US2926603A - Well perforator shaped charge - Google Patents

Description

March 1, 1960 w. H. LINDSAY, JR

WELL PEnFRAToR SHAPED CHARGE Original Filed March 12. 1952 'thick walled,

United States Patent WELL PERFORATOR SHAPED CHARGE Will H. Lindsay, Jr., Fullerton, Calif., assignor to Borg- Varner Corporation, Chicago, Ill., a corporation of linois Continuation of application Serial No. 276,156, March 12, 1952. This application December 18, 1957, Serial No. 703,670

This invention relates generally to' well perforators and more particularly to improvements in explosive shaped charges for perforating well casings and the surrounding earth formations in well boreholes. This application is a continuation of my copending application Serial No. 276,156, tiled March 12, 1952, fo'r Well Perforator Shaped Charge, now abandoned.

In the employment of a plurality of shaped charges for making a plurality of perforations through fluidlled well casings and into the surrounding formations, it has become accepted practice to mo'unt the shaped charges adjacent one another inside suitable huid-tight, cylindrical, steel housings, which are adapted to be lowered into the fluid-containing well boreholes to be perforated. In such apparatus, the shaped charges are usually positioned at suitable, longitudinally spaced intervals along the length of the interior bo're of the housing, with the perforating axes of the shaped charges directed laterally thereof in alignment with suitable ports formed in the housing walls, the ports being initially closed prior to firing of the shaped charges by suitable, relatively thin, frangible, fluid-tight port seals. Upon tiring of the shaped charges, the port seals are perforated, destroyed, or otherwise removed by the shaped charge perforating jets which continue on through the casing and into the surrounding formations. The cylindrical housing serves initially to confine therein the blast of the shaped charges other than that directed into the perforating jets.

It has been discovered that when shaped charges of the type heretofore employed are detonated together or nearly simultaneously within the cylindrical housing containing them, the explosive forces of the several charges react upon one another in manners unfavorable to the proper detonation and formation of the mo'st perfect and etlicient perforating jets. This interference between shaped charges is thus, at the same time, both the cause and the result of the inefficient utilization and direction of the explosive forces of the shaped charges.

lt is therefore an object of this invention to' provide a shaped charge perforating device of increased penetrating etliciency.

It is another object of this invention to provide a shaped charge perforating unit having increased penetrating power for a given overall size.

It is a further object of this invention to' provide a shaped charge unit of superior design whereby the perforating jet is of more effective shape and power.

It is a still further object of this invention to provide a shaped charge construction which more efficiently utilizes and directs the explosive forces thereof to produce a perforating jet of superior penetrating force.

It is a still further object of this invention to provide a shaped charge unit, the character and action of which is less susceptible to interference by the tiring of adjacent shaped charges.

It is a still further object of the invention to provide a shaped charge unit, the action of which when red causes r`ice less interference with the tiring action of other adjac shaped charges.

It is a still further object of this invention to pror shaped charge units which are more suitable to subst tially simultaneous tiring in relatively close proximit) one another in a gun housing, wherein the explo: forces from the explosive ignition means and the ex] sive forces of the shaped charges themselves othert tend to react detrimentally upon each other to impair penetrating efficiency of the device.

It is a still further object of this invention to prot a shaped explosive charge device having explosive shielding components that are Sealed against entrance moisture and retained firmly together in assembled lationship.

The objects of this invention are attained in gen1 by employing an improved shape o'f explosive cha: by employing means for precisely centered initiation ignition of the charge, and by employing means shielding the rear portions of the shaped charge fr external explosive forces and for confining and direct more o'f the explosive forces to the perforating jet.

'Ihe objects of this invention are more particularly tained in a shaped explosive charge device for a hol carrier well perforator including a forward, main cha unit having a compressed body of high explosive m1 rial, and a layer of metal covering the rearward 1 tion of the body of high explosive material and 1 viding therethrough a rearward opening, the body t Viding at the forward end thereof a forwardly o1: ing cavity. The device further includes a rearw: booster charge unit having a metallic booster cup hat side walls abutting the before-mentioned layer of m adjacent the opening therein and a thick rear end port providing a rearward aperture, and a compressed cha of booster material filling the booster cup and being substantial contact with the rear of the body o'f high plosive through the opening in the layer of metal. device still further includes a shell formed from resili material, the shell providing a forwardly facing holi conforming generally to and, in the relaxed state of shell, being slightly smaller than the lateral and rc ward exterior surfaces of the main charge unit and bo'oster charge unit, the shell being contracted about lateral and rearward exterior surfaces of the charge ur The shell provides a fuse hole therethrough adapted receive a detonating fuse and to position a portion of fuse rearwardly of the aperture of the booster cup detonating relation to the charge of booster mate through the aperture.

Other objects, advantages, and features of novelty the invention will be evident hereinafter.

In the drawings, which illustrate a preferred embt ment of the invention:

Figure 1 is a view, partly in elevation and partly longitudinal section, of a completely assembled perfora apparatus, illustrating atypical arrangement of the sha] charge devices of this invention; and

Figure 2 is a cross-sectional view, on an enlarged sc: taken on line 2-2 of Figure l, and showing the detai construction of the shaped charge unit of this inventi Referring rst primarily to Figure l, typical perfora apparatus adapted to contain the shaped charge u1 comprises a housing in the form of a thick walled, el gated, steel tube or cylinder 10 closed at its lower i by suitable means, such as a tapered bull plug 11, z closed and adapted .to be supported at its upper end b cable head 12 which is coupled to the top of the hous through an intermediate sleeve member 13 which ma threaded connection with the cable head 12 and the cyI der 10 through left-hand and right-hand threads 14 z spectively. A conductor cable 16, containing an '.ed conductor 17, enters and is anchored within head 12 and serves both as a means for lowering rforator apparatus into the well and for conducting ectrical firing impulse to the firing mechanism or therein. Typical cable head construction suitable connection is illustrated in the patent to Turechek ,043,341. The electrical conductor 17 within the :tor cable 16 may be connected through the cable l2 and through a suitable insulated electric con- 18 to an electric detonating cap 20. The detocap 20 is secured within the upper end of a tubular arminal union 21, which is in turn supported cenwithin the upper end of the housing by means entrally perforated diaphragm 23. A suitable fuse lich is threaded through the rear end portions of aped charge units, as hereinafter more fully del, enters and is crimped into the lower end of the erminal union 21 adjacent to or in contact with fore-mentioned electric detonator cap 20.

thick wall of the housing 10 is provided with a of longitudinally spaced, radially directed openings rts 25 extending between the outside and inside l bore or chamber 26, each port being enlarged outside end by a short counterbore 28 to receive a eal disc 27. Such series of ports 25 (only two of are shown in Figure 1, duplicate portions thereof been omitted) may be arranged along the housing any desired pattern. `One suitable arrangement or 1 which is frequently used is to place the ports 25 Jiral arrangement in the housing.

japed charge unit, such as shown at 30, is adapted mounted opposite each of the ports 25 and posiso that the jet-shaped blast projected from the forconcave end of the shaped charge will pass through nter of the port. In order to position and accumaintain each such shaped charge 30 in axial .ent with the center of its respective port 25, the vall of the cylindrical gun housing 10, diametrically te each port 25, is provided with suitable means to r and support the rear end portion of the shaped unit. Preferably such means takes the form of illy directed, cylindrical recess 32, and the rear end 1 33 of the shaped charge shell is formed to fit such recess 32. The forward end of the shaped unit 30 may be supported by any suitable means d to hold the rear end of the shaped charge 30 .y seated within the recess 32 and at the same time in accurate alignment of the axis of the shaped with the center of the port 25. For this purpose, ner, such as best shown at 35 in Figure 2, may be Jed. This retainer is in the general form of a holuncated cone, with thick end portions 36 and 37 for g telescoping engagement within the annular recess ned in the forward end of the shaped charge unit, thin the inside surface of the inner end portion of rt 25, respectively, and a thinner, coaxial, frustol, tubular, interconnecting portion 39 extending bethese thick end portions. The tubular portion 39 :rably of flexible, resilient material, such as rubber, ne, or the like material, to enable one end portion to be collapsed or be telescoped within the other rtion for initial installation of the shaped charge ithin the bore of the housing 10.

a more complete description of the retainer 35 operation in connection with the loading of the charges into the housing 10, reference may be had Patent No. 2,707,917, issued May l0, 1955, on Iplication of Lindsay and Phillips, Serial No. 7, liled luly 25, 1949, which application was cog with applicants parent application of which the application is a continuation.

rring now principally to Figure 2, in which the lction of the shaped charge of this invention is i1- ad in more detail, the explosive charge 45 of this invention is contained in a shell 46 of varying inside and outside diameter and shape from end to end. The exterior of the shell 46 is formed with a cylindrical forward end portion 47, a rearwardly converging, intermediate portion 48, and a cylindrical rear end extension portion or boss 33 of relatively small diameter as compared to the cylindrical forward portion 47. The cylindrical rear end boss 33 is of such size and shape as to adapt it to be inserted into any one of the hereinbefore-mentioned recesses 32 formed in the inside surface of the wall of the housing 10 diametrically opposite the ports 25, as illustrated in Figures 1 and 2. The forward end of the shell 46 is provided with the hereinbefore-mentioned annular recess 38 to receive the inner annular end portion 36 of the before-mentioned retainer 35.

The exterior surface of the explosive material 45 of the shaped charge fits the interior surface of the shell 46 and is shaped exteriorly with a forward cylindrical zone 50, an intermediate, rearwardly converging, frustoconical zone 51, an annular shoulder surface 53 lying in a plane normal to the axis of the shaped charge, with the outer circumference thereof joining the rear end of said frusto-conical zone 5l, and a rear, cylindrical zone 54 of reduced diameter relative to said forward zone 50 extending rearwardly from the inner circumference of said annular shoulder 53.

The body of explosive material 45 has formed in the forward end thereof a substantially conical, forwardly facing concavity 56 concentric with the before-mentioned exterior surface zones thereof. The conical concavity 56 is preferably lined with a layer of metal, as shown at 57. This inner layer or conical liner 57 may be made of a suitable non-explosive material preferably having a relatively high density, such as, for example, copper, aluminum, steel, or the like.

The exterior surfaces of the portion 45a of the explosive charge 45 at the intermediate, frusto-conical zone 51, and the annular shoulder surface 53, are also covered, as shown at 52, with a relatively thin layer of metal, which may be one of the same materials as employed for the before-mentioned conical liner 57 but usually of less thickness. The exterior surface of the portion 45b of the explosive charge 45 at the rear cylindrical zone 54 is also covered with a metal layer, the forward portion of which, as shown at 59, comprises a relatively thin, annular or tubular shaped portion of substantially the same thickness as the layer at 52, and the rear end portion of which comprises a relatively thick, annular closure member 60 provided in the center thereof with a central aperture 61. This central aperture may be closed, if desired, at the outer end by means of a relatively thin diaphragm 62 of metal foil, paper, or other suitable material. The tubular metal portion 54 and end closure member 60 thus containing explosive charge 45b may also be made of copper, steel, or the like material.

A bore 63 extends transversely through the rear end boss 33 of the shell 46, through which the detonating fuse, hereinbefore mentioned and illustrated at 24 in Figure 1, may be threaded. The detonating fuse 24 thus positioned lies closely adjacent the aperture 61 and diaphragm 62 in the end closure member 60 of the rear cylindrical zone 54 of the explosive charge. The fuse may be threaded through the bores 63 of the several shaped charge units in the housing, in the manner more fully shown and described in the before-mentioned Lindsay et al. Patent No. 2,707,917.

The fuse 24 is of an explosive or detonating type, such as, for example, that known commercially as P.E.T.N. Reinforced Primacord, designated as 50 gr./ft. The explosive body 45 of the shaped charge contained within the shell 47, as hereinbefore described, is preferably pressed or pelletized in two separate units, the forward or main charge unit 45a being preferably composed of a high explosive, such as A RDX (cyclotrimethylenetrinitramine), and the rearward unit 45b being preferably composed of pure Cyclonite, which is the trade name of a high explosive manufactured by E. I. du Pont de Nemours and Company. The charge 45b is preferably of a lower density than the main charge 45a and is thus more sensitive, whereby it may serve, in elfect, as a booster charge for the main charge.

In the operation of the apparatus, an electric potential is applied to the conductor 17, which is transmitted down through the conductor cable from the top of the borehole to the cable head, through conductor 18 within the cable head, and through the electric detonator cap 20 to ground. The resultant detonation of the detonator cap 20 in turn detonates the fuse 24, the explosive wave of which travels throughout its full length from the top to the bottom thereof at a high velocity. Since in each shaped charge unit the explosive fuse 24 extends through the transverse fuse bore 63 in the rear end boss 33 of the shaped charge shell, the explosive force is first applied thereby to the rear end closure member 60. Because of the relatively great thickness and mass of the rear end closure member 60, it offers a very high inertia force opposing the forces resulting from the detonation of the fuse 24, thereby initially permitting only the rupture of the diaphragm 62 and the detonation of the charge 45b contained within the rear cylindrical zone 54 at the central aperture 61. Thus the detonation of the charge 45b is initiated at a relatively small focal point or area at the rear end extremity thereof, accurately positioned on the axis of the shaped charge. The explosive wave thus initiated progresses radially from the aperture 61 as a focal center, forward through the relatively sensitive charge 45b within the rear end cylindrical portion thereof within the tubular container 59, and thence into the rearward central portion of the main charge 45a, in turn collapsing the conical liner 57 and producing a forwardly directed, high velocity jet of gases and metal having high penetrating power. As the detonating wave progresses in the main explosive body 45a into the space between the conical metal liner 57 and the external metal layer or covering at 51 and 53, the weight of the covering at 51 and 53 is such that it offers extremely high inertia to the outward and rearward dissipation of the explosive forces at that point, thereby resisting and retarding the outward dissipation of the explosive energy there and thereby confining a portion thereof to the body of gases which make up the perforating jet. Additionally, the metal covering at zones 51 and 53 and also the metal covering in the rear cylindrical zone 54 serve to shield these rear end portions of the shaped charge explosive material from the pressure waves and explosive forces generated by the adjacent portions of the detonating fuse 24 and neighboring shaped charges. The pattern of detonation of the shaped charge is thus shielded to a substantial and effective degree from external forces which otherwise tend to interfere with the symmetrical progress of the detonating wave from the central point of detonation at the aperture 61 to the forward edge of the cavity 56, and which thus otherwise would tend to distort the jet issuing from the shaped charge in such a manner as to impair its penetrating power. The metal coverings at 51, 53, and 60 thus serve both to shield the shaped charge from the detrimental effects of explosive forces from the adjacent explosive bodies and to confine and cause the explosive forces of the shaped charge to be more efficiently utilized to form the perforating jet.

The shaped charge shell 46 is preferably made of a resilient material, such as rubber or the like material, which serves in addition to being a holder for the shaped charge explosive, as an eicient seal against entrance of moisture, and shields the explosive material against variations in its performance which may be due to weather and temperature change. The resilient shell 46 is preferably made slightly undersize, and the explosive pellets 45a and 45b are pressed in place within it, causing the case to be expanded slightly, thereby applying a p loaded condition diametrally on the pellets, thereby suring that the pellets and cone will be retained iirn together under varying conditions. The cone liner may have a thickness in the order of .026, and i metal coverings at 51, 53, and 54 may have a thickn of the order of approximately .015". The thickness the rear end closure member 60 may be approximat` .093. The aperture 61 in the rear end closure meml 60 may have an inside diameter of approximately 1A When aperature closure 62 is used, it may be made metal foil having a thickness of from .002 to .001 These dimensions are suitable for a shaped charge h: ing an axial length of approximately 1%" from the i nular shoulder 53 to the forward edge of the coni liner 57 and containing approximately 2l grams of RI explosive material. The angle of the conical liner is dependent somewhat upon the diameter of the housi 10 in which it is to be installed, and may vary as quired to obtain an optimum stand-oif equal to the d tance from the charge to the port seal.

It is to be understood that the foregoing is illustrati only, and that the invention is not limited thereby, l may include various modifications and changes made those skilled in the art without distinguishing from t scope of the invention as defined in the appended clair I claim:

l. A shaped explosive charge device for a hollow c: rier well perforator comprising: a forward, main chai unit including a compressed body of high explosive n terial, a layer of metal covering the rearward portion said body of high explosive material and providing the: through a rearward opening, said body providing at t forward end thereof a forwardly opening cavity; a re: ward, booster charge unit including a metallic boost cup having side walls abutting said layer of metal z jacent the opening therein and a thick rear end porti providing a rearward aperture, and a compressed char of booster material filling said booster cup and being substantial contact with the rear ofsaid body of hi explosive through the opening in said layer of metal; a a shell formed from resilient material, said shell prov: ing a forwardly facing hollow conforming generally and, in the relaxed state of said shell, being slight smaller than the lateral and rearward exterior surfaces said units, said shell being contracted about the latei and rearward exterior surfaces of said units, said sh providing a fuse hole therethrough adapted to receive detonating fuse and to position a portion of the fuse rez wardly of the aperture of said booster cup in detonati relation to said charge of booster material through se aperture.

2. A shaped explosive charge device for a hollow ci rier well perforator comprising: a forward, pelletizf main charge unit including a compressed body of hi` explosive material, the external surfaces of which a surfaces of revolution about an axis of symmetry, a lay of metal covering the rearward portion of said body high explosive and providing therethrough a central, c cular axial opening, said body providing at the forwa end thereof a substantially conical, forwardly facir coaxial cavity, and a liner seated in said cavity; a rez ward, pelletized, booster charge unit including a rr tallic booster cup symmetrical about said axis havi: side walls abutting said layer of metal adjacent the p riphery of said circular opening and a thick rear ei portion providing an axial central aperture of reduc diameter, and a compressed charge of booster mater filling said booster cup and being in substantial conte with the rear of said body of high explosive through t4 circular opening in said layer of metal; and a coax shell formed from resilient material, such as rubber ai the like, said shell providing a forwardly facing hollc conforming generally to and, in the relaxed state of sa shell, being slightly smaller than the laterally and rea facing exterior surfaces of said said units, said :ing contracted about the laterally and rearwardly exterior surfaces of said units to retain the latter together, said shell providing a transverse hole rough rearwardly of said booster cup adapted to a detonating fuse and to position a portion of the :arwardly of the aperture of said booster cup in ting relation to said booster explosive material 1 said aperture. shaped explosive charge device for a hollow carell perforator comprising: a forward, pelletized, lharge unit including a compressed body of high ve material having a forward cylindrical outer merging at the rear into a coaxial, rearwardly ging, frusto-conical surface merging at the rear coaxial, annular shoulder surface lying in a plane to the axis of the cylindrical outer surface of idy, a layer of metal covering said frusto-conical and said annular shoulder surface and providing 'al opening extending radially inwardly from said r surface, said body providing in the forward end a substantially conical, forwardly facing, coaxial ity, and a liner seated in said concavity; a rearpelletized, booster charge unit including a forfacing, cylindrical, metallic booster cup having cylindrical side walls abutting said layer of metal xt the inner central opening thereof, the side walls cup being of substantially the same thickness as yer of metal, said booster cup having a rear end i substantially thicker than said layer of metal and ng an axial central aperture of reduced diameter,

and a compressed charge of booster explosive material filling said booster cup and being in substantial contact with the rear of said body of high explosive through the central opening in said layer of metal; and a coaxial shell formed from resilient material, such as rubber and the like, said shell providing a forwardly facing hollow conforming generally to and, in the relaxed state of said shell, being slightly smaller than the laterally and rearwardly facing exterior surfaces of said units, said shell being contracted about the laterally and rearwardly facing exterior surfaces of said units to retain the latter rmly together, said shell providing a transverse hole therethrough rearwardly of said booster cup adapted to receive a detonating fuse and to position a portion of the fuse rearwardly of the aperture of said booster cup in detonating relation to said booster explosive material through said aperture.

4. A shaped explosive charge device for a hollow carrier well perforator as defined in claim 3 wherein: said liner has its forward periphery in contact with the wall of the hollow of said shell, and said shell is contracted about said periphery of said liner to seal said explosive material from external atmospheric influences.

References Cited in the le of this patent UNITED STATES PATENTS 2,628,559 lasse Feb. 17, 1953 2,629,325 Sweetman Feb. 24, 1953 2,708,408 Sweetman May 17, 1955 2,785,631 Blanchard Mar. 19, 1957 1f. f a

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