US2990773A - Apparatus for perforating well casing - Google Patents

Description

July 4, 1961 1 W. TOELKE APPARATUS FOR PERFORMING WELL cAsING 5 SheebS-Sheet 1 Filed May 13, 1957 .il l` rm U Z J ZJ Z July 4, 1961 L. w. 'roELKE APPARATUS FOR PERFORMING WELL cAsI'NG 3 Sheets-Sheet 2 Filed May 13, 1957 /f /I /1 1 A. a l. .a

July 4, 1961 L. w. TOELKE APPARATUS FOR PERFORATING WELL CASING 3 Sheets-Sheet 5 Filed May 13, 1957 United States Patent O ree 2,990,773' APPARATUS FOR` PERFORATIN WELL CASING Lester W. Toelke, Houston'l2ex., assigner to Great'Lakes )Carbon CorporatiomzNew York, N.Y., a corporation of Delaware FiledMa'y I3; 1957', Ser. No. 658,612 3 Claims.` (Cl. 1021-20) This invention` relatesy to devices employed in the per'- forating ofwell` bores and casing positioned therein, and particularly to animproved form' ofcarrier assemblysupporting so-called4 lined shaped chargey explosiveA units of the je type. Y

The techniqueofperforatingcasingiandwell bores has been considerably advanced by the use of so-called explosivey hollow jet or: lined shaped charges. The construction ofV these. charges; and their utilization inperforating equipment has been described by McLemore in. the Oil and' Gas Journal,A December 281,. 1946', and in U.S. Letters Patents Nos. 2,399,211 and 2,494,256. It has been the practicel to install'` charges of this` typel in recoverableV carriers which.` are generally' of thetubular steel type. These carriers may be solid or hollow and are,V providedr with a plurality of barrels into which the perforating units may be inserted, usually being protected by sealing means to prevent intrusion of well iluids. A ll of the unitsV are fired by agsuitable detonating train, such .as- Primacord which extends. longitudinally through. the

interior of the carrier. These: recoverable carriers are very expensive to machine and require a` considerable amount ofsteel, often a critical. material. Constant maintenance is required because with eachv tiring of the gun, it becomes distorted until' thel barrels reach a diameter which render the gun unsafe to use. Itmust then. either be discarded? or extensivelyv reworked. Furthermore, such carriers are relatively heavy and bulky and must be of considerable length in order tol support the required number of charges employed. in'V a single run. Also, because of their size: -theyr are diicult to maneuver and retrieve from the welll bore.

In order to obviate some of the above difficulties several expendable carriers have been designed. However, these carriers also have many unsatisfactory features. Generally they are constructedI ofa thin strip ofi metal having large diameter holes in the medial or web portion ofthe strip to receive the charge cases. The charges are positioned in these holes by means of tape, clips, etc., none of which hold the charge firmly enough for rough usage in transporting the tool or in lowering it and maneuvering it in a well. Since the strips are qui-te exible they cannotv be handled roughly because the charges will become loosened and misaligned. resulting, in poor perforating performance.y Also it, is quite diicult to `accurately ascertain the depths to which such expendable carriers arelowered because they are quite 'exible and will not support much weight. Others. have` proposed to weight` the bottom' portion of such carriers but thisis undesirable because the weights are often sheared off by the explosion and left; in the well. Also, such: expendable strip carriers areA torn beyond use after each shootingoperationV and while they may, in some cases, be retrievable from the well, such carriers leave a considerable amount of fragmented junk metal in the hole.

Accordingly it is a principal object of this invention to provide a relatively' inexpensive yet durable carrier for lined shaped charge explosives which is completely retrievable from the well after firing, and which. leaves a minimum amount of material in the well resulting, only from the fragmentation of the explosive charge cases.

It is a further object of the invention to provide an Patented July 4, 1961 improved carried for lined shaped charge explosives which canbe retrieved from the well after firing.

It is a further object of the invention to provide an improved carrier for lined shaped charge: explosives which does not require the use of holes, slots, etc.y in the carrier body itself through which Primacordor other detonator is threaded, thereby eliminating the possibility of cutting and- Wetting the detonator in the well which often results in misiiring of the charges.

More specifically, the improved carrier assembly in accordance with one embodiment of my invention. comprises -a single pair of oppositely disposed and substantially parallel and uniformly spaced continuous strips of relatively thin, flexible and impact-resistant sheet material, a plurality of elongated shaped charge units securably positioned between and affixed to the strips, the longitudinal axes of the shaped charge units being substantially normal to the. longitudinal edges of the strips, means for connecting the upper end of said strips to a lower-ing means, and means for detonating the shaped charge units.

The foregong, as well as other objects of this invention; will become apparent from the -following detailed description and in- View of the accompanying drawings which. illustrate useful embodiments of the invention as well as modifications thereof.

In the drawings:

FIGURE 1 is a vertical section showing one form of the carrier assembly in accordance with this invention, after. llowering the device into a well bore lined with metal casing;

FIGURE 2 is an enlarged fragmentary View in section of. the lower portion of the device shown inV FIGURE l;

FIGURE 3- is a sidey elevation, partly in section, taken along the line 3--3 of VFIGURE 2 and showing the explosive charges inl minimum extension;

FIGURE 4 shows a modied form of the invention exemplifying means `for forming a gun wherein the explosive charges are in greater extension than FIGURE 3;

FIGURES 5 through l1 are cross-sectional views of modied Iforms of the carrier strips which. are a feature of this` invention,

Referring first Ito FIGURE l, which shows a preferred embodiment. of my invention, the device is. shown generally at 10 after having been lowered into well casing 32 backed upl by cement 33. The carrier assembly 10 consists of a single pair of relatively thin flexible continuous and impact-resistant metallic strips 13 which are disposed opposite each other in substantially parallel alignment and with substantially uniform spacing, except Where the strips are tapered inwardly or ared at the ends to join several sections of the carrier assembly. The strips 13 are spaced sufficiently apart to accommodate a number of lined shaped explosive charge units 18 which are' iixed and secured between the strips by threaded means, suchV asfastening screws 20 which traverse appropriate openingsin the strips. Only the exterior or casing portion of these charges is shownl in the drawings for purposes ofi1- lustration. In the particular embodiment shown in the. drawings the movement of the charges is further restricted by the employment of support screws 22 which are miachine screws intersecting the web of the strips 13 and which friotionally engage the outside of the explosive charge casing, as shown Itis to be understood, however, that the employment of the supporting screws 22 is not essential to the successful operation of the carrier assembly.

The strips 13 may be constructed of relatively pliable and impact resistant sheet material such `as ordinary mild steel /e" thick. Other equivalent materials may be used.

The width of theV strip is a matter of convenicncewand isthe inside diameter of the well casing. The length of the strips may be any suitable or desired length and several sections of the carrier assembly may be secured together by bolts 23 as shown in FIGURE 1. The side margins or longitudinal edges of the strips 13 are suitably reinforced by crimping the edges of the strips such as shown in FIGURES 5, 8, 9 and 10, or they may be suitably reinforced by strong steel wire 51 as illustrated in FIGURES 7 and 8.

The carrier strips 13 are fastened -a-t the top end of the carrier assembly to a coupling member 12 by means of bolts or screws 17. In the bottom portion of the carrier assembly the strips 13 are tapered slightly inwardly and fastened to aninwardly tapered member 15 by fastening screws 16. I'he tapered bottom member 15 facilitates lowering the carrier assembly through the casing.

Above the coupling member 12 to which the carrier assembly is attached there is provided a socket head 11 which contains an electrical conductor wire 29 attached to electrode terminal 30. This head is designed to permit increasing the weight of the carrier assembly for conditions where the casing size or the well fluid require extra weight for rapid descent of the gun. Theconductor wire 29 runs longitudinally through the coupling adapter mem.- ber 12 through a bore 26. Where the conductor wire leaves the coupling member 12 there is provided a plastic seal 28 fastened in position by compression nut 27. The conductor wire 29 runs longitudinally of and between the strips 13 to the bottom portion of the carrier assembly at which point it is attached to a detonater 31 such as a blasting cap and booster, which in turn is fastened and sealed to the end of a length of a detonating train such as Primacord 24. The Primacord is strung lengthwise upwardly and between the carrier strips 13 to contact the v rear face of each shaped charge casing 18, the latter being xed in a position substantially normal to the longitudinal edges of the strips 13 so that the high velocity gases which are produced by firing of the charges will be directed substa'ntially horizontally, or perpendicularly with respect to the casing wall. The upper end of the Primacord detonating train is sealed from well fluids as designated by No. 25. 'There is further provided a ground lead from the point where the lead wire 29 is attached to the detonator 31, the ground being to the bottom of the carrier assembly as shown.

The detonating trai-n for the shaped charge units 18 preferably consists of a length of flexible Primacord 24 which r-uns` lengthwise and inside of the carrier strips 13, passing successively over and in contact with the rear face of each perforating unit as shown in FIGURE 1, 3 and 4. The rear -faces of the shaped charge units are provided with notches or guide. lugs y19 to receive the Primacord. If desired, this cord may also be secured to the charge casing wall by tape, clips, or other fastening means. In the arrangement illustrated in the drawings the detonating train is ired 4from its lower end but it should be understood that either top or bottom tiring arrangements may be used successfully.

In operation 4the carrier assembly, having the perforating units 18 securably mounted and aligned between the carrier strips 13, as shown in FIGURES l, 3 and 4, is connected to a socket and electrical lead wire assembly 11 and coupling member 12. The carrier assembly is then lowered by means of a cable attached to the socket head. When the carrier assembly has reached the desired depth in the casing electric current is supplied from the surface slightly bowed in 'the immediate charge area resulting in a slight deformation where. each charge has exploded. This action is particularly beneficial to the operator because it enables him to ascertain whether all the charges have tired and adequate perforations have been obtained in the casing. Even though the carrier strips 13 may be slightly deformed they will nevertheless be completely intact and the entire. carrier assembly, including the bottom meniber 15 may be readily withdrawn from the well.

FIGURES 5 through 11 illustrate in cross section other suitable shapes for the strips 13 of the carrier assembly. FIGURE 6 shows a ilat metal strip which, -in FIGURES 5, 8, -9 and 10 has been bent back or crimped along the longitudinal edges to form` reinforcing beads. In FIG- URES 7 and 8, heavy wire 51 has been axed to the longitudinal edges of the stn'ps for reinforcing properties. In FIGURE 11 the metal strip of FIGURE 6 has been bent in opposite Vdirections along the two longitudinal edges.

The carrier assembly of this invention may be made in any desired length and may be made up of inter-connected sections as shown in FIGURE 1 to obtain a length suicient to support any desired number of perforating charge units.

It will thus be seen that this invention provides a retrievable perforating carrier assembly for shaped charge units which has suicient rigidity to support weight but still providing suicient flexibility to pass tight places in theicasing. The carrier assembly can yalso be spirally twisted to permit a shot pattern of any desired degree of angular orientation. The charges may be positioned to shoot uni-directional or in opposite directions (180), the latter being the pattern generally used. Also, the charges can be iixed at any of the location holes to `form a gun of various diameters to suit the well bore. This is evident from an analysis of FIGURE 4 wherein two lines of such location screw holes 20 are exemplified and employed in strip members 13. `It will be appreciated that the charges 18 whichare shown in this figure are at different levels just as are the charges shown in gure.

While the embodiment of the invention illustrated in the drawings shows certain preferred mechanical details, such as the means for securably iixingthe shaped charge units between the strip members 13 and yfor fastening several sections of carrier assembly together by means of correspondingly tapered and ared end portions of the strips, it should be understood that other equivalent means for accomplishing these results can be used and are contemplated by the invention which is limited in scope only by the appended claims.

I claim:

1. A retrievable shaped charge carrier assembly for perforating well casing comprising a single pair of oppovsitely disposed and substantially parallel and uniformly spaced continuous flat strips of relatively thin, flexible and impact-resistant sheet metal, a plurality of elongated shaped charge units secured in iixed position between and to said vstrips by threaded means which traverse openings in said strips and threadedly engage said units, the longituthrough lead wire 29 to blasting cap and booster assem- Y bly 31, thereby detonating the Primacord 24 and successively causing all of the shaped charge units 18 to explode. While the gaseous jets from the perforating units are primarily directed horizontally against and through the casing 32 and cement 33, there is a substantial radial force or moment developed which acts laterally against dinal axes of said shaped charge units being substantially normal to the longitudinal edges of and parallel to the flat faces of said strips, means for connecting the upper end of said strips to a lowering means, and a detonating train running longitudinally ofand between said strips and in contact with the rear Aface of said charge units.

2. A retrievable shaped charge carrier assembly for perforating well casing comprising a single pair of oppositely disposed and substantially parallel and uniformly spaced continuous flat strips of relatively thin, flexible and impact-resistant sheet metal, renforcing elements disposed longitudinally along the side edges of said strips, a plurality of elongated shaped charge units secured in fixed position between and to said strips by threaded means the strips 13. Since the latterare iexible these will be which traverse openings in said strips and threadedly e11- gage Said units, the longitudinal axes of said shaped charge units being substantially normal to the longitudinal edges `of and parallel to the flat faces of sai-d strips, means for connecting the upper end of said strips to a lowering means, and a detonating train running longitudinally of and between said strips and in contact with the rear face of sai-d charge units.

3. A device according to claim 2 wherein the rnetal strips are approximately inch thick and each longitudinal edge of said strips has been bent inwardly upon itself to form the reinforcing elements.

References Cited in the le of this patent UNITED STATES PATENTS Thompson et kal Mar. 6, 1951 McCullough July 31, 1956 Harcus Oct. 2, 1956 FOREIGN PATENTS Australia Nov. 9, 1955

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