Title:
SHAPED CHARGE DEVICES FOR WIRE CARRIERS
United States Patent 3636875


Abstract:
The particular embodiments described herein to illustrate the invention include encapsulated shaped charge devices having high-strength ceramic cases which are mounted on a wire carrier for movement into a well bore in which a perforating operation is to be conducted. As is typical, the wire carrier is comprised of a pair of paralleled rods or laterally spaced wire members respectively having spaced reversely curved portions and cooperatively arranged in relation to the other wire for defining a series of enlarged openings along the carrier which are respectively adapted for receiving an encapsulated shaped charge. To secure the shaped charges to the wire carrier, a lead band arranged around each charge case is provided with a pair of outstanding lugs respectively projecting outwardly from each side of the case and adapted to engage only a small portion of the rear face of each of the two carrier wires. In one embodiment of the invention, the forward faces of the two carrier wires are engaged against the rear of a circumferential flange formed around the ceramic case. In an alternative embodiment of the invention, one or more outstanding lugs are formed on each side of the lead band and spaced forwardly of the first-mentioned single lugs a distance corresponding generally to the thickness of the carrier wires. In either situation, upon detonation of the shaped charges, the lead bands will protect the carrier wires from laterally directed explosive forces and, by virtue of having only the single outstanding lugs in engagement with the rear face of each carrier wire, these rearward outstanding lugs will readily fail so as to prevent the forwardly directed explosive forces from twisting the carrier wires about their respective longitudinal axes which otherwise frequently causes failure of the wires at one or more points along their lengths.



Inventors:
DODSON A C
Application Number:
05/050490
Publication Date:
01/25/1972
Filing Date:
06/29/1970
Assignee:
SCHLUMBERGER TECHNOLOGY CORP.
Primary Class:
Other Classes:
175/4.6
International Classes:
E21B43/117; F42B3/08; (IPC1-7): F42B3/08
Field of Search:
102/20 175
View Patent Images:
US Patent References:
3405769Well perforating apparatus1968-10-15Shore et al.
3327630Vented shaped charge case1967-06-27Bell
3282213Wire carriers for oil well perforators1966-11-01Bell et al.
3276369Shaped charge device1966-10-04Bell



Primary Examiner:
Pendegrass, Verlin R.
Claims:
What is claimed is

1. Perforating apparatus comprising: a support adapted for suspension in a well bore and including first and second generally paralleled elongated wire members spaced apart from one another and lying in a common longitudinal plane; an encapsulated shaped charge explosive device positioned between said wire members and adapted for firing along a perforating axis intersecting said longitudinal plane and extending in a forward direction therefrom; means for holding said wire members in their said generally parallel spaced relation and including fastening means coupling said wire members to one another above and below said shaped charge device; and means for retaining said shaped charge device between said wire members and including first and second outstanding yieldable lugs secured on opposite sides of said shaped charge device and respectively engaged with the rear surfaces of said first and second wire members, said lugs being operatively sized and arranged to yield upon firing of said shaped charge device to at least minimize forwardly directed explosive forces acting on said wire members and tending to twist said wire members about their respective longitudinal axes.

2. The perforating apparatus of claim 1 wherein said retaining means further include a lead band secured around said shaped charge device and engaged with the opposed inwardly directed surfaces of said wire members to at least minimize laterally directed explosive forces acting on said wire members, said first and second lugs being formed integrally with said lead band.

3. The perforating apparatus of claim 2 wherein said retaining means further include third and fourth outstanding lugs formed integrally with said lead band on opposite sides of said shaped charge device and respectively engaged with the forward surfaces of said first and second wire members to prevent rearward movement of said shaped charge device in relation to said wire members.

4. The perforating apparatus of claim 2 wherein said retaining means further include means on said shaped charge device defining diametrically opposed shoulders on opposite sides of said shaped charge device and respectively engaged with the forward surfaces of said first and second wire members to prevent rearward movement of said shaped charge device in relation to said wire members.

5. Perforating apparatus comprising: a support adapted for suspension in a well bore and including first and second wire members having alternately occurring inwardly directed curved portions and outwardly directed curved portions along their respective lengths, said wire members being arranged in a common longitudinal plane along generally parallel longitudinal axes and oriented to position their respective inwardly curved portions adjacent to one another and to position their respective outwardly curved portions opposite to one another to define a plurality of longitudinally spaced generally oval openings between said wire members; a plurality of encapsulated shaped charge explosive devices respectively positioned in each of said generally oval openings, each of said shaped charge devices being adapted for firing in a selected forward direction along a perforating axis intersecting said longitudinal plane; means for holding said wire members in their said spaced relation and including fastening means coupling said inwardly curved portions of said wire members to one another; and means for retaining said shaped charge devices between said wire members and including a lead band secured around each of said shaped charge devices and engaged with the opposed inwardly directed surfaces of said outwardly curved portions to at least minimize laterally directed explosive forces acting on said wire members, and first and second diametrically opposed lateral lugs on said lead band projecting outwardly therefrom along the rear surfaces of said first and second wire members and being the sole means retaining said shaped charge device against movement forwardly in relation to said wire members, said lateral lugs being selectively sized to yield upon firing of said shaped charge device to at least minimize forwardly directed explosive forces acting on said wire members and tending to twist said wire members about their respective longitudinal axes.

6. The perforating apparatus of claim 5 wherein said retaining means on each of said shaped charge devices further include means on said shaped charge device defining diametrically opposed shoulders on opposite sides of said shaped charge device and respectively engaged with the forward surfaces of said first and second wire members to prevent rearward movement of said shaped charge device in relation to said wire members.

7. The perforating apparatus of claim 5 wherein said retaining means further include third and forth outstanding lugs formed integrally with said lead band on opposite sides of said shaped charge device and respectively engaged with the forward surfaces of said first and second wire members to prevent rearward movement of said shaped charge device in relation to said wire members.

8. A well-perforating device comprising: a hollow case of a ceramic or other glasslike material; shaped charge means in said case; a lead band secured around the midportion of said case; and means adapted for mounting said case between a pair of spaced wire-supporting members and including only a single integral lug extending laterally outwardly from said lead band on each side of said case and respectively adapted to be engaged with the rearward surfaces of such wire members to be the sole means retaining said perforating device against forward movement in relation to such wire members, said integral lugs being selectively sized to yield upon firing of said perforating device to at least minimize forwardly directed explosive forces acting on such wire members and tending to twist such wire members about their respective longitudinal axes.

9. The well-perforating device of claim 8 wherein said mounting means further include integral shoulders on opposite sides of said lead band ahead of each of said integral lugs and respectively adapted to be engaged with the forward surfaces of such wire members to retain said perforating device against rearward movement in relation to such wire members.

10. The well-perforating device of claim 8 wherein said mounting means further include integral shoulders on said case ahead of said lead band and on opposite sides of said case in front of said integral lugs, said integral shoulders being respectively adapted to be engaged with the forward surfaces of such wire members to retain said perforating device against rearward movement in relation to such wire members.

Description:
As disclosed in U.S. Pat. No. 3,276,369 where so-called "capsule" charges are mounted on an expendable wire or strip carrier, it is generally preferred to employ ceramic-encapsulated shaped charges instead of aluminum-encapsulated charges so as to avoid damage to the charges by either abrasion on the well casing or corrosive attack by well bore fluids. In particular, where a perforating operation is to be conducted in a gas well, ceramic cases are greatly preferred inasmuch as aluminum cases are more or less gas pervious. Moreover, as described in U.S. Pat. No. 3,282,213, wire carriers rather than strip carriers are usually employed for such ceramic-encapsulated charges, with a preferred form of such wire carriers being those disclosed in that patent.

As pointed out in this patent, it was found that wires having a generally rectangular cross section will better withstand the severe explosive forces imposed on the wires upon detonation of the ceramic-encapsulated shaped charges carried thereby which might otherwise part the wires at one or more locations. Although these new and improved wire carriers have been generally successful in liquid-containing well bores, it has been found that when ceramic-encapsulated shaped charges are employed in gas-filled well bores even these superior carriers will often be broken. Thus, since it is not at all desirable to leave pieces of the carrier wires in a well bore following a perforating operation, various arrangements have been attempted heretofore to minimize, if not completely eliminate, such malfunctions.

In one manner of attempting to eliminate this problem heretofore, arcuate strips or annular bands of lead have been secured around a ceramic-encapsulated shaped charge and provided with elongated opposed grooves of a suitable size for receiving the inner edges of the two supporting wires which are then bound together at spaced intervals to retain the shaped charges in operative positions therebetween. It has been found, however, that although such lead protective members will at least reduce the effects of the outwardly directed explosive forces, detonation of the shaped charges produce substantial forwardly acting torsional forces on the supporting wires which frequently cause breakage at one or more places along the wires.

Accordingly, it is an object of the present invention to provide new and improved means for securing shaped charge devices which are encapsulated in cases of a ceramic or a glasslike material and are to be mounted between a pair of generally paralleled support rods or wires.

This and other objects of the present invention are attained by mounting a lead ring around a shaped charge case formed of a ceramic or glasslike material. A pair of outstanding relatively weak lugs are arranged on opposite sides of the lead ring and suitably positioned for respectively engaging a minor portion of the rear face of generally paralleled support rods or wires. Either a circumferential flange is formed on the shaped charge container immediately ahead of the lead ring or one or more forwardly disposed pairs of second lugs are arranged on the lead ring for engagement with the forward faces of the carrier wires. By arranging the weakened lugs to have a minimum shear strength for withstanding forwardly directed impact forces, detonation of one or more shaped charges mounted on the carrier will, at best, only minimally damage the supporting wires.

The novel features of the present invention are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may be best understood by way of the following description of exemplary apparatus employing the principles of the invention as illustrated in the accompanying drawings, in which:

FIGS. 1 and 2 show alternate views of a prior art embodiment of an encapsulated shaped charge device;

FIGS. 3 and 4 are alternate views of a preferred embodiment of an encapsulated shaped charge device incorporating the principles of the present invention; and

FIGS. 5 and 6 respectively depict alternate views of a second embodiment of the present invention.

Turning now to FIGS. 1 and 2, a shaped charge device 10 typical of the prior art is illustrated as including a complementally fitted two-part case having a hollowed, generally cylindrical container 11 and a dished forward cover 12 which are preferably arranged in accordance with the ceramic-encapsulated shaped charges disclosed in U.S. Pat. No. 3,276,369. As is typical, the rear of the container 11 is shaped so as to form a transverse groove 13 sized and adapted to snugly receive and retain a suitable detonating cord (not shown) such as, for example, Primacord.

A lead band 14 is secured around the perimeter of the container 11. To secure the shaped charge 10 to a wire carrier comprising a pair of generally paralleled spaced wires, as at 15 and 16 (which are preferably arranged in accordance with U.S. Pat. No. 3,282,213), the lead band or ring 14 is formed with outwardly directed lateral projections 17 and 18 which are spaced a short distance to the rear of a circumferential flange 19 which surrounds the forward end of the container 11. In this manner, the longitudinal spacing between the flange 19 and the projections 17 and 18 define opposed peripheral grooves which are adapted for receiving at least the adjacent inwardly directed portions of the spaced carrier wires 15 and 16.

As fully explained in U.S. Pat. No. 3,282,213, the wires 15 and 16 are formed in a somewhat-sinusoidal configuration so as to define a series of spaced openings, as at 20, for receiving the shaped charges 10. Thus, as best seen in FIG. 2, by interconnecting the spaced wire members 15 and 16 as by wire clips 21 and 22 arranged thereon at spaced intervals between each of the several shaped charges, as at 10, the shaped charges will be secured between the spaced wires to permit their movement through a well bore in which a perforating operation is to be conducted. As previously mentioned, however, although the lead bands 14 on these prior art shaped charges 10 have been found to at least minimize damage to the wire supports 15 and 16 by laterally directed explosive forces, it has nevertheless been found that in gas-filled wells the supporting wires will be violently twisted about their respective longitudinal axis by explosive forces that are directed in a generally forward direction as to cause frequent failures of the supporting wires at one or more spaced locations therealong.

Accordingly, as shown in FIGS. 3 and 4, a shaped charge device 50 arranged in accordance with the principles of the present invention is depicted. As seen there, the shaped charge 50 includes a ceramic case having a forward cover 51 and a rearward container 52 which are either identical or similar to those shown in U.S. Pat. No. 3,276,369. The rearward portion of the container 52 is similarly formed to define a transverse notch 53 suitably shaped for snugly receiving a length of Primacord (not shown). Similarly, a pair of paralleled supporting wires 54 and 55 arranged generally as depicted in U.S. Pat. No. 3,282,213 are arranged for supporting one or more of the shaped charges 50 in operative positions for movement in a well bore.

A lead band or ring 56 is cooperatively secured around the shaped charge 50 and preferably positioned a short distance to the rear of a circumferential flange 57 surrounding the forward end of the container 52. As best seen in FIG. 3, the lead band 56 is arranged to have sufficient thickness to at least minimize, if not significantly reduce, the effects of laterally directed explosive forces on the carrier wires 54 and 55 whenever the shaped charge 50 is detonated. As best illustrated in FIG. 4, the carrier wires 54 and 55 are respectively confined between upper and lower opposed pairs of outstanding lugs 58-61 which are respectively adapted to extend outwardly along the forward faces of the carrier wires. Moreover, and of particular significance to the present invention, a pair of outstanding but relatively weak lugs 62 and 63 are further arranged on the lead band 56 so as to project laterally outwardly and be engaged with the rear face of the carrier wires 54 and 55. It will be recognized, therefore, that by virtue of the lugs 58-63, once the carrier wires 54 and 55 are placed around the shaped charge 50 and interconnected together as by wire clips 64 and 65, the shaped charge 50 will be securely retained in the illustrated position so as to remain in position as the perforating apparatus is moved through a well bore.

It has been found that upon detonation of the shaped charges 50 of the present invention, the outwardly directed lateral explosive forces which are impinged against the inner edges of the carrier wires 54 and 55 will be sufficiently minimized or reduced by the thickness of the lead band 56 that the carrier wires will not fail even where the perforating apparatus is employed within a gas-filled well bore. Moreover, of particular significance to the present invention, it has been further found that detonation of the shaped charges 50 of the present invention will result in the weak rearward lugs 62 and 63 being sheared so that little or no torsional strain is placed on the carrier wires 54 and 55 by the forwardly directed explosive forces that are imposed on the carrier wires by detonation of the shaped charge device. Accordingly, by inspection of carrier wires such as at 54 and 55 following the detonation of one or more shaped charges as at 50 that have previously been supported therebetween, it has been found that the carrier wires were, at best, only slightly twisted about their longitudinal axes. As a result, upon conducting such experiments in gas-filled wells, it has been found that little or no breakage of the wires 54 and 55 is experienced in even those wells having similar conditions in which shaped charges such as those shown at 10 in FIGS. 1 and 2 had often caused breakage of the supporting carrier wires 15 and 16.

Turning now to FIGS. 5 and 6, an alternative embodiment is shown of a shaped charge device 50' which is similar to the shaped charge device 50 and also incorporates the principles of the present invention. It will, of course, be appreciated by comparison of FIGS. 3 and 4 with FIGS. 5 and 6 that the shaped charge 50' is similarly arranged to the shaped charge 50. The difference, however, between the shaped charge 50 and the shaped charge 50' is that the lead band 56' employed with the latter shaped charge is provided with only a single pair of outstanding lugs as at 62' and 63' respectively adapted to be engaged with the rear face of the carrier wires 54' and 55' . The forward faces of the supporting carrier wires 54' and 55' are adapted to be retained against the rear face of the circumferential flange 57' around the container 52' of the shaped charge 50' . Accordingly, inasmuch as the shaped charge 50' is prevented from moving forwardly by only the single pair of weak outstanding lugs 62' and 63' , the carrier wires 54' and 55' will not be subjected to a torsional force of sufficient magnitude to possibly cause their breakage.

Accordingly, it will be appreciated that the present invention has provided new and improved shaped charge devices which, in their preferred form, are enclosed within fluidtight cases of a strong ceramic material. To support the shaped charge devices of the present invention, a pair of paralleled supporting rods or wires are suitably configured to confine the shaped charge devices of the present invention therebetween once the supporting wires are interconnected to one another at spaced intervals between the several charges arranged thereon. In the preferred manner of protecting the supporting wires from breakage upon detonation of the shaped charge devices carried thereon, lead bands are secured around each of the shaped charge devices, with each of these lead bands being provided with only a single pair of outstanding lugs of minimum strength which are engaged along the rearward face of each of the carrier wires. To retain the shaped charge devices against rearward movement in relation to the supporting carrier wires, either the circumferential flange on the shaped charge device or a pair of outstanding forwardly disposed lateral lugs formed on the lead band is arranged to be engaged with the forward face of each of the supporting carrier wires. Accordingly, upon detonation of either of the shaped charge devices, the thickness of the lead band will protect the adjacent portions of the supporting carrier wires from laterally directed explosive forces which might otherwise cause the rupture of the supporting carrier wires. By virtue of the relatively weak rearward lugs on the lead bands, forwardly directed explosive forces that would otherwise impart a severe torsional force on each of the two carrier wires are minimized by the ready failure of the weak outstanding lugs instead.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.