Patent Publication Number: US-2023154648-A1

Title: Lead alloy barrier tape splice for downhole power cable

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present document is a divisional application of U.S. application Ser. No. 16/150,970, filed Oct. 3, 2018, which is based on and claims priority to U.S. Provisional Application Ser. No. 62/567,649, filed Oct. 3, 2017, each of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     In many hydrocarbon well applications, power cables are employed to deliver electric power to various devices. For example, power cables are used to deliver electric power to electric submersible pumping systems which may be deployed downhole in wellbores. The power cables are subjected to harsh working environments containing corrosives, e.g. corrosive gases, elevated temperatures, high pressures, and vibrations. To protect power cable conductors from gases such as carbon dioxide (CO 2 ) and hydrogen sulfide (H 2 S), an extruded continuous lead barrier is provided around the conductors to block gas permeation. However, the continuous lead barrier can create difficulties with respect to splicing a power cable during repair operations or other cable related operations. Such repairs are particularly difficult if a suitable heat source and soldering capability are not available. 
     SUMMARY 
     In general, a methodology and system are provided which facilitate splicing of a power cable including splicing of a protective lead barrier. According to the technique, the power cable comprises conductors, e.g. copper conductors, which form individual phases of a multi-phase conductor assembly. The conductors may be individually spliced for each phase of the multi-phase conductor assembly. Additionally, splicing of the protective lead barrier may be performed by utilizing a lead based tape which is wrapped, e.g. helically wrapped, around the conductors. The wrapping technique provides a gas seal with respect to each individual insulated copper conductor within the multi-phase conductor assembly. Depending on the specifics of a given application and environment, additional layers may be added to ensure formation of a desirable splice. 
     However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and: 
         FIG.  1    is a schematic illustration of a well system comprising an example of an electric power cable coupled with an electric submersible pumping system, according to an embodiment of the disclosure; 
         FIG.  2    is an orthogonal view of an example of a power cable having a multi-phase conductor assembly with an end exposed for splicing, according to an embodiment of the disclosure; 
         FIG.  3    is an illustration of a lead alloy barrier tape which may be used to spice ends of a protective lead barrier in the power cable, according to an embodiment of the disclosure; 
         FIG.  4    is an illustration of the lead alloy barrier tape being applied during a splicing operation, according to an embodiment of the disclosure; 
         FIG.  5    is an illustration of the lead alloy barrier tape being applied to form a cross pattern during the splicing operation, according to an embodiment of the disclosure; 
         FIG.  6    is an illustration providing diagrams which show examples of constituents which may be used to form the lead alloy barrier tape, according to an embodiment of the disclosure; 
         FIG.  7    is an illustration of a supplemental tape being applied during the splicing operation to protect the lead alloy barrier tape against unraveling, according to an embodiment of the disclosure; 
         FIG.  8    is an illustration of protective tape being wrapped around the lead alloy barrier tape during the splicing operation to protect the lead alloy barrier tape, according to an embodiment of the disclosure; and 
         FIG.  9    is an illustration of metallic armor applied during the splicing operation, according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
     The present disclosure generally relates to a methodology and system which facilitate splicing of a power cable including splicing of a protective lead barrier. According to the technique, the power cable comprises conductors, e.g. copper conductors, which form individual phases of a multi-phase conductor assembly. By way of example, the power cable may have three copper conductors for delivering three-phase power to an electric submersible pumping system. 
     The conductors may be individually spliced for each phase of the multi-phase conductor assembly. Additionally, splicing of the protective lead barrier may be performed by utilizing a lead based tape which is wrapped around the conductors. For example, the lead based tape may be wrapped helically through the splice region from one end of a protective lead barrier to the other for each phase. In some embodiments, the lead based tape may utilize an additional layer or layers wrapped in, for example, a cross pattern to ensure production against gas permeation. 
     An example of the lead based tape may be a lead alloy barrier tape formed with a Pb—Sn—Sb crystal structure and having a suitable adhesive to enable the tape to bond to itself after application of pressure to thus form the gas barrier. As a result, the spliced, protective lead barrier protects against corrosive gases without using a heat source or soldering to form the sealed environment for the conductors. The wrapping technique may be employed to provide a gas seal with respect to each individual insulated copper conductor within the multi-phase conductor assembly. Depending on the specifics of a given application and environment, additional layers may be added to ensure formation of a desirable splice. 
     Referring generally to  FIG.  1   , a well system  20  is illustrated as comprising an electrically powered system  22  which receives electric power via an electric power cable  24 . By way of example, the electrically powered system  22  may be in the form of an electric submersible pumping system  26 , and the power cable  24  may be constructed to withstand high temperatures and harsh environments even when spliced. Although the electric submersible pumping system  26  may have a wide variety of components, examples of such components comprise a submersible pump  28 , a submersible motor  30 , and a motor protector  32 . 
     In the example illustrated, electric submersible pumping system  26  is designed for deployment in a well  34  located within a geological formation  36  containing, for example, petroleum or other desirable production fluids. A wellbore  38  may be drilled and lined with a wellbore casing  40 , although the electric submersible pumping system  26  (or other type of electrically powered system  22 ) may be used in open hole wellbores or in other environments exposed to high temperatures and harsh conditions. In the example illustrated, however, casing  40  may be perforated with a plurality of perforations  42  through which production fluids flow from formation  36  into wellbore  38 . The electric submersible pumping system  26  may be deployed into a wellbore  38  via a conveyance or other deployment system  44  which may comprise tubing  46 , e.g. coiled tubing or production tubing. By way of example, the conveyance  44  may be coupled with the electrically powered system  22  via an appropriate tubing connector  48 . 
     In the example illustrated, electric power is provided to submersible motor  30  by electric power cable  24 . The submersible motor  30 , in turn, powers submersible pump  28  which draws in fluid, e.g. production fluid, into the pumping system through a pump intake  50 . The fluid is produced or moved to the surface or other suitable location via tubing  46 . However, the fluid may be pumped to other locations along other flow paths. In some applications, for example, the fluid may be pumped along an annulus surrounding conveyance  44 . In other applications, the electric submersible pumping system  26  may be used to inject fluid into the subterranean formation or to move fluids to other subterranean locations. 
     As described in greater detail below, the electric power cable  24  is designed to consistently deliver electric power to the submersible pumping system  26  over long operational periods when subjected to high temperatures due to high voltages and/or high temperature environments. The construction of power cable  24  also facilitates long-term operation in environments having high pressures, deleterious fluids, and/or other harsh conditions. The power cable  24  is connected to the corresponding, electrically powered component, e.g. submersible motor  30 , by an electrical connector  52 , e.g. a suitable pothead assembly. The electrical connector  52  provides sealed and protected passage of the power cable conductor or conductors through a housing  54  of submersible motor  30 . 
     Depending on the application, the power cable  24  may comprise a plurality of electrical conductors protected by the insulation system. In various submersible pumping applications, the electrical power cable  24  is configured to carry three-phase current, and submersible motor  30  comprises a three-phase motor powered by the three-phase current delivered through the three electrical conductors of power cable  24 . Sometimes, the power cable  24  is spliced. In the illustrated embodiment, for example, the power cable  24  comprises a splice  56  which has been prepared according to methodologies described herein so as to protect the electrical conductors, e.g. copper conductors, within the power cable. The splice  56  joins exposed ends  58  of power cable  56 . 
     Referring generally to  FIG.  2   , an example of electric power cable  24  is illustrated. In this example, the power cable  24  is illustrated with one of the exposed ends  58  which can be spliced via splice  56  with a similar exposed end  58 . In this example the power cable  24  comprises a multi-phase conductor assembly  60  having a plurality of electrical conductors  62  for the separate phases. By way of example, the power cable  24  may be in the form of a three-phase power cable having three copper conductors  62  for supplying the three-phase power to, for example, electric submersible pumping system  26 . 
     The power cable  24  may be constructed with a variety of protective layers, insulative layers, and other layers depending on the application and environment in which it is used. The number of conductors  62  also may vary according to the parameters of a given application and may be arranged in, for example, a generally circular configuration as illustrated or a generally flat configuration as illustrated in inset  64 . In the circular/round example illustrated in  FIG.  2   , however, the power cable  24  comprises a plurality of the electrical conductors  62 , e.g. three electrical conductors, which may be made from copper or other suitable, conductive material. 
     In the illustrated example, each conductor  62  is surrounded by a conductor shield  66 , an insulation layer  68 , and an insulation shield  70 . A metallic shield  72  may be in the form of a protective lead layer and may be located at a suitable position such as a position surrounding the insulation shield  70 . The protective lead layer  72  may be surrounded by at least one barrier layer  74 , e.g. two barrier layers, to form individual conductor assemblies. The plurality of conductor assemblies may be seated in a cable jacket  76  which may be formed of an insulative material. The cable jacket  76  may be surrounded by an armor structure having, for example, a first layer of armor  78  and a second layer of armor  80 . 
     Depending on the parameters of a given application, the various components of power cable  24  may be made from a variety of materials. By way of example, the conductors  62  may be made of copper and the conductor shields  66  may be made from a high density polyethylene (HDPE), polypropylene, or ethylene propylene diene material (EPDM). The insulation layer  68  may be made from similar materials or other suitable insulation materials for use in a downhole, high temperature environment. The insulation shield  70  may be optional and may be made from various materials having voltage ratings in excess of, for example, about 5 kV. The metallic shield/protective lead layer  72  may be formed from a suitable lead alloy, such as a lead alloy having a Pb—Sn—Sb crystal structure. The barrier layers  74  may be formed from a fluoropolymer or other suitable material and the cable jacket  76  may be formed from an oil resistant EPDM or nitrile rubber. The one or more layers of armor  78 ,  80  may be formed from metal materials such as galvanized steel, stainless steel, MONEL™ or other suitable materials. 
     Although the exposed end  58  for combination with a similar exposed end  58  via splice  56  is illustrated as having the three ends of the copper conductors  62  cut to a similar length, the splice also may stagger the lengths. For example, the three conductors  62  may be cut to three different lengths, e.g. 3 inches apart, and then the insulation layers and protective lead layer  72  of each conductor  62  may be removed to expose the bare end of each conductor  62 . 
     According to an example, the exposed copper ends of the conductors  62  of one cable end  58  are aligned with corresponding copper ends of corresponding conductors  62  of an adjacent cable end  58  to be spliced. The copper ends may be joined with, for example, a crimping sleeve or a pneumatic cold weld. The joined conductors are then sanded and polished to remove sharp corners. As illustrated in  FIGS.  3  and  4   , the corresponding joined conductors  62  may then be protected via a plurality of taped layers. 
     For example, a high strain dielectric tape  81 , e.g. a high strain fluorinated ethylene propylene (FEP) tape, may be used to cover the joined area of the conductors  62  for each phase to allow for a reduction in dielectric stress by filling in contours and discontinuities across the joint area (see  FIG.  4   ). The ends of the protective lead layer  72  may then be smoothed, e.g. sanded and polished, to facilitate bonding of a lead alloy barrier tape  82 . The lead alloy barrier tape  82  may be wrapped along the joined conductors  62  of each phase from one end of the protective lead layer  72  (of a first cable end  58 ) to the corresponding end of protective lead layer  72  (of a second, adjacent cable end  58  being spliced to the first cable end  58 ) (see  FIGS.  3  and  4   ). In other words, the lead alloy barrier tape  82  overlays corresponding ends of the protective lead layer  72  and extends over the joined conductors  62  of each phase being spliced. Consequently, a continuous lead barrier is provided through the splice. 
     A high modulus tape, e.g. a high modulus polytetrafluoroethylene (PTFE) tape, may then be wrapped around the lead alloy barrier tape to provide an insulating material through splice  56  (see  FIGS.  7  and  8    along with description below). The lead alloy barrier tape and PTFE tape cooperate to continue the protective lead layer  72  through the splice  56  and to thus block gas exchange inside the splice  56 . 
     Referring again to  FIG.  3   , an example of the lead alloy barrier tape  82  is illustrated. In this example, the lead alloy barrier tape  82  is provided with a termination end  84  (see top of  FIG.  3   ) which may be cut to generally match an angle of wrapping. By way of example, the lead alloy barrier tape  82  may be wrapped around joined conductors  62  of each phase in a helical pattern extending through the region of splice  56  as illustrated in  FIG.  4   . An adhesive  85  of the barrier tape  82  ensures adherence and retention of the lead alloy barrier tape  82  in the desired pattern, e.g. in a desired helix. Depending on the parameters of a given application, the adhesive  85  may be part of the barrier tape  82  or applied separately. The helical wrap may be initiated at the end of protective lead layer  72  extending from one cable end  58  (see bottom of  FIG.  3   ) and wrapped until it covers the end of the corresponding protective lead layer  72  extending from the adjacent cable end  58 . This helical wrapping may be performed about each conductor  62  of the power cable  24  to form the overall splice  56 . 
     By way of example, the helical wrapping through the region of splice  56  may be arranged in a helix having a 50% overlap (or other suitable overlap) which enables the lead alloy barrier tape  82  to adhere and bond to itself via adhesive  85 . The wrapping may be terminated at an angle matching the angle of the helix. A forming tool may be used to apply pressure along the wrapped lead alloy barrier tape  82  so as to activate the adhesive  85  and bond the overlapping layers of barrier tape  82 . In some embodiments, a return pass may be helically wrapped with, for example, a 50% overlap to form a cross pattern  86  through the taped region after pressure is applied, as illustrated in  FIG.  5   . Additional passes of overlapping, wrapped lead alloy barrier tape  82  may be applied and extended past the ends of the underlying wraps in some applications. 
     The adhesive  85  may be in the form of a variety of adhesives, e.g. an acrylic based adhesive, resistant to hydrolysis and solvent attack at elevated downhole temperatures of, for example, 400° F. to 450° F. The adhesive  85  ensures sealing between overlapping portions of the lead alloy barrier tape  82  and between the lead alloy barrier tape  82  and the smoothed ends of protective lead layer  72 . Use of the forming tool, e.g. pressure application tool, can help ensure a desired activation of the adhesive  85  and thus sealing along the splice  56 . 
     The lead alloy barrier tape  82  may be constructed with a variety of lead alloys. In  FIG.  6   , for example, a ternary phase diagram (left side) and a ternary melt diagram (right side) are provided to illustrate examples of suitable lead alloys for use in the barrier tape  82 . In the illustrated ternary phase diagram, three regions R 1 , R 2  and R 3  are labeled where the region R 2  is a corridor (Pb+SbSn) having characteristics of a lead (Pb) plus SbSn crystal structure. As an example, a lead (Pb) alloy of a tape may be selected from region R 2 . 
     In the ternary melt diagram, lead (Pb) at 100 percent by weight is shown in a lower left corner; while increasing weight percent of antimony (Sb) is illustrated upwardly to the right; and while increasing weight percent of tin (Sn) is illustrated horizontally to the right. The ternary melt diagram shows melting temperature contours which are generally increasing toward 100 percent by weight lead. As an example, a lead (Pb) alloy of lead alloy barrier tape  82  may be selected from the region shown in the ternary melt diagram based at least in part on melting temperature. In such an example, the selected lead (Pb) alloy can be an alloy of region R 2  of the ternary phase diagram (noting that the ternary phase diagram is for about 109 degrees C.). 
     As an example, a suitable lead (Pb) alloy may include lead (Pb), tin (Sn) and antimony (Sb) and may comprise about 10 percent by weight tin (Sn) or less and about 10 percent by weight or less antimony (Sb); with the remainder substantially lead (Pb) (e.g., 80 percent by weight or more). According to another example, a suitable lead (Pb) alloy may include lead (Pb), tin (Sn) and antimony (Sb) and may comprise about 5 percent by weight tin (Sn) or less and about 5 percent by weight or less antimony (Sb); with the remainder substantially lead (Pb) (e.g., 90 percent by weight or more). According to another example, a suitable lead (Pb) alloy may include lead (Pb), tin (Sn) and antimony (Sb) and may comprise about 4 percent by weight tin (Sn) or less and about 4 percent by weight or less antimony (Sb); with the remainder substantially lead (Pb) (e.g., 92 percent by weight or more). In another example, a suitable lead (Pb) alloy may include lead (Pb), tin (Sn) and antimony (Sb) and may comprise about 0.5 to about 3 percent by weight tin (Sn) and about 1.5 to about 5 percent by weight or less antimony (Sb); with the remainder substantially lead (Pb) (e.g., about 92 to about 98 percent be weight). 
     As illustrated in  FIG.  7   , the ends of the wrapped lead alloy barrier tape  82  may be wrapped with a high modulus tape  88 , e.g. a high modulus PTFE tape, to protect the wrapped lead alloy barrier tape  82  from unraveling. In addition to protecting against unraveling, the wraps of high modulus tape  88  protect the termination ends  84  against damage, thus eliminating a potential failure mode. Subsequently, high modulus tape layers  90 , e.g. high modulus PTFE tape layers, may be applied, e.g. wrapped helically. The tape layers  90  are positioned around the lead alloy barrier tape  82  which, in turn, has been wrapped around each individual phase of the multi-phase conductor assembly  60  within splice  56 , as illustrated in  FIG.  8   . It should be noted  FIG.  8    illustrates a splice  56  being formed for a power cable  24  having a generally flat configuration but the same approach may be used for a power cable  24  having a generally round configuration, as illustrated in the round configuration of  FIG.  2   . 
     The high modulus tape layers  90  may be applied helically to reinforce and protect the layers of lead alloy barrier tape  82 . These taped conductors may then be splinted by alternating the tape wraps to form alternated tape wraps  92  along the length of the region of splice  56 , as also illustrated in  FIG.  8   . For round cables  24 , additional material may be added and secured along the region of splice  56  to help fill voids within the splice between conductors  62 . 
     In some embodiments, the high modulus tape layers  90  may then be covered with an insulating material, e.g. fiberglass tape, to provide padding. An armor material  94 , e.g. metallic armor material, may then be wrapped along the region of splice  56  around spliced conductors  62  to provide mechanical protection, as illustrated in  FIG.  9   . By way of example, the metallic armor material  94  may be applied as a strip wrapped helically with the aid of, for example, a forming tool to maintain a tight wrap. The metallic armor material  94  may then be secured along the region of splice  56  by suitable retainers, such as self-hooking mechanical retention mechanisms, to avoid soldering. In some embodiments, the armor material  94  may be constructed in a plurality of layers, e.g. a plurality of metallic armor material layers. In the illustrated example, the armor material  94  is an external layer which collectively surrounds the plurality of phases. 
     This splicing methodology may be adapted to various types of power cables  24  for use in many environments, including downhole environments involving H 2 S and CO 2  gases. The approach enables splicing to be completed at locations near a well where it may not be practical to have an open flame or soldering iron. By way of example, the methodology also enables removal of soldering equipment when installing a field attachable penetrator with a pigtail splice. 
     According to one specific embodiment of the methodology, cable ends  58  are properly terminated and aligned. The copper conductors  62  from each cable end  58  are then joined followed by a deburring and polishing of the joined copper area. The ends of the protective lead layer  72  associated with each conductor  62  may then be deburred and polished to properly expose the lead ends. The high strain dielectric tape  81  may then be applied over the joined conductors  62 . In some applications, various additional layers and/or components may be positioned over the joined conductors  62 , e.g. a high modulus dielectric tape cylinder and a subsequent high modulus dielectric tape may be applied over the insulation and conductor area. 
     Layers of the lead alloy barrier tape  82  may then be wrapped around the insulation materials to extend from one end of the protective lead layer  72  to the other end for each phase. The lead alloy barrier tape  82  may then be compressed to activate the adhesive and a high modulus tape may be wrapped over the ends of the lead alloy barrier tape  82  to secure them in place. A high modulus tape may then be wrapped to provide splinting between the phases followed by application of a high modulus tape and fiberglass tape to provide protection and insulation. The armor layer  94 , e.g. metallic armor layer, may then be wrapped over the group of phases and corresponding barrier tape  82  and insulated materials to complete the splice  56 . Mechanical retention members, e.g. hooks, may be used to hold the metallic armor layer  94  in place along splice  56 . 
     The number of phases/conductors in power cable  24  may vary. The number and type of insulative layers also may be selected according to the parameters of a given operation and/or environment in which the power cable  24  is utilized. The layers of insulation may be formed via insulating tapes or by other types of materials wrapped or otherwise positioned about each phase. The plurality of phases may be splinted or otherwise secured together by tape or other mechanisms prior to applying the layer of armor. Additionally, various types of materials may be used to adjust the conductors, protective layers, and insulative layers according to the anticipated environmental conditions. 
     Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.