Abstract:
An apparatus for providing electrical power through a downhole packer comprises a riser nipple engagingly insertable in a passage in the packer; a sleeve surrounding a portion of the riser nipple and slidingly moveable between a cable assembly position and an operational position enabling connection of a cable extending through the packer and the sleeve to an electrical connector; and a retaining nut engageable with the riser nipple capturing the sleeve in the operational position when the retaining nut is engaged with the riser nipple.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Application 60/978,203 filed on Oct. 8, 2007. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to the field of electrical connectors and more particularly to electrical feedthroughs for downhole packers. 
     2. Background Information 
     Numerous applications involve the use of electrical connectors. High power connectors are used in applications including subsea connections, and in submersible pump connections in both water wells and oil wells. The size, weight, and orientation of the cables and connectors induce mechanical loads on connector components that make reliable mechanical and electrical connection difficult. In addition, the physical environment may include high temperature, high pressure, and abrasive and/or corrosive liquids and gases. 
     Packers may be used in downhole applications to seal off separate producing zones. Electrical cables may be run through packers to power downhole equipment, for example, electric submersible pumps, downhole electric actuators, and downhole electronics and sensors. In some applications, a through-packer penetrator may be used that has an electrical cable with a connector on each end. Such configurations require a special packer and may be very costly. Alternatively, cables may be vertically spliced together. Splicing operations in the field may take an inordinate amount of time and result in a less reliable connection. 
     SUMMARY 
     In one aspect of the present invention, an apparatus for providing electrical power through a downhole packer comprises a riser nipple engagingly insertable in a passage in the packer; a sleeve surrounding a portion of the riser nipple and slidingly moveable between a cable assembly position and an operational position enabling connection of a cable extending through the packer and the sleeve to an electrical connector; and a retaining nut engageable with the riser nipple capturing the sleeve in the operational position when the retaining nut is engaged with the riser nipple. 
     In another aspect, a method for providing electrical power through a downhole packer comprises engagingly inserting a riser nipple in a passage of the downhole packer; sliding a sleeve surrounding the riser nipple into a cable assembly position; connecting a cable extending through the packer and the sleeve to an electrical connector; sliding the sleeve to an operational position; and engaging a lock nut with the riser nipple to retain the sleeve in the operational position. 
     In yet another aspect, an apparatus comprises a submersible pump in a wellbore; a cable having an electrical conductor in electrical communication with the submersible pump; an electrical feedthrough assembly enabling passage of the electrical conductor through a packer in the wellbore; and a gripping contact assembly engaging the electrical conductor conducting electrical power to the submersible pump. 
     Non-limiting examples of certain aspects of the invention have been summarized here rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions they represent to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       For a detailed understanding of the present invention, references should be made to the following detailed description of the exemplary embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein: 
         FIG. 1  shows an exploded view of a connector contact assembly according to one illustrative embodiment of the present invention; 
         FIG. 2  shows an assembled view of the elements of  FIG. 1 ; 
         FIG. 3  shows a portion of a contact receptacle according to one illustrative embodiment of the present invention; 
         FIG. 4A  shows an end view of a gripping contact according to one illustrative embodiment of the present invention; 
         FIG. 4B  shows a cross-section view along section line A-A of  FIG. 4A ; 
         FIG. 5  shows a non-limiting example of a portion of a connector assembly according to one illustrative embodiment of the present invention; 
         FIG. 6  shows a non-limiting example of a connector utilizing a contact assembly of one embodiment of the present invention to connect power to a submersible pump; 
         FIG. 7  shows an example of an electrical feedthrough used in a downhole submersible pump application; and 
         FIG. 8  shows an enlarged view of the example electrical feedthrough of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description presents non-limiting examples of embodiments of the present invention. Refer now to  FIGS. 1-4B .  FIG. 1  shows an exploded view of a connector contact assembly  5  according to one illustrative embodiment of the present invention. As shown in  FIG. 1 , a cable  40  has an electrical conductor  45  therein. Electrical conductor  45  may be a solid conductor, or, alternatively, a stranded conductor. 
     A gripping contact  15  has a cavity  16  sized to accept electrical conductor  45 . In one embodiment, the inner diameter of cavity  16  is a substantially a zero clearance fit with the outer diameter of electrical conductor  45 . Gripping contact  15  (see also  FIGS. 4A and 4B ) comprises a plurality of gripping fingers  20  with an outer surface  25  having a substantially conical shape. As seen, in  FIG. 4B , the conical surface  25  is defined by the angle β. In one embodiment, angle β is about 6°. Alternatively, angle β may be in the range of about 2° to about 10°. The internal surface  21  of fingers  20  substantially defines cavity  16 . While shown in  FIG. 4A  as comprising four fingers, any number of fingers may be used and are intended to be encompassed by the present disclosure. In one embodiment, the internal surface  21  of fingers  20  may be substantially smooth. Alternatively, in another embodiment, the internal surface  21  of fingers  20  may have a raised pattern (not shown) formed on surface  21 . Such a pattern may include, but is not limited to: a thread form, a tooth form, a knurling form, and any other raised pattern form used for gripping electrical conductor  45 . 
     On an opposite end of gripping contact  15 , an integral body  27  has an internally threaded bore  35 . Gripping contact  15  may be made out of an electrically conductive metal. Examples of such an electrically conductive metal include, but are not limited to: gold, silver, copper, copper alloys, aluminum, aluminum alloys, brass, bronze, and any other suitable electrically conducting metal. The surfaces  25  and  21  of fingers  20  may be plated with a suitable electrically conductive material to reduce galling and/or wear of the gripping fingers  20 . Any suitable plating may be used including, but not limited to: chrome plating, nickel plating, gold plating, and silver plating. 
     A contact receptacle  10  (see  FIGS. 1-3 ), has an internal conical surface  26  having an angle α where α≦β. In one embodiment, α is on the order of 1.0° smaller than β. Alternatively, α may be smaller than β from about 0.5° to about 1.5°. The difference in angles ensures that fingers  20  of gripping contact  15  are forced to collapse around and compress electrical conductor  45 , as shown in  FIGS. 1 and 2 , when gripping contact  15  is urged axially into contact receptacle  10 . Contact receptacle  10  may be made from any of the materials as described previously for gripping contact  15 . Similarly, contact receptacle  10  may be plated by any of the platings discussed previously with respect to gripping contact  15 . 
     As shown in  FIGS. 1 and 2 , threaded element  30  engages threads  35  in gripping contact  15  and, under tension, reacts against shoulder  31  in contact receptacle  10  such that gripping contact  15  is axially urged into contact receptacle  10 . This motion causes interaction between outer surface  25  and inner surface  26  such that fingers  20  of gripping contact  15  are forced to collapse around and compress electrical conductor  45  along substantially the length of the extension of electrical conductor  45  into gripping contact  15 . The use of threaded element  30  provides a substantially repeatable force urging gripping contact  15  into contact receptacle  10 , thereby providing a repeatable holding force between electrical contact  45  and connector contact assembly. In addition, the substantially repeatable axial holding force provides a repeatable electrical contact between fingers  20  of gripping contact  15  and both electrical conductor  45  and contact receptacle  10 . Threaded element  30  may be a suitably sized threaded fastener that may be commercially available. Alternatively, threaded element  30  may be designed for this particular application using techniques known in the art. 
       FIG. 5  depicts a non-limiting example of a portion of a connector assembly  100  according to one illustrative embodiment of the present invention. Connector assembly  100  may be a power connector for use in connecting a power source to a submersible pump in a well. Alternatively, connector assembly  100  may be a sub-sea connector. As shown in  FIG. 5 , a multi-conductor armored cable assembly  41  has at least one insulated cable  40  with an internal electrical conductor  45 . Armored cable assembly  41  is connected to connector assembly  100  by cable adapter  101 . Crossover  102  connects cable adapter  101  to lower housing  103 . 
     It will be appreciated by one skilled in the art that the portion of connector assembly  100  shown in  FIG. 5  may be immersed in a high pressure fluid such as, for example, a wellbore fluid. To seal high pressure fluid from the internal electrical connections, cable  40  is inserted through seal  120 . Seal  120  is an elastomer seal that is compressed around the insulation of cable  40  to preclude passage of fluid toward the electrical contacts  15  and  10 . Seal  120  is held in place by follower  130 . Seal  120  may be made of a suitable elastomer. Suitable elastomers include but are not limited to, natural rubber, synthetic rubber, fluoroelastomers, perfluoroelastomers, ethylene propylene diene rubber, and any other suitable elastomer. 
     Connector contact assembly  5  is inserted into an insulator  110  that is located above seal  120 . As shown, connector contact assembly  5  comprises gripping contact  15  assembled in contact receptacle  10  and held in place by threaded element  30 . To better facilitate field assembly, insulator  110  is located in lower housing  103  and upper housing  104  that are connected through coupling nut  140  and shoulder nut  135  acting against shoulder  145 . Insulator  110  may be a thermoplastic suitable for the particular environment encountered. Examples of such a thermoplastic include, but are not limited to, a polyetheretherketone material and a glass-filled polyetheretherketone material. Gripping contact  15  is in engaged contact, both mechanically and electrically with electrical conductor  45 . Connector assembly  5  conducts an electrical power signal to contact  105  which is electrically conducted to a surface power control system. One skilled in the art will appreciate that the connector assembly  5  and its components may be appropriately scaled to fit different size electrical conductors without undue experimentation. 
     One non-limiting example of an application of the present invention is shown in  FIG. 6 . In  FIG. 6 , a well  200  comprises a string of surface pipe  212  cemented in the upper portion of a bore hole  214  which extends into the earth to a location adjacent and usually below a subterranean oil productive formation (not shown). A wellhead  216  attaches to the surface pipe  212 . A set of slips  218  suspends a casing string  220  inside the bore hole  214  which is also cemented in place. A casing head  222  connects to the upper end of the casing string  220  and includes a tubing hanger  224 . 
     A tubing string  226  is suspended from the tubing hanger  224  and extends downwardly inside the casing string  220  to a location adjacent the productive formation. An electrically powered submersible pump  228 , of any suitable type, on the lower end of the tubing string  226  pumps oil or an oil-water mixture from the inside of the casing string  220  upwardly through the tubing string  226 . 
     Electric power is delivered to the downhole pump  228  through an armored cable  234  connected to a motor  236  comprising part of the submersible pump  228 . The cable  234  extends upwardly in the well  200  to a connector  100  of the present invention located immediately below the tubing hanger  224 . The connector  100  is secured to a mandrel or feed through socket  240  extending through the hanger  224 , seal assembly  230  and flange  232 . The connector  100  employs a contact assembly as described previously. In one embodiment, a pig tail connector  242  attaches the mandrel  240  to a power cable  244  extending to a source of power at the surface. 
       FIG. 7  shows an example of a downhole pump application where a packer is located uphole of the pump. Electrical submersible pump  228  is powered by electric motor  236  and is located proximate a producing formation  341 . Reservoir fluid  340  enters pump  228  and is forced up tubing string  226  to a surface system, for example, wellhead  216  in  FIG. 6  for distribution to surface storage and/or processing systems (not shown). Packer  310  is located uphole of pump  228  and may be expanded to seal off the volume of borehole  214  above packer  310  to the volume below packer  310 . Packer  310  seals against tubing string  226  where the tubing string passes through packer  310 . 
     Armored electrical cable  41  extends from motor  236  upward and through a passage  350  through packer  310 . Cable  41  extends through packer feedthrough assembly  300  and may be electrically connected to electrical connector  400  which may be an electrical connector as described above in  FIGS. 1-5 . Alternatively, cable  41  may be electrically connected to any suitable electrical connector adapted to interface with feedthrough assembly  300 . Electrical connector  400  may facilitate electrical connection to a suitable power and/or control system (not shown) at the surface. 
       FIG. 8  shows an enlarged view of the example electrical feedthrough of  FIG. 7 . As shown in  FIG. 7 , electrical feedthrough assembly  300  comprises riser nipple  320 , sliding sleeve  315 , and retaining nut  325 . Riser nipple  320  comprises a lower end having thread  322  formed thereon, and an upper end having an upset  316  formed thereon. Threads  322  on the lower end of riser nipple  320  are engageably inserted into threads  323  formed in a sleeve formed in packer  310 . The outer diameter of the upset  316  on riser nipple  320  fits closely in the inner diameter of sliding sleeve  315  such that elastomer seal  326  substantially excludes wellbore fluids from entering the clearance gap between the outer diameter of upset  316  and the inner diameter of sliding sleeve  315 . Sliding sleeve  315  has a shoulder section  317  on a lower end thereof. Retaining nut  325  has thread  318  formed on an inner diameter thereof. In an operational position, retaining nut  325  is threaded onto threads  319  on an outer diameter of riser nipple  320  such that retaining nut  325  captures shoulder section  317  of sliding sleeve  315  against upset  316  of riser nipple  320 . 
     In a cable assembly position, sliding sleeve  315  has an open upper end. Retaining nut  325  is unthreaded from riser nipple  320  and moved to position  325 ′ shown in  FIG. 8 . Likewise, sliding sleeve  315  is moved down to position  315 ′. In this configuration, a sufficient length of cable  41  is exposed above packer  310  to allow the cable to be stripped and dressed for connection of conductor  45  of each individual cable element  40  to a suitable contact receptacle, for example, gripping contact assembly  5  of  FIG. 1 . Gripping contact assembly  5  may then assembled in connector  400 , which in one embodiment is similar to connector  100  shown in  FIG. 5 . Alternatively, any suitable connector may be used. 
     Upon connection of conductors  45  to a suitable connector  400 , sliding sleeve  315  is raised to the upper operational position and connected to connector  400 , for example, at threaded connection  321 . Retaining nut  325  is moved upward and threaded onto riser nipple  320  by engaging threads  318  and  319 . Retaining nut  325  forces shoulder section  317  of sliding sleeve  315  against upset  316  of riser nipple  320  thereby capturing sliding sleeve  315  in the operational position. The packer electrical feedthrough and method of assembly described herein is intended to provide a substantial reduction in assembly time of a field connection while also providing enhanced reliability over spliced connections. 
     While the foregoing disclosure is directed to the non-limiting embodiments of the invention, various modifications will be apparent to those skilled in the art. It is intended that all variations within the scope of the appended claims be embraced by the foregoing disclosure.