US2980018A

US2980018A - Well perforator shaped charge

Info

Publication number: US2980018A
Application number: US556908A
Authority: US
Inventors: George F Turechek
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1956-01-03
Filing date: 1956-01-03
Publication date: 1961-04-18
Anticipated expiration: 1978-04-18

Description

April 18, 1961 e. F. TURECHEK WELL PERFORATOR SHAPED CHARGE 2 Sheets-Sheet 1 Filed Jan. 3, 1956 INVENTOR. M

April 18, 1961 Filed Jan. 5, 1956 G. F. TURECHEK WELL PERFORATOR SHAPED CHARGE 2 Sheets-Sheet 2 IN VEN TOR.

' the surrounding formation.

United States Patent ma WELL PERFORATOR SHAPED CHARGE George F, Turechek, Los Angeles, Calif., assignor, by mesne assignments, to Borg-Warner Corporation, Vernon, Calif., a corporation of Illinois Filed 12111.3, 1956, SerQ'No. 556,908

5 Claims. Cl. 102- 20 T This invention relates to well perforators, and .particularly to improvements in shaped charge means for producing openings in well casings and in the surrounding formations to permit entrance of production fluid into the well.

' Well perforating operations have heretofore been acc'omplished usually 'by firing one or more solid projectiles or shaped charge jets through the casing and into This permits flow of fluid into the casing from the desired strata in the surrounding formation.

With either the solid projectile or the more recently developed shaped charge units, a substantially round holeis usually produced through the casing and extending into the formation; Certain practical limits exist on the size of the explosive charge which may be used, and size of perforation which may be made,;sin'ce' it is usually necessary that the perforation be accomplished without damage tothe explosive carrier, and also always without permanent damage to the casing. If excessively large charges are used, the explosive carrierbody and also the casing may be weakened and deformed, or even shattered. I i V With either the solid projectile or the shaped charge this limitation has sometimes prevented the'formationof .holes of the size desired by-operat'ors in the field,

from a production capacity standpoint In order to tap larger areas, the operator may' shoot a .pluralityof charges in a single operation, as is conventional practice, but in view' of the physical limitations on. the spac-T ingot individual charges in a gun, the number of holesper. linear foot of casing which maybe shot is necessarily limited, and in turn, the effective perforated area of; the oilproducing formation, is correspondingly restricted. I

. Another disadvantage-of the formation of large'ro und. perforationholes residesin the relative freedomzforcn trance of sand into the well casing which thcy permit.

alsdproducie a linear slot in the casing, which will prevent'the entrance of sand and other particles of a size which would readily pass through around hole of the same. cross-sectional area and clog up the tubing. The

linearly slotted casing is thusf'rnore effective in screening out undesired material. 1

making possibletheformation of openings in the casing tapping largerareas without damage to the casing and with given weights of explosive; y It' is a further 'object to provide means for producing aalarger drainage area inthe surrounding formation for a givenweightpf charge. v

,{It f another'object of the invention to; provide means fpr perforating a greater vertical extent of a particular Figures 1 and r Patented Apr, 18, 1961 stratum surrounding the casing for a given weight of shaped charge units effective to produce a more readily controllable vertically disposed cutting sheet of gases.

It is still a further object to provide a shaped charge a unit adapted to produce a linear'jet of limited crosssectional extent in both length and width, but of substantially greater velocity and penetrating power for a.

given Weightof charge. I

The objects of this invention are accomplished by an improvement in the recently developed shaped charge type of-perforator which makes it possible to produce a linear slit through the casing of accurately controllable length and width.

The invention, comprises, in brief, an improved form of charge having a V-shaped cavity elongated inv the direction in which the vertical slot is to extend. The gaseous cutting sheet resulting from the explosive charge is'strengthened in -its' cutting form by the use of a vertically disposed barrier rod positionedbetwee'n the apical portion of the cavity liner and the booster charge, with the latter also extending parallel to'the means for initiating explosion of the charges. The vertical extent of the slot produced maybecontrolled by limiting it both top and bottom by the charge case itself,-which in some embodiments may be reinforced by relatively heavy metal backup plates extending over the top and bottom of the charge. An additional control'feature'is offered in one embodiment of the invention in which the booster charge flares outwardly from a central pointin a vertical plane throughthe explosion initiating ineans iand is terminally shielded therefrom by the case. In still anviding a charge -liner flaring outwardly in'a vertical plane,

with a portion of the explosive charge extending to the.

open end of the charge both above and below the liner, as well as along the sides thereof. These elements are all disposed evenly about an axis of symmetry.-

These andother objects, advantages and features of novelty of the invention will become more apparent from thefollowing specification, taken together with the accompanying drawing's,-in which:

; Figure 1 isa perspective 'view of a shaped charge unit incorporating the. present invention;

Figure 2 is a sectional view of the embodimentta ken along the line' indicated by 2-2 in Figure l;

Figure 3 is a sectional view of the embodiments of 2 taken as indicated byline 3 3 in Figure'Z; y 1

Figure 4 is a perspective view of the liner element employed' in the embodin'ients' ofFigures-l to}?! and 5 to 7,

inclusive;

Figure 5 is a sectional view, takenin a plane similar r the. shaped charge unit of'the invention, takenin a lane Iris thus the primary object of this invention to pro-- p a vide improvements in shaped charge perforating units,

. snt ia indicated 7 7i i u 6; i

Figure 8 is a-sectio nal view of still anothenembodi- 'ment of the invention, taken a plane indicated byline Figure is a perspective view of the liner element employed with the embodiment of Figures 8 and 9. The shaped charge unit as illustrated in the drawings is designed to be mounted within a carrier body or gun sealed against the entrance of well bore fluid under "pressureby frangible ports through which the shaped charge jets may readily penetrate'to perforate the'casing and the formation surrounding the borehole. The de tails ofsuch agun have not been illutrated here since they form no part of the present invention. A suitable carrier is disclosed in copending application entitled Gun Perforator, Serial No. 138,215, filed January 12, 1950, now: Patent'No. 2,742,857, to which attention is directed for details of construction.

The shaped charge unit of the invention has been illustrated in a preferredembodiment in Figures 1-4,

inclusive. In these figures is shown a unit, generally designated as 10, formed symmetrically about its longitudinal axis in planes parallel to and normal to substantially planar top and bottom portions. The unit 10 has an outer housing 11 formed preferably of frangible ceramic material providing rigid support but reducible to very fine fragments when subjected to the shock like metal into a V-shaped portion about a rounded apex 36. The liner is then pressed into the surface of the main charge 30 by a hydraulic press or other. suitable means of applying even pressure over the surface thereof. The 'width' of. the slot maybe controlled by varying the angle of divergence of the liner walls. t

The forward end 32 of the shaped charge unit is open, I I

it being well known to those skilled. in the art that such an open space is a requisite from the formation of aproper gaseous jet discharge. The unit is intended to be so mounted that an adequate stand-off distance is provided in the gun.

It will be observed that with this construction the apex 36 of the liner 34 is parallel to the barrier 26, the booster charge 25 and the detonator means 22. These elements are all disposed symmetrically about a plane through the central axis of the shaped charge unit so that a cutting sheet of gas will be formed in such projected plane at the open end 32 when the booster chargejis 'initiated'by a detonation wavetrav eling along the detohating means 22.

7 When. the Primacord is detonated by well known ini-,

' tiating means, not shown in the figures, it detonates the adapted to receive explosion initiating or detonator means 22. The detonator means may be any readily available commercial detonating fuse such as that known, under the trademark Primacord to identify a fuse such as the RDX type having 98% cyclonite and 2%.wax.

Cycloniteis an abbreviation for cyclotrimethylenetrinh is also used to designate the PETN type, which is 100% pentaerythrite tetranitrate.-

trarnine. Primacoro A satisfactory concentration is provided by using a fuse having 50 grains of either material per foot.

f The transverse rear wall also has formed in the inner portion thereof a rectangular booster seat 24 to which the rounded groove is substantially tangent. A booster charge is disposed in seat 24 and extends adjacent the Primacord 22 between the top 12 and the bottom 14 of the housing 11. 1" V The booster seat 24 may be open in some cases along a very narrow slot to the detonator means receiving groove 21. In the more usual case it is desirable that the housing wall therebetween be made very thin, of the order of .0l- -.02 inch. to assist in retaining the booster charge in position, while yetcifering a minimum of resistance to the transmission of the detonating wave from the Primacord to the booster.

Forwardly'of the booster charge 25 is normally disposed a barrier 26, which may be a substantially cylindrical rodof steel or equivalent material extending between the top 12 and bottom '14.' In the embodiment as" shown; a barrienreceiving recess 27 is formed in the bottom 14, while a bore 29 extending through the. top 12 permits the barrier to be inserted therethrough for assembly with the rest of the case. .After the booster charge 25 hasbeen placed in seat 24, barrier 26 is inserted and the main charge chamber 30' filled with the may blesimply and" economically formed by bending a thin flat rectangular strip of aluminum,-copper orfthe booster charge 25, which in turn initiates the maincharge 31 symmetrically about the beforementioned central plane of the case and charge. The presence ofthe barrier 26 tends to slow up the progress of the shock, waves along the central axis of the device, and ,the waves passingon either side thereof will re-combine. or impinge upon one another to produce a centrally directed cutting sheet of gaseous products having. a velocity greater than would havebeen the case had the. barrier not been present. j t

In Figure 5 is shown an embodiment, otherwise similarto that in Figures 1w 4, except that the booster charge 40 has a'restricted length of contact with the Primacord 22 and flares outwardly therefrom, when considered in section through the longitudinal axis of the Primacord, to obtain a more centralizedyinitiation of the booster charge 40 and a more uniformly timed initiation of the main charge, here indicated as 41. In this embodiment, as inthat ofFigures 1 to 4, the presence of the barrier 26 is.believed to assist in causing the building up, at lest momentarily, of a high pressure zone therebehind by the explosively produced gases. The pressures there developed are substantially greater than if a barrier had not been present, due to thexrestriction of theavailable area through which the high velocity detonation waves may proceed and due to their impingement upon.

one another forward of the barrier. In addition, the buildup isrnade more' even or uniform along the full vertical extent of the charge. This is accomplished by the use of a flared booster seat terminallyshortened by an angularly extending top shoulder 42 and bottom shoulder 44. These shoulders provide angular limitations onthe'length of the seat, and act as barriers to shield the top andbottom of the booster and main charges from interference effects from the detonating wave in ad jacent portions" of the Primacord. The result is a more central initiation of the booster and main charge, so that the top and bottom portions develop their full explosionfpressures more nearly simultaneously, thereby increasing the force, effectiveness and accuracy of thepenetrating action. j j Another variation in the construction of the embodiment of Figures 1 to 4 is illustrated insection from the side in Figure .6 and from the front in Figure 7. fln

Figures 6 and 7 additional means are disclosed for limit-- ing the vertical extent of the slit produced" Here the top and

bottom housing walls

12 and 14 are reinforced by heavy metal top and bottom barrierplates 51 and 52 respectively which provide additional insurance that the linear jet will not expand in a directionpa'rallel to the length of the slit andtothe axis of the Primaco'rd' Another embodiment is shown in Figures 8, 9 and g l in which the advantages of central initiation utilized in the embodiment of Figure 5 are retained, together with an alternative method of securing a limitation of the vertical extent of the cutting sheet. It will be seen in Figure 9 that the top and

bottom shoulders

42 and 44 respectively are used to shield the main charge and the booster charge near the top.and bottom ends of the t housing, as in the embodiment of Figure 5. The vertical limitation of the cutting jet sheet is obtained, however,

by forming the liner, generally indicated as 45, with a flare toward the open end along two mutually perpendicular axes. Thus the charge case not only flares away from the apex 36 in a horizontal plane, as did that shown in Figures 4 to 7, inclusive, but alsoin a, vertical plane, as may be seen in-Figures 9 and 10. The liner has not only'side

portions

37 and 38, as does the form shown in Figures 1 to 7 inclusive, but, in addition, has a top member 46 and a bottom member 47 extending divergingly toward theopen end of the housing, but at a lesser angle than that of the side portions, as seen in Figures 9'and 10.

With this embodiment the charge body .41 has top portions 49 and bottom portions 50 extending-toward the open end of the housing with the result that, when detonated, a portion of the explosive force is directed toward the center line of the device from the top and bottom portions, and combines with the remainder of the gaseous jet-forming explosive forces to produce a plaincutting sheet which will be of lesser vertical extent than that of the open end 32 of the housing.

In certain cases, the embodiments of Figures 6 and 7 described above may be modified by omitting the top and

bottom barrier elements

51 and 52 and relying, for the formation of a cut-ting sheet of gases of the desired character, on the means such as those described above in ,connection with Figures 8-10 to produce more even detonation.

The embodiments described may also be utilized with guns or carriers of other than the sealed type by suitable adaptation. For this type of operation, usually employed in connection with so-called open hole shooting, the shaped charge units must be individually sealed at their forward ends to prevent bore hole fluids from entering the charge cavity and so much of the space forward of the charge as is required for proper jet formation. Guns or carriers for this type of operation are well known in the art, and suitablesealing means which may be utilized in connection with this invention are disclosed in the pending application of Lorrain D. Meddick entitled Debris-free Perforating Gun filed Jan. 9, 1956, wit

Serial No. 557,953,

From the above description it will be apparent that I have provided a shaped charge device for cutting linear slits in casing and into the surrounding'bore-hole formations, which slits may be accurately controlled in their width and vertical extent and may be employed to obtain a much greater area of perforation and drainage than is possible with round holes in the casing and the adjacent strata as heretofore usually employed.

It is to be understood that the foregoing is illustrative only of the best mode contemplated for accomplishing I the invention, and that the invention is not to be limited adapted to receive elongated" initiating means; an elongated initiating means in said groove; .a booster'charge disposed within said housing adjacent saidinitiating.

me'ans;a main charge disposed lwithin said housing; a

parallel to said line of intersection and located between.

said booster and said liner, the ends of said barrier being supported by said container; said booster charge being of lesser extent in the portion thereof adjacent and parallel to said initiating means than the vertical extent of said main charge, and expanding symmetrically away from saidinitiating means to intersect with said main charge; said container being arranged to form barriers between said initiating means and said expanding portion of said booster charge.

2. A shaped charge perforator unit comprising in combination: a container of frangible material having an open end and a vertically grooved end opposite thereto adapted to receive elongated initiating means; an elongated initiating means in said groove; abooster charge disposed within said housing adj acent said initiating means; a main charge disposed within said housing; a recess symmetrically formed within said rnain charge having a pair of substantially planar walls diverging outwardly toward said open end of said housing, the line of intersection of the planes of said walls being parallel to said initiating means; a metallic liner for said recess; a solid, linear barrier disposed in said explosive charge parallel to said line of intersection and located between said booster and said liner, the ends of said barrier being supported by said container, said booster charge extending closely adjacent said initiating means centrally of said container and expanding symmetrically away therefrom to intersect said main charge adjacent the upper and lower boundaries thereof; said container extending centrally inward about said expanding portion of said booster charge to-shield it partiallyfrom said initiating means.

3. A shaped charge perforator 'unit comprising in adapted to receive elongated initiating means; an elongated initiating means in said groove; a booster charge disposed within said housing adjacent said initiating means; a main charge disposed within said housing; a recess symmetrically formed within said main charge having a pair of substantially planar walls diverging outwardly toward said open end of said housing, the line of intersection of the planes of said walls being parallel to said initiating means; a metallic liner for said recess; a solid, linear barrier disposed in said, explosive charge parallel to said line of intersection and located between said booster and said liner, the ends of said barrier being supported by said container, said booster charge extending closely adjacent said initiating means centrally of said container and expanding symmetrically away therefrom to intersect said main charge adjacent the. upper and lower boundaries thereof; said container extending centrally inward between, said expanding portion of said booster charge and said initiating means to shield the extremities of said charge partially therefrom.

4. A shaped charge perforator unit comprising in combination: a container having a pair of side walls, top and bottom walls transverse to said side walls, and front and rear ends extending in planes transversely of said walls; an explosive charge disposed in said container; a cavity formed in said charge having a pair of substantially planar'walls extending transversely of the top and .bottom walls of said'container and diverging from each other symmetrically toward the front end of said con tainer; metallic liner means disposed on said pair of substantiallyplanar walls; a solid, linear barrier disposed in said explosive charge extending parallel. toqthe line. of intersection of the planes of saiddiverging planar walls, said barrier being further disposed rearwardly of the, inner end of said cavity and symmetrically with respect to the plane bisecting the dihedral angle between said diverging planar walls, the bottom wall of said container providing a recess receiving the bottom end of said barrier and the top wall of said container providing a bore extending therethrough and receiving the top end of said barrier; and means for initiating detonation of said charge rearwardly of said barrier. v

5. A shaped charge perforator unit comprising in combination; a container having a pair of side walls, top and bottom walls transverse to said side walls, and front and rear ends extending in planes transversely of said walls; an explosive charge disposed in said container; a cavity formed in said. charge having a pair of substantially planar walls extending transversely of the top and bottom walls of said container and diverging from each other symmetrically toward the front end of said container; metallic liner means disposed on said pair of substantially planar walls; a solid, linear barrier disposed in said explosive charge extending parallel to the line of intersection of the planesof said diverging planar walls, said barrier being further disposed rearwardly of the inner end of said cavity and symmetrically with respect to the plane bisecting the dihedral angle between said diverging planar walls, said barrier extending from the top Wall to the bottom wall of said container; means connecting the upper and lower ends of said barrier to the top and bottom walls, respectively, of said container; and means for initiating detonation of said charge rearwardly of said barrier.

References Cited in the file of this patent UNITED STATES PATENTS