Note: Descriptions are shown in the official language in which they were submitted.
CA 02241'.78 1998-06-23
"MULTICONDUCTOR ELECTRICAL CABLE"
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to multiconductor electrical cables and, more
5 particularly, to multiconductor electrical cables for use in subterranean wellbores.
2. Description of Related Art
Multiconductor electrical cables that are used to power wellbore equipment, such
as electrical submergible pumping systems, must be capable of withstanding the high
temperatures, high pressures and/or corrosive fluids often encountered within
10 subterranean wellbores. As used herein, the term "high temperature" means
temperatures of greater than about 180 F and as high as about 500 F. The term "high
pressure" means pressures as high as about 5,000 psi. Further, the term "corrosive
fluids" means liquids and gases which can cause degradation to cable in~ ting materials
and/or corrosion to the electrical conductors, such as liquids and/or gases containing
15 hydrogen sulfide, carbon dioxide, brine, water, and the like.
Subterranean wellbore cables include several layers of different materials to
either protect the copper conductors from llle,h~ical damage and/or from damage from
corrosive ~luids. Usually, the copper conductors are sheathed in one or more layers of
ins~ tin~ materials, such as ethylene propylene diene methylene terpolymer ("EPDM"),
20 and a thin sheath of extruded lead to act as a fluid barrier. As a final protection, a metal
armor is applied over the electrical conductors.
To protect the thin sheath of extruded lead from mechanical damage, such as
cracks from bending and scratches from abrasion, a protective braid is woven around the
electrical conductors. When the electrical conductors leave the metal extruder, where
CA 02241~78 1998-06-23
the fluid barrier is applied, they are reeled onto a spool, transported to the braiding
machines, fed through the braiding machines, and then transported to the armoring
machines. Each of these steps greatly increases the chances for the fluid barrier to be
damaged, which directly results in power cable failures.
If damage does occur in the manufacturing process, then once the power cable
is installed and a failure occurs, then, the fluid production from the wellbore is ceased,
resulting in lost revenue to the operator. In addition, expensive and time-consuming
cable retrieval, repair and reinst~ tion procedures must be undertaken.
There is a need for a multiconductor power cable, and methods of manufacture
10 thereof, for use in subterranean wellbores that eliminates the braiding process to form
a protection of the metallic fluid barrier.
SUMMARY OF THE INVENTION
The present invention has been contemplated to overcome the foregoing
deficiencies and meet the above described needs. Specifically, the present invention is
15 a multiconductor electrical cable for use in a subterranean wellbore that includes at least
one electrical conductor surrounded by one or more layers of in~ul~ting material. A fluid
barrier, such as an extruded layer of lead or tin alloy, surrounds the in~ ting material.
To protect the fragile fluid barrier during the subsequent armoring process, a non-
braided protective material is applied as an extrusion or a tape. The non-braided
20 protective material can be applied immediately after the fluid barrier is applied, not as
a separate process as in the past with braided materials, thereby reducing the risk of
damage to the fragile fluid barrier during m~ f~ctllring. In addition, the non-braided
protective material can be applied with simple forms or wrapping machines that are less
complex and less costly than the prior braiding machines.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross-sectional, perspective view of one preferred embodiment of
a multiconductor electrical cable of the present invention, with a longitudinal wrap of
non-braided material above the fluid barrier.
Figure 2 is a cross-sectional, perspective view of an alternate preferred
embodiment of a multiconductor electrical cable of the present invention, with a spiral
wrap of non-braided material.
Figure 3 is a cross-sectional, perspective view of an alternate preferred
embodiment of a multiconductor electrical cable of the present invention, with an
10 extruded layer of non-braided material.
Figure 4 is a cross-sectional, perspective view of an alternate preferred
embodiment of a multiconductor electrical cable of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As described above, the present invention comprises a multiconductor electrical
15 cable for use in a subterranean wellbore. The cable includes at least one electrical
conductor surrounded by one or more layers of im~ ing material, with a fluid barrier
surrounding the in~ ting material. To protect the fragile fluid barrier during the
subsequent armoring process, a non-braided protective material is applied as an
extrusion or a tape. The non-braided protective material can be applied immediately
20 after the fluid barrier is applied, not as a separate process as in the past with braided
materials, thereby reducing the risk of damage to the fragile fluid barrier.
While the power cable of the present invention can be used in many differing
power tr~n~mission environments, for the purposes of the present discussion it will be
assumed that the power cable is used to supply electricity to an electric submergible
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pumping system ("ESP"). As is well known to those skilled in the art, the ESP is set
within a casing that is cemented within a subterranean wellbore that penetrates one or
more subterranean earthen formations. Typical ESP's comprises an elongated electric
motor, an oil-filled motor protector, and a multistage pump connected to a production
5 tubing. The electrical cable extends from a surface power source downwardly within the
casing and is operatively connected to the electric motor.
The electrical cable of the present invention is made to withstand relatively high
temperatures, high pressures and corrosive fluids encountered within subterranean
wellbores; however, it should be understood that the electrical cable of the present
10 invention can also be used in less difficult applications, such as surface power
tr~n~mi~sion, under water uses, and the like. As used herein, the term "high
teml)el~l~lre" means temperatures of greater than about 180 F and as high as about 500
F. The term "high pressure" means pressures as high as about 5,000 psi. Further, the
term "corrosive fluids" means liquids and gases which can cause degradation to
15 in~l-l,.ting materials and/or corrosion to the electrical conductors, such as liquids and/or
gases cont~ining hydrogen sulfide, carbon dioxide, water, and the like.
To aid in the underst~ntling of the features of the present invention, reference is
made to the accompanying drawings. Figure 1 shows one preferred embodiment of an
electrical cable 10 ofthe present invention of a relatively flat configuration, with three
20 electrical conductors 12 in parallel and side-by-side relationship. The electrical
conductors 12 are single drawn wires of copper or copper alloys, as shown in Figures
1-3, or from a twist of several wires, as shown in Figure 4. For typical wellbore
applications, the conductors 12 are single drawn wires having a diameter or gauge
thickness offrom about 0.160" (6 AWG) to about 0.414" (2/0 AWG). If the cable 10
CA 02241~78 1998-06-23
is to be used in extremely corrosive environments, the conductors 12 may have a
relatively thin coating (not shown) of lead, tin or alloys thereof, hot dipped, heat
extruded, or electroplated thereon. One or more ground wires (not shown) may be
included, as well as other wires, conductors, conduits, fiber optics, and the like, as may
S be used to transmit fluids and/or information and command signals through the power
cable 10.
At least one of the electrical conductors 12, and preferably all of the conductors
12, is sheathed in at least one layer of an inc~ tin~ material 14 selected from the group
consisting of ethylene propylene diene methylene, ethylene propylene rubber,
10 polychloroprene, polyimide, fluroelastomers, polypropylene, polyethylene, polyether,
and copolymers, mixtures, blends and alloys thereof. If a polyether ins~ ing material
is selecte~l, then preferred materials are selected from the group consisting of polyether-
ketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK),
polyetherketoneetherketoneketone (PEKEKK), and mixtures, blends and alloys thereof.
15 The in~ ting material 14 is applied to the conductor 12 by spiral or longitudinal
wrapping, or preferably by heat extrusion, as is well known to those skilled in the art.
To protect the conductors 12 and the insulation material 14 from damage caused
by corrosive fluids, a fluid barrier 16 is applied to the outer surface of the insul~ting
material 14. The fluid barrier 16 is preferably one or more extruded layers of a metal,
20 such as lead, tin, and/or alloys thereof.
As described previously, the fluid barrier 16 is fragile and very susceptible to
cracking and abrasion damage during the m~nllf~ctllring process. Therefore, a braid of
nylon threads has been applied to protect the fluid barrier during subsequent transport
and armoring process. As described previously, this braiding process is relatively
. CA 02241~78 1998-06-23
expensive as compared to extruding processes, uses relatively complex machines as
compal ed to extruding machines, and requires the insulated and sheathed conductors to
be spooled onto a reel, moved to the braiding machines, spooled through the braiding
m~çhines, respooled onto a reel, and then moved to the armoring machines. All of this
spooling and transport can lead to damage to the fluid barrier.
To eliminate or at least to greatly reduce the chances of damage to the fluid
barrier 16 during the manufacturing process, with the present invention the prior nylon
braid is elimin~ted and a new non-braided protective material 18 is applied in one or
more layers to the fluid barrier 16 as a tape or as an extrusion. The protective material
18 is selected from the group comprising fiberglass, nylon, ethylene propylene
copolymer, ethylene vinyl acrylate copolymer, ethylene ethyl acrylate copolymer,ethylene propylene diene methylene terpolymer, polychloroprene, polyolefin elastomer,
and copolymers, mixtures, blends and alloys thereof.
To assist in dissipating static electrical charges within the cable 10 to the outer
metallic armor, and to provide a grounding of the armor when the cable 10 is installed
in a wellbore, the non-braided protective material 18 is selected to be itself semi-
conductive, i.e., have a resistivity less than about 10 K ohm/meter, or include one or
more threads and/or fibers of semi-conductive materials, such as carbon impregnated
nylon threads or other similar material.
One or more layers of the non-braided protective material 18 can be applied to
the in~ ted and sheathed conductors 12 as a separate process, as before with the nylon
braid, or preferably as a process that is in-line and immediately adjacent to the machinery
that applies the fluid barrier 16. Specifically and for example, the protective material 18
can be in the form of a tape that is passed through a conical form and longitudinally
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wrapped around the insulated and sheathed conductor 12, as shown in Figure 1. The
tape of protective material 18 can be thermoplastic or thermoset, and as such a seam 20
of the protective material 18 can be sealed by the extemal application of heat to seal the
seam. In place of the application of heat or in addition thereto, a solvent or glue can be
5 used along the seam 20 to create a seal.
When the fluid barrier 16 is a heat extruded layer of metal, the fluid barrier 16
exits that extrusion machinery is at about 300 degrees F to about 400 degrees F.
Preferably, the seam 20 is sealed simply by applying the tape of protective material 18
immediately thereafter so that the residual heat from the immediately prior metal
10 extrusion will cause the seam 20 to seal.
The tape of the protective material 18 can be applied as a spiral wrap, as shown
in Figure 2, and as one or more extruded layers, as shown in Figure 3. The cable 10 can
also include a jacket of elastomeric material 22, as shown in Figure 4, that surrounds the
in~ul~ted and ~hP~thed conductors 12. This jacket 22 can be formed from tapes and/or
15 one or more extruded layers of elastomeric material selected from the group consisting
of nitrile rubber, ethylene propylene, ethylene propylene diene methylene terpolymer,
polychloroprene, polyolefin elastomer, polyethylene, polypropylene, polyethylene,
polyether, and copolymers, mixtures, blends and alloys thereof. A~er the protective
material 18 has been applied, an outer protective ammor 24 is spirally wrapped there
20 around, as is well known to those skilled in the art.
As can be understood from the previous discussion, the present invention
provides an electrical cable that does not need a separate braiding process, with its
illhel elll risks of damage to the fragile fluid barrier, and uses material and processes that
are less expensive than the prior braided material.
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Whereas the present invention has been described in particular relation to the
drawings attached hereto, it should be understood that other and further modifications,
apart from those shown or suggested herein, may be made within the scope and spirit
of the present invention.
