Abstract
An apparatus and method for connecting a detonating cord with a shaped charge.
Claims
1. A detonating cord retainer comprising: a base having a bottom end and a top end; a bore extending into the base from the bottom end; an aperture in the top end of the base adapted to allow detonation communication from the top end of the base into the bore; a first retention arm having an inner face extending substantially orthogonally from the top side of the base; a second retention arm having an inner face extending substantially orthogonally from the top side of the base; and wherein the inner face of the first retention arm is substantially parallel to and facing the inner face of the second retention arm.
2. The detonating cord retainer of claim 1 wherein the inner face of the first retention arm has a retention nub distal from the base extending toward the second retention arm; and the first retention arm and second retention arm are adapted to retain a detonating cord in proximity to the aperture.
3. The detonating cord retainer of claim 2 wherein the inner face of the second retention arm has a retention nub distal from the base extending toward the first retention arm.
4. The detonating cord retainer of claim 1 further comprising a circumferential ridge in the bore adapted to engage a corresponding groove in a shaped charge case.
5. The detonating cord retainer of claim 1 further comprising a circumferential groove in the bore adapted to engage a corresponding ridge in a shaped charge case.
6. The detonating cord retainer of claim 1 wherein the aperture extends from the top end of the body to the bore.
7. The detonating cord retainer of claim 1 wherein the bore extends through a portion of the top end of the body to form the aperture.
8. A detonating cord retainer comprising: a base having a bottom end and a top end; a bore extending into the base from the bottom end; an aperture in the top end of the base adapted to allow detonation communication from the top end of the base into the bore; a first retention arm having extending substantially orthogonally from the top side of the base and having an end distal from the base; and a second retention arm having an inner face extending substantially orthogonally from the top side of the base and having an end distal from the base.
9. The detonating cord retainer of claim 8 wherein the end of the first retention arm has a retention nub extending toward the second retention arm.
10. The detonating cord retainer of claim 9 wherein the end of the second retention arm has a retention nub extending toward the first retention arm.
11. A shaped charge comprising: a case with an apex end and an explosive end and an axis; a substantially conical liner located within and coaxially with the case; an explosive material located between the liner and the case; a detonating cord retainer adapted to interface with the apex end of the case further comprising: a base having a bottom end and a top end; a bore extending into the base from the bottom end; an aperture in the top end of the base adapted to allow detonation communication from the top end of the base into the bore; a first retention arm having an inner face extending substantially orthogonally from the top side of the base; a second retention arm having an inner face extending substantially orthogonally from the top side of the base; and wherein the inner face of the first retention arm is substantially parallel to and facing the inner face of the second retention arm.
12. The detonating cord retainer of claim 11 wherein the inner face of the first retention arm has a retention nub distal from the base extending toward the second retention arm; and the first retention arm and second retention arm are adapted to retain a detonating cord in proximity to the aperture.
13. The detonating cord retainer of claim 12 wherein the inner face of the second retention arm has a retention nub distal from the base extending toward the first retention arm.
14. The detonating cord retainer of claim 11 further comprising a circumferential ridge in the bore adapted to engage a corresponding groove in a shaped charge case.
15. The detonating cord retainer of claim 11 further comprising a circumferential groove in the bore adapted to engage a corresponding ridge in a shaped charge case.
16. The detonating cord retainer of claim 11 wherein the aperture extends from the top end of the body to the bore.
17. The detonating cord retainer of claim 11 wherein the bore extends through a portion of the top end of the body to form the aperture.
Description
DESCRIPTION OF THE DRAWINGS
[0029] For a thorough understanding of the present disclosure, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings in which reference numbers designate like or similar elements throughout the several figures of the drawing. Briefly:
[0030] FIG. 1 is a side cross sectioned view of a perforating gun.
[0031] FIG. 2 is a side cross sectioned view of a shaped charge that may be used in a perforating gun with a retainer fitting attached.
[0032] FIG. 3A is a detailed view of a retainer fitting.
[0033] FIG. 3B is a top view of a retainer fitting with a detonating cord in the unlocked position.
[0034] FIG. 3C is a top view of a retainer fitting with a detonating cord in the locked position.
[0035] FIG. 3D is a side view of a retainer fitting.
[0036] FIG. 3E is a bottom view of a retainer fitting.
[0037] FIG. 4 is a side view of a charge tube adapted for use with an example embodiment.
[0038] FIG. 5A is a perspective view of a detonating cord retainer.
[0039] FIG. 5B is a cross-section view of a detonating cord retainer.
[0040] FIG. 6 is a cross-section side view of a detonating cord retainer attached to a shaped charge case.
[0041] FIG. 7 is a perspective view of a detonating cord retainer.
[0042] FIG. 8 is a side view of a charge tube adapted for use with an example embodiment.
DETAILED DESCRIPTION OF EXAMPLES OF THE EMBODIMENTS
[0043] In the following description, certain terms have been used for brevity, clarity, and examples. No unnecessary limitations are to be implied therefrom and such terms are used for descriptive purposes only and are intended to be broadly construed. The different apparatus, systems and method steps described herein may be used alone or in combination with other apparatus, systems and method steps. It is to be expected that various equivalents, alternatives, and modifications are possible within the scope of the appended claims.
[0044] Referring to an example shown in FIG. 1, a typical perforating gun 10 comprises a gun body 11 that houses the shaped charges 12. The gun body 11 contains end fittings 16 and 20 which secure the charge holder 18 into place. The charge holder 18 in this example is a charge tube and has charge holes 13, 19, and 23 that are openings where shaped charges 12 may be placed. The charge holder 18 has retainer cutouts 31 that are adapted to fit a retainer fitting 30 in a predetermined orientation. Scallops 15, 21, and 22 provide a flat surface on the gun body 11 for the explosive charge to penetrate through. The gun body 11 has threaded ends 14 that allow it to be connected to a series of perforating guns 10 or to other downhole equipment depending on the job requirements. In this example, the retainer fitting 30 is separate from the charge holder 18, however in another variation of the embodiment, the retainer fitting 30 may be integral to the charge holder 18. Each shaped charge 12 has an associated retainer fitting 30 that secures each shaped charge 12 to the charge holder 18 and the detonating cord 32. The detonating cord 32 runs the majority of the length of the gun body 11 beginning at end cap 48 and ending at end cap 49. The detonating cord 32 wraps around the charge holder 18 as shown to accommodate the different orientations of the shaped charges 12. In this embodiment, the shaped charges 12 have an orientation that is rotated 60 degrees about the center axis of the gun body 11 from one shaped charge to the next. Other orientations may have zero angle, where all of the shaped charges 12 are lined up. Other orientations may have different angles between each shaped charge 12. This example using a 60 degree phase is illustrative and not intended to be limiting in this regard.
[0045] Referring to an example shown in FIG. 2, the shaped charges 12 includes a shaped charge case 28 that holds the energetic material 26 and the liner 27. The shaped charge case 28 typically is composed of a high strength metal, such as alloy steel. The liner 27 is usually composed of a powdered metal that is either pressed or stamped into place. The metals used in liner 27 may include brass, copper, tungsten, and lead. The retainer fitting 30 is secured to the apex end 46 of the shaped charge case 28 by snapping into place over a flange on apex end 46. The entire assembly 40 includes shaped charge 12 combined with retainer fitting 30. Alternatively, the retainer fitting 30 could be threaded onto the shaped charge case 28, secured with adhesive, snapped around the full length of the charge case, or formed integrally with the charge case. The fitting 30 could also be secured to the charge case 18 using set screws, roll pins, or any other mechanical attachment mechanisms. Alternatively, shaped charge case 28 could be integrally formed to retainer fitting 30. This would result in a single component, thus reducing cost and complexity.
[0046] Referring to an example shown in FIG. 3A, this is a detail drawing of the retainer fitting 30. The retainer fitting has a first detonating cord retainer 33 and a second detonating cord retainer 34. The retainer fitting 30 has a circular opening 35. The retainer fitting 30 has two rectangular base portions 36 and 37. Base portion 36 is longer than base portion 37. Base portion 36 is parallel to base portion 37.
[0047] The adaptor 39 has a base slot 44, in this example it is perpendicular to the rectangular base portions 36 and 37. The base slot 44 allows some flexibility in the adaptor 39. In this example the adaptor 39 is composed of a plastic material that may deform without yielding. The base slot 44 aids in helping the adaptor 39 yield. This added flexibility allows the adaptor 39 to snap over the apex end 46 of a shaped charge case 28 of FIG. 2.
[0048] In FIG. 3B the retainer fitting 30 has detonating cord retainers 33 and 34. Retainer 34 has an edge 42 that is angled 45 degrees with respect to the parallel axis of rectangular base portions 36 and 37. Retainer 33 has an edge 43 that is also angled 45 degrees with respect to the parallel axis of rectangular base portions 36 and 37. Edge 42 and edge 43 are parallel to each other, forming slot 40. Slot 40 is wide enough to fit detonating cord 51 as depicted in FIG. 3B. Each of the rectangular base portions 36 and 37 contain fillets 38 that are adapted to accommodate the radius of a detonating cord 51.
[0049] In at least one example, detonating cord retainers 33 and 34 are shaped as arches as viewed from the side in FIG. 3D. The adaptor 39 has an internal flange 47 designed to assist in attaching the retainer fitting 30 to the shaped charge case 28 apex end 46. The procedure for securing the detonating cord 51 is to first place it into slot 40 as shown in FIG. 3B. Then, rotating the retainer fitting 30 45 degrees detonating cord retainers 33 and 34 force the detonating cord 51 against the fillets 38 as shown in FIG. 3C.
[0050] FIG. 3B shows the detonating cord 51 as it is initially placed in the retainer fitting 30. FIG. 3C depicts the detonating cord 51 as it sits in the retainer fitting 30 after the retainer fitting 30 has been rotated and locked into place on the charge holder 18. As seen in FIG. 3E the retainer fitting 30 has an adaptor 39 which allows for the retainer fitting 30 to snap into place on the apex end 46 of the shaped charge case 28 upon installation.
[0051] Referring to FIG. 4, the charge holder 18 has the retainer cutout 31 and lock cutouts 54. Installation may include snapping a retainer fitting 30 on each shaped charge 12. The assembled shaped charge 12 with associated retainer fitting 30 is then placed through the charge hole 23 of the charge holder 18 until the retainer fitting 30 exits through the retainer cutout 31. The retainer fitting 30 has a lock block 45 shown in FIG. 3A. The charge holder 18 has a lock cutout 54 associated with each retainer cutout 31. The retainer fitting 30 can be rotated until slot 40 is aligned with the detonating cord 51 as shown in FIG. 3B. The detonating cord 51 is then placed into slot 40. Then the retainer fitting is rotated, or twisted, until the lock block 45 engages the lock cutout 54. Once twisted, the detonating cord 51 and retainer fitting 30 will look as depicted in FIG. 3C. As can be seen in FIG. 4, the retainer cutout 31 is shaped uniquely such that a retainer fitting 30 can only fit into the charge holder 18 in one specific angular orientation. Once the retainer fitting 30 is rotated to a second angular orientation it will interfere with the shape of the retainer cutout 31, preventing the retainer fitting 30 from being able to disengage unless it is rotated back to the original angular orientation.
[0052] The retainer fitting 30 has a lock block 45 that is adapted to fit into the lock cutout 54 on the charge holder 18 as shown in FIG. 4. The lock block 45 is engaged by twisting the retainer fitting until it reaches the desired orientation whereby the lock block 45 and lock cutout 54 are aligned. Engagement of the lock block 45 with lock cutout 54 will keep the retainer fitting 30 from rotating further. Alternatively, the lock block 45 may be eliminated or replaced by other mechanical or friction fit means, such as angling or texturing the undersides of the adaptor 39 as shown in FIG. 3A. Another alternative to the embodiments disclosed may include using the adaptor base 39 and combining it with the u-shaped upper portion 75 from the detonating cord retainer 50. The adaptor base may also have different oblong shapes, including oval shapes, triangular, or other polygons, to allow the adaptor base 39 to lock into the charge holder 18 when rotated.
[0053] As can be seen from the shape of the retainer cutout 31, it can only accommodate the retainer fitting 30 in a specific orientation. Once the retainer fitting 30 has cleared the retainer cutout 31, it will be oriented to lay the detonating cord 51 along slot 42, as shown in FIG. 3B. Then the shaped charge 12 and retainer fitting 30 assembly 40 is rotated, at least in this example, approximately 45 degrees. Rotating the assembly 40 causes the detonating cord 51 located with the slot 42 to be locked into place against the fillets 38 and the cord retainers 33 and 34, as shown in FIG. 3C. The arch design of retainers 33 and 34 force the detonating cord 51 against the fillets 38 upon alignment. Further, once rotated 45 degrees, the retainer fitting is locked into the charge holder 18 by the lock block 45 plugging into the lock cutout 54. The retainer fitting 30 can be composed of materials common in the industry, including metal and plastics. The retainer fitting 30 can be manufactured using injection molding techniques, casting, rapid prototyping, machining techniques, or other common manufacturing techniques known in the art.
[0054] Other alternatives to the embodiments disclosed include using a single base portion instead of the separate base portions 36 and 37. Alternatively, the base portion may have a different oblong shape such as an oval, triangle, or other polygon. Another alternative may have the retainers 33 and 34 contact and secure to one and the other through a fastening mechanism, allowing for a more secure connection between the retainer fitting and the detonation cord. Another variation may include using a circular base, with retainers that connect to one another, securing the detonation cord, and then using a circular adaptor such that the fitting could turn freely with respect to the charge case. This design would allow for optimal wiring of the detonation cord. Once the detonation cord is in its final orientation, a set screw, resilient tabs, or other retaining device could be used to secure the fitting to the case or to the shaped charge in order to prevent movement. In the embodiments disclosed above, two lock blocks 45 and two lock cutouts 54 are disclosed, however more or fewer of either item could be used to secure the retainer fitting to the charge tube. The fitting could be threaded onto the charge case, secured with adhesive, snapped around the full length of the charge case, or formed integrally with the charge case. The fitting could also be secured to the charge case using set screws, roll pins, or any other mechanical attachment mechanisms. Further, charge cases in the examples herein are shown as cylindrical devices with cutouts, however other configurations are possible for holding shaped charges in a perforating gun. For example, a charge strip can be used in which a long strip of metal containing holes for the retainer to engage with is used to hold a linear series of shaped charges in a perforating gun. Other examples may include cylinders with one a single cutout for the retainer and no cutout for the shaped charge. Another example may include a perforating gun that does not use a cylindrical charge holder to contain the shaped charges. Another example may include a charge holder that is integral to the perforating gun.
[0055] Another example embodiment is depicted in FIG. 5A and FIG. 5B. This detonating cord retainer 70 has a base 71 with a through hole 74, a middle portion 72 with a through slot 73, and a upper portion 75 that is shaped as a truncated conical with a u-shaped channel 76 that is sized to snap onto a detonating cord. The detonating cord retainer 70 has a first axis 102 aligning the base 71, middle portion 72, and upper portion 75. The u-shaped channel 76 also has an axis 101 that is perpendicular to the axis 102. The base 71 snaps onto the end of a shaped charge with the edge of the u-shaped channel 76 adapted to snap over a lip. The detonating cord retainer 70 can be secured to the shaped charge, but still rotate to its desired orientation in order to snap to a detonating cord. The u-shaped channel 76 is designed to securely snap onto a detonating cord and restrict the movement of the detonating cord. In this embodiment the detonating cord could explode through the thin material 77 between the u-shaped channel 76 and the thru slot 73, whereby the explosion would travel down the thru hole 74 and into the back of a shaped charge.
[0056] The thru slot 73 is perpendicular to axis 102. A clip may be placed through the thru slot 73 and adapted to engage a retainer cutout 93 as shown in FIG. 8, thus securing the detonating cord retainer 70 to a charge tube 90. Furthermore, detonating cord retainer 70 has a base 71 that has a shoulder 121 capable of engaging the charge tube 90 in such a way as to restrain the movement of the shaped charge along the axis 108, but allowing rotation about the axis 108. In the alternative, a thru hole or thru aperture could be located at 77 to facilitate explosive communication between the detonating cord and the shaped charge.
[0057] An alternative to the u-shaped channel 76 is a c-shaped cutout in which the channel 76 is rotated 90 degrees such that the detonating cord is accepted from the side rather than the top as shown. The shoulder 78 allows the retainer 70 to snap onto the apex end 60 of a shaped charge, as shown in FIG. 6.
[0058] In FIG. 6 the shaped charge case 58 is attached to the detonating cord retainer 50. The shaped charge case 58 is machined with an apex end 60. The apex end 60 has a lip 59. The detonating cord retainer 50 snaps over the lip 59. Alternatively, the detonating cord retainer 50 could be threaded onto the shaped charge case 58, secured with adhesive, snapped around the full length of the shaped charge case 58, or formed integrally with the shaped charge case 58. The detonating cord retainer 50 could also be secured to the shaped charge case 58 using set screws, roll pins, or any other mechanical fasteners. The detonating cord 61 is snapped into the u-shaped cutout 56. In this example the detonating cord retainer 50 can freely rotate when attached to the shaped charge case 58, however a set screw or other fastening device could be used to prevent rotation if desired. When the detonating cord 61 detonates the explosion will puncture through the thin material 57 and enter thru hole 64 of the shaped charge case 58. The explosion will then interact with the explosive material 62 causing it to explode. The detonation of explosive material 62 will then transform liner 63 into a plasma jet capable of puncturing out of the perforating gun. The thin material 57 may be solid, it could also have a thru hole, perforations, a window or other aid that facilitates the explosion traveling from the detonating cord 61 to the explosive material 62. Furthermore, in this embodiment the u-shaped cutout 56 is depicted as having a gap between the two retaining ends 65, however the gap could be narrower such that the retaining ends 65 touch each other either before or after the detonating cord 61 is put into place. The detonating cord retainer 50 may be constructed of plastic using for instance an injection molding process or a rapid prototyping process. The detonating cord retainer 50 in this embodiment restricts the ability of the detonating cord 61 to move sideways, but it may allow the detonating cord 61 to move through the detonating cord retainer 50 and allows for rotation of the detonating cord 61 with respect to the shaped charge case 58.
[0059] Another example embodiment of a detonating cord retainer 80 is shown in FIG. 7. It is adapted to interface with the apex end of a shaped charge case. Detonating cord retainer 80 includes a base 82 having a bottom end 83 and a top end 88. A bore 81 extends into the base 82 from the bottom end 83. An aperture 89 in the top end 88 of the base 82 is adapted to allow detonation communication from the top end 88 of the base 82 into the bore 81. A first retention arm 86 having an inner face 87 extends substantially orthogonally from the top end 88 of the base 82. A second retention arm 84 has an inner face 110 extending substantially orthogonally from the top end 88 of the base 82. The inner face 87 of the first retention arm 86 is substantially parallel to and facing the inner face 110 of the second retention arm 84.
[0060] The inner face 87 of the first retention arm 86 has a retention nub 111 distal from the base extending toward the second retention arm 84. The first retention arm 86 and second retention arm 84 are adapted to retain a detonating cord in proximity to the aperture 89. The inner face 110 of the second retention arm 84 has a retention nub 112 distal from the base extending toward the first retention arm 86. A circumferential ridge 113 is located in the bore 81 adapted to engage a corresponding groove in a shaped charge case. The circumferential ridge 113 may also be a circumferential groove adapted to engage a corresponding ridge in a shaped charge case. The aperture 89 extends from the top end 88 of the body 82 to the bore 81. The bore 81 may extend through a portion of the top end 88 of the body 82 to form the aperture 89.
[0061] Another example embodiment may include a charge detonating cord retention system having a charge tube 90 as shown in FIG. 8 with a first axis 107. One or more charge holes 92, each having a second axis 108 perpendicular to the first axis 107, are located along the charge tube 90. Each charge hole 92 has a corresponding shaped charge retaining cutout 91 coaxial with the second axis 108. Each shaped charge retaining cutout 91 is adapted to fit a detonating cord retainer in any angular orientation relative to the second axis 108. Each second axis 108 may be parallel to each other or offset by a certain number of degrees about the first axis 107 called a phase angle. For example, in FIG. 8 the phase angle is 60 degrees.
[0062] Although the embodiments have been described in terms of particular examples which are set forth in detail, it should be understood that this is by illustration only and that the embodiments are not necessarily limited thereto. Alternative embodiments and operating techniques will become apparent to those of ordinary skill in the art in view of the present disclosure. Accordingly, modifications of the embodiments are contemplated which may be made without departing from the spirit of the disclosure.
