High pressure electrical cable packoff and method of making

A high pressure electrical cable packoff and method of making. An integral packoff and seal includes a resin block bound to the insulation of an electrical cable where the metal exterior and jacket have been removed. A resilient sealing ring is molded around and encloses the block and the section of cable where the metal exterior and jacket have been removed. The integral packoff may be used in a wellhead in an oil well for restraining movement of the cable and for forming a high pressure seal.

BACKGROUND OF THE INVENTION 
The present invention is directed to the provision of a high pressure 
electrical cable packoff for sealing an electrical cable between two 
members and in particular to provide a sealed passageway of a production 
tubing and electrical cable through a wellhead in a well. 
It had been previously known to utilize rubber rings which have been 
compressed in a wellhead in an oilwell for sealing around an electrical 
cable and the production tubing. However, such seals have not been capable 
of sealing off against the cable at higher pressures. These prior art 
designs have resulted in the cable being extruded through the packoff by 
the differential pressure on the packoff as the force exerted on the cable 
exceeded the shear strength of the rubber ring. 
The present invention is directed to a high pressure electrical cable 
packoff which is made a permanent part of the electrical cable and capable 
of sealing around the cable and production tubing at high pressures, such 
as pressures above 3000 pounds per square inch. 
SUMMARY 
The present invention is directed to a high pressure electrical cable 
packoff for sealing an electrical cable between two members in which the 
cable includes at least one electrical conductor, insulation around the 
conductor, a jacket around the insulation, and a protective metal 
exterior. The packoff includes a resin block bonded to a longitudinal 
section of the insulation where the metal exterior and the jacket have 
been removed and the block extends outwardly beyond the outside of the 
cable. A resilient sealing ring is molded around and encloses the block 
and encloses the longitudinal section of the cable where the metal 
exterior and the jacket have been removed. 
A further object of the present invention is the improvement of a high 
pressure packoff in an oil well wellhead through which a production tubing 
and an electrical cable extends in which the packoff is integral with the 
cable for restraining and sealing when the packoff is compressed in the 
wellhead. A resin block is bonded to a longitudinal section of the cable 
where the metal covering and jacket have been removed and extends 
outwardly beyond the outside of the cable, and a resilient sealing ring is 
molded around and encloses the block and the longitudinal section of the 
cable. The ring includes an opening for fitting around the production 
tubing and a split is provided between the opening and the outer edge of 
the ring for allowing placement of the ring around the tubing. 
Still a further object of the present invention is the provision of a 
method of making a high pressure electrical cable packoff for an oilwell 
wellhead in a casing and surrounding a production tubing in which the 
cable includes at least one electrical conductor, an insulator around each 
conductor, a jacket around the insulators and a protective metal exterior. 
The method includes removing the metal exterior and removing the jacket at 
a longitudinal section of the cable, and bonding a resin block to the 
insulation where the metal exterior and jacket were removed, and extending 
the block outwardly beyond the outside of the cable. The method further 
includes molding a resilient sealing ring around and enclosing the block 
and the longitudinal section of the cable where the metal exterior and 
jacket have been removed. 
Still a further object of the present invention is wherein a shorter 
section of the jacket than the metal exterior is removed. That is, more of 
the metal exterior is removed than the jacket, and the method includes 
bonding the block and sealing ring to the remaining exposed jacket. The 
method further includes wherein the resilient sealing ring is bonded to 
the jacket. Preferably, the block is arcuately shaped for providing a 
greater support. 
A still further object of the present invention is wherein the ring is 
provided with an opening to accommodate the production tubing and the 
method includes splitting the ring between the opening and its outer edge 
to allow placement around the production tubing. 
Yet a further object of the present invention is wherein the shorter jacket 
section allows the jacket to be exposed at both sides of the longitudinal 
section for bonding to the resin block. 
Other and further objects, features and advantages will be apparent from 
the following description of a presently preferred embodiment of the 
invention, given for the prupose of disclosure, and taken in conjunction 
with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
While the high pressure packoff of the present invention will be described 
in connection with its use in a wellhead in an oilwell in an electrical 
submersible pump oilwell application, for purposes of illustration only, 
the present packoff may be used in other applications where a leak free 
seal must be provided around a cable and across a pressure differential. 
Referring now to FIG. 1, an oilwell installation is generally indicated by 
the reference numeral 10 having well casing 12, a production tubing 14 for 
receiving well fluids, and an electrical cable 16 for driving an 
electrical submersible pump (not shown) for producing well fluids from the 
installation 10. A wellhead is generally indicated by the reference 
numeral 20 and includes a packoff seal 22 which is compressed by members 
24 of the wellhead 20 to seal off against the production tubing 14 and the 
electrical cable 16 and against the inside of the casing 12. 
It has been known to utilize rubber compression rings as the packoff 22. 
However, such rings have not been capable of restraining and sealing off 
against the electrical cable 16 at higher pressures. That is, a pressure 
differential exists across the prior art packoff which resulted in the 
failure of the sealing at the electrical cable 16 and seal 22 interface at 
higher pressures causing a failure of the packoff. 
The present invention is directed to providing a packoff seal 22 which is 
made a permanent and integral part of the electrical cable 16 and is 
capable of sealing around the cable 38 and the production tubing 14 at 
high pressures such as above 3000 pounds per square inch and is capable of 
restraining the movement of the cable 16 relative to the packoff 22. 
The present invention can utilize various types of electrical cables, such 
as round cables, single or multiple conductor cables. One type of cable 
that may be used is an electrical cable 16, as best shown in FIG. 2, which 
is a flat three conductor cable. The cable 16 includes three conductors 26 
which may be multiple strand copper conductors which are individually 
insulated with a polymer insulation 28, such as EPDM elastomer, and a 
polymer or lead jacket 30, such as EPOM, is applied over the insultors 28. 
The cable is then wrapped with one or more layers of a protective metal 
exteriors such as conventional protective metal armor 32. 
Referring now to FIG. 3, the first step in the method of making the packoff 
22 of the present invention is best seen. At the longitudinal section, 
generally indicated by the reference numeral 36, where the packoff is to 
be made, a section of the protective metal armor 32 is removed, leaving 
armor ends 38. Also, a section of the jacket 30 is removed, leaving jacket 
ends 40. Preferably, a shorter section of the jacket 30 is removed than 
the protective metal armor 32. As best seen in FIG. 3, this step leaves 
the electrical conductors 26 and their insulators 28 exposed. 
Referring to FIG. 4, a resin 42 is bonded and completely fills the space 
around and between the exposed insulators 28, and extends beyond the 
outside of the cable 16. Preferably, the resin is also bonded to both of 
the ends 40 of the jacket 30. The resin 42 may be any suitable thermal 
setting resin such as epoxy or any suitable thermoplastic resin such as 
polyetheretherketone, and is preferably an epoxy block. The function of 
the epoxy resin block 42 is to bond to the insulators 28 of the conductors 
26, and to the ends 40 of the jacket 30 to distribute the forces created 
when a pressure differential is applied thereacross. The use of a 
non-conductive epoxy also prevents electrical stresses which might exist 
with the use of any type of metal support. Another advantage of bonding 
the resin 42 to the insulators 28 and jacket 30 instead of to the outside 
of the metal armor 16 is to prevent the migration of fluids or gases 
through the electrical conductor 16. 
Referring now to FIG. 5, a resilient sealing ring 44, such as rubber, is 
molded around the resin block 42, and longitudinal section 36 of the cable 
16 to enclose the ends 38 of the protective armor 32. Preferably, the 
electrical cable 16 is treated with an adhesive, such as Chemlok 250, 
prior to molding of the resilient ring 44. Preferably, the rubber is EPDM 
or nitrile type. 
As best seen in FIG. 6, the resin block 42 is preferably arcuately shaped 
for providing a greater support area in the resilient ring 44. In 
addition, the ring 44 is split at 46 to provide a split, extending from an 
opening 48, which accommodates the production tubing 14, to the outside 
edge of the ring 44. Therefore, the split 46 allows the ring 44 to be 
placed around the production tubing 14. The entire assembly is then placed 
in a conventional wellhead connector 20 which normally utilizes two 
members 24, which are shaped to match the top and bottom of the ring 44. 
When these plates are actuated to apply a compressive force 
perpendicularly to the top and bottom of the ring 44, the ring 44 
compresses forming a seal around the production tubing 14, the cable 16, 
and against the casing 12. The ends of the cables 16 are attached to cable 
in the well and on the surface through standard splicing techniques. In 
particular, the resin block 42 functions to distribute the forces created 
by the pressure differential between the well side of the seal 22 (the 
bottom of the cable 16), and the surface side of the seal 22 (the top half 
of the cable 16). This distribution of forces reduces local stresses in 
the cable 16 and at the interface between the cable 16 and the rubber ring 
44 which in prior art devices was enough to cause failure of the packoff. 
The present invention, therefore, is well adapted to carry out the objects 
and attain the ends and advantages mentioned as well as others inherent 
therein. While a presently preferred embodiment of the invention has been 
given for the purpose of disclosure, numerous changes in the details of 
construction, and steps of the method, will be readily apparent to those 
skilled in the art and which are encompassed within the spirit of the 
invention, and the scope of the appended claims.