United States Patent
`Whitfill, Jr.et al.
`
`(15;
`
`[54] METHOD FOR MAKING A GAS BLOCKED
`LOGGING CABLE
`
`[75]
`
`Inventors: William A. Whitfill, Jr.; Richard P.
`McNerney, both of Houston, Tex.
`[73] Assignee: Schlumberger. Technology
`Corporation, New York, N.Y.
`
`,
`
`= June 13, 1973
`Filed:
`{22}
`[21] Appl. No.: 369,665
`
`Related U.S.-Application Data
`{62} Division of Ser. No. 302,159, Oct. 30, 1972, Pat. No.
`3,800,066.
`
`[52] US. Ch weeseeeeeseeetseeens 264/103; 156/56;
`156/275; 264/174
`Int. Ch? wo.— HO1B 7/24; HOTB 7/02
`[51]
`[58] Field of Search...... we. 264/174, 103; 174/116;
`:
`156/275, 56
`References Cited
`
`[56]
`
`UNITED STATES PATENTS
`3/1951
`
`Kennedy u.........ceeceeeeeeeeneeeee 174/116
`
`2,544,233
`
`(11)
`[45]
`
`4,005,168
`Jan. 25, 1977
`
`............ 264/174
`Swartswelter et al.
`2,810,424 10/1957
`3,106,815
`10/1963 Nance ct al. oe 57/13
`3,236,939
`2/1966
` Blewis etal. oe 174/116
`3,433,687
`3/1969
`Price wo... cece wee 156/275
`3,541,682 11/1970 Hildebrandt .......0 156/275
`
`
`
`FOREIGN PATENTS OR APPLICATIONS
`
`403,371
`
`12/1933 United Kingdom ........0..... 174/116
`
`Primary Examiner—Jeffery R. Thurlow
`Attorney, Agent, or Firm—David L. Moseley; William
`R. Sherman; Stewart F. Moore
`
`ABSTRACT .
`[57]
`Method and apparatus for forming a well logging cable
`‘that is gas-blocked by virtue of having solid outer con-
`ductors cabled arounda stranded,filled center conduc-
`’ tor and interred in a monolithic matrix material. Sub-
`stantially all void spaces are thereby eliminated to pre-
`vent collection of gas anywhere within the cable at high
`temperatures and pressures.
`
`3 Claims, 5 Drawing Figures
`
`
`
`Nevro Corp.
`Ex. 1014
`U.S. Patent No. 7,891,085
`
`Nevro Corp.
`Ex. 1014
`U.S. Patent No. 7,891,085
`
`

`

`Jan. 25, 1977
`
`U.S. Patent
`
`4,005,168
`
`

`

`1
`
`4,005,168
`
`METHODFOR MAKING A GAS BLOCKED
`LOGGING CABLE
`This application is a division of application Ser. No.
`302,159, filed Oct. 30, 1972, now U.S. Pat. No.
`3,800,066, issued Mar. 26, 1974.
`This invention relates to methods and apparatus for
`forming electrical cable cores, particularly well logging
`cable cores that are gas blockedfor use in logging well
`bores containing gas-cut muds.
`A standard multi-conductor well logging cable has a
`core comprised of six outer conductors cabled around
`a single center conductor and embedded in a neoprene
`matrix. The outer conductors are usually formed by
`copper wire strands twisted around a single center
`strand, whereas typically the inner conductor has
`strands twisted around a plastic monofilament. Of
`course each conductor is covered with a layer of suit-
`able insulation material. Although the neoprene matrix
`fills substantially all
`the voids between conductors
`within the cable core, particularly where the cable is
`manufactured according to the teachings of U.S. Pat.
`No. 3,106,815, assigned to the assignee of this inven-
`tion, voidsstill may exist within the conductors them-
`selves between and aboutthe strands.
`Althoughthe use of the foregoing cable construction
`is highly satisfactory for many well logging operations,
`its use in wells containing substantial amounts of low
`molecular weight hydrocarbons such as methane gas
`involves a substantial risk of failure in the cable and/or
`the cable terminations when the cable is rewoundafter
`a logging job. Such failure is due to the fact in the
`depthsof the borehole and at temperatures above 150°,
`which is quite common,the gas can permeate the ma-
`trix of the cable and the insulation materials of the
`conductors due to a phenomenon that may be called
`activated diffusion, and causes pressure buildup and
`gas entrapmentin the conductorvoids. As the cable is
`removed from the well and wound back upon the drum
`at the surface, release of the entrapped gas is only
`accomplished through bleed out at the terminated ends
`of the conductors,or outright rupture of the insulation
`materials themselves. Either case can, and often does,
`result in highly undesirable cable failure due to electri-
`cal shorting.
`It is the principal object of this invention to provide a
`new and improved well logging cable having the con-
`ductors constructed in such a manneras to contain
`substantially no voids to thereby obviate the problem of
`cable failure after logging wells containing gas-cut
`mud.
`This and other objects are attained in accordance
`with the concepts of the present invention by providing
`a multi-conductor cable construction wherein the cen-
`ter conductor has strands twisted around a plastic
`monofilament. To eliminate internal
`interstices be-
`tween strands, the conductoris heated undertension to
`cause the strands to embedin the monofilament. Either
`subsequently or simultaneously, the outer interstices
`between strandsare filled to eliminate voids by com-
`pression extrusion of a thermoplastic resin, and then a
`final coating of insulation material is applied over the
`filled conductor. The outer conductors are solid wires
`that are cabled around thefilled center conductor and
`embedded within a neoprene matrix. The combination
`of the solid outer conductors and a completely filled
`inner conductorprovidesa resultant cable construction
`that contains substantially no voids whatever within
`
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`which gas can collect, and not containing the voids
`necessary for collection of permeated gas is not subject
`to rupture and failure upon withdrawal from the well.
`The present invention has other objects and advan-
`tages which will become more clearly apparent in con-
`nection with the following detailed description of a
`preferred embodiment, takenin conjunction with the
`appended drawings in which:
`FIG. 1 is a perspective view of a well logging cable
`with successive components broken away toillustrate
`details of the cable construction;
`FIG.2 is an enlarged cross-sectional view of the cen-
`ter conductor of the cable to illustrate the configura-
`tion of the various components after being formed in
`accordance with the present invention; and
`FIGS. 3A-3C are somewhat schematic view of appa-
`ratus for forming the cable illustrated in FIGS. 1 and 2.
`A cable 9 formed in accordance with the present
`invention as illustrated in FIG. 1 has a central, axial
`conductor 10 that includes wires stranded around a
`plastic monofilament and encased in an insulation ma-
`terial to be more fully described herebelow. The con-
`‘ductor 10 is centrally embedded in a core matrix mem-
`ber 11. Spirally wound about the member11 are outer,
`insulated, solid copper wire conductors 12, the spiraled
`conductors 12 being completely encased by additional
`embedding material 13 that joins with the matrix mate-
`rial 11 to provide a monolithic sheathing 14 having a
`generally cylindrical outer surface. Both the core ma-
`trix member 11 and the embedding material 13 prefer-
`ably are formed of an extrudable, semi-conductive, oil
`andgas resistant elastomerthat cures to a hardflexible,
`relatively incompressible form and maintains its physi-
`cal properties at borehole temperature and pressures.
`As an example,
`the acrylonitrile butadiene rubber
`known commercially by the trade name “Hycar”is well
`adapted for this purpose. It should be noted that the
`spiraled conductors 12 are firmly and uniformly sup-
`ported and separated from each other and from the
`axial conductor 10 by the sheathing material. Oppo-
`sitely spiraled armor wires 15 and 16 are received over
`the sheathing 14 to provide mechanical protection and
`strength to adapt the composite cable for use in well
`logging operations.
`Atthis pointit should be noted that in a typical prior
`art well logging cable, as previously mentioned,all the
`conductors are stranded. Thus the provision of solid
`copperwires for the outer conductors serves to elimi-
`nate void spaces for apparent reasons. However,it has
`been found that it is not appropriate to use a solid
`conductor in the center of the cable because of the
`elongation requirementsof a well logging cable. Thatis
`to say, a well logging cable which may be for example
`20-30,000 feet long, when suspended in a borehole
`undergoes considerable elongation that would exceed
`the elastic limit of a solid center conductorandresult in
`highly undesirable “Z”” kinks therein. Accordingly, the
`center conductor 10 is formed by stranded wires simi-
`lar to the prior art construction, however the conductor
`is completely filled in accordance with the present
`invention.
`The cross-section of the axially disposed conductor
`10 is shown in enlarged detail in FIG. 2, and is con-
`structed by a plurality, for example, six copper wire
`strands 20 around a center thermoplastic monofila-
`ment 21. The monofilament 21 is a fluorocarbon poly-
`mer such as FEP “Teflon”, a registered trade name of
`DuPont. The innerinterstices 22 of the conductor 10
`
`©
`
`

`

`3
`are filled in a particular manner by the simultaneous
`application of heat and tension causing the wire strands
`20 to embed in the monofilament 21 as will be ex-
`plained more fully herebelow. The outerinterstices 23
`are filled by compression extrusion of a thermoplastic
`resin material 24 that does not degrade at temperatures
`at least up to about 450° F, and which has acceptable
`flow properties at normal processable temperatures,
`for example about 625° F, so as to be capable offilling
`the external
`interstices of the strands. One suitable
`material is a copolymer sold under the trade name
`TEFZEL by DuPont. Finally an outer coating of insula-
`tion material 25 is applied by extrusion and is also a
`fluorocarbon polymer, preferably FEP ‘“Teflon”. The
`conductorwire strands 20 as shown are thus embedded
`in a monolithic body having substantially no void
`spaces or pockets into which gas that would permeate
`the insulation materials under high temperature and
`pressure can collect.
`Apparatusfor forming the cable 9 is shown schemati-
`cally in FIGS. 3A-C. In FIG. 3A,a typical high speed
`tubular strander 30 contains supply spools 31 for the
`copper wire strands 20 and a supply spool 32. for the
`plastic monofilament 21. The strands 20 feed to the
`outside of the tube 33 as it rotates, and at the forward
`end of the tube through a closing die 34 where they are
`formed around the monofilament 21. From here the
`conductorpasses to a capstan assembly 35 and then to
`a storage reel 36. At this point, the monofilament 21
`has a tubular form with the wires 20 stranded there-
`around in typical configuration. In order to imbed the
`strands 26 at least partially in the outer surface of the
`monofilament21, the stranded conductor 19 is paid off
`of a reel 40 as shown in FIG. 3B and is passed through
`a constant tension device 41, that may be, for example
`a combination ofa capstan and pulleys that incorporate
`either a mechanical brake oran electrical device such
`as a typical hysteresis brake. In any eventthe result is to
`place the conductor 10 under a substantially constant
`tension of predetermined magnitude. Under tension,
`the conductor is: passed through a heater 42 that. ap-
`plies sufficient heat to soften the monofilament. 21 so
`that radial inward forces on the strands 20 due to ten-
`sion cause them to imbed in the outer periphery of the
`monofilamentand to attain the cross-section configura-
`tion shown in FIG. 2. Next the conductor 10 passes
`through an extruder 43 with a compression extrusion
`set-up where the thermoplastic filler material 24 is
`applied to completely fill the external interstices as
`shownin FIG. 2, whereuponthefilled conductor passes
`through a second extruder 44 having a tubing extrusion
`set-up. Here the insulation material 25 is applied
`around the strands 20 and thefiller material 24. Then
`the conductor 10 feeds through a capstan assembly 45
`that preferably is driven by a constant speed motor and
`together with the constant tension device 41 dictates a
`carefully controlled tension for the conductor as it
`passes through the elements 42, 43 and 44.Finally, of
`course, the conductor is wound up ona storagereel 46.
`Referring now to FIG. 3C, the complete core of the
`cable 9 is formed by supplying the filled axial conduc-
`tor 10 from a spool 50 whereit is subjected to an ex-
`truding device 51 that applies the uncured, semi-con-
`ductive core material thereto to form the matrix mem-
`ber 11 with a generally cylindrical form. The member
`11 is then fed through a closing die represented at 52.
`Into the die are also fed the insulated solid copper
`conductors 12 that are supplied from spools 53
`mounted in a well known manner upon a rotatable
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`4,005,168
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`4
`frame. The frame and closing die 52 rotate about a
`commonaxis and the conductors 12 are embedded in
`the core member11 in passing through the closing die.
`The core member 11 is then fed through a second
`extruding device 54 where the uncured outer sheathing
`material 13 is applied under pressure to cause the ma-
`trix material to extrude about the outer parts of the
`spiraled conductors 12 and to merge with the inner
`core member 11. Next the assembly is subjected to
`curing action in an oven 55 which formsthe sheathing
`into a monolithic body that firmly embeds the conduc-
`tors therein again, with substantially no void spaces.
`Finally the inner and outer armor wires 15 and 16 are
`applied by known means(not shown) and thefinished
`cable is stored upon a reel or spool 56.
`As a working example to furtherillustrate the con-
`struction of the inner or axial conductor 10, the strands
`20 may be six 27 AWG (0.0142 inch O.D.) bright
`copperwire stranded around the thermoplastic mono-
`filament 21 having a diameter of 0.016 inches. This
`conductoris coated with a 0.005 inch wall thickness of
`the filler material 24 using minimum extruder screw
`speed and adjusting the wire speed to maintain the
`desired finished diameter of 0.053 inch. The heater
`current is set at 25 amps and the wire tension at 15
`pounds. These parametersdictate a line speed of about
`100 fpm using a 2 inch, 20:1, length to diameterratio,
`plasticating extruder with a temperature profile and
`extruder materials as recommendedby the supplier of
`the thermoplastic resin 24. The assembly is coated with
`0.010 inch wall thickness of the insulation material 25.
`The complete cable 9 havingthe filled axial conductor
`10 and the solid outer conductors 12 disposed in a
`monolithic body of matrix material 14 provides a well
`logging cable containing substantially no voids within
`which gas can collect, so that the cable is not subject to
`rupture and failure upon withdrawal from the well.
`Since certain changes or modifications may be made
`by those skilled in the art without departing from the
`inventive concepts involved, it is the aim of the ap-
`pended claimsto coverall such changes and modifica-
`tions falling within the true spirit and scope of the pre-
`sent invention.
`Weclaim:
`1. A process for making a gas blocked electrical
`cable, comprising the steps of: twisting a plurality of
`conductive wire strands around a thermoplastic mono-
`filament; embeddingsaid strandsatleast partially in the
`outer surface of said monofilament to eliminate inter-
`nal void spaces between strands; said embedding step
`being performed by heating said conductor while ap-
`plying tension thereto to soften said monofilament and
`force said strands at least partially into the external
`surfaces thereof; applying a thermoplastic filler mate-
`rial around said strands tofill the external void spaces
`between said strands and thereby form a completely
`filled conductor; extruding a layer of insulation mate-
`rial over said filled conductor; cabling a plurality of
`solid insulated conductors around said filled conduc-
`tor; and disposing all of said conductors within a void-
`free matrix forming material.
`2. The process of claim 1 wherein said applying step
`comprises compression extrusion ofsaid filler material
`to cause said material to flow inwardly into said exter-
`nal void spaces.
`3. The process of claim 1 including the further steps
`of applying inner and outer layers of armor wires
`around said conductors.
`*
`*
`*
`*
`*
`
`