US2742857A - Gun perforators - Google Patents

Description

GUN PERFORATORS George F. Turechek, Los Angeles, Calif., assignor, by

mesne assignments, to Lane-Wells Company, Los Angeles, Califl, a corporation of California Application January 12, 1950, Serial No. 138,215

14 Claims. (Cl. 102-429) This invention relates to gun perforators for use in deep wells to bring in the latter by perforating the well casings and the surrounding formations. More particularly it has to do with methods and apparatus for mounting explosive charges in gun bodies and in protecting the latter against damage and deformation from the firing of the same. It is particularly adapted for use with high explosive shaped charges of the type disclosed in the copending United States application of Will H. Lindsay, J r. and Robert A. Phillips, Serial No. 106,567, filed July 25, 1949,.now Patent No. 2,707,917, dated May 10, 1955.

Heretofore in the use of shaped detonating charges of the cone type in which the charge is contained in a casing or shell of plastic, such as Bakelite, Lucite, cellulose acetate or other such material, it has been the practice to exclude well fluid from the interior of the gun body by sealing the lateral ports through which the blasts or jets from the shaped charges are projected. This has resulted in many instances in leaving debris from sealing discs and the like in the well bore or wedged between gun body and well casing. Moreover, after several firings, the gun ports may become enlarged and distorted, the sealing discs no longer make a fluid tight fit and more and more repairs are required to keep the gun body in condition for further use. Moreover, it has been found that serious damage to the interior of the gun tube has been produced due to the violent impinging thereon of particles of the plastic casing or shell of the charges when the charges are fired.

It is a principal object of the present invention to avoid entirely, or greatly, to minimize the difficulties and disadvantages of prior methods of using shaped charge in gun perforators.

Another object is to devise ways and means to utilize shaped charges without sealing the gun body as a whole against entrance of well fluid.

Another object is to eliminate the need for repair of gun ports.

Another object is to protect the interior of the gun body against the impinging action of particles of the plastic or envelope of the detonating charges.

Another object is to distribute the pressure of the detonating charges over a greater area and to cushion the same in a manner to prevent localized damage or rupture of the gun body.

Still another object is to prevent displacement of the detonating charge and deforming of the perforating jet therefrom by reason of interference therewith of the explosive wave or surge in the gun body caused by adjacent shaped charges and by the detonation cord which fires the detonating charges.

Other objects, advantages and features of novelty will be apparent from the detailed description which follows:

atent According to the present invention each detonating charge is mounted in an individual fluid tight container which is insertable within the axial bore of the gun body and is rigidly centered and supported in line with a gun port. The container may be positioned by a projection or boss whichlseats in the gun port and may be held in place there by a set screw engaging the container at a point opposite the projection or boss. Suitable means within the container fixed the position of the detonating charge so that its firing end is directed to and centered upon the projection or boss seated in the gun port while the priming end of the charge is adjacent the set screw. The portion of the wall of the container which is engaged by the set screw is reduced in thickness to a relatively thin web by a groove in which a Primacord may be seated to detonate the charge, and the wall of the projection or boss is also of reduced thickness to facilitate passage of the blast or jet therethrough when the charge is detonated. By preference the containers are constructed of brittle and readily frangible material and since they are fluid-tight the interior of the gun body around the containers is permitted to fill with well fluid which serves to cushion and to equalize pressures within the gun body at the time of detonation. Moreover, the inner walls of the gun body are protected from the full effect of blast of the detonating charges by the frangible containers and by the intervening body of well fluid.

In order to illustrate the invention and the manner of its use, preferred embodiments thereof are shown in the accompanying drawings, in which:

Figure l is an elevational view, partly in longitudinal section of a gun perforator ready to be lowered into a well bore to perforate the casing thereof; I

Figure 2 is a longitudinal sectional view, on an enlarged scale, through one of the fluid-tight containers shown in Figure 1, parts of adjacent containers being shown in elevation, the section being on the line 22 of Figure 1;

Figure 3 is a cross-sectional view taken substantially on line 33 of Figure 2, certain parts being shown in plan view;

Figure 4 is a partial longitudinal sectional view of a gun body showing a modified form of fluid-tight container; and

Figure 5 is a cross-sectional view on an enlarged scale taken on line 5-5 of Figure 4, the shaped charge unit being shown in plan view.

Figure 1 shows a perforating gun according to the present invention, fully loaded and ready to be lowered into a well to perforate the casing thereof and the surrounding formation. The gun comprises an elongated hollow or tubular gun body 6 having a series of longitudinally spaced laterally directed firing ports 7 through the walls thereof, such ports being arranged spirally of the gun body as illustrated or in any other desired arrangement. Diametrically opposite each of the firing ports 7 is a smaller threaded port 8. The lower end of gun body 6 is closed by a plug 9 and its upper end is closed by a cable head 10 to which is attached a suspension conductor cable 11 containing an insulated conductor wire. An electrical conductor 12, attached at the top within the cable head to the conductor wire in the conductor cable, extends from within the cable head 10 to a blasting cap 13 from which a detonating cord, such as, for example, Primacord 14 leads to a series of fluid tight containers 15. These fluid tight containers are disposed in superposed relation with respect to one another within the axial bore of a gun body 6, each container 15 supporting therein a shaped detonatng charge C as best shown in Figures 2 and 3, in position to be fired through an adjacent gun port 7.

Figures 2 and 3 show the details of a container 15 which is constructed preferably of brittle or highly frangible material. Cast iron is a preferred material but glass, glazed ceramic and some forms of die casting pot metal may also be utilized. The container 15 as illustrated is cup-shaped and is provided with a removable top cover 15a which makes a fluid tight seal by the provision of an O ring 16 of rubber or other suitable resilient material which seats in anannulargroove 15b in the cover. On its interior, container 15 is formed with diametrically op posed recesses for the support of its shaped charge unit C, the rear or primingend ofwhich seats in" recess 17', as indicated, while its forward or firing end is supported by a'retainer ring'memb'er 19 seated in recess 18; :The retainer ring member 19 is provided with a plurality of flared spring fingers 19a which extend'into and engage the inner surface of an annular grooveC (Figure 3) formed in the forward end of the shell of the shaped charge C; Spring retainer 19 may be formed from cylindrical spring s'tockby'slitting'it lengthwise 'rnaking a plurality'of fingers IQzrand then bending and flaring the fingers 19a to the extent shown. The shape'dcharge unit C is mounted in container 15 by placing spring retainer 19 in the forward end' of the charge unit and then pressing the latter inwardlysufiiciently to permit charge C and retainer 19 to be inserted'into the open end of container 15," and moving the charge downwardly until charge and retainer snap into recess'lTand 18 respectively.

Container 15 is formed withexternal projections or bosses 27'and 28, boss 28 being of asize to fit and seat within'one of the lateral firing ports 7 of gun body 6,

Whereupon rearward. boss 27 is engaged by diametrically opposite plug or set screw 29 which is screwed into the threaded port 8 opposite the firing port to secure the container rigidly in place.- Plug 29 also serves to retain Primacord 14 seated in a groove 30, provided therefor'in boss 27, this groove also serving to reduce the thickness of the wall of container 15 between Primacord 14 and the rear end of charge C to a relatively thin web 31. Boss 28 on the forward side of the container 15 is also reduced in thickness, internally at 28a and externally at 28b, to weaken it at its central portion and thereby to forma relatively thin web 32 to be broken through by a blast or jet from the shaped charge unit C which is thus directed centrally through gun port 7. Small guide bosses 33niay be formed on the exterior of containers 15 to assistin properly positioning and centering the containers. within the gun 'body 6 during the loading.

In the alternative embodiment of the invention shown in Figures. 4 and 5, the. fluid tightcontainers are approximately spherical in shape when assembled asv shown at 35, 35a and occupy less space within the gunbody. 6. than thecylindrical containers 15, 15a shown in Figuresfl-S. Each spherical container is made up of a,rearward body part 35 and a forward 'bodypart 35a, both. parts, being hemispherical in shape, with the rearward. part 35a. partially telescoping over the forward part 35. toform an overlapping fiuid-tight seal at the telescoped joint. where an [ring sealing 36 is seated in a groove 35b impart-35, In this form of the invention shaped charge unit C ismounted between and within. parts 35 and 35a of the container without the intermediary ofv any retainer memberl The front or firing end of the shaped charge'unit C is received in a large circular recess formed by an inwardly projecting annular ridge 38 spacing and-centering the charge at the proper distance from projection or boss 48 on part 35, which, in turn, seats inv gun port-7. The small rear or priming end of charge unit C is received in a cylindircal recess 37 formed at boss 47 which in this instance is on rear part 35a. and projects inwardly instead of outwardly as in the form of invention. herein first described. Set screw 29in threaded opening 8 in the gun body, engages cover part 35a to. securely'hold container 35, 35ain place. In this instance set screw29 seats in a recess 47a which opens into groove 50 provided for Primacord 14, thelatterbeing separated from charge C merely .by the relatively thin wall or web 51 as in thefirst form of the. invention. Boss 48 is also'reduced in thickness, internally at 48a and externally at 48b to weaken it at its central portion formingthe relatively thin web 52. whichwill give way to the blast or-jet from charge C and will direct the same centrallythrgough Figures-4 and 5-external--guide bosses such as 33 shown in Figure 3 are not required since the overlap of cover part 35a at the joint between parts 35 and 35a serves this general purpose. i

In loading the gun perforator, a series of containers 15, 15a or 35, 35a are first assembled with a detonating charge C properly positioned and mounted in each. The end of a detonating cord or Primacord 14-issecured in groove or 5001? the :first of the containersto, be=introduced: into the gun body, and then in the; grooves of the otherrcontainers at proper intervals. Thezstring of containers is: then inserted in the open end of gun body 6 in proper relative position to line up projections or bosses 28 or 48 with thegun ports 7. By fishing through the, lowest gun port 7 and its opposite threaded port 8 the bottom container 15, 15a or 35, a, is positioned so as to seat its boss 28 or 48 in the gun port 7 whereupon screw plug 29 is threaded into port 8 and set up against boss '27o'r '47 over'groove 'Wor SU'cOntaining Primacord 14, thereby securely wedgingand holding the container in firing position within: the gunbody. The othercontainers of the string are mountedand secured in placeprogressively in the same, manner. "Primacord 1 is then attached to blastingcap 1'3'as' shown'inFigure 1, cable head '10 is attached to gun body fiandthe'assernblcd' gun perforator is ready. to be'lowere'd'into a well. During lowering'well fluid will seepinto the, bore of gun body 6- through gun ports 7 and around bo'sses 28 or- 48;Howeventoinsurethat the gun body 6 isfilled withiwell fluid overand around all the fluid tight containers'therein, a lower fluid entrance port and an upper vent port 61- (Figure 1) may beprovided; in gun body 6.

When the gun perforator is at the desired level in the well, electrical cable 12 will be'energized to fire blasting cap 13 anddetonatePrimacord 14 whichfwill; blow through webs 31 or 51 substantially" simultaneously to detonate all charges C. The blasts. or' jets fromthe shapedcharge units will breakthroughthe webs 32 or 52 ofbosses 28- or 48 to issue; through gun ports 7 and perforate adjacent casing anditormations'f Frang'ible containersv 15; 15a or 35, '35awill intercept" the flying bits of material from the envelopes'encasing the; shaped charge unitsiand together with the well fluid surrounding the containers will" absorb "and distribute the expanding gases and pressures from the explosions thusjprotecting the'gunjbody against local rupture and deformatiomand greatly prolonging itsiusefulilifef The debris fromthe containersrem'ains within the gun body and is emptied outwhen the gun perforator is hoisted to the surface. After cleaning out, thegun body is ready "to be reloaded for further use.

' From the above'it will be apparent that the present invention marks an important and highly practical ad'- vance in the" art of perforating well casings and' formations by the shaped charge method. By the use ofthe individual fluid- tight containers 15, 15a of 35", 35a for the detonating charges, as hereinbefore described, it. is no longer necessary to, exclude'well fluid from the. gun body. In fact, its" admission serves to cushion and.v to equalize the explosive forces-and pressures. within the gun bodythus minimizing damage thereto; The spherical form of container shown in Figures. 4 ands occupies less SpaceIthanthe cylindrical form shown in Fizurcs 1-=3 and so permits a larger body of well fluid. within the gun body. Deformation and jetcutting of, thegun ports 7 do not interfere with the use of the fluid, tight containers, with the result that expensivefand.timeconsurning repairs are infrequent. The Pritnacord .isfseparated frorneach explosive charge butis clam'ped'tightly against the wall of, the container by the heavy sets'crew or plug 29 which secures the container. rigidly inplace, Hy thismeans detonationofi-the :charge. is.,insure,dand displacing, or. misdirecting of the jet. by? reason 0f? socalled firiterference37. by. the explosive wave; resulting from the-cord detonation ol'f'adimtshmdzichm While the invention has been herein disclosed in what i are now considered to be preferredforms, it is to be understood that the invention is not limited to the specific details thereof but covers all changes, modifications and adaptations within the scope of the appended claims.

What is claimed is:

1. In apparatus for perforating well casings, the combination comprising: a hollow body having a central bore and a lateral port extending from said bore; a separate fluid tight container for insertion within" said bore of said body, said container having a separate shaped charge unit therein directed toward a relatively thin walled portion of said container; and means for supporting said container within the bore of said body with said thin walled portion and said shaped charge unit centered upon and directed toward said port sov that the charge of said shaped charge unit when detonated willfire through said relatively thin walled portion of said container and through said port. a

2. In a perforator for Well casings, the combination comprising: an elongated hollow body having lateral ports and a fluid inlet port through the walls thereof; a series of separate, closed, fluid-tight containers within said hollow body, each container having an outwardly projecting portion with a transverse relatively thin walled portion to extend within one of the lateral ports of said body; means for securing each container in place within said body with its projecting portion centered in one of said ports; a shaped charge unit in each of said containers; and means for supporting and maintaining each said charge shaped unit directed toward the said relatively thin walled portion of said projecting portion of its said container.

3. In a perforator for well casings, the combination comprising: an elongated hollow body having spaced lateral ports through the walls thereof and threaded openings through said walls opposite said ports; a series of separate, fluid-tight containers within said hollow body, each container having an outwardly projecting portion with a relatively thin transverse walled portion to extend and seat within one of the lateral ports of said body; a screw plug in each of the said threaded openings opposite each of said ports for engaging said containers to secure them in place; a notch in the exterior of the wall of each container adjacent the point of engagement therewith of said plug to receive a continuing portion of a detonating cord and to weaken the wall of said container at said point; a shaped charge unit in each container; and means for mounting and maintaining each said charge unit between and in axial alignment with the said notched and thin walled portions of the wall of its container and with the shaped charge therein directed toward the port in which the said projecting portion thereof is seated.

4. In a perforator for well casings, the combination comprising: an elongated hollow body having longitudinally spaced, laterally directed ports through the walls thereof and a threaded opening through said walls opposite each of said ports; a series of separate, fluid-tight containers within said hollow body, each container having an outwardly projecting portion with a weakened transverse wall to extend and seat within one of the said ports of said body; a screw plug in each of the said threaded openings opposite each of said ports for engaging one of said containers to secure it in place; a notch in the exterior of the walls of each container adjacent the point of engagement therewith of said plug to receive a detonating cord and to weaken the wall of said container at said point; a separate shaped charge unit in each of said containers and having a jet end; and a resilient retainer in each of said containers engaging the jet end of said shaped charge unit and the inside of the container to position the shaped charge unit with the jet end thereof in alignment with said port in which said projecting por- 8 tion is seated and to hold the opposite end of said charge unit securely against the inside surface thereof opposite said notched portion of said container.

5. In combination: an elongated hollow body having longitudinally spaced, laterally directed ports through the walls thereof and a threaded opening through said wall opposite each of said ports; fluid-tight containers within said hollow body in superposition, each of said containers having external, outwardly protruding bosses on opposite sides thereof, one of said bosses of each said container extending into one of said ports and the other of said bosses being engaged by a screw plug in one of the said threaded openings opposite said port, the walls of each said container being weakened at both said bosses; a separate shaped charge unit in each of said containers; means supporting said shaped charge unit in each of said containers with the forward jet end of the charge unit directed toward the port into which one of the said bosses thereof extends; and detonating means for each of said charge units comprising a detonating cord held against the exterior of the opposite weakened boss of each of said containers by one of said screw plugs.

6. A fluid tight container of frangible material for insertion and mounting within the bore of a tubular perforator body, said container having an external projection to seat in a lateral port in the perforator body wall and said projection having a weakened transverse wall portion; an external recess for a detonating cord in the wall of said container diametrically opposite said projection; and means within said container for mounting and centering a shaped charge unit therein so that when fired its jet will be directed through the said weakened wall portion of said projection and out through the said lateral port in the perforator body.

7. A fluid tight container of frangible material for insertion and mounting within the bore of a tubular perforator body, said container comprising: a cup and a cover therefor; bosses extending from diametrically opposite parts of said cup; a notch in one of said bosses to receive a detonating cord and to form a thin section or web in the wall of said cup, the wall of the other boss being also weakened by thinning; and means within said cup for mounting a shaped charge unit between said bosses and for maintaining said charge unit centered so that when detonated by said cord its jet will be directed through the thinned section of said other boss.

8. A fluid tight container of frangible material for insertion and mounting within the bore of a hollow perforater body, said container comprising: a cup and a cover therefor; bosses extending from diametrically opposite parts of said cup; a notch in one of said bosses to receive a detonating cord and to form a thin section or web in the wall of said cup, the wall of the other boss being also weakened by thinning; and means including a retainer for mounting a shaped detonating charge unit within said cup with the base of the charge unit against the inside surface thereof opposite the thin section or web of the said notched boss for the detonating cord and with the jet end of the charge centered and directed toward the weakened wall of said other boss.

9. A container for a detonating charge to be mounted within the bore of a hollow perforator body comprising: a container formed of hemispherical parts of frangible material which interfit with a fluid tight joint, one of said parts having an exterior projection to seat in a lateral port in the wall of the perforator body and the other part having an external socket diametrically opposite said projection, said other part having a notch through and forming an inward extension of said socket to receive a detonating cord and to reduce the thickness of the wall of said other part to a relatively thin web, said projection also being reduced in thickness to form a weakened central portion; and means on both said parts to engage and support a shaped detonating charge unit within said container with the base of the charge against the inside surface of the ing and centering the jet endofi said charg e.

12. Structureas set forthin claim 6 wherein the Wall, of said go ntainer isformedw-itha pair of internalrecessesu v; for respectiyely .seatingthe opposite ends of saidpharge g unitand,,alignsaidhcharge unit with saidprojection, 15

I 13. Structure asset forth in, claim 6 wherein idiametri; callyhoppositeninternal .wall. portions of said container are each formed with an internalvrrecessrfor respectively seatingrthe rear end-of said shaped chargetunit and s.up-, porting means ,for the jetend thereof. 20 14. In apparatus for perforating, ,well ,casings, the combination comprising: an elongated hollow -..,body adapted to-be lowered into arwell borehole, said body-rhaving a, plurality of lateral ports and a fluid inlet extend; ing through .the wall thereof;- a plurality of separate,.,- 5 closed, fluid-tight containers within. said.. body, said con-r, tainers each having a separate shaped charge unitfixed 1 portsn v I formed withaninternal recess to seata means for, mount; 10 i "Rfcrcnces cited in't'he ,file of this patent UNI EDELSTAIE S -PATENTS 1 BfiRtEFER-ENCESu Article meld? Gash"; 'Pfi With Shaped plosiYqCha e by R; McLemore, published i The" -V 011 $11Ki fisljloum 1946.

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