for use in high-temperature
downhole pumping
applications.
STATEMENT ABOUT GOVERNMENT SPONSORED RESEARCH
[003] Portions of this invention were made with government support under
government contract
DE-EE0002752 awarded by the Department of Energy. The government has certain
rights in the
invention.
BACKGROUND
[004] Electrical submersible pumping systems include specialized electric
motors that are used to
power one or more high performance pump assemblies. The motor is typically an
oil-filled, high
capacity electric motor that can vary in length from a few feet to nearly
fifty feet, and may be rated
up to hundreds of horsepower. The electrical submersible pumping systems are
often subjected to
high-temperature, corrosive environments. Each component within the electrical
submersible pump
must be designed and manufactured to withstand these hostile conditions.
[005] Like other electrodynamic systems, the motors used in downhole pumping
systems typically
include a stator and a rotor. The stator typically has a metallic core with
electrically insulated wire
winding through the metallic core to form the stator coil. When current is
alternately passed
through a series of coils, magnetic flux fields are formed, which cause the
rotor to rotate in
1
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
accordance with electromagnetic physics. To wind the stator coil, the wire is
first threaded through
the stator core in one direction, and then turned and threaded back through
the stator in the opposite
direction until the entire stator coil is wound. Each time the wire is turned
to run back through the
stator, an end turn is produced. A typical motor will have many such end turns
upon completion.
[006] In the past, motor manufacturers have used various insulating materials
on the magnet wire
used to wind the stator. Commonly used insulation includes polyether ether
ketone (PEEK)
thermoplastics and polyimide films. Insulating the conductor in the magnet
wire prevents the
electrical circuit from shorting or otherwise prematurely failing. The
insulating material is typically
extruded, solution coated or film tape wrapped onto the underlying copper
conductor. In recent
years, manufacturers have used insulating materials that are resistant to
heat, mechanical wear and
chemical exposure.
[007] Although widely accepted, current insulation materials may be inadequate
for certain high-
temperature downhole applications. In particular, motors employed in downhole
applications where
modern steam-assisted gravity drainage (SAGD) recovery methods are employed,
the motor may be
subjected to elevated temperatures. Extruded insulation material often suffers
from variations in
thickness, eccentricity and contamination as a result of the extrusion
process. Prior film-based
insulation requires the use of adhesive layers between the conductor and
layers of film, which often
has lower temperature performance than the film. There is, therefore, a need
for an improved
magnet wire that exhibits enhanced resistance to heat, corrosive chemicals,
mechanical wear and
other aggravating factors. It is to this and other deficiencies in the prior
art that the present
invention is directed.
SUMMARY OF THE INVENTION
[008] In a preferred embodiment, the present invention provides an electric
motor assembly
configured for use in a downhole pumping system. The electric motor assembly
includes a number
of electrically conductive components that are insulated from fluids,
mechanical abrasion, electrical
2
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
current and electrical grounds using an advanced polyimide film. Preferred
polyimide films include
poly(4,4'-oxydiphenylene-pyromellitimide) and biphenyl-tetracarboxylic acid
dianhydride (BPDA)
type polyimide films. Magnet wire, stator laminates, stator coil end turns,
motor leads and power
cables can all be insulated with the selected polyimide film.
[009] The polyimide insulating film can be surrounded with an external
insulator. In preferred
embodiments, the external insulator is extruded onto the internal polyimide
insulating film. The
extruded external insulator is preferably manufactured from PTFE, PEK, PEKEKK
or PEEK resins.
The extrusion of the external insulator over the internal polyimide insulator
produces a continuous
layer of insulation in crystalline state.
[010] In another aspect, the present invention provides a method of
manufacturing a motor
assembly for use in an electrical submersible pumping system. The method
includes the step of
providing an insulator film selected from the group consisting of poly(4,4'-
oxydiphenylene-
pyromellitimide) and biphenyl-tetracarboxylic acid dianhydride (BPDA) type
polyimide films,
wrapping the insulator film around an electrically conducive motor component,
heating the wrapped
insulator film to its melting point to create a sealed, insulated electrically
conductive motor
component and applying an external insulating layer to the internal polyimide
layer. In a
particularly preferred embodiment, the step of applying the external
insulating layer comprises
extruding PTFE, PEK, PEKEKK or PEEK resin around the internal polyimide
insulating layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[011] FIG. 1 is a back view of a downhole pumping system constructed in
accordance with a
presently preferred embodiment.
[012] FIG. 2 is a side elevational view of the motor assembly of the pumping
system of FIG. 1.
[013] FIG. 3 is a partial cross-sectional view of the motor assembly of the
pumping system of FIG.
1.
3
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
[014] FIG. 4 is a close-up cross-sectional view of the motor assembly of the
pumping system of
FIG. 1.
[015] FIG. 5A is a cross-sectional view of a piece of magnet wire from the
motor of FIG. 4.
[016] FIG. 5B is a cross-sectional view of a piece of magnet wire from the
motor of FIG. 4 that
includes an external insulator.
[017] FIG. 6 is a perspective view of a round power cable from FIG. 1.
[018] FIG. 7 is a perspective view of a flat power cable from FIG. 1.
[019] FIG. 8 is a top plan view of a laminate from the motor assembly.
[020] FIG. 9 is a cross-sectional view of a slot liner from the motor
assembly.
[021] FIG. 10 is a close-up partial top view of the stator core and magnet
wire.
[022] FIG. 11 is a side elevational view of the motor assembly with exposed
end-turns.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[023] In accordance with a preferred embodiment of the present invention, FIG.
1 shows a front
perspective view of a downhole pumping system 100 attached to production
tubing 102. The
downhole 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. The downhole
pumping system 100
is shown in a non-vertical well. This type of well is often referred to as a
"horizontal" well.
Although the downhole pumping system 100 is depicted in a horizontal well, it
will be appreciated
that the downhole pumping system 100 can also be used in vertical wells.
[024] As used herein, the term "petroleum" refers broadly to all mineral
hydrocarbons, such as
crude oil, gas and combinations of oil and gas. 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
4
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
of the pumping system 100 are primarily disclosed in a submersible
application, some or all of these
components can also be used in surface pumping operations.
[025] The pumping system 100 preferably includes some combination of a pump
assembly 108, a
motor assembly 110 and a seal section 112. In a preferred embodiment, the
motor assembly 110 is
an electrical motor that receives its power from a surface-based supply
through a power cable 114.
The motor assembly 110 converts the electrical energy into mechanical energy,
which is transmitted
to the pump assembly 108 by one or more shafts. The pump assembly 108 then
transfers a portion
of this mechanical energy to fluids within the wellbore, causing the wellbore
fluids to move through
the production tubing to the surface. In a particularly preferred embodiment,
the pump assembly
108 is a turbomachine that uses one or more impellers and diffusers to convert
mechanical energy
into pressure head. In an alternative embodiment, the pump assembly 108 is a
progressive cavity
(PC) or positive displacement pump that moves wellbore fluids with one or more
screws or pistons.
[026] The seal section 112 shields the motor assembly 110 from mechanical
thrust produced by
the pump assembly 108. The seal section 112 is also preferably configured to
prevent the
introduction of contaminants from the wellbore 104 into the motor assembly
110. Although only
one pump assembly 108, seal section 112 and motor assembly 110 are shown, it
will be understood
that the downhole pumping system 100 could include additional pumps assemblies
108, seals
sections 112 or motor assemblies 110.
[027] Referring now to FIGS. 2 and 3, shown therein are elevational and
partial cross-section
views, respectively, of the motor assembly 110. The motor assembly 110
includes a motor housing
116, a shaft 118, a stator assembly 120, and a rotor 122. The motor housing
116 encompasses and
protects the internal portions of the motor assembly 110 and is preferably
sealed to reduce the entry
of wellbore fluids into the motor assembly 110. Referring now also to the
partial cross-sectional
view of the motor assembly 110 in FIG. 4, adjacent the interior surface of the
motor housing 116 is
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
the stationary stator assembly 120 that remains fixed relative the motor
housing 116. The stator
assembly 120 surrounds the interior rotor 122, and includes stator coils 124
extending through a
stator core 126. The stator core 126 is formed by stacking and pressing a
number of thin laminates
128 to create an effectively solid stator core 126. The stator coils 124 are
formed by extending
magnet wire 130 through the stator core 126, as depicted in FIG. 4.
[028] FIG. 5A presents a cross-sectional view of the magnet wire 130. The
magnet wire 130
preferably includes a conductor 132 and an internal insulator 134. The
conductor 132 is preferably
constructed from fully annealed, electrolytically refined copper. In an
alternative embodiment, the
conductor 132 is manufactured from aluminum. Although solid-core conductors
130 are presently
preferred, the present invention also contemplates the use of braided or
twisted conductors 130. It
will be noted that the ratio of the size of the conductor 132 to the internal
insulator 134 is for
illustrative purposes only and the thickness of the internal insulator 134
relative to the diameter of
the conductor 132 can be varied depending on the particular application.
[029] In a first preferred embodiment, the internal insulator 134 is a heat-
bonding type polyimide
film. In a particularly preferred embodiment, the heat-bonding type polyimide
film is biphenyl-
tetracarboxylic acid dianhydride (BPDA) type polyimide film where the
thermoset polyimide film
is coated with thermal plastic polyimide. The thermal plastic polyimide melt
flows at temperature
above 300C, which permits heat bonding without the use of an intervening
adhesive layer which
usually melts below 300C. This increases the thermal capability of the
insulation. Suitable
polyimide films are available from UBE Industries, Ltd. under the "UPILEX VT"
line of products.
The polyimide internal insulator 134 can be heat laminated directly to the
conductor 132 without the
use of an adhesive.
[030] The process for laminating the BPDA type polyimide film directly to the
conductor 132
preferably includes the step of heating the conductor 132 and internal
insulator 134 to above about
6
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
300 C. To prevent the oxidation of the conductor 132 under these
temperatures, the conductor 132
can be nickel-plated. Alternatively, the heat bonding process can be carried
out in an inert gas
atmosphere to prevent oxidation of the conductor 132. The use of BPDA type
polyimide film for
the internal insulator 134 permits the use of the magnet wire 130 above about
250 C.
[031] In a second preferred embodiment, the internal insulator 134 is
manufactured from a water-
resistant polyimide film, such as poly(4,4'-oxydiphenylene-pyromellitimide).
Suitable water-
resistant polyimide films are available from E.I. du Pont de Nemours and
Company under the
KAPTON WR line of products and from UBE Industries, Ltd. under the UPILEX S
line of
products. These films provide an internal insulator 134 with significantly
increased resistance to
hydrolysis.
[032] In the preferred embodiments, the selected internal insulator 134 is
wrapped around the
conductor 132. In particularly preferred embodiments, two or more layers of
the internal insulator
134 film are wrapped around the conductor 132. It will be appreciated to those
of skill in the art
that alternative methods of wrapping the internal insulator 134 around the
conductor 132 are within
the scope of the present invention.
[033] The use of a melt-processable film internal insulator 134 permits the
omission of an
adhesive between the internal insulator 134 and conductor 132.
In presently preferred
embodiments, the internal insulator 134 is directly applied to the conductor
132 and then sealed
through application of heat to the internal insulator 134. In a particularly
preferred embodiment, the
internal insulator 134 is wrapped around the conductor 132 and then heated to
the polymer melt
point. Pressure is then applied to bring the molten polymer internal insulator
134 into full contact
with the conductor 132. Heat and pressure can be applied through the combined
use of heated
anvils or rollers, ultrasonic equipment or lasers.
7
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
[034] In these preferred embodiments, the heat-bonding type polyimide film
internal insulator 134
may optionally be used in combination with an external insulator 135, as
depicted in FIG. 5B. Once
the conductor 132 is film-wrapped with polyimide film and heat fused, the
internal insulator 134 is
then wrapped with the external insulator film 135. The external insulator 135
may include one or
more fluoropolymer films, polyether ketone (PEK) films, polyether ketone
etherketoneketone
(PEKEKK) films or PEEK films. Suitable fluoropolymer films include
polytetrafluoroethylene
(PTFE) film. The PTFE film is preferably calendared, sintered and etched for
better adhesion. In
particularly preferred embodiments, the PEEK film is a biaxially stretched
film that has a higher
modulus.
[035] Alternatively, the external insulator 135 may constitute one or more
extruded layers
surrounding the internal insulator 134. Once the internal insulator 134 has
been adhered to the
conductor 132, the insulated conductor 132 is then passed through one or more
extrusion processes
in which the external insulator 135 is extruded onto the outer surface of the
internal insulator 134.
In presently preferred embodiments, the external insulator 135 is manufactured
from PTFE, PEK,
PEKEKK or PEEK resins. The extrusion of the external insulator 135 over the
internal insulator
134 produces a continuous layer of insulation in crystalline state.
[036] Turning to FIGS. 6 and 7, shown therein are perspective views of a round
power cable 114a
and a flat power cable 114b, respectively. It will be understood that the
geometric configuration of
the power cable 114 can be selected on an application specific basis.
Generally, flat power cables,
as shown in FIG.7, are preferred in applications where there is a limited
amount of space around the
pumping system 100 in the wellbore 104. As used herein, the term "power cable
114" collectively
refers to the round power cable 114a and the flat power cable 114b. In the
presently preferred
embodiment, the power cable 114 includes power cable conductors 136, internal
power cable
insulators 138, a jacket 140 and external armor 142.
8
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
[037] The power cable conductors 136 are preferably manufactured from copper
wire or other
suitable metal. The power cable conductors 136 can include a solid core (as
shown in FIG. 6), a
stranded core or a stranded exterior 144 surrounding a solid core (as shown in
FIG. 7). The power
cable conductors 136 can also by coated with one or more layers of tin,
nickel, silver, polyimide
film or other suitable material. It will be understood that the size, design
and composition of the
power cable conductors 136 can vary depending on the requirements of the
particular downhole
application.
[038] The internal power cable insulators 138 preferably include at least one
layer of a heat-
bonding type polyimide film. In a particularly preferred embodiment, the
internal power cable
insulators 138 are manufactured from a biphenyl-tetracarboxylic acid
dianhydride (BPDA) type
polyimide film that permits heat bonding without the use of an intervening
adhesive layer. Suitable
polyimide films are available from UBE Industries, Ltd. under the "UPILEX VT"
line of products.
The polyimide film internal power cable insulator 138 can be heat laminated
directly to the
conductor 136 without the use of an adhesive. The internal power cable
insulators 138 are
preferably encased within the jacket 140. In the preferred embodiment, the
jacket 140 is
constructed one or more layers of lead, nitrile, EPDM, thermoplastic, braid or
bedding tape
constructed from polyvinylidene flouride (PVDF), Tedlar tape or Teflon tape,
or some combination
of these materials. The jacket 140 is protected from external contact by the
armor 142. In the
preferred embodiment, the armor is manufactured from galvanized steel,
stainless steel, Monel or
other suitable metal or composite. The armor 142 can be configured in flat and
round profiles in
accordance with the flat or round power cable configuration.
[039] Although the use of BPDA type polyimide film for the internal power
cable insulator 138
are disclosed herein with reference to the multi-conductor power cables 114,
it is also within the
scope of the present invention to use BPDA type polyimide film in the motor
lead cable 146 (shown
9
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
in FIG. 3). In the motor lead cable 146, BPDA type polyimide film is
preferably used to insulate
the multiple conductors between the power cable 114 and the motor assembly
110. The present
invention also contemplates the use of BPDA type polyimide film insulation to
protect the
connections or splices between adjacent conductors and conductors and motor
leads.
[040] The heat-bonding type polyimide film internal power cable insulator 138
may optionally be
used in combination with an external power cable insulator 139. Once the power
cable conductor
136 is film-wrapped with the internal polyimide film insulator 138 and heat
fused, the external
power cable insulator 139 is applied. In a first preferred embodiment, the
external power cable
insulator 139 includes an insulator film wrapped around the internal power
cable insulator 138. The
external power cable insulator 139 may include one or more fluoropolymer
films, polyether ketone
(PEK) films, polyether ketone etherketoneketone (PEKEKK) films or PEEK films.
Suitable
fluoropolymer films include polytetrafluoroethylene (PTFE) film. The PTFE film
is preferably
calendared, sintered and etched for better adhesion. In particularly preferred
embodiments, the
PEEK film is a biaxially stretched film that has a higher modulus.
[041] Alternatively, the external power cable insulator 139 may constitute one
or more extruded
layers surrounding the internal power cable insulator 138. Once the internal
power cable insulator
138 has been adhered to the conductor 136, the insulated conductor 136 is then
passed through one
or more extrusion processes in which the external power cable insulator 139 is
extruded onto the
outer surface of the internal power cable insulator 138. In presently
preferred embodiments, the
external power cable insulator 139 is manufactured from PTFE, PEK, PEKEKK or
PEEK resins.
The extrusion of the external power cable insulator 139 over the internal
power cable insulator 138
produces a continuous layer of insulation in crystalline state.
[042] Turning to FIG. 8, shown therein is a stator laminate 128 that includes
a plurality of stator
slots 148 and slot liners 150. In a first preferred embodiment, the slot liner
150 is manufactured
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
from a water-resistant polyimide film, such as poly(4,4'-oxydiphenylene-
pyromellitimide). Suitable
polyimide films are available from E.I. du Pont de Nemours and Company under
the KAPTON WR
line of products and from UBE Industries, Ltd. under the UPILEX S line of
products. These films
provide a slot liner with significantly increased resistance to hydrolysis.
[043] Referring now also to FIG. 9, shown therein is a cross-sectional view of
the slot liner 150
constructed in accordance with a second preferred embodiment. The slot liner
150 is constructed of
a polymeric film 152 sandwiched between first fabric 154 and a second fabric
156. The first and
second fabric layers 154, 156 are preferably either woven ceramic fabric or
glass fabric, or both
woven ceramic and glass fabric. The first and second fabric layers 154, 156
provide physical
spacing around the polymeric film layer 152 and a porous structure that allows
dielectric fluid to
flow or permeate through the slots 145 for better heat dissipation.
[044] The polymeric film 152 layer provides high dielectric strength and high
thermal stability in
the dielectric fluid. The polymeric film 152 layer is preferably manufactured
from a polyimide
film, such as UPILEX S, UPILEX VT, Kapton-E, Kapton WR Kapton PRN, and Kapton
CR, which
are available from UBE Industries, Ltd. and E.I. du Pont de Nemours and
Company, as discussed
above. Alternatively, the polymeric film 152 can be manufactured from a
fluoropolymer film, such
as perfluoroalkoxy polymer (PFA), sintered PTFE, super PTFE or
polyetheretherketone (PEEK)
film. Suitable PEEK films are available from the Victrex Company under the
APTIV brands. The
polymeric film 152 can also be a combination of polyimide film and PEEK film
as well as
polyimide film and PTFE films, e.g., the lamination of polyimide film and PEEK
film or
fluoropolymer films, where polyimide is sandwiched by either PEEK or
fluoropolymer films.
[045] As illustrated in FIG. 10, each stator coil 124 is preferably created by
winding a magnet wire
130 back and forth though the slot liners 150 in the slots 148 in the stator
core 126. The magnet
wire 130 is insulated from the laminates 128 by the slot liners 150. Each time
the magnet wire 130
11
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
is turned 180 to be threaded back through an opposing slot, an end turn 158
is produced, which
extends beyond the length of the stator core 126, as illustrated in FIG. 11.
It will be noted that FIG.
provides an illustration of multiple passes of the magnet wires 130. The coils
of magnet wire
130 are terminated and connected to a power source using one of several wiring
configurations
known in the art, such as a wye or delta configurations.
[046] Turning to FIG. 11, shown therein is a depiction of several end turns
158. In the preferred
embodiment, a first stator coil 124A is wound by first passing magnet wire 130
in one direction
through the length of slot 148A. When the wire 130 has reached the end of the
stator core 126, the
wire 130 is turned 180 and passed through the length of slot 148A' (not
visible in FIG. 11) in the
opposite direction, thereby creating an end turn 158. When the wire 130 has
been pulled through
slot 148A' the length of stator core 126, it is again turned 180 and passed
back through slot 148A.
This process is repeated until slots 148A and 148A' have been filled to a
desired extent by
subsequent passes of the magnet wire 130. Each of the end turns 158 is
preferably insulated with a
water-resistant polyimide film. Suitable polyimide films are available from
E.I. du Pont de Nemours
and Company under the KAPTON WR line of products and from UBE Industries, Ltd.
under the
UPILEX S line of products. These films provide the end turn 158 with
significantly increased
resistance to hydrolysis.
[047] 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
12
CA 02916162 2015-12-18
WO 2014/209737 PCT/US2014/043116
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.
13