Abstract:
An embodiment of a wellbore cable comprises a cable core, at least a first armor wire layer comprising a plurality of strength members and surrounding the cable core, and at least a second armor wire layer comprising a plurality of strength members surrounding the first armor wire layer, the second armor wire layer covering a predetermined percentage of the circumference of the first armor wire layer to prevent torque imbalance in the cable.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of co-pending U.S. patent application Ser. No. 12/465,769, filed May 14, 2009, which claims benefit of U.S. Provisional Patent Application Ser. No. 61/053,054, filed May 14, 2008. Each of the aforementioned related patent applications is herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. The present disclosure invention is related in general to cable systems and, in particular, to wireline cables. 
         [0003]    Typical wireline cable designs consist of a cable core of one or more insulated conductors (packed in an interstitial filler in the case of multiple conductors) wrapped in cabling tape followed by the application of two armor wire layers. The armor wire layers are applied counterhelically to one another in an effort to minimize torque imbalance between the layers. These armor wires provide the strength needed to raise and lower the weight of the cable and tool string and protect the cable core from impact and abrasion damage. In an effort to provide additional protection against impact and abrasion damage, larger-diameter armor wires are placed in the outer layer. Torque imbalance between the armor wire layers, however, continues to be an issue, resulting in cable stretch, cable core deformation and significant reductions in cable strength. 
         [0004]    In pressurized wells, gas can infiltrate through gaps between the armor wires and travel along spaces existing between the inner armor wire layer and the cable core. Grease-filled pipes at the well surface typically provide a seal at the well surface. As the wireline cable passes through these pipes, pressurized gas can travel through the spaces between the inner armor wires and the cable core. When the cable then passes over and bends over a sheave, the gas may be disadvantageously released. 
         [0005]    Typical wireline designs have approximately 98% coverage with each layer of armor wire. If the coverage is too low, the armor wires may disadvantageously move along the cable and the cable may have loose wires. 
         [0006]    Torque for a layer of armor wire can be described in the following equation. 
         [0000]      Torque=1/4  T×PD ×sin 2α
 
         [0007]    Where: 
         [0008]    T=Tension along the direction of the cable 
         [0009]    PD=Pitch Diameter of the Armor Wires 
         [0010]    α=Lay angle of the wires 
         [0011]    Referring now to  FIG. 1 , since the outer armor wire layer  12  of the cable  10  carries more loads and has a larger pitch diameter, the torque generated by the outer armor wire layer  12  (indicated by an arrow  13 ) is generally larger than the torque generated by inner armor wire layer  14  (indicated by an arrow  15 ), which disadvantageously results in torque imbalance for the cable  10 . 
         [0012]    Torque imbalance in the cable  10  is disadvantageous because a cable core  16  may deform into the interstitial spaces between the inner armor wires  14 , reducing the diameter of the cable  10 . The cable  10  may disadvantageously have more stretch and the core  16  may be damaged. As the diameter of the cable  10  is reduced, the pitch diameter of inner armor  14  has a larger percentage reduction than the pitch diameter of outer armor  12 , which may further complicate torque imbalance. 
         [0013]    It is desirable, therefore, to provide a torque-balanced and damage resistant wireline cable. 
       SUMMARY 
       [0014]    An embodiment of a wellbore cable comprises a cable core, at least a first armor wire layer comprising a plurality of strength members and surrounding the cable core, and at least a second armor wire layer comprising a plurality of strength members surrounding the first armor wire layer, the second armor wire layer covering a predetermined percentage of the circumference of the first armor wire layer to prevent torque imbalance in the cable. Alternatively, the predetermined percentage comprises about 50 percent to about 90 percent of the circumference of the first armor wire layer. Alternatively, the strength members of the second armor wire layer comprise at least one stranded armor wire member. Alternatively, the cable further comprises at least one layer of a polymeric material surrounding the cable core, the first armor wire layer and at least a portion of the second armor wire layer. The polymeric material may bond to the first armor wire layer, the second armor wire layer, and the cable core. The cable core further may comprise a polymeric insulating layer and the polymeric material may bond to the insulating layer of the cable core. 
         [0015]    Alternatively, the cable further comprises a polymeric jacket forming an outer layer of the cable, the jacket bonded to at least the outer strength members. The polymeric jacket may comprise a fiber-reinforced polymer. Alternatively, the cable core comprises one of a monocable, a coaxial cable, a triad cable, and a heptacable. Alternatively, a diameter of the strength members in the outer armor wire layer and the inner armor wire layer are substantially equal. Alternatively, a diameter of the strength members in the outer armor wire layer is greater than a diameter of the strength members in the inner armor wire layer. Alternatively, at least one of the conductors of the cable core comprises an optical fiber. 
         [0016]    An embodiment of a wellbore cable comprises at least three conductors each comprising a cable core encased in a polymeric jacket, at least one armor wire layer disposed against the cable core at a lay angle, and a polymeric layer encasing the at least one armor wire layer, the conductors cabled together helically at a lay angle opposite the lay angles of the respective strength members to prevent torque imbalance in the cable. Alternatively, torque balance between the cables is achieved by adjustments in the opposing lay angles of the armor wires and the completed cable. Alternatively, the cable further comprises a polymeric jacket encasing each of the three cables. Alternatively, the cable further comprises a soft polymer central element disposed between the three cables. Alternatively, a diameter of a circle passing through the centers of each of the conductors is approximately the same size as the individual diameter of each of the three conductors. Alternatively, the cable cores comprise at least one of a monocable, a coaxial cable, a triad cable, and a heptacable. Alternatively, at least one of the cable cores comprises an optical fiber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    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: 
           [0018]      FIG. 1  is a is a radial cross-sectional view of a prior art wireline cable; 
           [0019]      FIGS. 2   a  through  2   d  are radial cross-sectional views of an embodiment of a cable. 
           [0020]      FIGS. 3   a  through  3   d  are radial cross-sectional views of an embodiment of a cable. 
           [0021]      FIGS. 4   a  through  4   d  are radial cross-sectional views of an embodiment of a cable. 
           [0022]      FIGS. 5   a  through  5   d  are radial cross-sectional views of an embodiment of a cable. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Referring now to  FIGS. 2   a  through  2   d,  an embodiment of a cable is indicated generally at  200 .  FIGS. 2   a - 2   d  show a cable  200   a,    200   b,    200   c,  and  200   d,  respectively. The cables  200   a,    200   b,    200   c  and  200   d  comprise damage-resistant outer armor wires  202 , which may advantageously be applied to any basic wireline cable configuration or core. In non-limiting examples,  FIG. 2   a  shows a monocable cable core with stranded wires  206   a,    FIG. 2   b  shows a coaxial cable core  206   b,    FIG. 2   c  shows a heptacable cable core  206   c,  and  FIG. 2   d  shows a triad cable core  206   d  having multiple cable conductors as part of the core  206   d.  The conductors forming the cable cores  206   a,    206   b,    206   c,  and  206   d  may be any combination of (but not limited to) monocables, coaxial cables, copper conductors, optical fibers (such as those shown in  FIG. 2   d ) or the like and be insulated with any suitable polymeric material or materials as will be appreciated by those skilled in the art. As shown in  FIGS. 2   a - 2   d,  the inner armor layer  204  carries more load since its pitch diameter is smaller than outer armor layer  202 . 
         [0024]    The outer armor wires  202  shown in  FIGS. 2   a - 2   d  are sized similarly to the inner armor wires  204  but the layer of the outer armor wires  202  covers a predetermined percentage of the circumference of the inner armor wires  204  in order to prevent torque imbalance in the cable  200 . The predetermined percentage of coverage may be, but not limited to, about 50% to about 90% coverage of the circumference of the inner armor wire layer  204 , which is smaller than the percentage coverage of the armor wire layers  12  and  14  shown in the prior art cable  10  in  FIG. 1 . The predetermined percentage of coverage may be, but not limited to, about 50% to about 90% coverage of the circumference of the cable cores  206   a,    206   b,    206   c,  and  206   d,  which is smaller than the percentage coverage of the armor wire layers  12  and  14  and cable core  16  shown in the prior art cable  10  in  FIG. 1 . This smaller percentage of coverage of the outer armor wires  202  with respect to the inner armor wires  204  advantageously maintains the torque-balance of the cable  200   a - 200   d  and increases the ability of the outer armor wires  202  to withstand abrasion damage. In a non-limiting example, the number of armor wires in the inner armor layer  204  and the number of armor wires in the outer armor layer  202  are equal, providing a predetermined coverage in direct relation to the respective diameters of the individual armor wires  202  and  204  and radial spacing of the armor wire layers  202  and  204 . The predetermined coverage may be selected by a number of factors which may include, but are not limited to, the size and/or diameter of the cable  200   a - 200   d,  the size and/or diameter of the cable core  206   a - 206   d,  the size and/or diameter of the individual members of the armor wire layers  202  and  204 , and the radial spacing between the armor wire layers  202  and  204 . The inner armor wires  204  may cover a predetermined percentage of the circumference of the cable core  206   a - 206   d  that may be, but is not limited to, about 98% to about 99% of the circumference of the cable core  206   a - 206   d.    
         [0025]    A polymeric insulating material  208  may be disposed on the inner armor wire layer  204 , the cable core  206   a,    206   b,    206   c,  and  206   d  and a portion of the outer armor wire layer  202  and may bond the armor wire layers  202  and  204  to the cable core  206   a - d,  including the insulating layer of the cable core  206   a - d.  The insulating material  208  may be formed from any suitable material such as, but not limited to, the following: polyolefin or olefin-base elastomer (such as Engage®, Infuse®, etc.); thermoplastic vulcanizates (TPVs) such as Santoprene® and Super TPVs and fluoro TPV (F-TPV); silicone rubber; acrylate rubber; soft engineering plastics (such as soft modified polypropylene sulfide (PPS] or modified Poly-ether-ether-ketone [PEEK]); soft fluoropolymer (such as high-melt flow ETFE (ethylene-tetrafluoroethylene) fluoropolymer; fluoroelastomer (such as DAI-EL™ manufactured by Daikin); and thermoplastic fluoropolymers. The radial thickness of the insulating material  208  and thus the radial spacing between the armor wire layers  202  and  204  may be varied to achieve torque balancing of the cables  200   a - 200   d  and/or prevent torque imbalance of the cables  200   a - 200   d,  as will be appreciated by those skilled in the art. 
         [0026]      FIGS. 3   a - 3   d  show the of cables of  FIGS. 2   a - 2   d  having an outer jacket  320  bonded to the insulating material  208  to form a jacketed cable  300   a,    300   b,    300   c,  and  300   d  that correspond, respectively, to cables  200   a,    200   b,    200   c,  and  200   d.  Referring now to  FIG. 3 , there are shown embodiments of torque-balanced cables  300   a,    300   b,    300   c,  and  300   d  that comprise the cables shown in  FIGS. 2   a - 2   d  having with damage-resistant outer armor wires with a bonded outer jacket  320 . By providing the bonded outer polymeric jacket  320  over the embodiments shown in  FIG. 2 , the cable is preferably more easily sealed at the well surface. The outer jacket  320  may comprise any suitable material such as, for example, carbon-fiber-reinforced Tefzel®, carbon-fiber-reinforced ETFE (ethylene-tetrafluoroethylene) fluoropolymer or similar suitable material that is applied over the outer armor wire layer, bonding through the gaps in the outer strength members  204 , which creates a totally bonded jacketing cable system  300   a - 300   d.  The addition of the fiber-reinforced polymer  320  also provides a more durable outer surface. The outer jacket  320  may be bonded to the insulating material  208  and/or to the outer armor wires  202 . 
         [0027]      FIGS. 4   a - 4   d  show the of cables of  FIGS. 3   a - 3   d  comprising optional stranded wire outer armor wire layers  420  to form cable embodiments, indicated generally at  400   a,    400   b,    400   c,  and  400   d.  As an option to the embodiments shown in  FIGS. 2   a - 2   d  and  3   a - 3   d  described above, any solid armor wire  202  or  302  in the outer layer may be replaced with similarly size stranded armor wires  420 . The replacement of solid armor wire  202  with stranded armor wires  420  makes the cable  400   a,    400   b,    400   c,  and  400   d  more flexible. In addition, the stranded armor wires  420  have more friction and bonding with the jacket  320  and the jacket  320  over the stranded wires  420  also protects the small individual elements from abrasion and cutting. 
         [0028]    Embodiments of the cables  200   a,    200   b,    200   c,    200   d,    300   a,    300   b,    300   c ,  300   d,    400   a,    400   b,    400   c,  and  400   d  have a lower coverage, from about 50% to about 90%, in the outer armor layer  202 . The cables maintain the size and durability of outer strength members  202  while creating torque balance between inner armor layers  204  and the outer armor layers  202 . The weight of the cables is reduced because of the lower coverage percentage. The cable is preferably a seasoned cable and requires no pre-stress and also has less stretch. Because all interstitial spaces between the armor wires  202  and  204  are filled by polymers  208  and  320 , the cables need less grease for the seal (not shown) at the well surface (not shown). Embodiments of the cables may comprise an outer layer of polymer  320  to create a better seal. 
         [0029]    Embodiments of the cables  200   a,    200   b,    200   c,    200   d,    300   a,    300   b,    300   c ,  300   d,    400   a,    400   b,    400   c,  and  400   d  minimize the problems described above by filling interstitial spaces among armor wires and the cable core with polymers  208  and  320 , by using large diameter armor wires but a low coverage (50% to 90%) for the outer armor layer to reach torque balance, and by using a triad configuration, discussed in more detail below. 
         [0030]    The polymeric layers  208  and/or  320  provide several benefits including, but not limited to, filling space into which the inner armor wire might otherwise be compressed thereby minimizing cable stretch, keeping cable diameter while cable at tension, reducing torque since the reduction in pitch diameter is minimized, eliminating the space in the cable along which pressurized gas might travel to escape the well, protecting the cable core from damage caused by inner armor wires, cushioning contact points among armor wires to minimize damage caused by armor wires rubbing against each other, sitting low coverage outer armor wires to avoid loose wires, and produces seasoned alloy cables. 
         [0031]    The low coverage (about 50% to about 90%) of armor wire in the outer layer  202  or  420  provides several benefits including, but not limited to, maintaining torque balance, maintaining the size and durability of outer armor wires  202  or  420 , and lowering the weight of the cable by reducing the coverage of the armor wire  202  or  420 . 
         [0032]    Referring now to  FIGS. 5   a - 5   d,  there is shown an embodiment of a torque-balanced triad cable configuration  520  in which the armor wire may be any kind of strength member. The cable may be constructed as follows: 
         [0033]    As shown in  FIG. 5   a , individual conductors  500  may be constructed with a copper, optical fiber or other conductor or conductors  502  at the center contained in a hard polymeric insulation  504 . Armor wires  506  may be cabled helically in a direction indicated by an arrow  507  over the polymer  504  and a second layer of softer polymer  508  is extruded over the armor wires  506 . 
         [0034]    As shown in  FIG. 5   b , preferably three conductors  500 , as shown in  FIG. 5   a , are cabled together at a lay angle, indicated by an arrow  509 , opposite to that of the lay angle  507  of the armor wires  506  in the individual conductors  500 . Alternatively, a central member  510  with soft polymer insulation  512  is placed at the center of the three conductors  500 . 
         [0035]    As shown in  FIG. 5   c , when the three conductors  500  are cabled together, the soft polymer  512  on the central element deforms to fill the interstitial space between the three conductors  500 . The diameter of a circle passing through the centers of each of the three conductors  500  (indicated by an arrow  514 ) is preferably approximately the same size as the individual diameter of each of the three conductors  500 , which allows the cable to achieve torque balance by slight adjustments in the opposing lay angles of the armor wires  506  and the completed cable  500 . 
         [0036]    As shown in  FIG. 5   d , a final hard polymeric jacket  516 , which may be pure polymer or short-fiber-amended polymer or another suitable material, is extruded over the cabled conductors  500  to complete the cable  520 . 
         [0037]    The cable  520  comprises a low weight torque balanced cable in a triad cable configuration. This embodiment comprises only one layer of armor  506  in each conductor  500  of the triad cable. The lay direction of the armor wire  506  is preferably opposite to the lay direction of the triad  509  to reach torque balance. The triad configuration of the cable  520  provides several benefits including, but not limited to, keeping torque balance of the cable  520 , minimizing the contact points of armor wires to minimize damage caused by armor wires  506  rubbing against each other, and lowering the weight of the cable  520  by using only one layer of armor wire  506  in each conductor  500 . 
         [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.