Abstract:
A perforating gun that has a detonator section in which a window is formed is assembled by: disposing a detonating cord in an inner bore of the perforating gun; fixing a clip to a detonator; gripping the clip with an installation tool; inserting the clip laterally through the window of the detonator section using the installation tool; and attaching the clip to the detonator cord by pressing the clip against the detonator cord using the installation tool. The clip has a planar base, an opening formed in the base for receiving the detonator, and a pair of prongs extending from the base, wherein each prong of the pair of prongs extends from an edge of the base and has a gripping end.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 14/869,388, filed on Sep. 29, 2015, which takes priority from U.S. Provisional Application Ser. No. 62/058,487, filed Oct. 1, 2014, the disclosures of which are incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to devices and methods for energetically coupling a detonating cord to one or more detonating cords. 
     BACKGROUND 
     Hydrocarbons, such as oil and gas, are produced from cased wellbores intersecting one or more hydrocarbon reservoirs in a formation. These hydrocarbons flow into the wellbore through perforations in the cased wellbore. Perforations are usually made using a perforating gun loaded with shaped charges. The gun is lowered into the wellbore on electric wireline, slickline, tubing, coiled tubing, or other conveyance device until it is adjacent to the hydrocarbon producing formation. Thereafter, a surface signal actuates a firing head associated with the perforating gun, which then detonates the shaped charges. Projectiles or jets formed by the explosion of the shaped charges penetrate the casing to thereby allow formation fluids to flow through the perforations and into a production string. 
     Conventional perforating guns include detonating cords for transmitting a detonation between two locations. Detonating cords can be detonated using detonators. Illustrative detonators are disclosed in U.S. Pat. Nos. 4,762,067, 4,716,832, 4,542,695, 3,991,679, the contents of which are incorporated by reference for all purposes. The present disclosure addresses the need to easily form a reliable ballistic connection between a detonator and a detonating cord. 
     SUMMARY 
     In aspects, the present disclosure provides an apparatus for perforating a wellbore. The apparatus may include an enclosure receiving at least one shaped charge; a detonating cord connected to the at least one shaped charge; a detonator section associated with the enclosure, the detonator section a longitudinal bore and a window, wherein the detonating cord extends longitudinally through the bore of the detonator section; a detonator disposed in the detonator section and projecting into the bore of the enclosure, the detonator being configured to generate a high order detonation; and a clip connecting the detonator to the detonating cord, the clip having a planar base, an opening formed in the base for receiving the detonator, and a pair of prongs extending from the base, wherein each prong of the pair of prongs extends from an edge of the base and has a gripping end compressively securing the detonating cord against a face of the detonator. 
     In aspects, the present disclosure provides an apparatus for use with a perforating tool for perforating a wellbore. The perforating tool may include a section having a window and a detonating cord disposed in a bore of the section. The apparatus may include a detonator configured to generate a high order detonation; a clip connecting the detonator to the detonating cord, the clip having a base and prongs extending from opposing sides of the base, the base having an opening for receiving the detonator, and the prongs having gripping ends compressively securing the detonating cord against a face of the detonator; and an installation tool having: a handle, a pair of pincers extending from the handle, the pincers having ends complementary to the base of the clip, the pincers further having an expanded position wherein the base can be received between the pincer ends, and a plunger operatively connected to the pincer ends and expanding the pincers to an expanded position. 
     In still further aspects, the present disclosure provides a method for assembling a perforating gun that has a detonator section in which a window is formed. The method includes: disposing a detonating cord in an inner bore of the perforating gun; fixing a clip to a detonator; gripping the clip with an installation tool; inserting the clip laterally through the window of the detonator section using the installation tool; and attaching the clip to the detonator cord by pressing the clip against the detonator cord using the installation tool. The clip has a planar base, an opening formed in the base for receiving the detonator, and a pair of prongs extending from the base, wherein each prong of the pair of prongs extends from an edge of the base and has a gripping end. 
     It should be understood that examples of certain features of the invention have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will in some cases form the subject of the claims appended thereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For detailed understanding of the present disclosure, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein: 
         FIG. 1  illustrates a side view of a detonator with a clip according to one embodiment of the present disclosure; 
         FIG. 2  isometrically illustrates the  FIG. 1  embodiment; 
         FIG. 3  illustrates a side sectional view of a perforating gun section with a detonating cord; 
         FIGS. 4 and 5  schematically illustrate an installation tool according to one embodiment of the present disclosure for installing a detonating cord and clip into the perforating gun section of  FIG. 3 ; 
         FIG. 6  illustrates a side sectional view of a perforating gun assembly that may use a clip according to the present disclosure; and 
         FIG. 7  schematically illustrates well in which a perforating gun assembly constructed in accordance with the present disclosure may be used. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to devices and methods for facilitating the assembly and enhancing the reliability of wellbore perforating tools. The present invention is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the present invention with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. 
     Referring now to  FIG. 1 , there is shown one embodiment of a retention member  100  that energetically couples a detonating cord  20  to a detonator  102 . Merely for convenience, the retention member  100  will be hereafter referred to as a “clip.” However, it should be understood that no particular shape, dimension or other characteristic is implied by the term “clip.” The clip  100  presses a detonating cord  20  against the detonator  102  to energetically couple the detonating cord  20  to the detonator  102 . It should be noted that, in this embodiment, the contact between the detonator  102  and the detonating cord  20  is only along an outer circumferential surface of the detonating cord  20 . It should be further noted that, in this embodiment, the detonator  102  does not surround, cover, or otherwise partially or completely enclose an end (not shown) of the detonating cord  20 . The detonator  102  may be any device that generates a high-order detonation in response to an applied signal (e.g., electrical signal). The detonator  102  may be formed of one or more energetic materials (e.g., RDX, HMX, etc.). By energetically coupled, it is meant that there is sufficient contact between the detonator  102  and the detonating cord  100  to allow the energy released by the detonator  102  to detonate the detonating cord  100 . 
     The clip  100  provides ease of attachment to a detonating cord, which may have a circular cross-section. The clip  100  has a spring action in that the clip  100  opens up and then closes to shut around the detonating cord  20 . The resulting tight connection reduces the risk that the detonator  102  will separate from the detonating cord  20  under vibration and/or high temperatures. Moreover, removal is only possible by a user that intentionally pulls the clip  100  off the detonating cord  20 . 
     Referring now to  FIGS. 1 and 2 , in one embodiment, the clip  100  is a thin sheet-like “U-shaped” member that includes a base portion  110 , a central opening  112 , and converging prongs  114 . The base portion  110  may be planar and wider than the detonator  102 . The opening  112  is formed in the base portion  110  and has a diameter sized to fit substantially around the detonator  102 . While the opening  112  is shown as closely conforming to the cross-sectional profile of the detonator  102 , such a shape is not necessary. In embodiments, a fastening element  115  may be used to fix the clip  100  to the detonator  102 . For example, the fastening element  115  may be a ring, flange, or other annular member that captures the base portion  110  against a ledge or shoulder (not shown) formed on the detonator  102 . 
     The prongs  114  are flexible members that project from an edge of or juncture with the base portion  110  and terminate at gripping ends  116 . The prongs  114  may be formed of a resilient material that can generate a spring force when flexed or otherwise deformed. The gripping ends  116  can separate from one another to form a gap that allows the detonating cord  20  to pass through. The gripping ends  116  can also press the detonating cord  20  against a contact face  118  of the detonator  102 . As shown, the prongs  114  are not parallel as in a conventional “U-shape.” Rather, the prongs  114  more resemble a triangular shape. That is, the junctures of the prong ends and the base portion  110  are separated by a greater distance than the distance separating the gripping ends  116 . 
     Referring now to  FIG. 3 , there is shown an exemplary perforating device section  140  that includes the detonating cord  20 . The section  140  may include a window  142  for accessing an inner bore  144  in which the detonating cord  20  is disposed. The section  140  has a longitudinal axis  146  to which the detonating cord  20  is parallel. In embodiments, the clip  100  may be used to attach the detonator  102  to the detonating cord  20 . It should be noted that the clip  100  orients the detonating cord  20  substantially parallel with the longitudinal axis  146  and orients the detonator  102  transverse to the detonating cord  20 . By “substantially,” it is mean less than a forty-five degree angular offset. 
     Referring now to  FIG. 4 , there is shown an installation tool  160  that may be used to connect the clip  100  ( FIG. 1 ) and detonator  102  ( FIG. 1 ) to the detonating cord  20  ( FIG. 1 ). The installation tool  160  includes a handle  162  and pincers  164  that are biased to a closed position. A plunger assembly  166  may be used to expand the pincer ends  166  when needed. For example, the plunger assembly  166  may include a spring actuated detent that pushes the pincer ends  164  apart. Referring to  FIG. 5 , there is shown the clip  100  and the detonator  102  captured between the pincer ends  164 . In some embodiments, the pincer ends  164  may have curvature or profile that is complementary to the clip base  104 . 
     Referring now to  FIGS. 1, 3 and 5 , the clip  100  is first fixed to the detonator  102  with the fastening element  115 . Next, the installation tool  160  is expanded and then allowed to close around the clip  100 . Thereafter, the installation tool  160  may be used to insert the clip  100  and detonator  102  laterally through the window  142 . By lateral, it is meant a direction generally orthogonal to the longitudinal axis  146 . Once the clip  100  and detonator  102  is positioned next to the detonating cord  20 , the clip  100  is pressed until the prong ends expand to allow passage of the detonating cord  20 . The force needed to expand the prong ends  166  may be in the range of 10-20 lbs. Thereafter, the prong ends  166  snap back to the closed position and compress the detonating cord  20  against the face  108  of the detonator  102 . After the detonator  102  is secured to the detonating cord  20 , the plunger assembly  164  ( FIG. 3 ) is depressed to open the pincer ends  164  to release the clip  100 . Now, the installation tool  160  may be extracted from the perforating gun section  140 . 
     Before or after the installation tool  160  is disconnected from the clip  100 , the detonator  102  may be electrically connected to wiring used to activate the detonator  102 . Once the internal components are assembled, a cover or lid (not shown) may be used to cover and seal the window  144 . In some embodiments, the interior of the sub  140  may be fluid tight and pressurized. In embodiments, the detonator  102  is connected to only the clip  100  and the wiring (not shown) used to activate the detonator  102 . That is, the detonator  102  “floats” inside the section  140 , i.e., the section  140  does not have surfaces positioned to support or secure the detonator  102 . 
     It is contemplated that suitable materials for the described embodiments include hardened spring steel and other metallic and non-metallic flexible materials. However, the present invention is not limited to any particular material. That is, any material that is sufficiently elastic and provides the spring force needed to secure the detonating cord  20  to the detonator  102  may be used. 
     Referring now to  FIGS. 6 and 7 , there is shown a perforating tool and perforating gun system, respectively, that may utilize the teachings of the present disclosure. 
     Referring to  FIG. 6 , there is shown a conventional perforating tool or gun  10 . The gun  10  includes a charge strip or tube  12 , concentrically positioned in a carrier tube  14 . Fixed within the charge tube  12  are shaped charges  16 . Typically, the charge tube  12  is oriented in the carrier tube  14  such that the shaped charges  16  on each charge strip (not shown) align with weakened portions or scallops  18  formed in the carrier tube  14 . A detonating cord  20  runs through a bore  22  in the perforating gun  10 . The perforating gun  100  further includes a sub  30  in which the detonator  102  ( FIG. 1 ) is positioned and connected to the detonating cord  20  ( FIG. 1 ) with the clip  100  ( FIG. 1 ). Generally speaking, the carrier tube  14  and the sub  30  may be tubular or cylindrical enclosures that function as housings for various components. While shown as separate structures, the sub  30  may be integral with the carrier tube  14 . The perforating gun  10  is assembled at the surface and conveyed into a wellbore via the system shown in  FIG. 7 . 
     In  FIG. 7 , there is shown a well construction and/or hydrocarbon production facility  200  positioned over a subterranean formation of interest  202 . The facility  200  can include known equipment and structures such as a platform  206  at the earth&#39;s surface  208 , a rig  210 , a wellhead  212 , and cased or uncased pipe/tubing  214 . A work string  216  is suspended within the well bore  205  from the derrick  210 . The work string  216  can include drill pipe, coiled tubing, wire line, slick line, or any other known conveyance means. The work string  216  can include telemetry lines or other signal/power transmission mediums that establish one-way or two-way telemetric communication from the surface to the downhole tool  204  connected to an end of the work string  216 . In one arrangement, a telemetry system having a surface controller (e.g., a power source)  218  may be used to transmit electrical signals via a cable or signal transmission line  220  in the work string  216  to a perforating tool  10 . 
     After the perforating gun  10  is positioned at a desired target depth in the wellbore  205 , a control signal may be sent via the signal transmission line  220  to activate the detonator  102 . Alternatively, the hydraulic pressure may be increased in the wellbore  205  or a percussion-type drop tool may be used to impulsively impact the detonator  102 . Once activated, the detonator  102  emits a high order detonation that detonates the detonating cord  20 . Thereafter, the detonating cord  20  detonates the shaped charges  16 . 
     The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope of the invention. It is intended that the following claims be interpreted to embrace all such modifications and changes.