Patent Publication Number: US-10781675-B2

Title: Charge tube with self-locking alignment fixtures

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage entry of PCT/US2014/054881 filed Sep. 10, 2014, said application is expressly incorporated herein in its entirety. 
     FIELD 
     The present technology pertains to systems and methods used in perforation tool assemblies, and more specifically pertains to charge tubes and self-locking alignment fixtures. 
     BACKGROUND 
     Wellbores are drilled into the earth for a variety of purposes including tapping into hydrocarbon bearing formations to extract the hydrocarbons for use as fuel, lubricants, chemical production, and other purposes. When a wellbore has been completed, a metal tubular casing may be placed and cemented in the wellbore. Thereafter, a perforation tool assembly may be run into the casing, and one or more perforation guns in the perforation tool assembly may be activated and/or fired to perforate the casing and/or the formation to promote production of hydrocarbons from selected formations. Perforation guns may comprise one or more explosive charges that may be selectively activated, the detonation of the explosive charges desirably piercing the casing and penetrating at least partly into the formation proximate to the wellbore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only exemplary embodiments of the disclosure and are not therefore to be considered to be limiting of its scope, the principles herein are described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG. 1  is a diagram of a wellbore and workstring according to an embodiment of the disclosure. 
         FIG. 2  is a diagram of a partially-assembled gun body with a charge tube and alignment fixture received in the gun body according to an embodiment of the disclosure. 
         FIG. 3  is a diagram of an alignment fixture secured to a charge tube and inserted in a gun body, as viewed from the end of the gun body, according to an embodiment. 
         FIG. 4  is a diagram of an alignment fixture secured to a charge tube, as viewed in cross-section along line A-A of  FIG. 3 , according to an embodiment of the disclosure. 
         FIG. 5  is a diagram of an alignment fixture with integrated alignment finger engaging an interior surface of the gun body, according to an embodiment of the disclosure. 
         FIG. 6  is a diagram of an alignment fixture having a plurality of openings and an integrated alignment finger, as viewed from an end of the alignment fixture, according to an embodiment of the disclosure. 
         FIG. 7  is a diagram of the alignment fixture having a plurality of openings that are adapted to releasably engage a plurality of protrusions on a charge tube, as viewed from the side, according to an embodiment of the disclosure. 
         FIG. 8  is a diagram of an alignment fixture engaged with a charge tube and having been rotated into a first “connected” state, according to an embodiment of the disclosure; 
         FIG. 9  is a diagram of an alignment fixture engaged with a charge tube in a second “locked” state, according to an embodiment of the disclosure; 
         FIG. 10  is a diagram of an alignment fixture inserted into a charge tube, according to an embodiment of the disclosure. 
         FIG. 11  is a diagram of an alignment fixture once inserted onto a charge tube and then twisted into a locking position, according to an embodiment of the disclosure. 
         FIG. 12  is a diagram of a charge tube with an alignment fixture secured thereto as it is partially inserted within a gun body, as viewed from the side, according to an embodiment of the disclosure. 
         FIG. 13  is a diagram of an alignment fixture with integrated alignment finger, as alignment fixture is secured to a charge tube, according to another embodiment of the disclosure. 
         FIG. 14  is a diagram of the alignment fixture with integrated alignment finger secured to the charge tube and the alignment finger engaging an interior surface of the gun body, according to the other embodiment of the disclosure. 
     
    
    
     DESCRIPTION 
     Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the disclosure. 
     It should be understood at the outset that although illustrative implementations of one or more embodiments are illustrated below, the disclosed systems may be implemented using any number of techniques. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated herein, but may be modified within the scope of the appended claims along with their full scope of equivalents. 
     Unless otherwise specified, any use of any form of the terms “connect,” “engage,” “couple,” “attach,” or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and also may include indirect interaction between the elements described. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Reference to up or down will be made for purposes of description with “up,” “upper,” “upward,” or “upstream” meaning toward the surface of the wellbore and with “down,” “lower,” “downward,” or “downstream” meaning toward the terminal end of the well, regardless of the wellbore orientation. The term “radial” and/or “radially” means substantially in a direction along a radius of the object, or having a directional component in a direction along a radius of the object, even if the object is not exactly circular or cylindrical. The term “axially” means substantially along a direction of the axis of the object. If not specified, the term axially is such that it refers to the longer axis of the object. 
     The term “zone” or “pay zone” as used herein refers to separate parts of the wellbore designated for treatment or production and may refer to an entire hydrocarbon formation or separate portions of a single formation such as horizontally and/or vertically spaced portions of the same formation. The various characteristics described in more detail below, will be readily apparent to those skilled in the art with the aid of this disclosure upon reading the following detailed description, and by referring to the accompanying drawings. 
     Reference is now made to  FIG. 1  showing a wellbore servicing system  10 . The system  10  comprises servicing rig  20  that extends over and around a wellbore  12  that penetrates a subterranean formation  14  for the purpose of recovering hydrocarbons from a first production zone  40   a,  a second production zone  40   b,  and/or a third production zone  40   c,  collectively the “production zones  40 ”. The wellbore  12  may be drilled into the subterranean formation  14  using any suitable drilling technique. While shown as extending vertically from the surface in  FIG. 1 , the wellbore  12  may also be deviated, horizontal, and/or curved over at least some portions of the wellbore  12 . For example, the wellbore  12 , or a lateral wellbore drilled off of the wellbore  12 , may deviate and remain within one of the production zones  40 . The wellbore  12  may be cased, open hole, contain tubing, and may generally comprise a hole in the ground having a variety of shapes and/or geometries as is known to those of skill in the art. In this illustrated embodiment, a casing  16  may be placed in the wellbore  12  and secured at least in part by cement  18 . 
     The servicing rig  20  may be one of a drilling rig, a completion rig, a workover rig, or other mast structure and supports a workstring  30  in a wellbore  12 , but a different structure may also support the workstring  30 . The servicing rig  20  may also comprise a derrick with a rig floor through which the workstring  30  extends downward from the servicing rig  20  into the wellbore  12 . In other environments, such as in an off-shore location, the servicing rig  20  may be supported by piers extending downwards to a seabed. Alternatively, in some examples, the servicing rig  20  may be supported by columns sitting on hulls and/or pontoons that are ballasted below the water surface, which may be referred to as a semi-submersible platform or rig. In an off-shore location, a casing  16  may extend from the servicing rig  20  to exclude sea water and contain drilling fluid returns. It is understood that other mechanical mechanisms, not shown, may control the run-in and withdrawal of the workstring  30  in the wellbore  12 , for example a draw works coupled to a hoisting apparatus, a slickline unit or a wireline unit including a winching apparatus, another servicing vehicle, a coiled tubing unit, and/or other apparatus. 
     The workstring  30  may comprise a conveyance  32  and a perforation tool assembly  34 , such as a perforation gun assembly for example. The conveyance  32  may be any of a string of jointed pipes, a slickline, a coiled tubing, and a wireline. The workstring  30  may further comprise one or more downhole tools (not shown in  FIG. 1 ), for example the perforation tool assembly  34 . The workstring  30  may comprise one or more packers, one or more completion components such as screens and/or production valves, sensing and/or measuring equipment, and other equipment which are not shown in  FIG. 1 . In some contexts, the workstring  30  may be lowered into the wellbore  12  to position the perforation tool assembly  34  to perforate the casing  16  and penetrate one or more of the production zones  40 . 
     Reference is now made to  FIG. 2  which is a diagram of a partially-assembled gun body with a charge tube and alignment fixture received in the gun body according to an embodiment of the disclosure. A gun body  210 , as part of an overall perforation gun assembly, for example the assembly  34  shown in  FIG. 1 , has a plurality of recesses or “scallops”  215  on an exterior surface of the gun body  210 . The scallops  215  provide a path for the charge material to more easily blast through after detonation of the charges. The gun body  210  is for receiving a charge tube  220 . The charge tube  220  has a plurality of openings  225  for receiving charges (not shown in  FIG. 2 ). A “charge” generally has a steel outer casing that contains an explosive powder or similar material that is activated and pierces through the scallops  215  of the gun body  210 . An alignment fixture  240  is secured to each end of the charge tube  220  and includes an alignment finger  245  that engages with a slot  230  on an interior surface of the gun body  210 . A snap ring  250  can be implemented to secure the charge tube  220  and attached alignment fixture  240  within the gun body  210 . The snap ring  250  can be designed to compress along the interior surface of the gun body  210  during insertion and then snap into an appropriate groove in the gun body once inserted within the gun body. The alignment finger  245  integrated on the alignment fixture  240  allows for tool-less (i.e. without any tools) installation of the charge tube and alignment fixture at the appropriate location with respect to the scallops of the gun body. The alignment finger  245  replaces any need for a set screw to secure the alignment fixture  240 , and thereby the charge tube  220 , into place in the gun body  210 . 
     Reference is now made to  FIGS. 3 and 4  showing a diagram of an alignment fixture secured to a charge tube and inserted in a gun body, as viewed, respectively, from the end of the gun body and in cross-section, according to an embodiment.  FIG. 4  shows the cross-section as taken along line A-A of  FIG. 3 . The gun body  310  has an alignment fixture  320  placed therein. The alignment fixture  320  is secured to the charge tube by charge tube protrusions  330  that engage openings in the alignment fixture  320 , as shown in greater detail in  FIGS. 6-9 . With reference to  FIG. 4 , the charge tube  410  has an alignment fixture  320  secured on each end. A gunconnector  420  can be provided as a connector between the various gun bodies within an overall perforating tool assembly. 
       FIG. 5  is a diagram of an alignment fixture with integrated alignment finger on the alignment fixture engaging an interior surface of the gun body to properly align the charge tube  520  with respect to scallops (for example scallops  215  in  FIG. 2 , not shown in  FIG. 5 ) on exterior surface of the gun body  510 . The gun body  510  has a charge tube  520  received therein. The charge tube  520  has an alignment fixture  530  secured thereto. The alignment fixture  530  has at least one alignment finger  535  integrated thereon that engages with at least one slot  540  on an interior surface of the gun body  510  to properly align the charge tube  520  (and thereby the charges, not shown, but contained in the charge tube) with the proper scallops on the exterior surface of the gun body  510 . See, for example, scallops  215  in the embodiment of  FIG. 2 . Although a single alignment finger is illustrates as engaging a single slot on the gun body, multiple alignment fingers can engage multiple slots as should be apparent to those having ordinary skill in the art. 
       FIG. 6  is a diagram of an alignment fixture having a plurality of openings and an integrated alignment finger, as viewed from an end of the alignment fixture. The alignment fixture is connected to and aligns the charge tube with respect to the gun body in which the charge tube and alignment fixture are received. The alignment fixture  610  has an alignment finger  620  integrated thereon that is adapted to engage a milled slot on the interior surface of the gun body. The alignment fixture  610  includes a plurality of openings (collectively “ 630 ”), including a first opening  630   a,  a second opening  630   b  and a third opening  630   c.  Although depicted as slots, it should be clear to those ordinarily skilled in the art that any appropriate opening, hole or through structure capable of engaging the charge tube, can be implemented. 
     Reference is now made to  FIG. 7  which is a diagram of the alignment fixture  610  having a plurality of openings adapted to releasably engage a plurality of protrusions on a charge tube  710 , as viewed from the side. The alignment fixture  610  includes the alignment fmger  620  and the openings or slots  630   a ,  630   b  and  630   c . Each slot  630  receives a protrusion on a charge tube for securing the alignment fixture  610  to the charge tube  710 . The charge tube  710  has a plurality of protrusions (collectively “ 720 ”), including a first protrusion  720   a  that engages with the first opening  630   a , a second protrusion  720   b  that engages with the second opening  630   b , and a third protrusion  720   c  that engages with the third opening  630   c.   
     To centralize the charge tube  710  on each end, the alignment fixtures  610  have an outer diameter that is approximately equivalent to the drift diameter of the gun body, or approximately 0.015-inches to 0.05-inches under the minimal gun inner diameter and is variable depending upon the size of the charge tube and the gun body in which it is received, as well as the particular application in which the perforation tool assembly is being used. Using the alignment fixture  610  having slots  630  that engage the protrusions  720  on the charge tube  710 , there is no longer any screws to secure the alignment fixture to the charge tube. Moreover, the alignment fixture locks onto the charge tube without the use of any tools (i.e., tool-lessly) and self-locks onto the tube. Once aligned and inserted (as shown in  FIG. 8 ), the alignment fixture is turned counter-clockwise to lock it onto the charge tube (see arrow  910  in  FIG. 9 ). The locking action is obtained by the protrusions on the charge tube locking onto the alignment fixture. If or when desired, the alignment fixture can be turned clockwise (in a direction opposite to arrow  910 ) to unlock the alignment fixture from the charge tube. This eliminates any screws from the gun assembly and improves assembly and dis-assembly time. It should be apparent to those of ordinary skill that the alignment finger and charge tube can be formed to lock when turned clockwise and unlock when turned counter-clockwise. The alignment fixtures can be formed of a powdered metal, such as steel or aluminum, or a plastic material or a rubber material, but other materials within ordinary skill can be employed. The alignment fixtures can be cut or otherwise manufactured using typical manufacturing methods such as machining, molding, and casting, as well as cutting with a water jet. This alignment fixture desirably maintains the centralization of the charge tube within the gun body. 
     Referring to  FIG. 8 , the alignment fixture  610  is now engaged with the charge tube  710  in a first “connected” state, according to an embodiment of the disclosure. Note that the ends of the protrusions  720  each extend longitudinally outward past the end of the alignment fixture  610  in this embodiment. In other embodiments, for example as shown in  FIGS. 10-12 , the protrusions on the ends of the charge tube are flush with the end of the alignment fixture when engaged. The protrusions may also lie longitudinally inward so as to no extend past the ends of the alignment fixture in some applications. 
     Now turning to  FIG. 9 , the alignment fixture  610  is engaged with the charge tube  710  in a second “locked” state, according to an embodiment of the disclosure. Note that the alignment fixture has been rotated counter-clockwise (in the direction of arrow  910 ) to lock the alignment fixture into place. The protrusions on the charge tube  710  are fully engaged with the slots of the alignment fixture. 
     Reference is now made to  FIGS. 10-12  showing an embodiment of alignment fixture and charge tube where ends of charge tube protrusions are flush with an end of an alignment fixture when engaged.  FIG. 12  shows the charge tube and self-locking alignment fixture as partially inserted within the gun body. 
     An alignment fixture  1010  is inserted onto a charge tube  1011 . The alignment fixture  1010  includes an alignment finger  1020  for engaging a groove in a gun body of a perforation tool assembly (see groove  1230 , for example, in  FIG. 12 ). The alignment fixture  1010  includes a plurality of openings or slots  1030   a,    1030   b,  and  1030   c  (collectively alignment openings “ 1030 ”). The charge tube  1011  includes a plurality of protrusions  1032   a,    1032   b  and  1032   c  (collectively charge tube protrusions “ 1032 ”), which respectively engage the openings  1030   a,    1030   b  and  1030   c.  The alignment fixture is twisted counter-clockwise (in the direction of arrow  1110  in  FIG. 11 ) to lock the charge tube protrusions  1032  into place. As shown in  FIG. 12 , a charge tube  1215  with attached alignment fixture  1225  is inserted into a gun body  1210 . An alignment fixture  1220  includes alignment finger  1225  that engages a slot  1230  on the gun body  1210 . The charge tube and alignment fixture are slid into the gun body and end caps are installed in accordance with ordinary skill. 
     Reference is now made to  FIGS. 13 and 14  showing is a diagram of an alignment fixture with integrated alignment finger, as alignment fixture is secured to a charge tube, according to an embodiment of the disclosure. 
     A charge tube  1310  engages with an alignment fixture  1320  to align the charge tube at an appropriate location within a gun body. The alignment fixture  1320  has a plurality of protrusions  1325  that create openings in the alignment  FIG. 1230  that engage protrusions on an end of the charge tube  1310 . An alignment finger  1330  integrated on the alignment fixture  1320  is for engaging a slot (for example slot  1420  in  FIG. 14 ) on an interior surface of a gun body. As shown in  FIG. 14 , a gun body  1410  includes a slot  1420  that receives the alignment finger  1330  of the alignment fixture  1320  for aligning the charge tube  1310  with respect to the gun body  1410 . 
     The alignment fixture in accordance with the disclosures herein provides for centralizing the charge tube within the gun body. The alignment fixture can further include an alignment finger in any embodiment that aligns the charge tube, and more importantly the charges contained therein, with respect to a desired position along the gun body, for example, at a proper location with respect to scallops on an exterior surface of the gun body. 
     Although a variety of examples and other information was used to explain aspects within the scope of the appended claims, no limitation of the claims should be implied based on particular features or arrangements in such examples, as one of ordinary skill would be able to use these examples to derive a wide variety of implementations. Further and although some subject matter may have been described in language specific to examples of structural features and/or method steps, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to these described features or acts. For example, such functionality can be distributed differently or performed in components other than those identified herein. Rather, the described features and steps are disclosed as examples of components of systems and methods within the scope of the appended claims. Moreover, claim language reciting “at least one of” a set indicates that one member of the set or multiple members of the set satisfy the claim.