US3025794A

US3025794A - Perforating apparatus

Info

Publication number: US3025794A
Application number: US659241A
Authority: US
Inventors: Maurice P Lebourg; Herbert C Fagan
Original assignee: Schlumberger Well Surveying Corp
Current assignee: Schlumberger Well Surveying Corp
Priority date: 1957-05-15
Filing date: 1957-05-15
Publication date: 1962-03-20
Anticipated expiration: 1979-03-20

Description

March 20, 1962 M. P. LEBOURG ETAL 3,025,794

PERFORATING APPARATUS Filed May 15, 1957 FIG.2

INVENTORS MAURICE P. LEBOURG HERBERT C. FAGAN BY W 3,025,794 PEMQRA'HNG APPARATUS Maurice P. Lehourg and Herbert (J. Fagan, Houston,

Tex., assignors to chlumberger Well Surveying Corporation, Houston, Tex, a corporation of Texas Filed May 15, E57, Ser. No. 659,241 6 Claims. (Cl. 1tl224-) This invention relates to perforating apparatus and, more particularly, pertains to new and improved perforating apparatus employing shaped explosive charges.

Shaped or hollow charges are widely and effectively used as cutting or perforating devices in many welllsnown applications. Usually, a shaped charge intended for such purposes comprises a block or a cylinder of explosive material into the front face of which a conical recess is formed. The recess is fitted with a suitable liner so that upon detonation of the explosive material, the explosive forces travelling in the direction of the liner transform part of the liner material into a high velocity jet along the axis of the recess. In practice, this jet is capable of penetrating many inches of steel, for example. However, in addition to the high velocity jet, a so-called slug of liner material is formed which follows the path of the jet but travels at 'a substantially lower velocity. It has been found that such slugs tend to plug the hole or perforation made by the jet. For example, in well casing perforating operations with shaped chm'ges employed heretofore, some of the perforations made by the charges may be clogged by the slugs, thus causing a reduction in the beneficial effect of the deep penetrations produced by the high velocity jets.

With a view to obviating this disadvantage, it has been proposed to replace the usual form of liner made, for example, of copper, with a copper liner to which a layer of zinc is intimately connected. Experience has shown that with such a bi-metallic liner a perforation is obtained which is as good and as deep as that obtained with an ordinary copper liner, but the slug heretofore obtained is minimized in size if not altogether eliminated. It is thought that since the copper liner portion has a relatively high vaporization point a typical, highly penetrative jet may be formed while the zinc which is readily vaporizable cannot form a low velocity slug which undesirably plugs the perforation made by the high speed jet. Thus, bi-metallic liners have found ready acceptance in the shaped charge art.

It is an object of the present invention to provide new and improved perforating apparatus employing a shaped charge having a bi-metallic liner which may be fabricated more easily than heretofore possible.

Another object of the present invention is to provide a new and improved bi-Inetallic liner for a shaped charge featuring all the beneficial results attained heretofore with such a liner, but requiring no adherence between the elements of the liner.

Still another object of the present invention is to provide a new and improved method for fabricating bimetallic shaped charge liners.

In accordance with the present invention, a liner for the forward hollowed-out portion of a shaped explosive charge comprises a first element disposed adjacent the surface of the hollowed-out portion and a second element unadherently superimposed on the first element. One of the elements is made of a relatively dense and releatively ductile material and the other element is made of a relatively light, vaporizable material. Means are provided for maintaining the first and second elements in substantially fixed spatial relation.

According to another aspect of the present invention, to fabricate a liner of the foregoing type, at least one of BfiZEJh i Patented 2Q, 1952 the elements is made of a malleable or ductile material and the elements are formed by means of one or more die-stages. At some point in the fabrication of the shaped explosive charge, the elements are compressed together so as to deform at least one and bring adjacent surfaces into relatively close contact. For example, this may occur in one of the die-stages. Thereafter, the elements are mechanically locked together in fixed spatial relation.

Alternatively, the elements may be formed separately, for example, by passing a material for each through a common set of die-stages. Thereafter, they are superimposed and forced into an explosive material for the shaped charge thereby to pack the explosive "and deform at least one to bring adjacent surfaces of the liner elements into close contact.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which:

FIG. 1 is a view in longitudinal cross section of one form of shaped explosive charge perforating apparatus embodying a bi-metallic liner constructed in accordance with the invention; and

FIG. 2 is a view similar to the one shown in FIG. 1, but illustrating an alternative embodiment of the invention.

In FIG. 1 of the drawing, there is shown a shaped ex plosive charge comprising a hollow container 10 of generally conical form receiving in close interfitting relation an explosive charge 11. The container may be constructed of any material of sufiicient strength to act as a retainer of the explosive material. For example, it may be fabricated of a heavy or dense material, such as lead or steel, properly shaped to minimize the effects of undirected pressure waves while increasing the penetration power of the device for a given amount of explosive charge.

The charge 11 is formed with a hollowed-out or conically shaped forward end 12 which receives a closely fitting conical liner 13 constructed in accordance with the present invention. Liner 13 is comprised of a first element 14 of generally conical form disposed adjacent and in interfitting relation to the surface of hollowed-out portion 12. Element 14 is made of a relatively dense and relatively ductile material, such as copper or soft iron. Liner 13 further comprises a second element 15 of generally conical form interposed between elements 14 and portion 12 of charge 11. Element i5 is made of a relatively light, vaporizable material such as zinc or aluminum and is unadherently superimposed on element 14-, in intimate contact therewith.

To maintain

elements

14 and 15 in fixed spatial relation housing 10 is provided with an inwardly deformed, annular ridge 16 which engages the

base ends

17 and 18 of the liner elements. Thus, element 14 is maintained in engagement with element 15 which, in turn, is maintained in engagement with the surface of hollowed-out portion 12 of explosive 11.

The shaped charge thus-far described may be detonated in a suitable manner, as by a Primacord 19 disposed at the rear end of explosive charge 11 and adapted to be detousted by an electric blasting cap (not shown). Where, for example, the charge is employed in well perforating operations, it is suitably supported in a housing or carrier adapted to be lowered into a well (not shown) and the blasting cap is ignited by an operator from the surface of the earth.

In operation, Primacord 19 is detonated and it, in turn,

detonates the rear end of explosive charge 11. Thus, an explosive front is generated which creates a stream of flowing metal from liner 13 comprised mainly of the copper material in element 14. This stream extends outwardly rom explosive charge 11 to form a high speed jet capable of producing deep penetrations in a target material.

During the collapse of liner 13 wherein a portion thereof constitutes the perforating jet, any slug which might have been formed by material in the position occupied by element 15 cannot be formed because element 15 is Vaporized at the temperatures produced during the formation of the perforating jet. Heretofore, it was thought that

elements

14 and 15 should be bonded together or otherwise adhered to one another to prevent distortion of the jet formation stream resulting in an undesirable loss of penetration power. ,7 Comparative tests have shown, however, that a shaped charge provided with a liner embodying the present invention is entirely satisfactory and as efficient as a charge having bonded liner elements. This analysis is presented merely as an aid to an understanding of the utility of the invention, but should not be considered as restrictive or in any way limiting the scope of the invention.

Since the

elements

14 and 15 need not be adhered to one another throughout their adjacent surfaces, a shaped charge liner embodying the present invention may be conveniently and easily constructed. For example, the elements is and 15 may be formed by a conventional and relatively inexpensive die stamping process using malleable or ductile materials. Thus, fiat strips of copper and Zinc stock may be placed in face-to-face relation and run through a set of dies which progressively form the desired conical form. In this way these elements are in close or intimate contact and there is requirement for adherence or cohesion therebetween. Of course, they are physically maintained in place by means of annular ridge 16 of housing 10.

Instead of forming the

elements

14 and 15 together, they may be stamped separately, preferably by means of the same set of die-stages, and then superimposed to constitute liner 13. Thereafter, explosive 11 is loaded into container and the liner 13 is forced into the explosive with a force on the order of 20,000 pounds. This, of course, forms the hollowed-out section 12 in the explosive, packs the explosive to a desired density, and deforms either or both of elements 14- and to bring their adjacent surfaces into intimate, but non-adherent, contact. Mechanical locking of the elements may then be effected.

It is thus evident that

elements

14 and 15 may be brought into close association by exerting a force sulficient to deform one or both of them. Accordingly, either or both of the elements should be malleable or ductile so as to permit this deformation. Moreover, the deforming force may be applied at some Stage of the fabrication to the shaped explosive charge, that is, this may occur during the formation of the liner or at the time the liner is pressed into the explosive material of the charge.

in the modified arrangement illustrated in FIG. 2, components which have their counterparts in FIG. 1 are represented by the same reference numerals. Here, a modified liner 13' is comprised of a relatively dense conical liner element Li made, for example, of copper disposed in interfitting relation within a liner element 15' composed of a relatively light, vaporizable material, such as zinc. As in the arrangement of FIG. 1, elements Idand 15' are unadherently superimposed, however, to maintain them in fixed spatial relation element 14 is slightly shorter than element 15' and the latter is crimped or inwardly deformed to provide an annular ridge which engages the base end 17 of element 14.

To construct liner 13 flat copper and Zinc stocks are run together through a number of progressive die stages on a conventional stamping machine. Each successive die operation forms a piece of the composite material into a shape more closely approaching that of a cone. The final stage produces a cone which is then trnnrned at the base by means, for example, of an appropriate set of dies.

The same or another set of dies may be arranged to undercut element 14, and in a further step, element 15 is crimped over the edge 17 of element 14 thereby to lock the elements together. If desired, this last set of dies may be appropriately arranged to effect the final trimming of element 15, although this operation may take place during a preceding stage.

From the foregoing discussion it is evident that although the elements of

liner

13 or 13 are not adherent to one another, the effectiveness of a shaped explosive charge embodying the present liner performs efiiciently and eflectively. Furthermore, the liner can be fabricated by means of simple stamping operations and is thus considerably less expensive to construct than heretofore possible.

Obviously, other arrangements may be employed for mechanically locking, the elements of the liner together. a

For example, the inner element may be provided with a series of openings annularly spaced about its base and the outer element may be, appropriately deformed so as to enter these openings thereby locking the elements together. Alternatively, the elements may be joined together at their base ends by one or more solder points or they may be spot welded together at a number of points.

In constructing a bi-metallic liner according to the present invention for a specific practical application, two

sheets of metal each 0.012" thick were run simultaneously through a set of die-stages. One was composed of 99% pure copper, fully annealed, while the other was composed of an alloy known as deep drawing zinc containing lead in about 0.08%. The sets of dies were constructed of chrome-plated hard steel and a thrust of 5,625 lbs. was employed. The dies were appropriately lubricated to prevent scoring or galling of the zinc. The resulting conical liner had a base diameter of 1 7 and a height of l% and a wall thickness of 0.024" at the base end and 0.027 near the apex end. The liner Was forced into a powder charge of 15 grams to complete a shaped explosive charge. Of course, the foregoing is presently only by way of example and should not be considered in any way as limiting the scope of the invention. For example, other thicknesses of the metals and/ or other amounts of thrust may be employed. Moreover, by means of dies of appropriate size, liners of any desired dimensions and shape may be produced.

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.

We claim:

1. A shaped charge device comprising a shaped explosive charge having a cavity at the forward end thereof, and a layered structure having the same shape as the surface of the charge cavity and including a first outer layer of material which is in contact with the explosive charge when the liner is placed within the cavity and a second inner layer in nonadherent intimate contact with the outer layer along the inner surface thereof, the inner layer being made of a relatively dense and ductile material, having a relatively high vaporization point so as to form a high velocity perforating jet of the material when the charge is detonated and the outer layer being made of a relatively light material having a relatively low vaporization point such that it tends to vaporize upon detonation of the charge, thereby inhibiting the formation of a low velocity slug.

2. A shaped charge device according to claim 1 Wherein the layered structure has a conical shape.

3. A shaped charge device according to claim 1 wherein the outer layer is made of zinc and the inner layer is made of copper.

4. A shaped charge device according to'claim 1 wherein each layer of the structure comprises a sheet of material formed in the shape of the charge cavity surface.

5. A shaped charge device according to claim 1 wherein the outer layer of material includes an inwardly projecting portion adapted to engage the inner layer and retain it in intimate contact with the outer layer.

6. A shaped charge comprising a generally cylindrical housing having an open end portion, a charge of explosive material within the housing formed with a cavity directed inwardly from the open end of the housing, and a liner for the charge comprising a layered structure Within the cavity having the same shape as the surface of the charge cavity and having an edge portion engaging the inside surface of the housing about the periphery of the cavity including a first outer layer of material in contact with the explosive 'material at the surface of the cavity, and a second inner layer in nonadherent intimate contact With the outer layer along the inner surface thereof, the inner layer being made of a relatively dense and ductile material having a relatively high vaporization point so as to form a high velocity perforating jet of the material when the charge is detonated and the outer layer being made of a relatively light material having a relatively low vaporization point such that it tends to vaporize upon detonation of the charge, thereby inhibiting the formation of a low velocity slug.

References Cited in the file of this patent OTHER REFERENCES American Institute of Mining and Metallurgical Engineers, Technical Publication No. 2158, class A, Mining Technology, 1947.