Abstract:
A system for splicing coiled tubing used in deploying downhole equipment and having an internal power cable. The system includes first and second segments of coiled tubing each having power cable disposed therein. Additionally, mounting fixtures are attached to the ends of the coiled tubing segments that are to be joined. The system further includes a movable canister that may be slid over the spliced segments of power cable and selectively engaged with the mounting fixtures. The canister provides structural integrity to the overall deployment tubing while protecting the internal power cable splice.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to tubing deployment systems, such as those used to deploy electric submergible pumping systems within a wellbore, and particularly to a splice system for splicing together segments of tubing, such as coiled tubing, having internal power cable. 
     BACKGROUND OF THE INVENTION 
     Various types of equipment are used in the production of fluid, such as petroleum, from subterranean locations. For example, pumping systems are utilized in pumping oil and/or other production fluids from producing wells. An exemplary pumping system is an electric submergible pumping system that includes components such as a motor, motor protector, pump and pump intake. The system is deployed within a wellbore by a deployment system, such as tubing used to suspend the system as it is moved to a desired location in the wellbore. Tubing, e.g. coiled tubing, can be used to locate components at substantial subterranean depths. 
     In some systems, the central hollow opening of the tubing is used for the production of fluid therethrough. In other applications, however, the internal opening of the tubing is used to hold power cable routed to the submergible components that require power. An electric submergible motor is an example of a component requiring power. In such systems, the production fluid typically is produced external to the tubing. 
     For a variety of reasons, it can become necessary to splice together two or more segments of tubing when delivering a downhole system or component to a desired depth within the wellbore. Heretofore, no one has had significant success in developing a dependable system for splicing adjacent sections of coiled tubing having an internal power cable. 
     It would be advantageous to have a system that readily permitted the formation of a splice for adjacent segments of tubing having power cable disposed therein. 
     SUMMARY OF THE INVENTION 
     The present invention features a coiled tubing system in which sequential segments of coiled tubing are spliced together for deployment of downhole equipment. The system includes a first segment of coiled tubing having a first power cable disposed within its hollow center. The system also includes a second segment of coiled tubing having a second power cable disposed within its hollow interior. First and second mounting fixtures are connected to the first and second segments of coiled tubing, respectively. Additionally, a canister is designed to provide a rigid connection between the first and the second mounting fixtures. The canister is designed for release such that it may be slid along either the first or second segment of coiled tubing to accommodate splicing of the first and the second power cables intermediate the first and the second mounting fixtures. The canister is further designed to securely engage both the first and the second mounting fixtures and to contain the cable splice therein. 
     According to another aspect of the invention, a system is provided for connecting sections of tubing that carry power cable therein for providing power to well-related equipment. The system includes a pair of fixtures attachable to individual sections of tubing. Additionally, the system includes a canister that may be selectively engaged with the pair of fixtures to connect the individual sections of tubing. The canister includes a hollow interior to accommodate a power cable splice. Also, the canister is sized to slide over at least one of the pair of fixtures to permit formation of the power cable splice. 
     According to another aspect of the invention, a method is provided for splicing two sections of coiled tubing in which each section has an internal power cable for supplying power to well equipment. The method includes mounting a fixture to each adjacent end of two sections of coiled tubing that are to be connected. The method also includes splicing the internal power cable intermediate the fixtures. Furthermore, the method includes enclosing the spliced internal power cable within a canister connected between the fixtures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and 
     FIG. 1 is a front elevational view of an exemplary downhole pumping system deployed within a wellbore by deployment tubing, according to one embodiment of the present invention; 
     FIGS. 2 illustrate a partially cut-away view of an exemplary coiled tubing connector for use with the splice system illustrated in FIG. 1; 
     FIG. 3 illustrates an initial step in forming the splice system illustrated in FIG. 2; 
     FIG. 4 illustrates a subsequent step in the formation of the splice system; 
     FIG. 5 illustrates an additional step in the formation of the splice system; 
     FIG. 6 illustrates an additional step in the formation of the splice system; 
     FIG. 7 illustrates an additional step in the formation of the splice system; and 
     FIG. 8 illustrates an exemplary completed splice system shown as a partially cut-away view, according to one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring generally to FIG. 1, an exemplary deployment system  10  is illustrated in a wellbore environment. Deployment system  10  is attached to an electric submergible pumping system  12  and preferably a bottom intake system. Deployment system  10  can be utilized in the deployment of a wide variety of devices or systems, but the unique design of deployment system  10  is particularly amenable to deployment of electric submergible pumping systems  12 . 
     A typical bottom intake pumping system  12  may comprise a variety of components depending on the particular application or environment in which it is used. Typically, system  12  includes at least a submergible pump  14 , a pump intake  15 , a submergible motor  16 , a motor protector  17  and a packer assembly  18 . However, a variety of other or additional components can be utilized in the system. 
     For example, system  12  may include a thrust section  19  and a connector  20  by which submergible pumping system  12  is coupled to deployment system  10 . Also, a variety of component types may be utilized. For instance, an exemplary motor  16  is a three-phase, induction-type motor, and an exemplary pump  14  is a multi-stage centrifugal pump. In this type of system, submergible pump  14  draws wellbore fluid through pump intake  15  and discharges it through a packer discharge head  21  above the packer assembly  18  into the annulus formed about deployment system  10 . A variety of packer assemblies also may be utilized, such as a mechanically set packer or a hydraulic packer, e.g., the Camco HRP-1-SP Hydraulic Set Packer available through Camco of Houston, Tex. 
     In the example illustrated, system  12  is designed for deployment in a well  22  within a geological formation  24  that contains desirable production fluids, such as petroleum. In a typical application, a wellbore  26  is drilled and lined with a wellbore casing  28 . Wellbore casing  28  may include a plurality of openings  30 , often called perforations, through which production fluids flow into wellbore  26 . 
     Although deployment system  10  may have a variety of forms and configurations, it typically comprises tubing, and preferably a coiled tubing  32 . A power cable  34  is disposed within a hollow interior  36  of the tubing  32 . The power cable  34  is supported within tubing  32  by appropriate anchors, buoyancy fluid or other means. 
     As illustrated, deployment system  10  comprises two or more segments  38  connected by one or more splice systems  40 . Each segment  38  includes an outer tube, e.g. coiled tubing  32 , and an internal power cable  34 . 
     An exemplary embodiment of splice system  40  is illustrated in FIG.  2 . Splice system  40  facilitates the joining of adjacent segments  38 . Specifically, splice system  40  provides for the splicing of a first power cable section  42  with a second power cable section  44  at a power cable splice junction  46 . Splice system  40  also provides for the splicing of two sequential or adjacent segments of tubing  32 . The splicing of tubing  32  must provide sufficient structural integrity to permit deployment of an appropriate system, such as electric submergible pumping system  12 , while protecting power cable splice  46 . 
     In the illustrated embodiment, a lower fixture  48  is securely affixed to an end  50  of the tubing  32  of the lower segment  38 . Preferably, one or more seals  52  are disposed between lower fixture  48  and the external surface of the corresponding segment  38  to prevent the seepage or flow of liquid therethrough. 
     Although a variety of fixtures may be utilized, a preferred fixture  48  comprises an external coiled tubing connector, e.g. a slip-type connector, such as those available from Camco of Houston, Tex., a division of Schlumberger Corporation. As is known to those of ordinary skill in the art, such slip-type connectors utilize a sloped surface that facilitates the tightening of the fixture against tubing  32 . 
     An exemplary lower fixture  48  and its use is illustrated in FIGS. 2A through 2D. In this example, fixture  48  includes a housing  53 , a body portion  54 , a slip-lock  55  and a washer  56 . 
     To assemble fixture  48  on tubing end  50 , housing  53 , slip-lock  55  and washer  56  are slid over tubing end  50 , as illustrated in FIG.  2 A. The tubing end  50  is then inserted into body portion  54  and slid past seal  52  and into abutment with an annular abutment ledge  57 , as best illustrated in FIG.  2 B. The slip-lock is then slid into an abutting engagement with body portion  54 , as illustrated best in FIG.  2 C. Subsequently, housing  53  is threaded into engagement with body portion  54  via a threaded region  58 , as best illustrated in FIG.  2 D. As housing  53  and body portion  54  are threaded together, slip-lock  55  is forced tightly against tubing end  50  by the tapered internal wall of housing  53 . The tapered internal wall is disposed to slide along slip-lock  55  as the fixture is tightened. This holds the entire fixture securely to tubing end  50 . 
     An upper fixture  60  is connected to the external surface of tubing  32  at upper segment  38 . Upper fixture  60  preferably is similar to lower fixture  48  and includes one or more seals  62  disposed between the upper fixture  60  and corresponding segment  38  to prevent flow of liquid between segment  38  and fixture  60 . Upper fixture  60  is designed for placement at a lower end  64  of the upper segment  38 , which is disposed for connection with the upper end  50  of lower segment  38 . 
     As described with respect to lower fixture  48 , fixture  60  preferably is an external coiled tubing connector, e.g. a slip-type connector, such as those available from Camco. Upper fixture  60  may include a housing, body portion and slip-lock as described above with reference to FIGS. 2A-D. This permits fixture  60  to be tightened against the outside surface of segment  38 , as known to those of ordinary skill in the art. 
     In the illustrated embodiment, upper fixture  60  is slightly modified relative to lower fixture  48 . Specifically, the upper fixture  60  has been created with a smaller cross-sectional area to accommodate sliding engagement with a canister  72  that is designed to couple together lower fixture  48  and upper fixture  60 . 
     In the embodiment shown, canister  72  is generally tubular and has a hollow interior  74  designed to accommodate power cable splice  46 . Preferably, canister  72  includes a lower threaded region  76  and an upper threaded region  78 . Lower threaded region  76  is disposed for threaded engagement with an externally threaded area  80  on lower fixture  48 . (See FIGS.  2  through  2 D). Similarly, upper threaded region  78  is disposed for threaded engagement with an externally threaded area  82  disposed on upper fixture  60 , as illustrated in FIG.  2 . 
     Preferably, canister  72  includes a narrowed or constricted region  84  disposed at upper threaded region  78  to prevent canister  72  from sliding past fixture  60  when the lower threaded region  76  is moved towards engagement with lower fixture  48 . For example, the diameter of externally threaded area  82  may be slightly less than that of externally threaded area  80  to permit movement of the lower threaded region  76  of canister  72  past externally threaded area  82  as the splice is completed. Also, it is preferred that the lower and upper threaded regions  76 ,  78  and the externally threaded areas  80 , 82  have self-sealing threads to prevent the influx of wellbore fluids into hollow interior  74 . Furthermore, canister  72  may include a vent  86  to permit the escape of gas from hollow interior  74  and the interior of the upper segment  38  if that segment is filled with fluid, e.g. a buoyancy fluid. 
     Referring generally to FIGS. 3 through 7, the method of assembling splice system  40  is illustrated. With reference to FIG. 3, end  64  of a tubing segment  38 , including first power cable section  42 , are brought into proximity with end  50  of the next consecutive segment  38 , including its corresponding internal power cable section  44 . 
     End  64  then is inserted through narrowed region  84  of canister  72 , and canister  72  is slid along segment  38  until end  64  is left protruding through the opposite end of canister  72  (see FIG.  4 ). When canister  72  is in this position, both upper fixture  60  and lower fixture  48  are attached at segment ends  64  and  50 , respectively. 
     Following the positioning of canister  72  and fixtures  48 ,  60 , power cable sections  42  and  44  are electrically connected. Typically, each power cable section includes at least three conductors for carrying three-phase power to submergible motor  18 . The multiple conductors are connected, as illustrated in FIG. 5, and wrapped to form power cable splice  46 , as illustrated in FIG.  2 . The power cable splice may be formed in a variety of conventional ways, and typically is formed as a field splice, as known to those of ordinary skill in the art. At this time, upper fixture  60  is tightened such that locking portion  68  firmly forces gripping portion  66  into engagement with the exterior of segment  38 . 
     After upper fixture  60  is tightened, canister  72  is slid downwardly over power cable splice  46  until lower threaded region  76  engages external threaded region  80  and upper threaded region  78  engages external threaded region  82 , as illustrated in FIG.  6 . Then, canister  72  is rotated until it is firmly engaged with both upper fixture  60  and lower fixture  48 . After tightening canister  72 , housing  52  and body portion  54  may be threaded together to securely engage lower fixture  48  with end  50  of the lower segment  38 , as illustrated in FIGS. 7 and 8. 
     As best shown in FIG. 8, the completion of splice system  40  provides a secure liquid-tight splice that protects the internal power cable. Additionally, the use of a relatively rigid canister, preferably formed from a metallic material, such as steel, provides sufficient structural integrity to facilitate deployment of a variety of well-related equipment. Depending on the downhole application and/or the depth of well  22 , this type of splice system can be used to join two or more sections of tubing having integral power cable. 
     It will be understood that the foregoing description is of preferred exemplary embodiments of this invention, and that the invention is not limited to the specific forms shown. For example, a variety of fixtures may be used to rigidly engage the tubing; other types of tubing may be utilized in place of the preferred coiled tubing; the canister is preferably made from a metallic material, e.g. steel, although other materials may be appropriate for certain applications; the canister may be engaged with the fixtures by a variety of mechanisms other than screw threads; and a variety of other types of power cable splices may be utilized within the canister. Additionally, the method steps and their order may be modified for a given design or downhole application. These and other modifications may be made in the design and arrangement of the elements without departing from the scope of the invention as expressed in the appended claims.