US2925775A - Well casing perforator - Google Patents

Description

Feb. 23, 1960l D. s. MKEE WELL cAsING PERFoRAToR Filed Dec. 13, 1955 INVENTOR,

n w f/ /7 L. Tl////////////////// n :|11 7/ /7/ |.i .l MW N am w E /M IIL 1L w WELL CASING Bannon/tron DonovanaS'. McKee, Girlahoma City,"0kla., assignor, by

mes'n'e assignments; to"`Borg-lvarne'rA Goitporation, Vernon, Calif., acorporationI of Illinois `This invention relates to improvements in means for performing perforating operations in oil and` gas wells, andmore specifically to improvements inso-called perforating guns. 'v A In the processof completing an oil or gas well `after the borehole has been drilled and casing run in and cemented, perforationsaretformed through the casing and cementfat ther level of the productive strata, to permit inflow of fluid into the well. The perforations are commonly produced by bullets, or by shapedl explosive charges, `which are fired from a gun orV perforator suspended in the well. The present invention relates particularlyto perforating apparatus using the shapedcharge type ofperforating unit, andspecifically to improvements in the means employedy to initiate explosion or detonation of the shaped-charges.

It is customary practice to detonate or initiate a plurality or string of shaped-charges in rapid succession by detonating la length of Primacord or similar detonable fuse which extends through or adjacent-,to each ofv the. shaped-charges. The Primacordor other detonable means is structurally similar to an elongate cord, and for reasons of safety andconvenience, among others, is `formed withf an explosive which is not detonable by ordinary heat orvmechanical or other handling shock. Accordingly, a special means, *such as a blasting cap, has customarily been employedv to initiate detonation of the Primacord. As is Well' known, blastingcaps a-nd simi-lar detonating means are sensitive to heat, shock, and other environmental conditions, which renders their employment hazardous to personnel and equipment in their vicinity and necessitates special caution in handling. Since well casing perforat-ing guns must oftenbe serviced or reloaded in the held; the hazard presentedl by the use of blasting caps or similar sensitive detonators is accentuated by the unfavorable environmental conditions there encountered, Vand by the fact that loading might have to be performedby relatively unskilled personnel.

Efforts have been made to overcome the dangers inherent in or' presented by the use of the aforementioned sensitive detonators; and one markedly successful and relatively safe detonator means for 'detonating a Primacordo'r other safe type of shaped-charge detonator has been introduced into commercial well casing perforating operations, the detonator means comprising onlyV substances and materials quite insensitive; to thermal and mechanical shock and abrasioni.` That detonator means, as 'employed in a typical shaped-charge perforating gun, is disclosed in a co-pending applicationof Houck and Bradshaw, Serial No'. 399,032, led December 18, 1953, now US. Patent No. 2,883,931, issued April 28, 1959. The present inventionr constitutes an improvement upon the detonator means disclosed in that application'.

They detonator means disclosed in the aforementioned application comprises means to position and hold af portion of a length of Primacord or other shock-insensitive .detonable fuse in' the pathA of a projectile in the form arent 2,925,775 Patented Feb.` 23, 1960 of; a fragment or' pellet propelled at high (detonating) speed by` other relatively safe shock insensitive means. The latter means includes a chamber means in which a deagrable charge is adapted to burn under the initiating actionjof an electric fuse or wire. The combustible charge is confined' in the chamber until sufficient pressure is produced tol shear a pellet or particle out of a disc seated in one end ofthe chamber; and the pellet, when sliearedI from the disc, is propelled with great speed into detonatingf contact or impingement with the Primacord` (or with a booster charge attached to the Primacord), preferably being guided meanwhile by suitable pellet path defining or restricting means.

While the aforedescribed previously disclosed structure presents no hazard from the eld loading standpoint in so far as shock conditions are concerned, there remains the possibility of premature electrical firing of the gun prior to lowering into the well, when the electrical cable or apparatus is connected to the gun. For example, stray currents or potentials, induced by other apparatus, or accidental connection of a live electrical circuit to the gun or cable, may initiate deflagration of the bursting charge inthe chamber and shearing and ring of the pelletl prior to the time the perforator is ready to be lowered intothe casing. As is evident, premature detonation of the-seriesv off shaped-charges while the perforator is outside the well would almost inevitably result in severe injury to nearby personnel and/or apparatus. The present invention` provides means which permits the mentioned remaining hazard to be eliminated by (a) positioning the detonable fuse out4 of the path of the pellet or particle, so that even if the pellet is tired or shot it will not, by itself, detonate the fuse, and by (b) positioning a readily inserted and readily removable detonable auxiliary charge means in the path of the pellet and in proximity to the fuse, but subsequent to connection of the electrical apparatus and positioning` of the perforator above the well and otherwise ready for lowering into the casing. The auxiliary charge, as Well as the detonable fuse and any booster charge thereon, are of shock-insensitive types, by which isA herein meant of types insensitive to ordinary mechanical and heat shock. encountered in normal handling operations inf the field.

In view of the foregoing, it is a primary object of the present invention to provide a detonator system whose employment eliminates the aforementioned remaining danger of premature initiation of firing of the shaped charges in a perforating gun.

Another object of the invention is to provide a safe detonator system for use in shaped-charge perforating guns.

An additional object of the invention is the provision of a casing perforator apparatus comprising only materials insensitive to ordinary handling shock and which will not be capable of premature detonation.

A- further object of the invention is the provision of safety means for a shaped-charge casing-perforating gun.

Other objects and advantages of the present invention will become or be made evident upon consideration of the hereinafter described preferred physical embodiment of apparatus illustrating the principles of the invention, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a view in elevation of a casing perforator incorporating the principles or improvements of the present invention, with sections removed to improve the scale -of the drawings;

Figure` 2 is a sectional View in elevation of part of the structure depicted in Figure 1, showing the disposition of apparatus in a section of a perforator, with parts broken' away;

Figure 3 is a detail view, partly in section, of a plug member employed in closing ports in a perforator'body;

only one such section may be employed, or two or more, l

as conditions and requirements of the vperforating operation dictate. Each of sections 12V above` the lowermost thereof isv provided with a substitute joint or sub 14 at its lower end, vthe bull plug 13 serving in lieu of a sub for the lowermost of the sections. The upper part of y body section 11 is provided with an upstanding cable 16 which comprises one or more insulated electrical conductors 17 whose purpose is to supply the suspended apparatus electrical current in a conventional manner.

Each perforator section 12v is provided with a plurality of ltapped and counterbored apertures 18' (see Figure 2) each ofy which is provided with a gasketed aperture-closing and element-supporting plug 19 readily removable therefrom by conventional driver means. The apertures 18 may be distributed around the periphery and along the length of the perforator sections in any desired pattern or patterns. Each plug 19 is provided with an internal tapered recess 20 arranged to receive and seat alternatively the frusto-conical end of ashapedcharge aligner 21 forming part of an explosive-containing shaped-charge unit 22, or a means hereinafter described in detail. Diametrally opposite each aperture 18 is a respective recess 23 formed in the interior wall of the perforator body section, the recess being adapted to alternatively receive a tubular elementhereinafter described or the cylindrical base 24 of a shaped-charge unit 22. Units 22 may be of conventional commercial form and may be of the type disclosed in the application for patent to Lindsay et al., Serial No. 106,567 tiled July 25, 1949, now U.S. Patent No. 2,707,917, issued May A length of relatively safe and shock-insensitive detonable fuse 25 (such as, for example, Primacord 50 grain PETN, manufactured by Ensign-Bickford Company) is arranged in each perforator section 12 for detonating the shaped-charge units 22 in the respective section, the fuse extending through holes formed in the bases 24 of units 22, as indicated in the central section of Figure 2. One end of the detonable fusey 25 (or an auxiliary ycharge secured thereon) is fitted in a transverse aperture formed adjacent one end of a frangible tube 28 mounted transversely in the perforator section. Tube 28 is mounted in one of the endmost recesses 23 where it is secured by a respective plug 19 in a manner evident from consideration of the upper portion of Figure 2. The secured end of the Primacord 25 or, preferably and as shown, a detonable but handling-shock insensitive auxiliary charge 29 crimped to the end of the detonable fuse, is secured in the transverse aperture of tube 28 by suitable means such as an elastic band or grommet 30 secured in the aperture as indicated'in Figures 2 and 4. Tube 28, which may be formed of phenolic resin or other frangible material, is preferably so formed and dimensioned as to t securely in recess 23 and be tightly engaged by the tapered interior surface 20 of the associated plug 19. Auxiliary charge 29 may be in the form of a du Pont P-3 metal-enclosed compressed charge of RDX type explosive of about eleven grains weight and is preferaoly, but not necessarily, employed to insure detonation of detonable fuse 25 in a manner hereinafter more fully explained. Mounted in the upper end of a section 12 of the perforator and in substantially axial' alignment 4 therewith, is a detonator device 32 seated and held in the perforator in a manner and mode indicated in the upper portion of Figure 2. 'Detonator device 32, which may be like or similar to thecorresponding device in the aforementioned application of Houck et al., comprises 'a main chambered cylinder 33 having a threaded bore into which is turned a barrel or guide member 34 adapted to be firmly seated against the inner end wall of the threaded portion of the bore. Mounted in successive reduced diameter bores formed in cylinder `33 are a shaped shear disc 35, a fiber cylinder or aligner 36, and an electrically fired deflagrable charge 37 mounted on an electrically operated igniter 38. The igniter comprises an insulated terminal pin 39 which extends through but out of contact with the upper portion of cylinder 33. The detonator components are so made and arranged that upon application of a suitable electric potential to pin 39 the charge contained within cylinder 36 is defiagrated and produces su'icient pressure to cause a slug or fragment to be sheared or broken from disc 35 and propelled along the restricted path provided in part by barrel 34, at high velocity. YIn the structure disclosed in the mentioned Houck and Bradshaw application, one end of a detonable fuse, or an auxiliary charge secured thereto, was positioned in the path of the fragment, to be detonated by the latter upon firing of the defiagrable charge. It is evident that if a potential is inadvertently or accidentally applied to the igniter pin prior to lowering of the gun into a well, serious damage and injury could be caused, since in that event the perforating units would be fired without protection for personnel and property.

In accordance with the present invention a detonable fuse means in the form, for example, of a length of Primacord or similar shock-insensitive fuse. with or without an auxiliary or booster charge, is positioned out of the path of the fragment. whereby premature ignition of the deflagrable charge will not, in the absence of other means hereinafter described, result in detonation of the fuse means. Rather, premature tiring of the combustible charge 37 will only result in disruption of the shear disc and harmless firing of a fragment along a path in the interior of the perforator body. According to the principles of the invention. a readily inserted second auxiliary detonable charge is placed in the path of the fragment, but only after all electrical connections have been made and the perforating gun is otherwise ready to be lowered into the well. This second auxiliary charge is insensitive to ordinary shocks and is so positioned as to be in the path of the fragment, to be detonated thereby; and is also positioned in contact or close proximity with the detonable fuse means. Thus, when inserted in the perforator just prior to lowering of the latter into the well, the second auxiliary charge is adapted, when detonated by the fired fragment, to detonate the fuse means due to its close proximity to the latter means. Prior to this arming of the perforator by insertion of the second auxiliary charge, the entire device and all its components are quite safe against all handling hazards in so far as personnel and nearby apparatus are concerned.

In accordance with the considerations hereinbefore expressed, a second auxiliary charge 40 is adapted to be inserted in tube 28 and held in proper position therein by means of a compression spring 41, just prior to the perforator being lowered into the casing. Thus the perforator, including all of the explosive elements with the exception of auxiliary charge 40, may be suspended ready for lowering into the casing, and the electrical connections made, without danger of the shaped-charges or the detonable fuse being accidentally prematurely exploded. Immediately prior to lowering of the perforator into the casing the appropriate plug 19 is removed from the perforator body, an auxiliary charge 40 and its cornpression spring 41 inserted in the tube 28, and plug 19 replaced, to effectively arm the perforator before nal lowering operations are effected. Thereafter, passage of an electric current into terminal pin' 39 in the manner explained inthe aforementioned Houck andBr'adshaw application initiates deagr'ation of charge 37 which in turn shears a pellet or fragment from shear disc 35 and propels it into detonating impingement with the secondary auxiliary charge 40, detonating the latter, and initiating detonation of the detonable fuse means which in this case includes primary auxiliary charge 29. The latter is elective to detonate the detonable fuse 25 with great degree of certainty and thus initiate firing of the shapedcharges through which fuse 25 is trained. The auxiliary charge 40 may, for example, be a duPont type P-lO auxiliary charge comprising, for example, approximately 45-49 grains of RDX explosive in a metal container. The two auxiliary charges 29 and 40, being insensitive to handling shock, permit complete safety to be attained with the operation of the perforator. Also, eld reloading or servicing of a perforator may be carried on by relatively unskilled labor without danger to personnel or apparatus in the vicinity of the casing. Further, loaded but unarmed perforators may be transported without exercise of the degree of caution heretofore necessary.

In this specication and the appended claims, the terms shock-insensitive and the like are employed as meaning insensitive to ordinary thermal and mechanical shock to which well casing perforating guns and components may be subjected during normal handling procedures and including shock of such degree as would be suicient to explode ordinary blasting caps and like shock-sensitive explosive devices, but excluding shock of the degree or intensity necessary to detonate, for example, RDX explosive. By the term initiate is meant the igniting of a deagrable charge, the exploding of an explosive charge, or the detonation of a detonable charge, as the case may be.

As may be evident from consideration of the aforementioned copending application of Houck and Bradshaw, and as is known in the art, it is immaterial in so far as the principles of the present invention are concerned, whether the detonator device 32 be arranged in the perforator section so as to fire from the bottom, or from the top, of the section. In case a plurality of perforator sections are employed, one or more electric ignition wires 17 may be coursed through suitable apertures formed through the detonator devices as indicated in the upper portion of Figure 2, or in the manner and by means as disclosed in the Houck et al. application mentioned, whereby each perforator section and each detonator device may be supplied with ignition energy.

Further, it will be evident from consideration of the preceding disclosure that modifications in form and structure of the disclosed preferred embodiment of apparatus according to the invention will occur to those skilled in the art; and accordingly it is not desired to be limited to the exact details of the disclosed embodiment of apparatus, but what is claimed is:

1. A well casing perforator comprising in combination: a perforator body; casing-perforating units in said body; a detonator device positioned in said body, constructed and arranged to propel a projectile along a given path in said body; shock-insensitive detonable fuse means positioned in said body out of said path and arranged to initiate said casing-perlorating units; arming means for said fuse means including a shock-insensitive auxiliary charge detonable by impact of said projectile and capable upon detonation of detonating said fuse means; means providing a path for the translation of said auxiliary charge from a rst position outside the path of said projectile to a second position in the path of said projectile with a portion of said auxiliary charge in detonating proximity to said fuse means; and means retaining said auxiliary charge in said second position.

2. A Well casing perforator comprising in combination: means including casing-perforating units arranged to be initiated by detonation of a detonable fuse means; a detonable fuse means; means including a projectile and a projectile propellant charge and an igniter' for said charge; means to guide said projectile along a restrictedpath; means positioning said detonable fuse means out of said path; means including a shock-insensitive auxiliary charge detonable by impact of said projectile and capable upon detonation of detonating said fuse means; means providing a path for the translation of said auxiliary charge from a first position outside the path of said projectile to a second position in the path of said projectile with a portion of said auxiliary charge in detonating proximity to said fuse means; and means retaining said auxiliary charge in said second position.

3. A well casing perforator comprising in combination: a perforator body; a detonator device positioned in said body and including a shock-insensitlve deagrating charge and an igniter therefor, a projectile to be propelled by said deflagrating charge, and means to guide the projectile along a restricted path; a shock-insensitive detonable fuse means and means for positioning said detonable fuse means out of said path; arming means for said fuse means including a shock-insensitive auxiliary charge detonable by impact of said projectile and capable upon detonation of detonating said fuse means; means providing a path for the translation of said auxiliary charge from a irst position outside the path of said pro- I and a plurality of explosive casing perforating units therein arranged to be initiated by detonation of a detonable fuse means, in combination with said body and units: a detonable fuse means in said body arranged to detonate said perforating units and positioned out of a restricted path therein; a projectile and means in -the body to propel the projectile along said path at-high speed; auxiliary detonable means positioned in said tubular body with a portion thereof in said restricted path and adapted to be detonated by said projectile and another portion thereof in close proximity to said fuse means and adapted to detonate the latter; support means in said tubular body supporting said auxiliary detona-ble means; and means including aperture means in the wall of said tubular body through which said auxiliary detonable means is inserted into said tubular body and into said support means.

5. A well casing perforator comprising, in combination: a tubular perforator body section having a plurality of lateral apertures therein and internal recesses each diametrally opposite a respective lateral aperture; a plurality of shock-insensitive detonable shaped-charge perforating units, each disposed at a respective one of said recesses; a plurality of plugs, one for each of said apertures; shock-insensitive detonable fuse means arranged to detonate said perforating units upon being detonated; supporting means extending transversely of said body section and mounted in one of said apertures and its respective recess, and arranged to support an end of said fuse means in a predetermined location; shock-insensitive means in said body section including a projectile and means for firing the projectile along a path outside said location and intersecting said supporting means; and shock-insensitive detonable auxiliary charge means, insertable through the aperture in which said supporting means is mounted, disposed in said supporting means in said path and in detonating proximity to said end of said fuse means, whereby detonation of said fuse means and said perforating units may be initiated only by insertion of said auxiliary charge means in said supporting means prior to tiring of said projectile along Said path.

(References on following page) UNITED STATES PATENTS 1,322,083 Barlow NOV. 18, 1919 2,265,982 Bolton Dec. 16, 1941 2,452,072 Schatz Oct. 26, 1948 55 Muskat et al. Jan. 10, 1950 Martin NOV. 21, 1950 Morris Nov. 11, 1952 Sweetman Feb. 24, 1953 Turechk et al. Dec. 15, 1953

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