US2766690A - System for setting off explosive charges - Google Patents

Description

Oct. 16, 1956 M. P. Ll-:BOURG 2,766,690

SYSTEM FOR SETTING OFF EXPLOSIVE CHARGES Filed Nov. 29, 1951 INVENTQR ATTORNEY5 ,f Lair United States Patent SYSTEM` FOR SETTING OFF EXPLOSI'VE CHARGES Maurice P. Lebourg, Houston, Tex., assignor, by mesne assignments, to Borg-Warner Corporation, Chicago, lll., a corporation of Illinois Application November 29, 1951Serial-'Noty 258,949'

2 Claims. (Cl. 10i- 20) This invention` relates to systems for settingot; explosive charges and more particularly to systems whereby a plurality of explosive charges may-be setfoff in succession.

Explosive charges such, for example, as a string of shaped explosive charge units adapted to be detonated in succession in a borehole, are. conventionally detonated by means of a pn'macord fuse which is threaded through each unit in series so that as the detonation wave travels along its length to a point within each unit, theexpl'osive charge therein4 will be detonated. The primacord fuse is brought into the units by means of throughrbores disposed near the rearward ends of the explosive? charges and having cylindrical walls to prevent the escape of explosive material therefrom. I'n order to insure el'ective detonation of the explosive charges by the. detonation wave from the primacordA fuse, these. cylindrical walls must be made very thin. A shaped explosive charge assembly embodying this construction is shown in. Figure 9B of the. pending U. S. application. Serial No. 123,003.

The construction described briefly above has been found effective Where theV entire stringy of explosive charge units is shielded or encased ina pressure-resistanty housing. to keep out the borehole liquid. In'perforating oil wells, however, it is often desirableA and sometimes necessary that the apparatus be expendable and so constituted that the energy developed upon detonation of the charges breaks it into small pieces whichY may beallowed to drop harmlessly to the bottom of the well. In apparatus of this type, the shaped charge containersand the primacord fuse are all exposed to the pressure in the boreholey which may bel very highl atthe depths at which well perforating operations are conducted. It hasi been found'v that this pressure may bel sufficiently highto break down the thin cylindrical walls which define the through-bores for receiving the primacord fuse, thereby permitting: borehole liquids to enter the` shaped charge container with theresult that the action of the shaped chargeis seriously if not whollyimpaired..

One method of preventing the admission of borehole liquids into the individual shaped charge containers isto strengthen` the thin cylindrical walls. However', the strengthening of these walls shields the explosive charge from the detonation wave of the primacord fuse and tends toV prevent effectivedetonation of the explosive charge.

It. is, therefore, an object of this invention to provide an improved system for tiring a plurality of explosive charges in succession.

Itis another object of the invention` to provide means for setting ott a series of explosive charges which` are housed in individual containers adapted to: withstand high external pressures.

It isianother object of the invention toprovide a system for setting off a series of explosive' charges successively without the use'l of physical connecting meansV between the charges prior to detonation;

- It is another object' of the invention to provide means lrice for setting oi an explosive chargeY without the` use of aprimacord fuse.

The above and other features and objects of the invention maybe attained by providing an explosive charge unit comprising a container havingwalls sealing it against external media under pressure. Within each container there is provided a' first chamber for receiving. a main explosive charge, a second chamber communicating with the 'rstl chamber for receiving meansV such as a. booster charge. for settingv off the main explosive charge, andla third, chamber communicating, with the other chambers for receiving an auxiliary shaped explosive charge adapted to be set ot with the main explosive charge.

A. series or string of. these units may be stacked in a supporting frame with the. auxiliary; shaped charge inthe first unit. arranged to direct thev explosive jet,v which will emanate therefrom upon detonation, toward the chamber containing the means for. setting on` the main. explosive charge inthe next unit. Thus, when theauxiliary shaped charge of the rst unit is set ot, an explosive jetwillbe produced. which will penetrate the container of the second unit to set,- oif the explosive charges therein. With each suncessiveunit arranged to be set` olf by the explosive jet from the auxiliary shaped charge of, the preceding unit, all ofthe units will be set ofl in rapid succession without the use of physical connections between the units'prior to detonation.

Itwill be understood that the: explosiveV jet from each of the auxiliary shaped explosive charges is suflciently potent tofpenetrate the strong container wallwhich Seals the means for setting olf theexplosive charges in the next or adjacent unit. Also, the nature of the explosive jet formed by shaped explosive chargesy is such that Wall means of considerable strength maybe used to seal the charges themselves against the admission of external media under pressure without destroying the effectiveness of the jet. As a result the external container'wallsj of each unit may be made strong throughout.

In order to set otf the explosive charges. of the first unit of the series, a pressure resistant; container may be mounted in the supporting frame adjacent the. first unit. This container may bei provided with a startingA shaped explosive charge having its jet: axis directed toward the means for setting off the first unit; Detonation of the starting shaped explosive charge may be effected by any suitable means such as a short primacord fuse attached to a blasting cap which is in turn adapted to be set oi by any suitable means such as an electric current derived through electrical conducting means running to a remote point, such as the surface of the earth, for example.

The invention may be better understoodI from the description of a preferred form thereof by the following specication which is'r taken in conjunction with the. draw mg.

The drawing comprises a single figure which is a fragmentary View in longitudinal section of a portion of a frame carrying a string of explo-sive charge units constructed and arranged in accordance with the invention. For purposes of illustration the sectional views of the respective explosive charge units have been developed so that where possible the componentl parts of each of the units appear in` full lateral projection.

Referring' to the drawing, the invention is `shown as cin-bodied 'in .an :explosive lcharge assembly including a frame 1 (partially illustrated) yarranged toY support a string of explosive `charge units 2 1, 2 2, 2-3`, etc. rEhe units are ldisposed with their respective longitudinal axes in parallel planes spaced apart alongV the length of the frame :and ytransverse with respect thereto, land each successive unit is `angularly ydisplaced in its plane ninety degrees from the preceding unit. The frame 1 is Iopensided so that eachV of the several explosive charge units is 4almost fully exposed. I'he illustrated frame is adapted to be lowered by means of a cable (not shown) into a borehole drilled into the earth so that the explosive charge units might be used to perforate the casing in the borehole, for example.

A Each of the explosive charge units is Isubstantially `the same with minor exceptions as will be pointed out below, .and like identifying numerals lare applied to like parts of each unit. Each of the uni-ts comprises :a pressure-resistant container 3, preferably made of a dense material such, for example, as lead, formed on one end with a threaded, recessed cylindrical opening 4 communicating coaxially with a conical chamber '5 which joins at its `apex a smaller cylindrical chamber 6. The other end ot each of the units is formed with an outwardly diverging 'tail portion 7 of substantially circular cross section and entered by a flared lrecess 8 which communicates with ya cylindrical chamber 9 which iu tu-rn joins the cylindrical chamber 6 at a steep angle. The tail portion 7 is also entered by a cylindrical opening 10, followed by a conical chamber 11, the apex of which is joined to the chamber 6 by means of acharnber 12.

As best seen in the unit 2 1, 1a main explosive charge 13 is tte-d in ythe chamber '5. The explosive charge 13 'is formed with a lined cavity 13 in its forward end and will, upon detonation starting at its rearward end, provide yan explosive jet of extremely high penetrating power directed forwardly along the axis of the charge. Received in the chamber 6 is :a booster charge `6' for detonating the explosive charge 13.

For convenience of assembly, the shaped explosive charge 13 may be housed in a contoured casing 14 made of :a thin plastic, which may be easily inserted in the chamber ofthe `container 3 and followed by a retaining and 'sealing cover 15 threaded into the opening 4. If necessary, a gasket may be used between fthe cover 15 .and the container 3 to keep Iborehole liquid from filling the cavity 13. Alternatively, the explosive charge may be poured ydirectly into the chamber 5.

The cover 15 may be marde amply strong to withstand any pressures which might be encountered in a borehole Without destroying the effectiveness of the explosive jet, the intensity of which is lsuch ltha-t the cover may be readily shattered.

Received within the chamber 9 and in 4communication with the booster charge in the chamber 6 is a booster charge 16. The booster charge 16 is Isealed in by a pressurearesistant barrier or cap 17, and is radapted to be i set oft :through the barrier by means described more fully below. Received within the chamber 11 is an auxiliary shaped explosive charge 1S retained and shielded by a frangible, pressure-resistant cap 18. A small booster charge 12 is received vin the chamber 12 behind the explosive charge '18. The `auxiliary explosive lcharge 1S -is similar -to the main explosive charge 13 but is of sub- I stantially smaller proportions, and its booster charge 12 ,is disposed in communication with fthe booster charges alignment with the booster charge 16 of the next unit 2 3. Thus, when the first unit 2 1 is set oil, an explosive jet will emanate from its auxiliary shaped charge 18 which will activate fthe booster charge 16 of the next unit 2 2, and so on. l

Mounted at the upper end of the fname 1 isa waterproof, pressure-resistant lcontainer 19 having formed at its `lower end suitable cavities for receiving a downwardly -directed auxiliary shaped charge 20 -shielded by 'a cap 21 and aligned with 4the booster charge 16 of fthe uppermost explosive charge unit 2 1. The upper or apex end of the auxiliary shaped charge 20 communicates with a closed chamber 22 which receives a firing head 23, which may comprise, for example, a simple primacord fuse 24 and an electrically operated blasting cap 25 for igniting 'the primacord fuse. T-he iiring head 23 may `be connected by means of an electrical conduit 26 to the surface of fthe earth, the conduit 26 preferably being incorporated in the supporting cable (not shown) whereby the frame 1 is ylowered into the borehole. It will Ibe understood, however, that yany suitable detonating means may be used for setting off the shaped charge 20. Because 'the shaped charge 20 is, the illustir-ated form of the invention, directed vertically ydownwardly from la point spaced laterally from the center line of 'the frame, the booster charge 116 of the unit 2 1 is also disposed vertically. In this one respect the first unit 2 1 differs from subsequent units 2 2, 2 3, etc. in which the booster charge 16 forms an angle with the vertical in order to be in alignment with corresponding shaped charges of preceding units.

In operation, the firing head 23 `is set olf from .a remote point, such as Ithe surface of the earth, after Ithe lframe has been lowered `to a `desired depth in ithe borehole, thereby detonating the auxiliary shaped charge 20. rIhis sets up an explosive jet in the direction of Ithe unit 2--1 which enters lthe recess 8 'in alignment with the booster charge 16, perforates the barrier Y17 and sets ofi the booster charge 16, this in Iturn setting off Athe main explosive charge 13 as well as fthe auxiliary shaped charge 18 of the unit 2 1. 'Ph-e main explosive charge will send a jet radi-ally outwardly into the wall or casing of the borehole and the auxiliary shaped charge will direct la jet downwardly at `an 'angle 'toward the next succeeding unit 2 2. This jet will enter 'the recess 8 in alignment with the booster charge 16 to penetrate the barrier 17 and set Iolf the booster charge of the unit 2 2. Thereafter the main explosive charge of the unit 2 2 will be set ofi, as will the .auxiliary shaped charge 18. In this fashion the vcharge Will be set off in rapid succession without the use oi an interconnecting primacord fuse. The rapid series of explosions will cause the frame 1 as Well as the respective units 2--1, 2 2, 2 2, etc. to be broken into small pieces which drop harmlessly to the bottom of `the borehole. The nature of the jets formed by the 'auxiliary shaped charges is fsu-ch that Vsuccessive, sealed units may be set off in the prese-nce of borehole liquids which might envelope the units. Moreover, lthe respective units 2 1, 2 2, 2 3 etc. are able, by virtue of their novel construction, to withstand the high pressures which Iare encountered in a borehole.

While the invention has been described with reference to the drawing showing one preferred form thereof, it will be understood that numerous modifications may be made in the design without departing from the scope of ythe invention. Thus, for example, the tir-ing head 23 at the upper end of the frame which is adapted to initiate the chain or sequential detonating action may be modified to utilize any suitable detonating means and if preferred the tiring head might be incorporated within the first unit 2 1. Also, within the respective explosive charge units other suitable means, such as a small primacord fuse may be used to interconnect the main and auxiliary explosive charges and the booster charge, if such is used. Further, the arrangement for aligning and orienting the respective chambers and cavities in the units may be modiied to sui-t the Iparticular geometrical requirements of the apparatus. Thus other forms and embodiments of the invention coming within the proper scope of the appended claims will readily suggest themselves to those skilled in the art.

What is claimed is:

f1. A system whereby .a series of exposed explosive charge units may be set off in succession comprising two or more explosive charge units; each unit including a sealed, pressure-resistant container, a main shaped explosive charge, an auxiliary shaped explosive charge and detonating means for the charges housed within the conftainer; said shaped ycharges each having .a hollowed out portion sealed by a frangible, pressure-resistant cover; the main and auxiliary charges being arranged within the container to direct the explosive jets, which result therefrom, in dierent direct-ions; said detonating means being .constructed and arranged to be activated by an explosive jet emanating from a poi-nt spaced from the unit; an externally exposed pressure-resistant barrier seal- .ing said detonating means in the contain-er and adapted to be pierced by the explosive jet from said point; support means comprising an open-sided frame for carrying said lunits in spaced .apart relationship with each unit exposed and the auxiliary shaped explosive charge of a iirst unit aimed to direct its explosive jet toward the detonating means of a second unit; and means for activating the detonating means of the first unit.

2. A system as set forth in claim 1, said means for activating the detonating means of the rst unit comprising a sealed housing carried by the support means and spaced from the first unit, an auxiliary shaped explosive charge mounted in the housing and aimed to direct its explosive jet toward the detona-ting means of the first unit, and means for setting off the said auxiliary shaped explosive charge in said housing from a remote point.

References Cited in tne le of this patent UNITED STATES PATENTS

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