Shaped charge retainer system

Abstract

An apparatus and method for locking a detonating cord against a shaped charge.

Claims

1. A cylindrical charge holder for use in a perforating gun comprising: at least one charge hole located axially about the center adapted to fit at least one shaped charge disposed therein; at least one retainer cutout located axially about the center and opposite of the at least one charge hole and having an irregular rectangular shape, wherein the retainer cutout is adapted to accept a retainer fitting adapted to couple to the end of a shaped charge and inserted or removed therethrough in only a first angular orientation, and once inserted may be locked into position by rotating it to a second angular orientation.

2. The apparatus of claim 1, further comprising a first locking cutout located adjacent to the at least one retainer cutout, wherein the first locking cutout locks with a portion of a retainer fitting at the second angular orientation.

3. The apparatus of claim 1, further comprising a plurality of charge hole cutouts and a plurality of corresponding retainer cutouts.

4. The apparatus of claim 3, further comprising a plurality of corresponding first locking cutouts, each located adjacent to its corresponding retainer cutout.

5. The apparatus of claim 4, wherein the first locking cutouts have a rectangular shape.

6. A retainer fitting for use on a shaped charge in a perforating gun comprising: a base portion having an opening adapted to attached a shaped charge, a cutout adapted to allow the base portion to snap onto a shaped charge, and having an overall irregular rectangular shape adapted to fit into a corresponding irregular rectangular shaped retainer cutout on a charge holder in only a first angular orientation and locking into position at a second angular orientation; and a detonating cord retainer portion.

7. The apparatus of claim 6 wherein the base portion is integral to a charge case.

8. The apparatus of claim 6, wherein the overall irregular rectangular shape of the body portion further comprises a first rectangular portion and a second rectangular portion substantially parallel to the first rectangular portion.

9. The apparatus of claim 6, the detonating cord retainer portion further comprising a first detonating cord retainer.

10. The apparatus of claim 9, the detonating cord retainer portion further comprising a second detonating cord retainer.

11. The apparatus of claim 9 wherein the first detonating cord retainer comprises an arch.

12. The apparatus of claim 10 wherein the second detonating cord retainer comprises an arch.

13. The apparatus of claim 10 wherein the first detonating cord retainer and the second detonating cord retainer are adapted to accept a detonating cord at the first angular orientation and to substantially restrain the detonating cord when rotated to the second angular orientation.

14. A method for installing a shaped charge onto a charge holder comprising: with an irregular rectangular shape attached thereto inserting the retainer fitting through an opening in the charge holder at only a first angular orientation; rotating the retainer fitting to a second angular orientation; and locking the retainer fitting at the second angular orientation.

15. The method of claim 14, wherein the charge holder is a charge tube with a charge hole.

16. The method of claim 15, further comprising inserting the shape charge through a charge hole.

17. The method of claim 14 further comprising installing a retainer fitting onto the end of the shaped charge.

18. The method of claim 14, wherein the second angular orientation is approximately 45 degrees.

19. The method of claim 14, mer comprising snapping the retainer fitting onto the shaped charge.

Description

DESCRIPTION OF THE DRAWINGS

(1) For a thorough understanding of the present invention, 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:

(2) FIG. 1 is a side cross sectioned view of a perforating gun.

(3) 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.

(4) FIG. 3A is a detailed view of a retainer fitting.

(5) FIG. 3B is a top view of a retainer fitting with a detonating cord in the unlocked position.

(6) FIG. 3C is a top view of a retainer fitting with a detonating cord in the locked position.

(7) FIG. 3D is a side view of a retainer fitting.

(8) FIG. 3E is a bottom view of a retainer fitting.

(9) FIG. 4 is a side view of a charge tube adapted for use with a retainer fitting.

(10) FIG. 5A is a perspective view of a detonating cord retainer.

(11) FIG. 5B is a cross-section view of a detonating cord retainer.

(12) FIG. 6 is a cross-section side view of a detonating cord retainer attached to a shaped charge case.

DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION

(13) 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.

(14) 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 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. 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 that retainer fittings 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.

(15) 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 end fitting 46 of the shaped charge case 28 by snapping into place over a flange on end fitting 46. The entire assembly 40 includes shaped charge 12 combined with retainer fitting 30. Alternatively, the fitting 30 could be threaded onto the charge case 18, 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 retaining fitting 30. This would result in a single component, thus reducing cost and complexity.

(16) 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. Each of the rectangular base portions 36 and 37 contain fillets 38 that are adapted to accommodate the radius of a detonating cord 51.

(17) 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 end fitting 46 of a shaped charge case 28. The adaptor 39 has an internal flange 47 designed to assist in attaching the retainer fitting 30 to the shaped charge case 28 end fitting 46.

(18) 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 32 as depicted in FIG. 3B.

(19) In at least one example, detonating cord retainers 33 and 34 are shaped as arches as viewed from the side in FIG. 3D. 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 32 against the fillets 38 as shown in FIG. 3C.

(20) 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.

(21) 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 end fitting 46 of the shaped charge case 28 upon installation.

(22) 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. 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.

(23) 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.

(24) 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. 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. 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 46. 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.

(25) Another embodiment of the invention is depicted in FIGS. 5A and 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 cutout 76 that is sized to snap onto a detonating cord. The base 71 snaps onto the end of a shaped charge with the edge of the u-shaped cutout 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 cutout 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 cutout 76 and the through slot 73, whereby the explosion would travel down the through hole 74 and into the back of a shaped charge. In the alternative, a through hole could be placed at the thin material 77 to facilitate the explosion traveling from the detonating cord into the shaped charge. An alternative to the u-shaped cutout 76 is a c-shaped cutout wherein the cutout 76 is rotated 90 degrees such that the detonating cord is accepted from the side rather than the top as shown.

(26) In FIG. 6 the shaped charge case 58 is attached to the detonating cord retainer 50. The shaped charge case is machined with an end adaptor 60. The end adaptor 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 charge case 58, secured with adhesive, snapped around the full length of the charge case 58, or formed integrally with the charge case 58. The detonating cord retainer 50 could also be secured to the 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 through 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 through 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 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.

(27) 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.

(28) 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 include have the retainers 33 and 34 contact and secure to one and other through a fastening mechanism, allowing for a more secure connection between the retainer fitting and the detonation chord. Another variation may include using a circular base, with retainers that connect to one another, securing the detonation chord, 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 chord. Once the detonation chord 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 wherein 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.

(29) Although the invention has been described in terms of particular embodiments which are set forth in detail, it should be understood that this is by illustration only and that the invention is 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 invention are contemplated which may be made without departing from the spirit of the claimed invention.