Abstract:
A cable and a method of making the cable includes an electrically conductive cable core for transmitting electrical power and at least one layer of a plurality of armor wires surrounding the cable core. At least one of the armor wires is a bimetallic armor wire having a coaxial inner portion and a surrounding outer portion. The inner and outer portions are formed of different metallic materials and the bimetallic armor wire provides a return path for the electrical power transmitted through the cable core.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is entitled to the benefit of, and claims priority to, provisional patent application Ser. No. 61/025,007 filed Jan. 31, 2008, the entire disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0003]    Embodiments of cables relate generally to oilfield cables and, in particular, to wireline and slickline cables, and methods of making and using such cables. 
         [0004]    Mono-cables with alloy armor wires typically comprise a single insulated copper conductor at the core for both electrical transmission and telemetry functions. With mono-cables, electric power is transmitted down the central, insulated power conductor and the electric power returns along the armor. However, with long length alloy cables, electrical power return on them is not possible as a galvanized steel armor package is utilized and the highly resistive nature of alloy wires, such as MP35N and HC-265), effectively precludes the production of long length mono-cables with alloy armors. In order to overcome this issue, coaxial cables were introduced. With coaxial cables, the electrical power is transmitted down a central, insulated conductor, and returns along a serve layer of stranded copper wires covered by a thin layer of polymeric insulation located near the outer edge of the cable core. Both mono-cables and coaxial cables have disadvantages. 
         [0005]    Mono-cables are disadvantageous because the amount of electrical power that can be transmitted in long length cables is limited depending on the type of armor wire used. While standard galvanized improved plow steel (GIPS) armor wires have a fairly low resistance, armor wires composed of MP35N/HC-265 or high-carbon alloys (such as those used in wells with a presence of H 2 S) can have up to 20 times the resistance to electrical current. Thus the length of the cable with alloy armor wires is limited. 
         [0006]    Coaxial cables are disadvantageous because of the potential of breaking the relatively small size of the coaxial cable insulation, which could lead to electrical discharge to armor, and because the small size of the copper wire is difficult to strand block, which increases the possibility of gas migration between the serve layer and the insulation. There is shown in  FIGS. 1A and 1B  common potential failures associated with prior art coaxial cables. As shown in  FIG. 1A , a typical coaxial cable  10  has a core formed from a central, multi-stand conductor  11  encircled by a layer of stranded copper shielding wires  12 , and the core is encircled by metallic armor wire strength members  13  at the outside of the cable. The conductor  11  and the wires  12  are embedded in a polymeric insulation  14 . The wires  12  are separated from the strength members  13  by a thin layer  15  of the polymeric insulation  14  located at the outer edge of the cable core. As shown in  FIG. 1B , damage  16  to the insulation layer  15  allows the shielding wires  12  to contact the armor wires  13 , creating monocable-like electrical current transmission conditions. 
         [0007]    Coaxial cables are also disadvantageous because in H 2 S environments, the copper typically has to be plated with nickel, which reduces the effectiveness of the power return on the serve layer because the total area of the copper on the serve layer is reduced and because serve layer manufacturing is extremely challenging and time consuming and often results in a higher final cost. Coaxial cables are also disadvantageous because the strand layer defines a large area, which reduces the power carrying capacity of the cable. 
         [0008]    To improve power return efficiency in H 2 S resistant hepta cables with alloy armors, alloy wires are replaced by polymer-insulated, nickel-plated copper wires used as drain wires and placed within the inner armor wire layer, as shown in  FIG. 2 . A cable  20  has the central, multi-stand conductor  11  encircled by the layer of stranded copper shielding wires  12 . The conductor  11  and the wires  12  are embedded in the polymeric insulation  14  with the thin layer  15  of the polymeric insulation  14  located at the outer edge of the cable core. The core is surrounded by an inner layer of alloy armor wires  21  which is surrounded by an outer layer  22  of alloy armor wires wires. Several of the inner alloy wires  21  are replaced by polymer-insulated, nickel-plated copper drain wires  23 . This cable  20 , however, is disadvantageous because the mechanical load carrying capacity of the cable is effectively reduced and because of potential issues with z-kinking of the nickel plated copper wires due to dynamic loading which exists in an oil well environment. 
         [0009]    Another cable  30  includes three insulated stranded copper conductors cabled in a triad configuration over a conductor insulated with a soft polymer, as shown in  FIGS. 3A through 3D . The cable core  30  is assembled as follows. In a step “A”, a stranded copper conductor  31  insulated with a soft polymer  32  is placed at the center of the cable core ( FIG. 3A ). Alternatively, the conductor is formed from any suitable electrically conductive material. In a step “B”, three insulated conductors  33 ,  34 ,  35  are cabled helically over the central conductor  31  in a triad configuration ( FIG. 3B ). Three un-insulated copper conductors  36 ,  37 ,  38  are then cabled into the spaces between the insulated conductors  33 ,  34 ,  35  for potential for providing power return, as shown in  FIG. 3C . A relatively thick layer of polymeric insulation  39  is extruded over the top of the cabled conductors to complete the small-diameter cable core  30 , as shown in  FIG. 3D . This cable, however, disadvantageously defines a large area due to insulation required for each conductor, reducing the copper cross section and compromising electrical power delivery. 
         [0010]    Copper plated steel wires have been used in various industries with great success for some time. These wires provide excellent power transmission capabilities and strength. However these wires are not suitable for wireline applications due to the severe downhole environment, where alloy cables are used, because copper gets rapidly consumed by H 2 S gas and other corrosive gases and fluids which exist in the downhole environment. 
         [0011]    As shown in  FIG. 4 , a conductive slickline core consist of single conductor  41  extruded with polymer material  42  then served with copper wire  43  for electrical power return and extruded with an outer polymer material  44 . The slickline core is covered with metal or alloy tubing/cladding  45  which acts as a strength member and/or corrosion protective armor layer. This cable  40  is disadvantageous because the serve layer manufacturing is extremely challenging and time consuming, the serve layer defines a large area, the metallic tube/clad typically has a short lifespan due to limited fatigue life, and enclosing the core with the metallic tube/clad is not cost-effective. 
         [0012]    It is desirable, therefore, to provide a cable that overcomes the problems encountered with current mono-cable and coaxial cable designs. 
       SUMMARY 
       [0013]    An embodiment of a cable includes an electrically conductive cable core for transmitting electrical power and at least one layer of a plurality of armor wires surrounding the cable core. At least one of the armor wires is a bimetallic armor wire having a coaxial inner portion and a surrounding outer portion, the inner and outer portions being formed of different metallic materials. The at least one bimetallic armor wire is adapted to provide a return path for the electrical power transmitted through the cable core. The cable core includes a conductor extruded with at least one surrounding insulating polymeric material. The cable core can include a bimetallic cable core wire having a coaxial inner portion and outer portion, the inner and outer portions of the bimetallic cable core wire being formed of different metallic materials. A matrix formed from a polymeric material can encase the cable core and the at least one layer of armor wires. 
         [0014]    Alternatively, the cable core includes a conductor extruded with at least one surrounding insulating polymeric material. Alternatively, the cable core includes a bimetallic cable core wire having a coaxial inner portion and outer portion, the inner and outer portions of the bimetallic cable core wire being formed of different metallic materials. Alternatively, the cable further comprises a matrix formed from a polymeric material and encasing the cable core and the at least one layer of armor wires. Alternatively, the inner portion of the bimetallic armor wire includes at least one of copper material, aluminum material, and beryllium copper material. Alternatively, the outer portion of the bimetallic armor wire is formed of a metal alloy material which includes at least one of MP35N material, HC-265 material, Inconel material, Monel material, and Rene material. 
         [0015]    Alternatively, the plurality of armor wires includes corrosion resistant alloy armor wires. Alternatively, the at least one layer of armor wires is an inner layer and including an outer layer of a plurality of armor wires surrounding the inner layer, and wherein the at least one bimetallic armor wire is disposed in the inner layer. Alternatively, the at least one layer of armor wires is an outer layer and including an inner layer of a plurality of armor wires surrounded by the outer layer, and wherein the at least one bimetallic armor wire is disposed in the outer layer. Alternatively, the plurality of armor wires comprises an inner layer and an outer layer and wherein the at least one bimetallic armor wire is disposed in the inner layer and including at least another bimetallic armor wire disposed in the outer layer. 
         [0016]    An embodiment of a cable includes an electrically conductive cable core formed from a first metallic material, a metallic shell encasing the cable core and being formed from a second metallic material different than the first metallic material, and a polymer jacket encasing the cable core and the shell. The cable can include a bonding material disposed between and attaching an outer surface of the shell and an inner surface of the polymer jacket. The bonding material can be a thin layer of copper material. The cable can include at least one layer of a plurality of armor wires surrounding the polymer jacket. 
         [0017]    Alternatively, the first metallic material includes at least one of copper material, aluminum material, and beryllium copper material. Alternatively, the second metallic material includes at least one of MP35N material, HC-265 material, Inconel material, Monel material, and Rene material. 
         [0018]    A method of forming a cable includes: providing an electrically conductive cable core for transmitting electrical power; providing at least one bimetallic armor wire having a coaxial inner portion and a surrounding outer portion, the inner and outer portions being formed of different metallic materials; and surrounding the cable core with at least one layer of a plurality of armor wires including the at least one bimetallic armor wire, wherein the at least one bimetallic armor wire provides a return path for the electrical power transmitted through the cable core. The method can include extruding at least one insulating polymeric material surrounding a conductor to form the cable core and encasing the at least one layer of armor wires in a matrix formed from a polymeric material. The method may further comprise providing the cable core with a bimetallic cable core wire having a coaxial inner portion and outer portion, the inner and outer portions of the bimetallic cable core wire being formed of different metallic materials. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
           [0020]      FIGS. 1A and 1B  are a radial cross-sectional views of a prior art coaxial cable; 
           [0021]      FIG. 2  is a radial cross-sectional view of a prior art hepta coaxial cable; 
           [0022]      FIGS. 3A through 3D  are radial cross-sectional views of a prior art triad configuration cable core; 
           [0023]      FIG. 4  is a radial cross-sectional view of a prior art slickline coaxial cable with metallic tubing/cladding; 
           [0024]      FIG. 5  is a radial cross-sectional view of a cable core; 
           [0025]      FIG. 6  is a radial cross-sectional view of a coaxial cable including the cable core shown in  FIG. 5 ; 
           [0026]      FIGS. 7A and 7B  are radial cross-sectional views of a slickline cable; and 
           [0027]      FIGS. 8A through 8D  are radial cross-sectional views of embodiments of slickline or wireline cables. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Embodiments of cables also provide an alternative way of electrical power return utilizing corrosion resistant alloy armor wire. Embodiments of the cables employ mono cable core with contra helically wound alloy armor wire around the mono cable core, with the electrical return path through at least one armor wire(s) formed from bimetallic materials. The bimetallic armor wire preferably comprises highly conductive metal or alloy on an inside portion and a corrosion resistant metal alloy on an outside portion. The bimetallic armor wire could be utilized in slickline applications in the similar manner. 
         [0029]    Embodiments of cables advantageously overcome the problems encountered with current alloy mono cable and coaxial cable designs while providing the ability to deliver power in excess of 0.5 kW over 30,000 feet of cable while also providing good telemetry capabilities. 
         [0030]    Illustrative embodiments are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
         [0031]    There is shown in  FIGS. 5 and 6  an embodiment of a cable  50  with a small-diameter, high-power cable core with return path through bimetallic armor wire(s). The cable  50  includes a core comprising the conductor  41  extruded with insulating polymeric materials  42 ,  44 , which is further served with two sets  54 ,  55  of armor wires contra helically wound around the core. One or more of the armor wires comprise bimetallic armor wires  51  to accommodate electrical power return. The bimetallic armor wire  51  comprises a coaxial inner portion  52  and an outer portion  53  formed of differing metals and/or alloys. The inner portion  52  comprises a highly conductive metal such as, but not limited to, copper, aluminum, beryllium copper or any other suitable highly electrically conductive material for electrical power delivery and telemetry evaluation. The outer portion  53  comprises a metal or alloy which acts as a strength and/or corrosion preventive metal alloy such as, but not limited to, MP35N, HC-265, Inconel, Monel, Rene or any other suitable corrosion resistant alloy or steel. The bimetallic armor wire  51  may be placed in either the inner armor layer  54  and/or the outer armor layer  55  as shown in  FIG. 6 . The number of bimetallic wires  51  in the cable  50  may vary depending upon power requirements, as will be appreciated by those skilled in the art. 
         [0032]    There is shown in  FIG. 7A  an embodiment of a small diameter highly conductive slickline cable  60 . The slickline cable  60  comprises a single conductor  61  encased or covered with alloy or steel tubing/cladding  62  and further encased or covered by an extruded polymer jacket  63 . The polymer jacket extrusion  63  is preferably directly applied over the alloy/steel shell  62 , as shown in  FIG. 7A . Alternatively, a thin layer of copper  71  is applied to the alloy/steel shell  62  prior to the polymer extrusion  63 , as shown in  FIG. 7B  to form a slickline cable  70 . The copper layer  71  in  FIG. 7B  acts as a bonding media between the alloy/steel shell  62  and the polymer jacket  63 . Power return is preferably accomplished via the well casing (not shown). 
         [0033]    There is shown in  FIGS. 8A through 8D , embodiments of small diameter highly conductive, low weight slickline or wireline cables with an alloy armor package utilizing a bimetallic armor wire, such as the armor wire shown in  FIGS. 5 and 6  as the conductor or core and encased in an insulating polymer, and further encased or covered by a pair of armor wire layers in a matrix formed from a polymeric material. At least one of the armor wires is a bimetallic armor wire layer, providing the capability of electrical return via the armor wire. 
         [0034]      FIG. 8A  shows a cable  80   a  having the armor wire  51  utilized as a core conductor  51   a  encased in the insulating polymer  42 . The polymer  42  is surrounded by an inner armor wire layer  81  which is surrounded by an outer armor wire layer  82 . The layers  81 ,  82  are formed of stranded conductors and are encased in a matrix of polymeric material  83 . At least one of the wires  51   b  in the layer  81  is the armor wire  51 .  FIG. 8B  shows a cable  80   b  similar to the cable  80   a  except that an inner armor wire layer  84  and an outer armor wire layer  85  are formed of solid conductors.  FIG. 8C  shows a cable  80   c  similar to the cables  80   a  and  80   b  with the inner armor wire layer  84  and the outer armor wire layer  82 .  FIG. 8D  shows a cable  80   d  similar to the cables  80   a,    80   b  and  80   c  with the inner armor wire layer  81  and the outer armor wire layer  85 . 
         [0035]    Embodiments of cables eliminate the issue associated with serve layer manufacturing, prolong the life of the cable, and minimize the amount of real estate required for the comparable power delivery and mechanical functionality. Also the bimetallic center conductor could be replaced with a stranded nickel plated copper conductor which effectively results in an alloy slickline mono-cable configuration with return via the bimetallic armor wire. Furthermore, the electrical return path could be achieved on the inner or outer armor wire layers or both. 
         [0036]    The bimetallic armor wire may be advantageously used as an electrical return path in any cable such as cables with mono, triad, quad or hepta configurations with alloy armor wires as strength members. The use of bimetallic armor wires advantageously allow alloy mono-cables to be constructed in excess of 30,000 feet in length. 
         [0037]    The polymeric materials useful in the cable embodiments may include, by nonlimiting example, polyolefins (such as EPC or polypropylene), other polyolefins, polyaryletherether ketone (PEEK), polyaryl ether ketone (PEK), polyphenylene sulfide (PPS), modified polyphenylene sulfide, polymers of ethylene-tetrafluoroethylene (ETFE), polymers of poly(1,4-phenylene), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA) polymers, fluorinated ethylene propylene (FEP) polymers, polytetrafluoroethylene-perfluoromethylvinylether (MFA) polymers, Parmax®, and any mixtures thereof. 
         [0038]    The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood as referring to the power set (the set of all subsets) of the respective range of values. Accordingly, the protection sought herein is as set forth in the claims below. 
         [0039]    The preceding description has been presented with reference to presently preferred embodiments of the invention. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principle, and scope of this invention. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.