US 3781456 A
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Description (OCR text may contain errors)
United States Patent [191 Knowles et al.
[ PRESSURE SEALED CABLE PACKOFF AND METHOD FOR MAKING AND USING SAIVE  Inventors: Charles R. Knowles, Anchorage,
Alaska; Douglas J. Ruckel, Corpus Christi, Tex.
 Assignee: Atlantic Richfield Company, New
 Filed: Aug. 1, 1972  App]. No.: 277,057
174/20, 22 R, 23 R, 23 C, 65 R, 65 SS, 70 S, 76, 77 R, 151; 156/48; 166/65 R, 66, 75, 88, 315; 277/1, 4, 12; 339/117 R, 218 R, 218 C,
 References Cited UNITED STATES PATENTS 2,232,872 2/1941 Seitz 174/20 2,890,268 6/1959 Berry 174/23 R X 2,924,467 2/1960 Burch 277/1 3,059,210 10/1962 Luenberger 339/218 R X 3,432,612 3/1969 Spiegel et al 174/21 R X 3,437,149 4/1969 Cugini et al 339/218 R X FOREIGN PATENTS OR APPLICATIONS 200,636 11/1958 Austria 174/76 GREASE FITTING Dec. 25, 1973 1,138,615 l/l957 France... 174/65 SS 1,473,304 2/1967 France 174/151 1 12,289 12/1917 Great Britain 174/65 R 776,890 6/1957 Great Britain 174/76 Primary Examiner--Laramie E. Askin Attorney-M. D. Folzenlogan et a1.
[5 7] ABSTRACT Apparatus for feeding a multi-conductor cable through a wall separating two environmental zones, such as pressure zones of a Christmas tree of a wellhead, includes a hollow body inserted through the wall separating the zones. The hollow body is filled with epoxy and a pressurized packing material forced into nonconducting interfaces between the epoxy and the hollow body. Conductor spacers are provided in one embodiment to prevent the conductors of the cable from shorting.
9 Claims. 3 Drawing Figures 6! EPOXY 58 PATENTEDUEBZ'SIQH 3.781.456
MET 2 (If 2 /GREASE FIG. 2
6/ -EPOXY GREASE 58 FITTING PRESSURE SEALED CABLE PACKOFF AND METHOD FOR MAKING AND USING SAME BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to apparatuses for carrying cables between two environmental zones and more particularly to apparatuses for carrying cables from zones of one pressure or atmosphere to zones of different pressure or atmosphere, and to methods for making and using same.
2. Description of the Prior Art It is desirable in many instances to monitor certain conditions such as temperature, pressure, or the like at various depths within a well hole. To carry instrumentation signals from within the well to recording or monitoring apparatus at the surface, a multi-conductor cable, may be run into the well hole with, for example, temperature sensing devices wired to specific conductors in the cable corresponding to desired well depths. At the ground level the cable may be removed from the well through a Christmas tree (the enclosing valve arrangement at the head or top of the well to control the fluid products and other components within the well).
In the construction of oil or gas wells or the like a plurality of pipes commonly are runv to subterranean regions at which the well product is located. For example, it may be desirable in a single well to run a first pipe to a gas producing region, a second pipe to an oil producing region, and so forth. In many cases, an outside pipe or casing is additionally included,- at least for some depth from the surface of the well, within which the other pipes may be located. This outside casing may be used to restrain gravel or other loose materials to ease the initial drilling of the well, and'to seal the well to prevent underground seepage of the well product which may flow outside the product carrying pipes.
The area, or annulus, between the outer casing and the other pipes is generally filled with a fluid, such as an oil base drilling fluid, and additionally may be used to receive the instrumentation cable. Often, however, a pressure is created in the fluid within the annulus, especially in areas of permafrost in which frozen ground is encountered to a considerable depth beneath the surface. In such permafrost regions the ground is thawed during the drilling process, but subsequently it refreezes, generating by its expansion forces a considerable pressure upon the contained drilling fluid, which is transmitted by the fluid along the length of the well and exerted upon the Christmas tree.
Thus, a cable packoff or pressure sealed feedthrough is required to conduct the cable through a wall of the Christmas tree to the desired required equipment external to the well but at the same time isolating the pressures to prevent the fluid within the annulus from escaping.
SUMMARY OF THE INVENTION In light of the above, it is, therefore, an object of the invention to provide an apparatus for conducting a cable through a wall separating two environmental zones.
It is another object of the invention to provide an apparatus for conducting a cable from a first zone having a fluid therein under pressure to a second zone.
It is another object of the invention to provide an apparatus for conducting a cable from within a well to outside the well casing.
It is another object of the invention to provide a method for conducting a cable from within a first zone under pressure to a second zone at a different pressure.
It is still another object of the invention to provide an apparatus for conducting a cable having multiple conductors from a zone having a first pressure to a zone at a second pressure.
These and other objects, features, and advantages will become apparent to those skilled in the art from the detailed description herein below set forth when read in conjunction with the appended claims and accompanying drawing.
The invention, in its broad aspect, presents an apparatus for conducting a multi-conductor cable through a wall between environmental zones. The apparatus includes a cylinder or sleeve having a closed bottom and open top, the closed bottom having a hole therethrough for receiving the cable. A top member is provided which engages the open top of the sleeve to define an enclosed chamber with the walls and bottom of the sleeve. The top member additionally has a hole therethrough for receiving the cable. A first packing material is included within the enclosed chamber, and a second packing material is forced under pressure into areas between the first packing material and the sleeve and the top member.
Also presented, in its broad aspect, is a method for feeding a multi-conductor cable having insulation covered conductors within an outer casing through a wall between environmental zones. The method includes the steps of locating the cable within a sleeve defining an enclosure mountable to the wall, whereby the cable will run between the environmental zones when the sleeve is mounted to the wall; removing the outer casing over a portion of the cable within the enclosure; and removing the insulation from conductors of the cable over a portion within the enclosure. A first packing material is then inserted within the enclosure to contact the conductors from which the insulation has been removed, the sleeve and the enclosure subjected to a pressure, and a second packing material injected under pressure to areas between the first packing material and the walls of the enclosure.
BRIEF DESCRIPTION OF THE DRAWING The invention is illustrated in the accompanying drawing wherein:
' FIG. 1 is a side plan view of a portion of a well, partially in cross section, incorporating a cable feedthrough apparatus in accordance with the principles of the invention.
FIG. 2 is a side plan view of a cable feedthrough apparatus, in cross section, in accordance with the invention.
FIG. 3 is a side plan view of a cable feedthrough apparatus in cross section, in accordance with an alternative preferred embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The cable feedthrough apparatus, in accordance with the invention, has a principal application in conducting a multiconductor cable from the interior of a well to circuitry or the like exterior the well. As shown in FIG.
l, a well may include within the drilled hole 11 any number of pipes, two pipes 12 and 13 being shown for illustration, extending along the length of the hole 11. For a portion of the depth of the well, an outer casing 15 may be included to prevent grave] or other loose particles from falling into and filling up lower portions of the well, and for isolating the'well from the adjacent surrounding ground area 16.
A cable may be run within the annulus 21 between the outer well pipe 12 and the outer well casing 15, and may have the desired instrumentation 22 connected to various of its conductors at desired well depths. A cable type commonly encountered is a FIG. 8-PVC-24 conductor type, and it is with this type cable that explanation and illustration'of the cable feedthrough of the invention is primarily directed herein, although it will be apparent that the cable feedthrough of the invention may be used with practically any type cable presenting any number of conductors.
The cable feedthrough 25 may be mounted onto a Christmas tree 26 through a wall thereof, extending within the annulus 21 wherein the cable 20 is disposed. Thus, signals generated from the various instrumentation devices 22 along the length of the cable 20 are conducted along the length of the cable, through the feedthrough 25 to the outside of the Christmas tree 26, and connected to meters or other instruments (not shown) external to the well 10. v
The feedthrough may be alternatively mounted on the top of the Christmas tree 26, for example, if the well is static and not producing. In this instance the cable 20 is run directly through the various valves of the Christmas tree 26.-On the other hand, if it is desired to run the cable directly into the well without traversing the valves, it may be mounted, as shown, on the Christmas tree at a location directly entering the annulus 21.
As shown in FIG.'2, the cable packoff or feedthrough 27 includes a cylinder 30 having an interior chamber 31, and a closed bottom 32 having an opening 33 through which the cable 34 may be run. The top 38 of the cylinder 30 is open, and is enclosable with a top member or plug 40 which engages threads 41 on the interior wall 42 of the cylinder 30 with its threads 43. A hole 44 is provided through the plug 40 through which the cable 34 may be run from the interior chamber 31 of the cylinder 30. I
Formed around the interior wall 42 of the cylinder 30 are one or more grooves 49, which serve to maintain a cable packing material 52 within the enclosure 31. The choice of the particular packing material depends upon the pressures to be encountered, the particular materials the feedthrough interfaces, and so forth. It has been found, for instance, that in application in an oil well having water at one interface under pressure of approximately 300 to 500 pounds per square inch that a resinous material which will set up to present a strength and hardness, such as epoxy, is suitable.
A grease fitting hole 55 is provided through one wall of the cylinder 30 through which grease 62 under pressure may be injected, as below discussed. The grease fitting hole 55 may be closed by a button head grease fitting 56 to enable the pressurized grease to be conveniently injected.
Within the enclosure of the cylinder 30, the individual wires 58 of the cable are separated from the outer cable sleeve 59, and stripped of their insulation 60 along a length 61 of them to effect the pressure seal, as
will become apparent. If the feedthrough 27 is to additionally support the cable 34 within the well, an eyebolt 65 may be mounted onto the bottom 32 of the cylinder 30 from which the cable 34 may be suspended by hangers (not shown) or the like or by an outer conductor tied or fixed to it by an appropriate hanger (not shown).
Formed on the outer-cylinder 30 of the feedthrough 27 are threads 47 and 48 to threadably engage mounting flanges, one such flange 50 being illustrated engaging threads 47. A similar flange engaging threads 48 may be mounted directly onto a manifold wall of the Christmas tree in a position such as shown in H6. 1. The flanges may include one or more holes 65 to receive bolts (not shown) to hold the flange in the mounted position or to hold external equipment (not shown) in contact therewith.
Because the parts of the feedthrough structure may be subjected to considerable pressure and other deleterious influences, the variousparts are made of strong, durable material, such as 4140 steel, or the like.
To fabricate and achieve a completed packoff connection, with particular direction toward feeding a FIG. 8-PVC-24 conductor type cable from within a well to a point external the well, the outside cylinder 30 is machined, as shown. Two or three feetof the cable 34 is prepared by stripping the outside cable covering 59 along a several inch length to expose the inner insulation covered conductors 58. Then, the insulation 60 is stripped from each of the conductors over a short distance 61, such as an inch or so, and the conductors are flared or separated, as shown, to prevent them from shorting one against the other. The cylinder 30 and the exposed wire are then cleaned with acetone or some other suitable solvent to remove any oil, grease or other matter which may be deposited on them which would interfere with the seal to be effected. The cable is then positioned, as shown, with the bare wire over the stripped length 61 within the chamber 31 of the cylinder 30.
A cable maintaining material 52'is then poured into the enclosure 31 of the cylinder 30'. As described above, any material which sets up to a solid or semisolid state is suitable, such as epoxy or the like. If epoxy is used, the epoxy may in addition to filling the chamber 31 of the cylinder 30 be placed on the threads 41 of the cylinder to form a union between the plug 40 and the cylinder 30 when inserted. Before the epoxy sets, the conductors 58 should be tested to ensure that there are none shorting together. When this is completed, the epoxy is allowed to set for the required period.
After the epoxy has set, the packing plug port 55 is drilled and tapped, and the packing plug 56 inserted. When the threads of the packing plug port 55 are tapped, the tap is stopped before the bottom of the port is reached so that the threads extend only part of the way through it to ensure that the packing plug 56.does not extend into the epoxy 52 within the cylinder 30 to enable the grease to be subsequently inserted.
A fluid pressure is then applied to the cylinder approximately equalling the pressure expected to be encountered when the feedthrough 27 is installed on the well. This pressure minutely separates the epoxy 52 and the inner wall 42 of the cylinder 30 along their interfaces, and separates as well some of the other structures from the epoxy, such as the cable through the hole 33 in the bottom 32, the inner wall 42 of the cylinder 30, the grooves 49, and the cable in the hole 44 in the top member 40. Additionally, the pressure may separate the insulation 60 of the conductors 58 from the epoxy 52, up to the metal epoxy junction along the length 61 of the conductors 58 over which the insulation 60 has been stripped. The pressure, however, ordinarily will not separate the epoxy contact to the exposed metal of the conductors 58 along the length 61 over which the insulation 60 has been stripped.
The packing material 62 is then injected through the packing plug 56 into the separated areas. A suitable packing material may be any heavy grease; a sealant sold under the tradename Rockwell Norstrum 555-WG sealant has been found satisfactory to seal pressures of up to 5,000 psi. The sealant is injected until it oozes from the interior of the feedthrough through an exit hole, such as hole 44 in top member 40. Thus, the fluid is sealed from one side of the feedthrough 27 to the other by the injected grease and by the solid epoxy metal contact to the conductors 58.
If desired, suitable Twist-Lock multi-conductor plugs 68 or the like may be installed on the lower end of the cable 34 so that the cable may be pulled off the plug and valves of the Christmas tree closed above the plug, if necessary. The instrument cable is then run down the well hole, supported from the eyebolt 65, as shown in FIG. 1.
If equipment for applying a fluid pressure to the feedthrough 27 to generate a force sufficient to separate the epoxy 52 from the walls of the cylinder 30 is unavailable, the feedthrough may be mounted directly onto the Christmas tree and exposed to the actual pressure with which its operation is intended, and the grease sealant injected after installation.
An alternative embodiment of the feedthrough structure of the invention, shown in FIG. 3, is similar to the structure of the feedthrough above described with reference to FIG. 2, and includes two spaced apart perforated boards 70 and 71 within the chamber 72 of the cylinder 73, each presenting a plurality of holes 74 through which the wires 75 are run to space them apart and to maintain the spaced apart relationship to lessen the chances of shorts between them. Holding the spaced apart perforated boards are shoulders 76 and 77 formed on the interior wall 78 of the packoff cylinder 73. The chamber 72 is, as above, filled with epoxy and the noncontacting interfaces packed with grease 80 through a grease fitting 79.
Although the invention has been described and illustrated with a certain degree of particularity, it is to be understood that the present disclosure is made by way of example only and that numerous changes and modifications will be apparent to those having ordinary skill in the art without departing from the spirit and scope of the invention, as hereinafter claimed.
1. Apparatus for conducting a multiconductor cable through a wall between environmental zones, comprismg:
a multi-conductor cable, said cable being stripped of insulation along a length to expose the conductors of said cable,
a sleeve having a closed bottom and open top, the closed bottom having a hole therethrough receiving the cable,
a top member engaging the open top of said sleeve to define an enclosed chamber within the walls and bottom of said sleeve, said top member having a hole therethrough receiving the cable,
a first packing material within the enclosed chamber contacting the exposed conductors of said cable,
a second packing material under pressure in areas between said first packing material and said sleeve and said top member.
2. The apparatus of claim 1 wherein said sleeve and top member are of 4140 steel.
3. The apparatus of claim 1 wherein said sleeve has a plurality of channels along an interior wall thereof within the enclosed chamber.
4. The apparatus of claim 1 wherein said first packing material is epoxy and said second packing material is a grease.
5. The apparatus of claim 4 further comprising a grease fitting extending through a wall of said sleeve to within the enclosed chamber.
6. The apparatus of claim 1 further comprising means within the enclosed chamber holding the conductors of the cable spaced apart from each other.
7. The apparatus of claim 6 wherein said means for holding the conductors comprises two boards each having a plurality of holes through which the conductors of the cable are positioned, and wherein said sleeve comprises two shoulders within the enclosed chamber on which each of said boards respectively is carried.
8. A method for feeding a multi-conductor cable having insulation covered conductors within an outer casing through a wall between environmental zones comprising,
removing the outer casing along a length of the cable,
removing the insulation from conductors of the cable along the length of the cable within the length from which the outer casing is removed,
locating the cable with the conductors disposed within a sleeve defining an enclosure mountable to the wall, whereby the cable will run between the pressure zones when the sleeve is mounted to the wall,
inserting a first packing material within the enclosure to contact the conductors from which the insulation has been removed,
subjecting the sleeve defined enclosure to a first pressure,
injecting a second packing material under pressure higher than said first pressure to areas between the first packing material and the walls of the enclosure.
9. The method of claim 8 further comprising disposing at least one conductor separating element within the enclosure to prevent the cables from which the insulation has been removed from shorting.