Abstract:
Submersible pump power cable is inserted into a length of tubing. The device comprises an anchoring system attachable to the cable affixed to the tubing inner surface. The anchoring system includes an anchoring sleeve slideable over the cable and insertable into the tubing. Coiling the tubing with the cable and anchoring system inside energizes the sleeve into an anchoring configuration to anchor the cable within the tubing. The anchoring system continues to anchor the cable after uncoiling the tubing and inserting it into a wellbore.

Description:
FIELD OF THE INVENTION  
       [0001]    This invention relates in general to supporting a power cable within downhole tubing, and in particular to a method and device enabling installation of an electrical power cable into coiled tubing disposed within a wellbore. 
       BACKGROUND OF THE INVENTION  
       [0002]    Electrical submersible pumps (ESP) are normally installed on the bottom end of jointed production tubing within a cased wellbore and powered by a power cable typically attached to the outside of production tubing. In this configuration, an annulus is formed between the tubing and the wellbore casing and the produced fluids are pumped up the production tubing to the surface. 
         [0003]    Oil well completions are being developed to deploy ESPs on the bottom of continuous coiled tubing where the power cable is placed inside the coiled tubing. In these installations, produced fluids are pumped up the annulus between the coiled tubing and the production tubing, or well casing or liner. Many advantages are gained through the use of coiled tubing such as faster deployment, the elimination of a need for large workover rigs, and less frictional pumping losses. 
         [0004]    Submersible pump cable has limited yield strength and will break if too long a length of cable is suspended from a support point. Thus when assembling the cable within coiled tubing, the cable is drawn through the coiled tubing on a line while the coiled tubing is horizontally oriented—which is a time consuming effort. Because cable cannot support its total vertical weight, cable support must be provided by the coiled tubing at regular intervals. Various proposals have been made to provide support, such as the use of mechanical anchors. A need exists for anchors which can be used in fairly small diameter coiled tubing, which will accommodate movement associated with thermal expansion and which will accommodate bending of coiled tubing. 
       SUMMARY OF THE INVENTION  
       [0005]    Disclosed herein is a method of assembling a power cable with tubing. The method may include coupling an anchoring system to the power cable where the anchoring system includes an anchoring sleeve that is selectively changeable between an inserting configuration and an anchoring configuration. The power cable with anchoring system is inserting into the tubing and the anchoring sleeve is selectively changed from the inserting configuration into the anchoring configuration. Selectively changing the configuration can be accomplished by coiling the tubing thereby bending the anchoring sleeve and uncoiling the tubing. The anchoring sleeve remains in the anchoring configuration after uncoiling the tubing. The anchoring system can also include anchoring collars that can be secured adjacent at least one end of the anchoring sleeve. In one embodiment the anchoring sleeve is a helical member. Coupling the helical anchoring sleeve involves forming a helical member having a first dimension then radially and elastically compressing the anchoring sleeve from its first diameter to a small diameter anchoring configuration to its tubular inserting configuration and affixing a frangible retaining element to the anchoring sleeve thereby maintaining the anchoring sleeve in its inserting configuration. Bending the anchoring sleeve can break the frangible element and release the anchoring sleeve into its anchoring configuration. The frangible retaining element can be solder applied along the slot as well as a breakable cover provided over at least a portion of the anchoring sleeve. Optionally, the anchoring sleeve can be a tubular member formed from a material having an elastic limit less than the tubing elastic limit so that when bent by coiling the tubing, the sleeve remains bent when the tubing is subsequently straightened. Yet further optionally, the present method includes attaching a rotary pump system to an end of the tubing, connecting a pump motor of the pump system to the power cable, and disposing the pump system with attached tubing and power cable into a wellbore. 
         [0006]    The present disclosure also includes a borehole assembly with tubing disposed in the borehole, a length of power cable suspended in the tubing, and an anchoring system joined to the power cable. In one embodiment, the anchoring system includes a sleeve circumscribing a section of the cable and coupled to the inner surface of the tubing and an anchoring collar affixed to the cable, the collar configured for mating engagement with the sleeve. The sleeve is selectively changeable between an inserting and an anchoring configuration. The sleeve may comprise a helical member or a tubular member. The helical member is retainable in its inserting position with a frangible element that is breakable when the member is bent to release the member into engaging position. The tubular member may have an elastic limit less than the tubing elastic limit, thus bending the tubing bends and deforms the member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0007]      FIG. 1  is a side view of a power cable with an embodiment of an anchoring system being inserted into tubing. 
           [0008]      FIG. 2  is a side view of the power cable with the anchoring system of  FIG. 1  in tubing, the anchoring system in an anchoring configuration. 
           [0009]      FIG. 3  is a side view of a power cable with an additional embodiment of an anchoring system being inserted into tubing. 
           [0010]      FIG. 4  is a side partial sectional view showing the tubing with cable therein of  FIG. 3  in a coiled arrangement with inserted power cable. 
           [0011]      FIG. 5  is a side view of the power cable with the anchoring system of  FIG. 3  in tubing, the anchoring system in an anchoring configuration. 
           [0012]      FIG. 6  is a side partial sectional view of an embodiment of a cable anchoring system in accordance with the present disclosure disposed in a wellbore. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. For the convenience in referring to the accompanying figures, directional terms are used for reference and illustration only. For example, the directional terms such as “upper”, “lower”, “above”, “below”, and the like are being used to illustrate a relational location. 
         [0014]    It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims. 
         [0015]    One example of an anchoring system  20  combined with a power cable  12  is illustrated in side view in  FIG. 1 . The anchoring system  20  is depicted in an insertable configuration being slid into coiled tubing  10 . In the embodiment of  FIG. 1 , the anchoring system  20  comprises an annular anchoring sleeve  24  that circumscribes a portion of the power cable  12 . The anchoring sleeve  24  comprises a tubular body, preferably of steel, having a helically arranged slot  26  formed along the body to define a helix. Slot  26  extends completely through the wall of the sleeve  24 . The slot  26  is cut in the sleeve  24  while it is in natural diameter. Then the sleeve  24  is radially compressed. Shown radially compressed in  FIG. 1 , the sleeve  24  is insertable into the downhole tubing  10  with the slot  26  defining a line of contact where adjacent portions of the helix are next to one another. The material and slot width are selected so that the deformation from the natural larger diameter to its small diameter of  FIG. 1  is not permanent. There is a natural bias tending to cause the sleeve  24  to spring outward to the position of  FIG. 2 . 
         [0016]    The sleeve  24  is expandable both longitudinally and radially into an anchoring configuration. In the anchoring configuration the slot  26   a  defines a gap between the adjacent portions of the helix. The original diameter of the sleeve  24  was greater than in  FIG. 2  and the slots  26  had greater widths. When allowed to spring outward, preferably a spring force exists in sleeve  24 , causing it to grip the tubing  10  inner diameter. The sleeve  24  may be retained in the insertable configuration of  FIG. 1  by a frangible element. Examples of a frangible element include solder  27  applied along at least a portion of the slot  26  and optionally a breakable cover  29  circumscribing at least a portion of the anchoring sleeve  24 . Optionally, the cover  29  may circumscribe the entire length of the anchoring sleeve  24 . The sleeve  24  will expand outward due to its own resilience after the solder  27  or cover  29  is broken. 
         [0017]    Also on the cable  12  are anchoring collars  28  provided on either end of the sleeve  24 . The collars  28  comprise collar halves  30 ,  32  having a semicircular cross-section and joined along their respective ends with each other. Each collar half  30 ,  32  includes a threaded aperture  33  registerable with a corresponding threaded aperture  33  when placing the halves  30 ,  32  over the cable  12 . Screw bolts or other fasteners may be inserted through the threaded aperture thereby securing the halves  30 ,  32  together on the cable  12 . Collars  28  are preferably spaced apart from each other a greater length than the length of the sleeve  24  when expanded. The anchoring collars  28  may have an inner circumference shaped to match the undulations  14  running along the cable  12  outer surface. 
         [0018]    Shown in a partial sectional view in  FIG. 2 , the cable  12  with anchoring system  20  is disposed within a portion of the tubing  10 , and the anchoring sleeve  24   a  has been selectively changed into an anchoring configuration. In this configuration, the body of the sleeve  24   a  is radially and longitudinally expanded that correspondingly expands the slot  26   a  width. In the anchoring configuration, the sleeve  24   a  has an outer circumference that elastically expands into engagement with the tubing  10  inner circumference thereby affixing the sleeve  24   a  at that location in the tubing  10 . The collars  28  will engage the respective ends of the sleeve  24   a,  thereby limiting cable  12  travel within the tubing  10 . In one example of assembly, the anchoring sleeves  24 ,  24   a  of  FIGS. 1 and 3  may be slid on an end of the cable  12  before the cable  12  is slid into the tubing  10 . 
         [0019]    The sleeve  24   a  of  FIG. 2  is shown in a more relaxed or lower potential energy state than the configuration of the sleeve  24  of  FIG. 1 . Changing the sleeve  24   a  into the insertable configuration shown in  FIG. 1  requires radially and longitudinally compressing the sleeve  24  thereby storing potential energy in the sleeve  24 . Generally a length of tubing  10  is uncoiled from a tubing spool and laid horizontally on a surface before inserting the cable  12 . The tubing  10  is then coiled back onto the reel. Fracturing or removing the frangible elements, i.e., the solder  27 , the breakable cover  29 , or some other element, removes the retaining means associated with the sleeve  24 , thereby allowing the sleeve to expand to its anchoring state shown in  FIG. 2 . Coiling the tubing  10  onto a reel bends the sleeve and fractures frangible element that allows the sleeve  24  to expand to its lower energy state and engage the tubing  10  inner circumference. Due to the inherent internal stresses within the sleeve  24 , a subsequent uncoiling or straightening of the tubing  10  will not return the sleeve  24  to the insertable configuration. Instead the system  20  remains in the anchoring configuration to retain the cable  12  within the tubing  10 . 
         [0020]    Shown in side view in  FIG. 3  is an alternative anchoring sleeve  34  that comprises a portion of an anchoring system  20 b. In this embodiment, the anchoring sleeve  34  is a substantially tubular member circumscribing a cable  12  and between a pair of anchoring collars  28  spaced apart a greater length than the anchoring sleeve  34 . The cable  12  with sleeve  34  is shown being inserted into tubing  10 . The anchoring sleeve  34  of this embodiment preferably comprises a material whose elastic limit is less than the tubing  10  elastic limit. Examples of such material include aluminum, copper, brass, bronze, and alloys thereof. The tubing  10  may comprise steel. The anchoring sleeve  34  is also changeable from its insertable configuration of  FIG. 3  into an anchoring configuration of  FIG. 5 . 
         [0021]    With reference now to  FIG. 4 , a side partially sectional view of tubing  10  formed into a coil is shown with the cable  12  and anchoring system  20 . The anchoring sleeve  34  should be sufficiently elongated so coiling the tubing  10  creates a bent anchoring sleeve  34 . The anchoring sleeve  34  is plastically deformed due to the coiling force and remains in the bent position. Tubing  10  does not plastically deform when coiled onto a reel. As shown in a partial sectional view in  FIG. 5 , the anchoring sleeve  34  is plastically deformed and has its ends  35  engaging the tubing  10  inner circumference along an azimuth of the tubing  10 . When the tubing  10  is again straightened for insertion into a well, the sleeve  34  remains bent. The bent or deformed sleeve  34  has its midsection  37  engaging the tubing  34  inner circumference at a location approximately 180 degrees from the azimuth of contact between the sleeve ends  35 . Accordingly, sufficient plastic deformation of the sleeve  34  effectively wedges the sleeve  34  within the tubing  10  at a particular location within the tubing  10 . Clearance between the sleeve  34  outer diameter and tubing  10  inner diameter allows the tubing  10  to be uncoiled and straightened without fully straightening the sleeve  34 . Although the tubing  10  will unbend the sleeve  34  somewhat. As seen in  FIG. 5  however, the sleeve  34  will not fully respond to tubing  10  deformation due to the clearance between the tubing  10  and sleeve  34  inner and outer respective dimensions. The added anchor collars  28  are configured for mating engagement with the ends  35  to thereby anchor the cable  12  with respect to the sleeve  34 . 
         [0022]      FIG. 6  depicts is partial sectional side view an embodiment of the anchoring system described herein for use in a wellbore. Borehole tubing  10  is illustrated being uncoiled from a tubing reel  16  and inserted into a borehole  5  through a wellhead housing  9 . Power cable  12  is supported within the tubing  10  on multiple anchoring systems  20 . The anchoring systems have been energized by coiling the tubing after the cable  12  was inserted into the tubing  10  while horizontal. The anchoring systems retain the cable  12  within the tubing  10  after subsequent uncoiling of the tubing  10  to thereby anchor the cable  12  in the tubing. As is known, downhole cable can break under its own weight; therefore the distance between adjacent anchoring systems  20  is dictated by the cable strength and density. 
         [0023]    An electrical submersible pumping (ESP) system  40  is illustrated attached to the lower terminal end of the tubing  12 . In this embodiment, the ESP system  40  comprises a pump motor  42 , a pump  44 , and an equalizer or seal section  46  between the pump  44  and motor  42 . The power cable  12  is shown attached to the pump motor  42  for providing electrical power to the pump motor  42  for running the pump  44 . 
         [0024]    The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims. While the invention has been shown in only two of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.