U.S. patent number 3,832,481 [Application Number 05/403,579] was granted by the patent office on 1974-08-27 for high temperature, high pressure oil well cable.
This patent grant is currently assigned to Borg-Warner Corporation. Invention is credited to Clinton A. Boyd, Donatas Tijunelis.
United States Patent |
3,832,481 |
Boyd , et al. |
August 27, 1974 |
HIGH TEMPERATURE, HIGH PRESSURE OIL WELL CABLE
Abstract
An electrical conducting cable for submersible motors adapted
for use in high temperature high pressure oil wells. The cable
includes separately insulated conductors disposed within an
epichlorohydrin rubber jacket. The conductors are insulated with a
layer of high temperature, high molecular weight, extrudable
fluorcarbon, such as 1:1 copolymer of ethylene and
chlorotrifluoroethylene, and a layer of high temperature
thermosetting rubber, such as ethylene propylene copolymers and
terpolymers, either layer being suitable as the primary insulation
and the other layer as the secondary insulation. The jacketed cable
unit is protected by an outer armor formed of a suitable metal. The
cable thus formed is flexible, abrasion resistant, solvent
resistant, liquid impervious, heat insensitive and unaffected by
well environment.
Inventors: |
Boyd; Clinton A. (Tulsa,
OK), Tijunelis; Donatas (Buffalo Grove, IL) |
Assignee: |
Borg-Warner Corporation
(Chicago, IL)
|
Family
ID: |
23596285 |
Appl.
No.: |
05/403,579 |
Filed: |
October 4, 1973 |
Current U.S.
Class: |
174/102R;
174/110FC; 174/120AR; 174/110AR; 174/116; 174/120SR |
Current CPC
Class: |
H01B
7/2806 (20130101); H01B 7/046 (20130101); H01B
7/292 (20130101) |
Current International
Class: |
H01B
7/28 (20060101); H01B 7/04 (20060101); H01B
7/29 (20060101); H01B 7/17 (20060101); H01b
003/18 (); H01b 007/18 (); H01b 007/02 () |
Field of
Search: |
;174/113R,116,12AR,12R,12SR,12R,107,108,11FC,11AR |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Grimley; A. T.
Attorney, Agent or Firm: McCurry; William S.
Claims
What is claimed is:
1. A multicomponent electrical cable adapted for use with a
submersible motor comprising at least one electrical conductor;
primary and secondary layers of insulating material surrounding
said conductor, one of said layers being formed of an extrudable
fluorcarbon and the other of said layers being formed of a
thermosetting rubber; a resilient jacket surrounding said
insulators and comprising an epichlorohydrin rubber of high
molecular weight; and an outer armor surrounding said resilient
jacket.
2. A multicomponent electrical cable adapted for use with a
submersible motor, comprising at least one electrical conductor;
primary and secondary layers of insulating material surrounding
said conductor, one of said layers being formed of a high
temperature, extruded 1:1 copolymer of ethylene and
chlorotrifluoroethylene, and the other layer being formed of a
thermosetting rubber; a resilient jacket surrounding said
insulators and comprising an epichlorohydrin rubber of high
molecular weight; and an outer armor surrounding said resilient
jacket.
3. A multicomponent cable as in claim 2 wherein said outer armor is
metal.
4. A multicomponent cable as in claim 2 wherein said primary layer
is formed of said fluorocarbon engaging and covering said
conductor, and said secondary layer is formed of said thermosetting
rubber covering said primary layer, and said layer of jacketing
material surrounds said secondary layer.
5. A multicomponent cable as in claim 4 wherein said outer armor is
metal.
6. A multicomponent cable as in claim 4 wherein said primary layer
is formed of said thermosetting rubber engaging and covering said
conductor, and said secondary layer is formed of said thermosetting
rubber covering said primary layer, and said layer of jacketing
material surrounds said secondary layer.
7. A multicomponent cable as in claim 6 wherein said outer armor is
metal.
8. A multicomponent cable as in claim 1 wherein said thermosetting
rubber is an ethylene propylene copolymer.
9. A multicomponent cable as in claim 1 wherein said thermosetting
rubber is a terpolymer.
Description
BACKGROUND OF THE INVENTION
This invention relates to electrical cable, and particularly to
electrical cable utilized to deliver electrical energy to
submersible motors adapted for use in high temperature, high
pressure oil wells.
Submersible pumps used in oil, mineral and water wells normally
include a prime mover in the form of an electric motor directly
coupled to the pump and disposed deep within the well. It is
necessary to provide an electrical connection between the motor and
a source of electrical energy at the surface as by the use of an
electrical conducting cable which extends between the source of
electrical energy and the motor.
In many instances, the motors operate at relatively high power
levels, in some case exceeding 200 horsepower. Normally, the motors
used are of the three-phase type and the associated cable includes
three separate electrical conductors.
The electrical cable must have adequate current carrying capability
and must be of sufficient dielectric strength to prevent electrical
losses even under the adverse environmental conditions usually
found within the well. The environmental conditions of the well
vary generally depending upon geographical location. In some cases
the well fluid is highly corrosive and in many instances well
temperatures exceed 275.degree.F. Most oil well fluids include
brines containing dissolved H.sub.2 S gas, carbonates and salts,
and large volumes of oil. The fluid pressure in wells may be quite
high and in many instances exceeds 4,000 psig. Additionally, the
wells are quite deep, averaging 8,000 to 10,000 feet. The
electrical cable must possess sufficient physical strength to allow
insertion of the motor and cable to these depths and the outer
surface of the cable must resist the abrasion associated with
insertion. Since the cable is normally wound upon storage or
transportion reels, it must possess the additional property of
flexibility, so that it will resist physical damage caused by
reeling.
Typical cable construction presently being utilized includes three
conductors of copper separately insulated are helically wound to
form a single unit. The conductors are insulated with a material of
high dielectric strength such as polyethylene or polypropylene. The
helically wound and insulated conductors are sheathed in an
extruded jacket of nitrile rubber surrounding the insulated
conductors.
One common form of jacketed cable is covered with an outer armor in
the form of a continuous wrapped band of metallic material. This
band is lapped as it is wound. The armor provides abrasion
resistance. Usually, the armor is formed of steel or bronze;
however, in many special applications, such as wells which are
excessively corrosive, stainless steel or exotic metals such as
monel metal must be used.
Polyethylene has also been employed to a limited extent as the
outer armor, but it has been found that the same does not stand up
under severely high temperatures.
Proper material selection for the cable armor has always presented
difficulties. Many different armor materials must be utilized
depending upon the well conditions and no single cable construction
has been found suitable for universal application. This is
especially true for the deep, high pressure and high temperature
wells.
Electrical power cables constructed as previously described which
have been used in high temperature, high pressure oil wells, fail
because of temperature distortion of the thermoplastic cable
components, corrosion of the armor, or chemical and solvent attack
of the elastomer jacket. Since most oil wells contain dissolved
H.sub.2 S gas, carbonates, water, salts and large volumes of oil,
no single material has heretofore been found which has the
resistance to solvents, heat and pressure to operate for prolonged
periods in such an environment.
An additional problem encountered by cable in such an environment
is deformation under load. The cables are subject to both
compressive and tensile forces and, under high temperatures, there
is a marked tendency for the thermoplastic insulation to deform
resulting in dislocation of the conductors and phase to phase or
phase to ground short circuitry.
Rupture of the armor due to swell of the jacket is another example
of deformation which occurs in such an environment. Rupture of the
total construction also occurs during retraction of the cable from
the well as a result of the depressurization of fluids which have
permeated the cable.
These and other associated difficulties have clearly dictated the
need for an improved impermeable, environment-insensitive cable
construction.
SUMMARY OF THE INVENTION
The present invention relates to an improved multi-component
electrical cable for submersible motors adapted for use in high
temperature, high pressure oil wells. A cable constructed according
to this invention comprises an outer armor of metal, an inner
jacket of epichlorohydrin rubber, and high temperature, synthetic,
organic insulators surrounding the electrical conductors.
The insulators, according to this invention, are useful in high
temperature, high presure oil wells. One of these insulators is a
high temperature, high molecular weight, extrudable thermoplastic
fluorocarbon polymer, which is an excellent electrical insulator at
elevated temperatures when unaffected by oil and brine. While the
thermoplastic fluorocarbon is suitable for use in high temperature
and pressure oil wells, it is very expensive and, accordingly, a
very thin insulation layer is employed. Due to this factor, it is
desirable to provide further insulative protection by using, in
combination with the fluorocarbon insulator, another insulation in
the form of a high temperature thermosetting elastomer rubber, such
as ethylene-propylene copolymers and terpolymers, having the
required heat resistance and electrical properties necessary for
use as commercially manufactured oil well cable insulation.
The epichlorohydrin rubber used for the jacket is compounded for
the minimum of oil and water permeability and swell. The
epichlorohydrin rubber jacket is oil and water insensitive and
impermeable providing a barrier which protects the insulators from
any loss of dielectric strength and electrical protection to the
conductors. Furthermore, the insulators, being temperature
insensitive, will not deform and change electrical insulation
thickness. The impermeability of the jacketing further insures that
there be no permeating fluids to plasticize or soften the
insulators and thus reduce their insensitivity to temperature
deformation.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary perspective view of a section of electrical
conducting cable for submersible motors illustrating various
features of the invention;
FIG. 2 is a cross-sectional view of the cable of FIG. 1 taken
generally along the lines 2--2 of FIG. 1:
FIG. 3 is a fragmentary perspective view of a section of a second
embodiment of electrical conducting cable, similar to FIG. 1;
and
FIG. 4 is a cross-sectional view of the cable of FIG. 3 taken
generally along the lines 4--4 of FIG. 3.
DETAILED DESCRIPTION
Referring now to the FIGS. 1 and 2 of the drawings, there is shown
a multi-component electrical conducting cable for a submersible
motor designed for use in high temperature, high pressure oil wells
which is illustrative of the principles of the present
invention.
FIG. 1 shows a cable section which includes conductors 11, a
resilient jacket 13 and an outer armor 15.
Each conductor 11 is illustrated as being formed of stranded wire
17 helically wound to prevent separation of strands. These separate
strands may be tinned to minimize chemical interaction between the
conductor and the insulating material. Solid conductors may be used
without departing from the spirit of the invention.
In the illustrated embodiment each conductor includes seven
strands. The number of conductors, the diameter of the conductor
and number of wires is, of course, dependent upon the load carrying
capabilities required for a particular cable application. It should
additionally be noted that any suitable conducting material may be
used, such as, for example, copper, aluminum.
Each wound set of wire strands forms a single conductor and is
separately insulated by an insulation layer 19. The conductor
insulation 19 is formed of a high temperature, organic, synthetic
material of high dielectric strength. High temperature, high
molecular weight, extrudable fluorocarbon polymers have been found
to be satisfactory for this purpose. The thickness of the layer 19
may have a different relationship to the dimensions of the other
elements of the cable than what is inferred by the drawing.
However, the drawing illustrates the various elements which make up
the cable without reference to actual dimensions.
A preferred embodiment of a high temperature, high molecular
weight, extrudable fluorocarbon polymer is a 1:1 copolymer of
ethylene and chlorotrifluoroethylene insulating material,
commercially available under the trade name HALAR from Allied
Chemical Co. This material has a formula
(CH.sub.2 CH.sub.2 CF.sub.2 CFCl).sub.n
and has been found to possess the following physical
properties:
Tensile Strength at 23.degree. C. 7000 psi at 340.degree. F. 400
psi Elongation at 23.degree. C. 200% at 340.degree. F. 350% Melting
Point 460.degree. F. Dielectric Strength Initial 18.7 KV Dielectric
Strength, 4 days at 410.degree. F. 15.0 KV Cut Through, 1000 g., at
120.degree. F. 137 hrs.
It will be apparent that the extrudable
ethylene-chlorotrifluoroethylene copolymer is particularly suited
for use in cable constructions intended for applications to oil
well environments. Despite the fact of being a thermoplastic and
therefore capable of melting and flowing under high temperature and
pressures, it retains physical strength at elevated temperatures
and dielectric strength at temperatures as high at 410.degree.F.
The resistance of the ethylene-chlorotrifluoroethylene copolymer to
high temperature and high pressure fluid environments can also be
improved by irradiation and by sheathing in an oil-and-brine
resistant jacket. The comparative properties of irradiated and
unirradiated films of the ethylene-chlorotrifluoroethylene
copolymer are:
Solvent Swell** High Temperature After Exposure Deformation 4500
psig, 275.degree. 50 psi, 275.degree. F. 7 Days
______________________________________
______________________________________ ASTM1-A oil BRINE
______________________________________ HALAR, unirradiated 50%
elongated, 2.0% -2.5% broke in 1 day HALAR, 10 megarad 50%
elongation, 0.5% -0.5% exposure* no break, 5 days HALAR, 50 megarad
10% elongation, -0.5% 2.0% exposure* no break, 5 days High
Temperature Polyproplylene 10% elongation 40% 1% broke first day
______________________________________ *Exposure to Co.sup.60
irradiation source. **Per cent change in volume
It will be apparent that for use under very stringent well
conditions, wire insulation will be most suited if irradiated, and
the irradiated insulation is a preferred embodiment of this
invention. It will also be apparent that other extrudable
thermoplastic fluorocarbon polymers may be employed for this
purpose. Such compositions as DuPont's commercial PFA polymers
Teflon 9704 and Teflon 9705, the known FEP polymeric materials, and
the commercially available FEP/PE copolymers, such as Dupont's
Tefzel products and other extrudable fluorocarbon polymers and
copolymers which possess the necessary extrusion characteristics
are considered to be equivalent materials for this particular
purpose, and therefore within the scope of the present
invention.
While the above-described thermoplastics are exceptionally
qualified for oil well cables in view of their extrudability and
resistance to a very high temperature and high pressure fluid
environment, they are very expensive and, accordingly, in use must
be necessarily restricted to a required minimum quantity to provide
economical manufacture of the cables. Therefore, a further
protective layer is necessarily present.
To provide the further protective layer, a layer of an insulating
material having the needed heat resistant and electrical
properties, such as ethylene propylene copolymers and terpolymers,
which is suitable for oil well cable insulation is employed to
cover the thermoplastic insulation layer 19 as the conductor
insulation 21.
An example of a suitable class of such an insulating material is
heat-stablized ethylene-propylene copolymer rubber, including
ethylene-propylene terpolymer rubber. One example of such materials
is found described in U.S. Pat. No. 2,933,480.
Further protection at the insulated wire is necessary in order that
it be usefully employed over the great lengths necessary to extend
to the bottoms of oil wells. In order to minimize entangling,
rupture and similar damage while being installed down a well casing
together with the pump motor, pump, ancilliary equipment and the
production pipe, it is necessary to further jacket the insulated
wire with an oil and brine-resistant outer covering. While many
materials have been employed in the past for such purposes,
including nitrile rubber and neoprene, and they have found general
application in shallow, low temperature well environments, they
have been generally unsuitable for the high temperature and high
pressure deep well environments. For the practice of this
invention, it is essential that the flexible jacketing material
resist oil and brine under the bottom hole conditions and that the
wire insulation be protected to avoid permeation of gases and
fluids which would cause rupture on depressurization and to avoid
permeation by oil to plasticize or by water to reduce electrical
resistance.
The wound conductor unit is thus disposed within the jacket 13
which is comprised of a high molecular weight epichlorohydrin
rubber compounded for the minimum of oil and water permeability and
swell. This jacket may be extruded about the wound conductors and
preferably is formed to fill interstices 23 between adjacent
conductors.
One preferred embodiment is a formulation of epichlorohydrin
compounded of the materials and in approximately the ratios as
follows:
TRADE NAME MATERIAL PARTS/100 PARTS OF RUBBER AVAILABLE FROM
__________________________________________________________________________
Herclor H High molecular weight epichlorohydrin rubber 100.0
Hercules, Inc. Span 60 Surface active agent comprised of partial
esters of hexitol anhydrides 1.5 Atlas Chemical Industries Dyphos
XL Di-Basic Lead Phosphite (heat stabilizer) 10.0 National Lead
Company N B C Nickel dibutyl dithiocarbamate (anti-oxidant) 1.0 Du
Pont Cumate Copper, dimethyl dithiocarbamate (accelerator) 0.125 R.
T. Vanderbilt Company Phenothiazine Phenothiazine 1.0 Fisher
Scientific Company Vulcan Carbon Black (filler) 30.0 Cabot
Corporation Hi Sil 233 Silica (filler) 10.0 P.P.G. Industries TE-70
Plasticizers 0.5 Technical Processing, Inc. TP-95 Plasticizers 1.0
Thiokol Chemical Corp. Azelaic Acid Dispersant 4.0 Eastman Organic
Chemicals NA-22 2 mercaptothiazoline (accelerator) 1.0 Du Pont
__________________________________________________________________________
The extruded epichlorohydrin jacket completely fills the voids
formed about the separately insulated conductors. This precludes
exposure of the insulation to well fluid and further prevents flow
of well fluid along the cable length in the event that a rupture
occurs at some point along the outer armor 15 and the outer
periphery of jacket 13.
The jacket 13 of the cable is surrounded by an outer armor 15 such
as metal as previously stated.
Use of a multi-component cable such as that described provides a
cable construction which is abrasion resistant, impervious to well
fluids, flexible and unaffected by corrosive well environments and
high temperature.
A typical well cable, constructed according to the present
invention, includes three seven-wire stranded copper conductors,
each of which is surrounded and covered by a layer of high
temperature, high molecular weight, extrudable 1:1 copolymer of
ethylene and chlorotrifluoroethylene insulation 19 having an
average thickness of 0.010 inch to 0.080 inch. The insulation layer
19 is covered by a layer of a high temperature thermosetting rubber
in the form of an elastomer, such as ethylene propylene copolymers
and terpolymers, having needed heat resistance and electrically
protective properties, having an average thickness of 0.10 inch to
0.80 inch. The separate conductors are helically wound to form a
single unit. The insulated conductors are helically wound to form a
single unit. The insulated conductors are jacketed with an
epichlorohydrin rubber. The jacket thickness is 0.040 inch minimum
average. The jacket is provided with additional protection by
surrounding it with a metal armor which may be wound in a
conventional manner.
Another and alternate embodiment of the cable, according to this
invention, is illustrated in FIGS. 3 and 4. In this embodiment, the
parts are identified by a suffix A; they are the same as described
with reference to FIGS. 1 and 2. It will be observed that the
thermosetting rubber or elastomer insulation layer 21A surrounds
and covers the three seven-wire stranded copper conductors 11 and
provides the primary insulation cover, and the fluorocarbon
insulation layer 19A surrounds the layer 21A and provides the
secondary insulation cover. Because of the cost of the extrudable
fluorocarbon, a minimum quantity of the insulation layer 21A is
used. The layer 21A is surrounded by the jacketing layer 23A of
epichlorohydrin rubber. The insulation layer 24A is extruded onto
the insulated conductors 11A.
As can be appreciated, the cable construction of the present
invention provides an efficient and durable conducting unit for use
in the adverse environment associated with high temperature, high
pressure oil wells.
While the epichlorohydrin rubber utilized for the jacket 13 and 13A
is described as HERCLOR H (Hercules, Inc.), an epichlorohydrin
homopolymer [poly (alpha - chloropropylene oxide) ], other
homopolymers of epichlorohydrin such as HYDRIN 100 (B. F. Goodrich)
are suitable for this application. Also epichlorohydrin rubbers
prepared from epichlorohydrin and ethylene oxide are suitable for
the jacket 13. These copolymers are sold under the trade name
HERCLOR C (Hercules, Inc.) and HYDRIN 200 (B. F. Goodrich).
The cable is illustrated as being substantially round in section;
it should be understood that this invention also comtemplates a
flat cable configuration in which the conductors are in
side-by-side relationship.
* * * * *