US2916991A - Jet gun - Google Patents

Description

B. GILBERT Dec, 15, 1959 JET GUN 2 Sheets-Sheet 1 Filed Aug. 11. 1954 .Bruc e 6x/ber f INVENTOR.

A TTORNE Y B. GILBERT JET GUN 2 Sheets-Sheet 2 Filed Aug. 11. 1954 .Bruc e Gilberz INVENTOR.

A TTORNIE Y United States Patent JET GUN Bruce Gilbert, Midland, Tex., assignor to The Western Company, Midland, Tex., a corporation of Delaware Application August 11, 1954, Serial No. 449,167

9 Claims. (Cl. 102-20) This invention pertains to jet guns and methods of loading and unloading same, and more particularly to jet perforating of open holes, well casing, and/or well tubing.

The invention pertains especially to jet guns employing a tubular steel carrier having jet ports in the sides thereof and which are loaded from the ends in order that the ports need not be as large as the charges. A jet gun of this general type is shown in United States Patent 2,662,474 issued December 15, 1953 to Lane- Wells Company on the application of George F. Turechel; and Will H. Lindsay, Jr., entitled Well Casing Perforator, and reference is to be made to said patent for details of the operation of jet guns and of this particular type of jet gun.

In jet guns it is desirable that the time of travel of the reaction through the prirna cord plus the time of travel of the flame along a charge be less than the time of travel of the shock wave from one charge to the succeeding charge. This is desirable to prevent interference or the initiation of one charge from another rather than from the prima cord, since initiation of one charge by another usually causes initiation at a point other than the end thereof adjacent to the cone apex,

which prevents the formation of a proper jet from the charge.

It is the primary object of the invention to reduce the length of prima cord between charges in such a jet gun, so that the distance between charges can be reduced, with the ultimate object in view of permitting more perforations per unit axial length of gun to be made at the same time, that is, per run of the gun into Well.

Prior to this invention considerable difficulty was experienced in attempting to shoot more than four holes per foot per run, although in many cases six holes per foot were desired. Repeated runs with guns shooting less than six holes per foot are unsatisfactory because the spacing will not be uniform, neither axially nor in azimuth, because of the uncertainty of the position of a gun at the lower end of a suspension means of several thousand feet. With the present invention the shooting of six holes per foot per run with charges of adequate size to produce deep penetration has been easily achieved. In addition the ability to perforate a section in one run is much less costly.

The present invention aiso improves the operation of all guns of this type, including guns shooting less than six holes per foot as well as those of closer spacing, as will be brought out more clearly from the following description of a preferred embodiment thereof, reference being made to the accompanying drawings wherein:

Figure 1 is a side elevation of gun embodying the invention, partly broken away to show the location of the charges inside the gun;

Figure 2 is a horizontal section taken on line 2-2 of Figure l;

Figure 3 is a horizontal section taken on line 3-3 of Figure 4; r r

2,916,991 Patented Dec. 15, 1959 Figure 4 is an axial section through the tool shown in Figure 3 showing the manner of loading same using loading tongs; and

Figure 5 is a side elevation of the loading tongs and a charge held thereby with the tubular carrier and other parts of the gun omitted for clarity, the tongs being shown from a different azimuthal angle than in Figure 4.

Referring now to Figure 1, there is shown a jet perforating gun comprising a carrier 10 of tubular or sleevelike configuration and preferably made of steel. The lower end of the carrier is closed by a screw plug 11 having a tapered or conical guide portion 12 at the bottom thereof. Screwed into the upper end of the carrier is the usual rope socket 13 in which is secured the lower end of an electric cable 14 from which extends electric conductor 15 to electric blasting cap 16. Cap 16 is connected to prima cord 17 which is threaded through the reduced cylindrical rear ends or ferrules 18 of jet charges 19.

There are a plurality of axially and azimuthally spaced ports 29 in the sides of carrier 10, each of which is closed by a screw plug 21. Each plug has a thin walled central section 22 adapted to be destroyed by firing of a jet charge therethrough. Plugs 21 seal with carrier 10 to prevent the entrance of liquids and solids. Each jet charge 19 is disposed with its front end adjacent to one of the ports 20 and coaxial therewith.

The term jet charge used herein corresponds generally to the shaped charge elements of the aforementioned Patent No. 2,662,474 (see column 3, line 32 et seq. and column 4, line 52 et seq.). It comprises a charge of explosive shaped or molded with a suitable concavity or conical depression at the front end thereof, that is, the end from which the principal effect of the explosion jets forth toward the ports 20. The charge is contained within a casing which is all that is visible in the exterior views of the jet charge 19 shown in the drawings.

Referring now also to Figure 2, the cylindrical front end 29 of each jet charge is received in a counterbore or recess 30 around the inner end of port 20. Around the tapered middle conical portion 31 of each jet charge is a flat spring 32 having a central portion 33 apertured at 34 to receive charge portion 31 and having ends 35 extending therefrom at acute angles with respect to the center portion of the spring. Springs 32 urge the jet charges 19 into the recesses 30 and hold them firmly in position.

It will be seen that by virtue of the foregoing construction the rear end of each charge is brought nearer to the carrier axis than would be the case if the carrier were not recessed at the inner end of each port. This shortens the length of the prima cord required to connect the rear ends of the charges so that the charges can be placed closer together without interference. The forward displacement of each charge achieved by virtue of the recesses also separates the large cylindrical front ends thereof, and the middle portions of the charges which take the positions otherwise occupied by the cylindrical portions are tapered so that there is a larger spacing between them. Thus, the forward displacement of the charges increases the intercharge distance for any given axial spacing of the charges, so that for this additional reason the number of charges per unit length of carrier can be increased without interference.

The foregoing construction has further advantages in that the flat spring acts as a baffle to protect the interior of the gun against the charge detonation and the placement of the charge closer to the port results in less damage to the gun.

It is also found that though the standoff distance of the charge from the port plug is reduced, a greater penetrat ion is achieved, which may be due to absence of the ordinary alignment means in front of the charge.

The foregoing construction also results in less damage to the plug due to more positive alignment so that there 15 less likelihood of its being lost in the well.

The construction described is less expensive because of the use of fewer support pieces, the reduced number of carriers needed and most important the reduced length of operating time.

By the foregoing construction, holes per unit length of carrier effective charges can then be used tion is always achieved.

A further advantage of the invention lies in the fact that the gun is' easier to load, as will now be described.

Referring to Figure 4, the prima cord 17 is first threaded through the carrier and fixed at one end in any suitable manner (not shown) such as tying it to a post. Next the charges and springs are assembled and threaded on the prima cord from the free end thereof. Then a loading tong 40 is used to grasp each charge and assembled spring in turn and push it through the carrier until the charge snaps into the recess at the desired port. As the charge passes over other ports it may snap into them and then by exerting pressure with the tongs the spring may be compressed to release the charge from the recess and push it farther along. This is easier than trying to maintain pressure on the spring to keep it compressed at all times, for it is desirable that the front end of the charge bear against the inside of the carrier as it is pushed along so that it will not tip over and twist or cut the prima cord.

The gun is loaded from the midpoint to each end. The seal caps or guide plugs are screwed into the ports in the sides of the carrier. Then the prima cord is connected to the blasting cap and the rope socket and guide plug are screwed in at each end.

The loading tongs are shown in detail in Figure 5. They comprise a long hollow tube t having an arm 51 fixed on one end thereof adapted to engage the front face of the charge. At the same end of the tube 50 is another arm 52 having a right angle end portion 53 pivotally mounted at 54. The other end of arm 52 is forked, having two tines 55, adapted to engage the middle portion 33 of the spring 32 on opposite sides of ferrule or rear end portion 13. Arm 52 is moved on pivot 54 by means of a long rod 56 extending through tube 50 and pivotally connected at one end 57 to end portion 53 of arm 52. The other end of rod 56 is connected to a handle 58 extending through a slot 59 in tube 50. If desired the arms 51 and 52 may be spring biased toward each other. By pushing on handle 58 the arms 51 and 52 can be moved together or apart as shown in dotted lines in Figure 5.

The tongs can be used to release the charges if it is necessary to reload the gun or replace a charge Without firing it. However, after firing the gun there will he no charge casings left that will require the use of tongs for removal, the springs and charge casing debris largely falling free out the end of the carrier when turned on end.

While a preferred embodiment of the invention has been shown and described, many modifications thereof can be made by one skilled in the art without departing from the spirit of the invention and it is desired to protect by Letters Patent all forms of the invention falling Within the scope of the following claims.

I claim:

1. A jet gun comprising a tubular carrier having a plurality of ports in the sides thereof extending from the interior surface of the carrier to the exterior surface thereof, the portion of said carrier forming the interior surface thereof being integral with the portion forming the exterior surface thereof, a recess adjacent each port, each said recess being formed in the portion of said carrier forming the inner surface thereof, each recess being adapted to receive the front end of a shaped charge if maximum number of is not required, more so that greater penetracasing, the part of said carrier immediately adjacent each of said ports and recesses and forming the Walls thereof being integral with the rest of the carrier, a plurality of shaped charges disposed inside said carrier, each of said charges including a casing having explosive therein formed to have a concavity at the front end thereof, said casings being too large to pass through said ports, the casing of each charge having its front end disposed in one of said recesses, each casing having a conical external surface tapering down toward the rear thereof, and means to hold said casings in said recesses comprising a plurality of leaf springs, each spring having an aperture through .the middle portion thereof fitting over said conical sur- 3. The method of loading a jet gun having a tubular carrier with a plurality of ports in the side thereof and an interior recess around each port comprising threading a prima cord through said carrier, placing an apertured spring over the rear end of each of a plurality of jet charges having apertured rear ends, threading said charge and spring assemblies onto said prima cord, and positioning said charges in said carrier with the front end of each charge in one of said recesses and the spring on said charge bearing against the inside of said carrier and urging the charge into said recess, characterized by the fact that each charge is allowed to snap into each recess it passes on its wayto its final position and each charge is freed from each recess it snaps into before reaching its final position by pressing it out of such recess with tongs passed into the carrier from one end thereof.

4. A jet gun comprising an integral tubular carrier having a generally cylindrical interior, said carrier having a plurality of ports in the sides thereof, the interior of said carrier having a recess therein adjacent the inner end of each port, the interior of said carrier opposite each port being a smooth cylindrical surface forming a portion of said generally cylindrical surface of the carrier, a shaped charge disposed opposite each of said ports, each of said charges including a casing having ex plosive therein formed to have a concavity at the front end thereof, each of said charge casings having acylindrical front end larger in diameter than the port disposed in the recess adjacent to the port that is opposite said charge, each of said charge carriers having a conical portion to the rear of said cylindrical portion, a spring retainer for each of said charges, each spring comprising a flat U-shaped spring with an aperture at the center portion thereof disposed over said conical portion, the ends of each spring bearing against said smooth cylindrical portion and pressing the charge casing into the recess.

5. A jet gun comprising an integral tubular carrier having a generally cylindrical interior, said carrier having a plurality of ports in the sides thereof, the interior of said carrier having a recess therein adjacent the inner end of each port, the interior of said carrier opposite each port being a smooth cylindrical surface forming a portion of said generally cylindrical surface of the carrier, a shaped charge disposed opposite each of said ports, each of said charges including a casing having explosive therein formed to have a concavity at the front end thereof, each of said charge casings having its front end disposed in the recess adjacent the port that is opposite said charge, means at the rear end of each charge casing to receive a fuse cord, and spring means bearing against each charge casing holding its front end in said.

recess and said rear end away from the interior of the carrier and nearer to the axis thereof.

6. The combination of claim in which said recesses are interior counterbores concentric with said ports leaving flat shoulders at the ends of the counterbores and the front ends of said charge casings are flat.

7. A jet gun comprising a tubular carrier having a generally cylindrical interior, a plurality of ports in the sides thereof, a counterbore surrounding each port in the interior of said carrier, the interior of said carrier opposite each port being a smooth cylindrical surface forming a portion of said generally cylindrical interior surface of the carrier, a shaped charge including a casing having explosive therein disposed opposite each of said ports, each of said casings having its front end disposed in the counterbore surrounding the port that is opposite said charge, means at the rear end of each charge casing to receive a fuse cord, and spring means bearing against each charge casing holding its front end in said counterbore and said rear end away from the interior wall of the carrier and nearer to the axis thereof.

8. A jet gun as defined by claim 7 including a fuse cord disposed longitudinally of said carrier and received in the rear end of each charge casing, the fuse cord being throughout its length closer to the axis of the carrier than to the interior surface of the carrier.

9. A jet gun comprising a tubular carrier having a generally cylindrical interior surface, a plurality of ports in the walls of said carrier, a countcrbore surrounding each port in the interior of said carrier, the interior of the carrier opposite each port being a smooth cylindrical surface forming a portion of said generally cylindrical interior surface, a shaped charge including a casing having explosive therein disposed opposite each of said ports with the front end of each casing disposed in the counterbore surrounding the port that is opposite said charge, and spring means bearing against each charge casing so as to hold the front end of the casing in the counterbore and the rear end of the casing away from the wall of the carrier and near to the axis thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,649,736 Phillips Aug. 25, 1953 2,662,474 Turechek ct al. Dec. 15, 1953 2,680,406 Austin June 8, 1954 2,687,823 Whitmore Aug. 31, 1954 2,695,665 Box et al. Nov. 30, 1954 2,696,169 Lassiter Dec. 7, 1954 2,764,937 Schlurnberger Oct. 2, 1956 2,765,739 Mohaupt et al. Oct. 9, 1956 FOREIGN PATENTS 989,329 France Mar. 23, 1951 677,824 Great Britain Aug. 20, 1952

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