Abstract:
A tubing connector comprising a rigid member having a first end and a second end; a crimping groove disposed about the rigid member; and a sleeve fixably attached to the rigid member and covering the crimping groove. A method for connecting a tubing section to a rigid member, the method comprising fixably attaching a sleeve over one end of the rigid member to cover a crimping groove disposed on the rigid member, disposing the tubing section over the sleeve, and plastically deforming the tubing section and sleeve to form a plurality of dimples that project into the crimping groove of the rigid member.

Description:
BACKGROUND 
   The present invention relates generally to methods and apparatus for connecting lengths of coiled tubing. More particularly, the present invention relates to spoolable coiled tubing connectors that maintain the pressure and tensile strength ratings of the tubing. 
   Conventional tubing strings are constructed in thirty foot long straight sections that are connected in series. A coiled tubing string generally includes a continuous length of small diameter tubing that is much more flexible than conventional tubing and can therefore be spooled onto a reel. The coiled tubing is unwound from the reel and directed over a gooseneck and through a tubing injector head into a wellbore. Coiled tubing is used for a variety of wellbore processes, including injecting gas or other fluids into the wellbore, inflating or activating bridge plugs and packers, transporting well logging tools downhole, performing remedial cementing and clean-out operations in the wellbore, and delivering or retrieving drilling tools downhole. 
   As the utilization of coiled tubing expands into applications involving greater depths, pressures, and more remote operating locations, the complexity and size of a coiled tubing system increase. Transportation and handling constraints often limit the size of the reel and the corresponding length of coiled tubing able to be stored on a given reel. To overcome this limitation, lengths of coiled tubing from multiple reels can be connected in series and used in a single operation. These multiple lengths can then be spooled back onto a single, larger reel for more efficient storage. Although lengths of coiled tubing can be welded together, welding requires special equipment, personnel, and a closely controlled environment. In connecting lengths of coiled tubing, a mechanical connector that does not require welding at a well site can simplify the connection process by enabling faster connections in a wider variety of environmental conditions. 
   In operation, coiled tubing is subjected to bending stresses both when being spooled onto and off of the reel and when being fed over the gooseneck into the injector head. A mechanical connector joining lengths of coiled tubing will also be subjected to these bending stresses. As the length and stiffness of a connector increase, areas of stress concentration will develop in the regions of the coiled tubing immediately adjacent to the connector. Therefore, it is desirable to minimize both the overall length and stiffness of a coiled tubing connector. 
   Thus, there remains a need to develop methods and apparatus for connecting lengths of coiled tubing, which overcome some of the foregoing difficulties while providing more advantageous overall results. 
   SUMMARY 
   Disclosed herein is a tubing connector comprising a rigid member having a first end and a second end, a crimping groove disposed about the rigid member, and a sleeve fixably attached to the rigid member and covering the crimping groove. 
   Further disclosed herein is a method for connecting a tubing section to a rigid member, the method comprising fixably attaching a sleeve over one end of the rigid member to cover a crimping groove disposed on the rigid member, disposing the tubing section over the sleeve, and plastically deforming the tubing section and sleeve to form a plurality of dimples in that project into the crimping groove of the rigid member. 
   Further disclosed herein is a spoolable tubing connector comprising a flexible tubing section having first and second ends, a first rigid member fixably attached to the first end of the flexible tubing member, the first rigid member comprising at least one crimping groove, a first sleeve fixably attached to the first rigid member, wherein the first sleeve covers the crimping groove on the first rigid member, a second rigid member fixably attached to the second end of the flexible tubing member, the second rigid member comprising at least one crimping groove, and a second sleeve fixably attached to the second rigid member, wherein the second sleeve covers the crimping groove on the second rigid member. 
   Thus, the present invention comprises a combination of features and advantages that enable it to overcome various problems of prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the following embodiments of the invention, and by referring to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more detailed description of representative embodiments of the present invention, reference will now be made to the accompanying drawings, wherein: 
       FIG. 1  is a partial sectional view of a coiled tubing connector; 
       FIG. 2  is a partial sectional view of a coiled tubing connector engaged with a tubing section; 
       FIG. 3  is a partial sectional view of a double ended coiled tubing connector; and 
       FIG. 4  is a partial sectional view of a coiled tubing connector. 
   

   DETAILED DESCRIPTION 
   Referring now to  FIG. 1 , a coiled tubing connector  10  is shown comprising a rigid member  12 , first tubing section  14 , sleeve  16 , and seal  20 . Rigid member  12  is a tubular member having an inner diameter defining an axial flow passage  13  and a maximum outer diameter  15  that is closely matched to the outside diameter of first tubing section  14 . The outside surface of rigid member  12  includes first tubing interface  21 , sleeve interface  23 , and second tubing interface  25 . 
   First tubing interface  21  includes first end  22  and first shoulder  24 , which is adjacent to maximum outer diameter  15 . First end  22  has a diameter sized so as to closely fit within first tubing section  14 . First end  22  is inserted into first tubing section  14  such that the end of the first tubing section  14  is disposed in close relation to first shoulder  24 , enabling weld  26  to be formed between rigid member  12  and first tubing section  14 . Weld  26  prohibits axial and radial movement of first tubing section  14  relative to rigid member  12 . 
   Sleeve interface  23  is on the opposite end of rigid member  12  from first tubing interface  21 . Sleeve interface  23  includes crimping groove  18 , second end  28 , and shoulder  19 . Sleeve interface  23  has a diameter sized so as to fit in close relationship with the interior of sleeve  16 . Second end  28  is inserted into sleeve  16  such that one end of the sleeve  16  is disposed in close relation to shoulder  19 , enabling weld  30  to be formed between rigid member  12  and sleeve  16 . Weld  30  prohibits axial and radial movement of sleeve  16  relative to rigid member  12 . Crimping groove  18  extends continuously, or discontinuously, around the perimeter of rigid member  12  and is positioned axially along rigid member  12  so that sleeve  16  covers the crimping groove  18  when the sleeve  16  is welded to the rigid member  12 . 
   Second tubing interface  25  is located between sleeve interface  23  and first tubing interface  21  and includes seal groove  32  and shoulder  34 . Second tubing interface  25  has an outer diameter approximately equal to the outer diameter of sleeve  16 . Second tubing interface  25  continues axially from shoulder  19  to shoulder  34 , where the diameter increases to maximum diameter  15 . The diameter of second tubing interface  25  is sized so as to fit within, and in close relationship with the inner diameter of, a second tubing section  36 , as shown in  FIG. 2 . 
   Rigid member  12  is constructed from a material suitable for use with the coiled tubing string. Rigid member  12  may be constructed from metallic materials, such a steel, stainless steel, high-chrome steel, or other machinable, weldable material. The inside diameter of rigid member  12 , which forms flow passage  13 , may include sloped ends  40  where the diameter gradually increases in order to provide a smooth transition and eliminate any internal ledges. The overall length of rigid member  12  is minimized so as to reduce the stiffness of connector  10 . As the length of rigid member  12  increases, the stiffness of connector  10  and the stress developed in the coiled tubing string also increase. 
   Sleeve  16  is a relatively thin walled tubular member that is constructed from a material suitable for use with the coiled tubing string. Sleeve  16  has an outer diameter sized so as to fit in close relationship with the inner diameter of second tubing section  36 , as shown in  FIG. 2 . The outside surface of sleeve  16  may have a longitudinal groove so as to accommodate a weld seam projecting from the inside surface of second tubing section  36 . End  42  of sleeve  16  may also be sloped so as to provide a smooth transition between the inner diameters of second tubing section  36  and rigid member  12 . 
   Sleeve  16  may be extended past the end of rigid member  12  in order to provide support to second tubing section  36 . As the coiled tubing string and connector  10  are spooled on a reel or run over a gooseneck, the bending stresses imparted on the coiled tubing string will tend to create stress concentrations in second tubing section  36  immediately adjacent to connector  10 . Sleeve  16  operates to decrease these stress concentrations and increase the useful life of the coiled tubing string. 
   Seal  20  is disposed within seal groove  32  positioned within second tubing interface  25 . As shown in  FIG. 2 , seal  20  engages the inner wall of second tubing section  36 . Seal  20  is a static, permanent seal that may be constructed of any seal material that is compatible with the environments in which the coiled tubing string may be used. For example, seal  20  may be constructed from an elastomeric material, such as nitrile rubber, or a polymeric seal material, such as VITON™ or PEEK™. Seal  20  may include a combination of seal members and backup members as necessary to meet the sealing requirements of the system. 
   Referring now to  FIG. 2 , connector  10  is shown engaged with a second tubing section  36 . Sleeve  16  and second end  28  are inserted into second tubing section  36  such that one end of the second tubing section  36  is adjacent to shoulder  34 . The outer diameter of second tubing section  36  closely matches the maximum outer diameter  15  of rigid member  12  and the outer diameter of first tubing section  14 , such that the outer diameter remains substantially constant across connector  10 . 
   A series of dimples  38  are formed in second tubing section  36  by applying a localized force to plastically deform second tubing section and push a small area of the tubing section  36  wall and sleeve  16  into engagement with crimping groove  18 . Thus, by forming dimples  38  in the second tubing section  36 , dimples  17  are also created in sleeve  16 . Dimples  38  may be formed by pins, or some other member, being pushed against tubing section  36  by hydraulic or mechanical force. The pins may be axially located by a jig, or other structure, that can be temporarily attached to connector  10  so as to reliably align the pins with crimping groove  18 . Dimples  38  can be placed at any desired radial location on the perimeter of second tubing section  36 , and do not require radial alignment within crimping groove  18 . The number of dimples  38  required will depend on the size of connector  10  and the axial loads for which the coiled tubing string is rated. 
   Dimples  38  engage crimping groove  18  and prohibit axial movement of rigid member  12  relative to second tubing section  36 . Dimples  38  also prohibit axial and rotational movement of second tubing section  36  relative to sleeve  16 , which is connected to rigid member  12  by weld  30 . As discussed above, weld  30  prohibits axial and rotational movement of sleeve  16  relative to rigid member  12 . Therefore, second tubing section  36  is prohibited from axial and rotational movement relative to rigid member  12 . Axial and rotational movement of rigid member  12  relative to first tubing section  14  is prohibited by weld  26 . Therefore, axial and rotational movement of first tubing section  14  relative to second tubing section  36  is prohibited by rigid member  12  of connector  10 . 
   Referring now to  FIG. 3 , a coiled tubing connector  44  is shown including two connectors  10  connected by a flexible tubing section  46 . Each connector  10  has a rigid member  12  with a corresponding sleeve  16 , crimping groove  18 , and seal  20 , as described previously. Connector  44  may be used to connect two lengths of coiled tubing to effectively create a longer string of tubing with the same pressure and tensile load characteristics of the component strings, without the need for welding at the job site. 
   Flexible tubing section  46  is constructed from a material having a diameter, length, and wall thickness selected so as to provide a desired amount of flexibility between rigid members  12 . This flexibility allows connector  44  to bend as the coiled tubing string is being spooled onto a reel or being run over the gooseneck. Flexible tubing section  46  may be a section of coiled tubing similar to the coiled tubing strings with which connector  44  will be employed. Alternatively, flexible tubing section  46  may be some other material selected for its flexibility and performance under repeated bending loads. In one embodiment, flexible tubing section  46  has an outside diameter no larger than the outside diameter of the coiled tubing string with which it is used. 
     FIG. 4  illustrates an alternate embodiment of a connector  48  including a rigid member  50  having multiple crimping grooves  52  and redundant seals  54 . Sleeve  56  covers each of crimping grooves  52 . Multiple crimping grooves  52  may be utilized in certain applications requiring connector  48  to withstand higher axial and rotational loads. Multiple seals  54  may be utilized in certain applications where sealing redundancy and reliability are especially valuable. The overall length of rigid member  50  is still minimized so as to reduce the stiffness of connector  48 . 
   Connectors for coiled tubing as described above may find use in many tubing applications. These types of connectors could be used to join two lengths of tubing or to provide end connectors for connecting the tubing to a bottom hole assembly, or some other component. Connectors such as those described could also find use in other tubing applications outside of coiled tubing. 
   While representative embodiments of this invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teaching of this invention. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system and apparatus are possible and are within the scope of the invention. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied, so long as the coiled tubing connector apparatus retain the advantages discussed herein. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.