Patent Publication Number: US-9853394-B2

Title: Pressure-blocking feedthru with pressure-balanced cable terminations

Description:
TECHNICAL FIELD 
     This invention generally relates to a feedthru for a well. 
     BACKGROUND 
     In some oil and gas well systems, power cables are run through certain components, such as the wellhead and the packer. As such, a feedthru is often used to safely and reliably pass electrical power through the pressure barrier. Among other things, the feedthru protects the connection between cables and restricts fluid from escaping the well. Some feedthrus are exposed to harsh environments that include varying pressures, temperatures, and deleterious gases. 
     SUMMARY 
     An embodiment of the present invention is directed to a pressure-blocking feedthru that is exposable to varying temperatures and pressures. In one embodiment, the pressure-blocking feedthru includes a first and a second pressure-blocking assembly, each of which includes a respective pressure-barrier shell and insulated pin assembly. The pressure-blocking feedthru also includes an interface assembly that couples the first and second pressure-blocking assemblies to one another. The interface assembly includes a double-ended socket for coupling the insulated pin assemblies and a sleeve that circumscribes the doubled ended socket and at least part of the first and the second insulated pin assemblies. 
     In another embodiment, the present invention includes a ceramic pin assembly for providing an electrical connection between two electrical conductors in a pressure-barrier feedthru. The ceramic pin assembly includes an elongated electrical conductor and pins that are coupled to respective ends of the elongated electrical conductor. The pin assembly also includes a ceramic insulating sleeve at least partially encasing the elongated electrical conductor, the ceramic sleeve having a larger-diameter middle portion that is flanked by a first and a second smaller-diameter portion. In addition, the pin assembly caps brazed to respective ends of the smaller-diameter portions of the ceramic insulating and coupled to respective pins. 
     In another embodiment, pressure-balanced cable terminations are integrated directly to ends of the pressure-blocking feedthru. The pressure-balanced cable terminations include a cable-housing tube partially encased in a connector shell, which is connectable to the pressure-barrier shell of the pressure-blocking assembly. A chamber is defined between the cable-housing tube and the connector shell and a shuttle is slidably positioned in the chamber together with viscous dielectric medium. 
     Embodiments of the invention are defined by the claims below, not this summary. A high-level overview of various aspects of the invention is provided here to provide an overview of the disclosure, and to introduce a selection of concepts that are further described below in the detailed-description section. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in isolation to determine the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative embodiments of the present invention are described in detail below with reference to the attached figures, which are incorporated herein by reference, wherein: 
         FIGS. 1A and 1B  depict cross-section views of a pressure-blocking feedthru with pressure-balanced cable terminations in accordance with an embodiment of the present invention; 
         FIG. 2  depicts an isometric view of an insulated pin assembly in accordance with an embodiment of the present invention; 
         FIG. 3  depicts a side view of the insulated pin assembly in accordance with an embodiment of the present invention; and 
         FIG. 4  depicts a cross-section view of the insulated pin assembly in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The subject matter of embodiments of the present invention is described with specificity herein to meet statutory requirements. But the description itself is not intended to necessarily limit the scope of claims. Rather, the claimed subject matter might be embodied in other ways to include different elements or combinations of elements similar to the ones described in this document, in conjunction with other present or future technologies. 
     As indicated in other parts of this specification, the present invention is generally directed to a pressure-balanced feedthru that is usable to pass electrical power through components of a well system. The feedthru includes various components that block pressure and withstand temperature and pressure conditions experienced in a well environment. In addition, the feedthru is coupled to pressure-balanced cable terminations on each end to form an integrated safety-barrier penetration device. Typically, power cables are coupled to respective ends of the device to allow electrical power to pass from one side of a well component (e.g., wellhead) to the other side of a well component. Generally, field installation of the integrated device is achieved with minimal resources and processes, such as a crimped-on contact pin and cable-jacket preparation. In addition, the integrated device is configurable to be utilized with a wide variety of cables having different sizes, jacket configurations, materials, sheaths, or the like. 
     Referring now to  FIGS. 1A and 1B , cross sections are depicted of a feedthru  10  in accordance with an embodiment of the present invention. Although  FIGS. 1A and 1B  include a cross-section depiction, many of the components are cylindrical in shape.  FIG. 1A  depicts the integrated unit as a whole, and illustrates the near symmetrical nature of the integrated unit. That is,  FIG. 1A  illustrates that a left side of the integrated unit (as depicted in  FIG. 1A ) and a right side of the integrated unit are substantially symmetrical, except the right side of the unit include a male-configured shell  58  and the left side includes a female-configured shell  26 . To more clearly illustrate some of the smaller details of the feedthru  10 , a larger depiction of the left side of the feedthru  10  is provided in  FIG. 1B  with the understanding that the right side includes many substantially similar components. 
     Referring to  FIGS. 1A and 1B , the feedthru  10  generally includes a first pressure-blocking assembly  12  and a second pressure-blocking assembly  14 . In addition, the feedthru includes a first pressure-balanced cable-connection assembly  16  and a second pressure-balanced cable-connection assembly  18 , each of which is coupled to a respective pressure-blocking assembly. The cable-connection assemblies are also referred to as cable terminations in this description. Generally, a first cable  20  and a second cable  22  are positioned in a respective cable-connection assembly, and the pressure-blocking assemblies  12  and  14  allow electrical power to pass from one cable to the other. When used in a well system, the feedthru  10  might be positioned in a wellhead, a packer, or another component to allow electrical power to pass from one side to the other. 
     The pressure-blocking assembly  12  includes an insulated pin assembly  24  that is positioned within a pressure-blocking shell  26 . Referring now to  FIGS. 2-4 , the insulated pin assembly  24  will be described in more detail. The insulated pin assembly  24  includes an elongated electrical conductor  28  that is positioned within an insulator sleeve  30 . Pins  32  and  34  are coupled to ends of the electrical conductor  28 , and each pin  32  and  34  is coupled to the insulator sleeve  30  by a respective cap  36  and  38 . In one embodiment, the insulator sleeve  30  includes a ceramic insulator sleeve, such that the insulated pin assembly  24  includes a ceramic pin assembly. Although a ceramic assembly is described with respect to some embodiments of the present invention, other insulating materials could be used as an alternative to, or in combination with, ceramic. 
     The electrical conductor  28  might include various types of conductors, and in one embodiment, the electrical conductor  28  includes a copper conductor. In another embodiment, the electrical conductor  28  includes a gold-plated, braided conductor. In addition, as depicted in  FIG. 4 , a gap  39  exists between the electrical conductor  28  and an inner surface  40  of the ceramic insulator sleeve  30 . Among other things, the gap  39  provides a space into which the conductor  28  might thermally expand in some conditions, such as when a braided conductor unwinds at different temperatures. 
     The ceramic insulator sleeve  30  includes various elements. For example, the ceramic insulator sleeve  30  includes a through hole or hollow central portion extending from one side to the other side, and the electrical conductor  28  is positioned in the through hole. As such, the ceramic insulator sleeve includes an inner surface  40  that forms a circumscribing wall of the through hole and that faces the conductor  28 . The ceramic insulator sleeve  30  also includes two smaller-diameter end portions  41  and  42  that flank a larger-diameter middle portion  43 . The larger-diameter middle portion  43  is formed in part by external shoulders  44  and  46 . 
     The ceramic insulator sleeve  30  is optimized in different ways. For example, at least part of the ceramic insulator  30  might be metalized. In one aspect, part or all of the inner surface  40  is metalized extending from one cap to another. Metalizing the inner surface  40  helps to provide a reliable connection when a signal or electricity is passed from one cable to another. That is, the metalized inner surface  40  helps to reduce the likelihood that a high electric field is created in the air gap  39 , thereby contributing to ceramic dielectric breakdown. The metal is at the same potential as portions  36  and  38 , such that there is no electric field across the gap  39 . 
     In another aspect, at least part of an outer surface  52  is metalized. The portion of the outer surface  52  that is metalized might be selected for metallization based on other components of the feedthru that interface with, or contact, the ceramic pin assembly. For instance, in one aspect, the larger diameter portion  43  is metalized, including the shoulders  44  and  46 . Metalizing these portions of the pin assembly helps to reduce corona discharge when the pin assembly is positioned in the feedthru  10 . In addition, a portion of the smaller-diameter portion  42  is metalized extending from the shoulder  46  to a position  48  part-way down the opposing smaller-diameter end portion  42 . 
     In a further embodiment a leaktight connection is utilized to attach the caps  36  and  38  and pins  32  and  34  to the ceramic insulator sleeve  30 . For instance, in one embodiment the ceramic pin assembly is brazed or TIG welded, both of which contributes to a reliable connection along the ceramic pin assembly. 
     Referring back to  FIGS. 1A and 1B , the pressure barrier shell  26  encases the ceramic pin assembly  24 . In addition, one or more c-seals  50  are positioned at the interface between the shoulder  46  of the ceramic pin assembly  24  and an internal shoulder of the shell  26 . The c-seals  50  might be metallic or any other suitable material. In one embodiment, c-seals are positioned back-to-back between an OD and ID placement. In an alternative embodiment, the c-seals are arranged in a front-to-front arrangement. 
     In addition, the metalized outer surface  52  of the ceramic pin assembly  24  (i.e., from the shoulder  46  to the position  48  in  FIGS. 2-4 ) is also positioned at the interface with the shell  26  and abuts an inward protrusion  54  of the shell  26 . The metalized outer surface  52  is positioned at the interface with the shell  26  to contribute to the pressure-barrier features of metallic c-seals. For instance, if the c-seals are silver-plated alloy (e.g., Inconel®), then plating on both the c-seals and the metalized portion of the ceramic pin assembly cooperate to improve the seal. 
     In an embodiment of the present invention, the second pressure-barrier assembly  14  also includes a ceramic pin assembly  56  that is within the pressure-barrier shell  58  and that is substantially similar to the ceramic pin assembly  24 . The pressure-barrier shells  26  and  58  mechanically couple to one another, such as by mechanical threads or other fasteners. When the pressure-barrier shells  26  and  58  are coupled to one another, the ceramic pin assemblies  24  and  56  are electrically connected by way of an interface assembly. 
     The interface assembly that couples the ceramic pin assemblies  24  and  56  includes a double-sided sleeve  60 . The sleeve  60  includes ports into which respective pins of the ceramic pin assemblies are inserted. In addition, the interface assembly includes an air gap  62  that surrounds the sleeve. The air gap  62  provides an inner cavity that is maintained at atmospheric pressure during operation. In contrast, the other portions of the pressure-barrier feedthru and pressure-balanced cable terminations are pressure balanced to the well pressure. The air gap  62  is further encased by a dielectric sleeve  64  constructed of a dielectric material. For example, the dielectric sleeve  64  might be constructed of polytetrafluoroethylene (PTFE), a molded on thermoplastic, or another viscous dielectric medium. The dielectric sleeve  64  is encased within the pressure-barrier shells  26  and  58  when they are coupled. 
     In an embodiment of the present invention, the pressure-barrier shells  26  and  58  prevent the feedthru from collapsing and protect the inner components of the feedthru from well conditions. The pressure-barrier shells  26  and  58  might be constructed of various materials, and in one embodiment, are constructed of a stainless steel. The stainless steel shells might be at least partially coated to provide additional characteristics, and in one embodiment, the shells are partially coated by molydisulfide. 
     In addition, the shells  26  and  58  might be coupled to one another using any suitable mechanical fastener. In  FIG. 1 , the shell  26  includes female threads that mate with male threads on the shell  58 . In addition, a sealing ring  59  might be fitted in the interface between the shells  26  and  58 . In one embodiment, the sealing ring  59  includes a backup O-ring constructed of perfluoro-elastomers (FFKM), or some other high-temperature elastomer. 
     In a further embodiment, each of the pressure-barrier assemblies  12  and  14  include additional components. For instance, each of the pressure-barrier assemblies  12  and  14  includes a ceramic sleeve  66  and  68  around a portion of the ceramic pin assembly  24  and  56 . In one embodiment, a force-exertion component  61  is inserted between the ceramic sleeve  66  and  68  and a respective cable-connection shell (e.g.,  88 ). The force-exertion component biases the ceramic sleeve and the ceramic pin assembly in a direction toward the c-seals, such that the c-seals function as a pressure block even if there are breaches in other portions of the feedthru. For instance, the force-exertion component  61  might be seated between an ID counter bore of the cable-connection shell  88  and the ceramic sleeve  66 . In one embodiment, the force-exertion component provides at least about 15,000 lbs. of force. The force-exertion component might include various components, such as wave springs or Belleville washers. In one embodiment, the force-exertion component includes a stack of about 37 Belleville washers. 
     In addition, each of the pressure-barrier shells  26  and  58  includes a coupling mechanism for attachment to a respective cable-connection assembly  16  and  18 . For example, both of the shells  26  and  58  are depicted to include female threads. Similar to the connection between shells  26  and  58 , the metal-to-metal seal between the shell  88  and the shell  26  might also include a sealing ring  89 , which includes a backup O-ring constructed of perfluoro-elastomers (FFKM), or some other high-temperature elastomer. 
     The cable-connection assemblies  16  and  18  are substantially similar and although only one of the cable-connection assemblies might be described or referenced, it is understood that the same description applies to the other cable-connection assembly. Each cable-connection mechanism  16  and  18  couples a respective cable to the feedthru  10 . 
     The power cable  20  includes a copper conductor  70 , a pin  72  that is fixedly mounted to the conductor  70 , an insulative shield  74  that surrounds the copper conductor  70 , and a lead barrier  76  that is positioned over the insulative shield  74 . The lead barrier  76  protects the insulative shield  74  from exposure to harmful gasses and liquids that surround the power cable  20  in use. The lead barrier  76  is an optional component of the power cables and may be omitted. 
     The cable-connection assembly  16  also includes a cable-housing tube  78  that surrounds each lead barrier  76 . The tube  78  may be composed of stainless steel, for example. A flange  80  is positioned at an end of the tube  78  and includes an external shoulder that engages an inner surface of the connection-assembly shell  88 . The flange  80  is machined to include passageways to a hollow inner portion of the tube and the external shoulder is machined to include passageways to portions  83  of the feedthru between the shoulder and the c-seals. The tube  78  might not be considered as forming part of the respective power cables  20  and instead might be considered part of the cable-connection assembly  16 . Alternatively, the tube  78  may be considered as a separable part that form part of the power cable assembly  20 . 
     In another embodiment of the present invention, the cable-connection assembly  16  includes a rubber boot seal  81  fitted onto an end of the tube  78 . The rubber boot seal  81  extends beyond the end of the tube  78 , such that the rubber boot seal  81  also fits tightly against a cable (e.g., lead barrier  76 ) inserted into the tube  78 . As such, the rubber boot seal  81  seals a juncture between the cable and the tube  78  to help protect the inner components of the feedthru from well conditions. In one embodiment, the rubber boot seal  81  is constructed of a pressure and temperature resistant material, such as a perfluoro-elastomers (FFKM), or other high temperature elastomer with an exo-skeleton of thermoplastic material to hold the outer-diameter of the boot in place and provide seal compression of the elastomer. 
     The feedthru  10  further comprises a double-ended socket  82 , which electrically couples a pin  32  of the ceramic pin assembly  24  with the pin  72  of the cable  20 . The double-ended socket  82  might include various types of sockets, such as a push-in-contact socket. In one embodiment, the socket  82  is positioned within a dielectric insulative sleeve  84 , which has a hollow cylindrical body. One end of the dielectric insulative sleeve  84  is partially encased by the ceramic sleeve  66  when the cable-connection assembly  16  is coupled to the pressure-barrier assembly. The opposite end of the sleeve  84  partially surrounds and overlaps another dielectric insulative sleeve  86 , and might be further protected with viscous dielectric medium filled between the sleeve  84  and the shell  88 . The sleeve  86  includes a hollow cylindrical body and is partially sandwiched by the flange  80 . The dielectric insulative sleeves  84  and  86  may be composed of any dielectric insulative material, such as a polyketone material. 
     The cable-connector shell  88  that encases and protects the cable-connection assembly  16  includes male threads that are threadedly connectable to the pressure-barrier shell  26 . In addition, a sealing ring  89  might be provided at the interface between the cable-connection shell  88  and the pressure-barrier shell  26 . 
     In the cable-connection assembly  16 , the inner surface of the cable-connection shell  88  is space apart from the outer surface of the tube  78 , such that a gap is between the two structures. In one embodiment, a tubular-shaped shuttle  92  is positioned in the gap between the cable-connection shell  88  and the tube  78 , such that the space is divided into a pressure-balanced chamber  94  and an annular space  90 . The shuttle  92  is sealingly compressed between an inner surface of the cable-connection shell  88  and outer surface of the tube  78 . For instance, the shuttle  92  includes two inner sealing rings  99   a  and  99   c  that are retained on the shuttle and slidably engage the tube, and the shuttle  92  includes an outer sealing ring  99   b  retained on the shuttle  92  and slidably engaging the shell  88 . The tube  78  provides a smooth surface upon which the shuttle  92  can translate. 
     The shuttle  92  divides the space between the pressure-balanced chamber  94  and the space  90 . The chamber  94  is filled with a viscous dielectric medium, and the shuttle  92  blocks the passage of the viscous dielectric medium between the chamber  94  and the space  90 . An end  98  of the space  90  is left at least partially open to allow pressure to enter the space  90 . In operation, the shuttle  94  moves rightward (based on the view provided in  FIG. 1 ) when it is exposed to external pressure as any air pockets or compressible elements within the medium will contract in volume. The assembly  10  is shown exposed to some external pressure in  FIG. 1 . The shuttle  92  may return to its initial position once the external pressure subsides. The pressure-balanced cable termination contributes to blocking well-fluid ingress since there is no driving pressure differential between the environment and the chamber. 
     In a further embodiment, the feedthru is pressure-balanced from the shuttle  94  to the c-seals  50 . For instance, viscous dielectric medium is added to fill any gaps in the feedthru components extending from the shuttle  94  to the c-seals  50 . As explained with respect to the tube  78 , the flange  80  is machined to include passageways through which the viscous dielectric medium is allowed to flow. 
     The feedthru  10  includes various features that are helpful to provide resistance to the high-temperature and high-pressure well environment. For example, the boot  81  helps to provide protection at the juncture between an inserted cable and the cable-connection assembly. In addition, the pressure-blocking chamber and shuttle  92  help to further alleviate the effects of pressure fluctuations. Further, in the pressure-barrier assemblies  12  and  14 , the ceramic pin assemblies provide a reliable connection that is resilient to extreme pressures and temperatures. In some testing, the feedthru has shown temperature ratings that exceed 500 degrees Fahrenheit and pressure ratings up to about 20,000 psi. Additional advantages based at least in part on the pressure-balanced cable terminations include high decompression rates, protection of cable insulation inside the cable-termination assemblies, and a gas permeation barrier. 
     In addition, the feedthru is easily modifiable to include varying lengths. For example, the feedthru might include relatively smaller lengths that are at or below about 3 feet. However, the length of the feedthru can be adjusted up to about 10 feet by modifying the dimensions of only three components: the pressure-barrier shell, the ceramic pin assembly, and the interface assembly. A substantially similar cable-connection assembly is still usable with the modified-dimension components. 
     Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the scope of the claims below. Embodiments of our technology have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to readers of this disclosure after and because of reading it. Alternative means of implementing the aforementioned can be completed without departing from the scope of the claims below. Certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims.