US2216145A - Gun perforator for well casings - Google Patents

Description

Oct. 1, 1940. s. F. TURECHEK 2,216,145

' GUN PERFORATOR FOR WELL CASINGS Filed May 8, 1939 11v VENTOR F1634 GEORGE I? ERECHEK ATTORNEY Patented Oct. 1, 1940 GUN'PERFORATOR- FOR WELL CASINGS Application May 8, 1939, Serial N0. 272,377

11 Claims.

My invention relates to gun-perforators for well casing, that is, to devices which are adapted to be lowered within the metallic casing of a well-bore for the purpose of discharging bullets through the easing into the surrounding formation, in order that fluid from the formation may enter the casing.

Gun perforators are now employed extensively in the oil industry. These are lowered on a cable, usually on a conductor cable, and fired electrically. The bullets used range from a quarter to a half inch in diameter and penetrate several inches beyond the casing into the formation, to form drainage channels. As gun perforating has become acceptable to the oil industry, the desire on the part of the industry for a greater number of perforations has increased. It is not uncommon to perforate several hundred holes in a. well casing. The limiting factor is the cost involved. The cost is not due alone to the charge of the service company which performs the gun perforating, but to the rig-time of the customer required by the service company in order to place the requisite number of perforations.

Heretofore, from ten to fifteen shots have been fired for each round trip of the gun perforator. Formerly this number has been a limiting factor for the reason that the weight of the gun perfora-tor must be held down to a point where it can be handled readily at the surface. Attempts have been made to increase the number of gun units by merely lengthening the gun, but this has been accomplished only by increasing the weight of the gun beyond practical limits. This not only sacrifices portability of the gun by necessitating its construction in sections to permit transportation, but also increases the weight on the cable. The cable, by reason of the fact that it must function not only as means of suspension, but also as a means of furnishing electrical energy to the gun for its operation, has rather limited tensile strength.

Furthermore, it is desired that the gun have maximum diameter for a given size casing. The diameter is dependent upon thlength of the gun for the reason that as the gun length is increased, provision must be made for passage of the gun around dog legs," that is, crooks or bends in the casing.

One convention-a1 gun perforator, for example, a ten-shot 6 /8-inch gun (that is, a gun having an actual diameter of 5% inches so as to fit inside of a 6 /8-inch casing) has a length of 50 inches, excluding the casing for its controller mechanism and the cable head. In running into a. well 6000 feet deep, the time consumed per round trip is approximately 30 to 40 minutes; the loading consumes approximately 5 to 8 minutes; consequently, to perforate 500 holes the rigtime is approximately 29 to 40 hours. 5

With the above outline of the problem involved in mind, the objects of my invention are as follows:

First, to provide a gun perforator which incorporates a maximum number of gun units per 10 foot of length, whereby the maximum number of gun perforations may be made for each round trip of the gun perforator;

Second, to provide a gun perforator which offers a. maximum resistance to the destructive 1% force of the explosive, so that high pressures may be developed to efiect maximum penetration;

Third, to provide a gun perforator in which each gun unit has a barrel of maximum length in proportion to the total diameter of the gun in: body, whereby a given powder charge imparts mazdmum velocity to the bullet;

Fourth, to provide a gun perforator of this character wherein the explosive force of the powder charge is exerted with maximum efficiency $5 to the bullet;

Fifth, to provide a gun perforator which incorporates anovel means of retarding or delaying initial expansion of the explosive charge so as to increase the acceleration of the bullet;

Sixth, to provide a multiple unit gun perforator which is particularly simple and economical of construction, and which incorporates a unitary gun body in which the gun units are formed integrally therewith; and

Seventh, to provide a gun perforator which is particularly simple to clean and reload.

With the above and other objects in view, as will appear hereinafter, reference is made to the accompanying drawing, in which:

Figure 1 is an elevation-a1 view of the gun perforator;

Figure 2 is a typical transverse sectional view taken through one of the gun units;

Figure 3 is a further enlarged fragmentary sectional view taken through 3-3 of Figure 2, illustrating the electrical firing means;

Figure 4 is another fragmentary sectional view through 4-4 of Figure 2, illustrating the explosive expansion retarding ring; and

Figure 5 is a fragmentarysectional view similar to Figure 3, illustrating a modified means, for discharging the gun.

The gun perforator comprises essentially a gun body I connected at its upper end to a controller 55 case 2 and cable head 2 fastened to the lower end of a suitable cable 4, in which is provided a conductor, so that electrical energy may be supplied to the gun perforator. The controller case and controller therein, as well as the cable head and cable and its associated surface equipment, are, insofar as this invention is concerned, conventional'.

The gun body I is provided with a plurality of laterally directed gun bores 2. The gun bores are preferably arranged in sets in diametrically.

opposite directions, and are positioned alternately so that the bullets are discharged alternately, first from one side and then the other, of the gun body.

Each gun bore 2 is uniform in diameter throughout its length and extends almost all of the way through the gun body. The breech, or-

inner, end of each gun bore is preferably rounded, as indicated by 5, whereby that portion of the body member which closes the ,breech end of the gun bore has a maximum shearing strength. Each gun bore receives a cartridge 6 and bullet 1. As shown in Figures 2 and 3, the cartridge I comprises a shell 8 rounded and closed at its breech end, and open at its other end to receive the heel 9 of the bullet I. The cartridge 8 is filled with an explosive powder to a point near the bullet I. Between the powder charge proper and the bullet is placed a fuse disk III which may comprise a mixture of explosive powder and metallic filings to form a conductive material which, upon the passage of current therethrough, ignites and sets off the powder charge. The fuse disk is grounded through the bullet I to the gun body I. The cartridge is preferably formed of an inflammable insulating material such as Celluloid, so as to be destroyed when the gun discharges.

In order to retain the bullet I in place prior to discharge of the cartridge, and also to provide an explosive-expansion retarding means, an annular groove l I is formed in the gun bore 2. The groove ll receives a split ring I2 which extends partly into the gun bore 2 so as to bear against the conical or pointed end I! of the bullet. The powder charge in the cartridge 6 has sufllcient resiliency so that when the bullet and cartridge are inserted in the gun bore the bullet may be pressed inwardly a sufficient distance to enable the ring l2 to be inserted in the bore and permitted to snap into the recess II. The ring I 2 is formed of brass or other material, the shearing strength of which is calculated to offer the desired resistance to the initial movement of the bullet, but which is certain to give way before the pressure generated by the cartridge exceeds the strength of the gun body.

The outer end of each gun bore 2 is provided with a rudimentary counterbore l4, in which fits a cup-Ishaped sealing disk I, the skirt of which is directed inwardly. The disk I! is outwardly convex so that hydrostatic pressure tends to increase its diameter and effect-a water-tight seal against the counterbore.

The body member I is provided with a series of Sockets [6 intersecting the gun bores 2 at points substantially centered with respect to the position assumed by the fuse disks III: that is, opposite the forward end of the cartridges 6. Inasmuch as the gun bores are arranged in diametrically opposite directed sets, the sockets II are likewise arranged in sets on diametrically opposite sides of the gun body, as indicated by solid lines and dotted lines in Figure 2.

Each socket It is screwthreaded and receives a threaded plug IT. The outer end of each socket II is counterbored, as indicated by ll, to form a shoulder I9 and each plug fly is provided with a head 20 which seats against a gasket 2| interposed between the head 20 and shoulder l9. Each plug I1 is provided with a bore 22 therethrough of extremely small diameter. This is enlarged at the outer end of the plug to form a recess 22. The

recess 23 has, preferably, polygonal walls so that.

a suitable tool may be inserted for the purpose of screwing the plug into place. Each plug II receives a connector unit 24 which comprises a semi-flexible lead wire 25 butt-welded to a needle 26. The needle is covered by an insulating sleeve 21, while the lead wire 25 is covered by an insulating sleeve 28. The sleeve 28 is provided at its ends with sealing fianges 29. One of the seal: ing fianges 29 is adapted to fit into the recess 23 of the plug l1 and is undercut in such a manner that hydrostatic pressure exerted on the plug l1 tends to force the sealing flange tightlyagainst thewalls of the recess. The needle 28 and its insulating sleeve 21 fits in the bore 22 and the end of the needle 26 is adapted .to be thrust through the shell 8 of the cartridge 6, and into the fuse disk I, as shown best in Figure 3. Inasmuch as the pressures generated within the gun bore reach tremendous values, in fact, in the neighborhood of 150,000 pounds per square inch, the diameter. of the bore 22 is made extremely small; the diameter of .040 of an inch has been found satisfactory.

The gun body I is provided, along opposite sides, with a pair of channels 20 which receive conductors 3| and which are covered by plates 22. Opposite each socket I! the channels are intersected by passages 22 communicating with the sockets. Each passage 22 is provided with a terminal plug 24 adapted to receive the outer end of the conductor 25. The remaining sealing fiange 22 of the insulating sleeve 28 fits into the passage 32 to seal the terminal plug 34. After the con- ,ductors II have been assembled in thechannels 20 the channels are completely filled with suitable insulating compound 25 so as to exclude the entrance of water. The channels communicate at their upper ends with a suitable socket 26 provided in the gun body, which socket is likewise filledwith the insulating compound 35.

The several conductors 2| are connected to a conventional controller or sequencing switch (not shown) adapted to connect the several gun units in sequence to a source of electrical energy.

Reference is now directed to Figure 5, in which is illustrated a modified form of firing device: This construction differs principally from the preceding structure, in that the fuse disk is not incorporated in the cartridge, but is provided within the plug which fits the threaded socket I. This plug, designated 4|, is provided near its inner end with a'small chamber 42 communicating with the inner end by a small passage 43. outwardly from the chamber 42 the plug 4! is provided with an internally threaded bore which receives a plug 44. The plug 44 is provided with a passage therethrough in which fits a contact needle 45, which is insulated as in the first de scribed structure and projects into the chamber 42.

The chamber 42 receivesa small capsule or firing charge 44 which may comprise a mixture of metallic filings and explosive powder, or a suitable resistance element for igniting the powder.

The inner end of the bore 2 receives a cartridge 41 which is similar to the cartridge 8, except that 16 2,216,145 its outer end is covered by a thin cover disk 48 in place of the fuse disk. 1

The bullet 49 may likewise be different from the preceding structure. may be frusto-conical, as indicated by 50, and covered by a cap 5| formed of softer material than the bullet, and having a socket atits torward end which is complementary to the frustoconical portion 50. The cap 5| is provided with an annular groove 52 which is adapted to align with a groove 53 provided in the wall of the bore 2. The groove 52 receives a ring as and issufficiently deep that the ring 56 may be contracted to the diameter of the bore 2 so that the bullet may be inserted, the ring 54 having suflicient resiliency to expand into the groove 53 when the bullet is in position. The back end of the cap 5| may be made slightly concave, as indicated by 55, so that the pressure generated by the explosive charge tends to expand the cap 5| against the walls of the bore 2 and seal against the escape of pressure by the bullet.

As in the first described structure, the shear strength of the ring 5a is calculated to give way when a predetermined pressure has been built up by ignition of the cartridge. By retarding initial expansion of the explosive charge and permitting this pressure to build up before release, the acceleration given to the bullet is materially enhanced, so that the muzzle velocity of the bullet is equal to that obtained by conventional means in a much longer barrel.

Irrespective of the retarding ring, barrel length is of primary importance. In this regard, it should be noted that the ratio of the efiective barrel length to the diameter of the gun body is quite high, so that maximum muzzle velocity is obtained.

By reason of the fact that the bore of the several gun units are integral with or formed in the body member itself, and their diameters are uniform, very close spacing of the gun units is made possible; in fact, if the gun bores are about a half inch in diameter they need only be spaced approximately an inch from center to center. In contrast to this, the center to center spacing between gun units of a conventional gun periorator of similar diameter is approximately four and one-half inches. Thus, with the construction herein illustrated, over four times as many gun units may be provided per foot of gun body as is possible with the conventional type of gun perforator.

Various changes and alternate arrangements may be made within the scope of the appended claims, in which it is my intention to claim all novelty inherent in the invention as broadly as the prior art permits.

I claim:

1. A gun perforator for well casing, comprising: a gun body having laterally directed and independent bores, each forming a powder chamber at its inner end and a bullet passage continuing outwardly therefrom, the material of the gun body itself forming the entire walls of the several bores; said gun body defining a common longitudinally extending conductor passage and independent branch passages leading to the chamber portions of the bores; electrically responsive ignition means associated with each powder chamber; and conductors connected through said passages to said ignition means.

2. A gun perforator having'a plurality of laterally directed gun bores, arranged in closely disposed parallel planes, each gun bore extending The heel of the bullet 4! from one side of the gun body to a point in close proximity to the opposite side of the gun body, whereby the length oisaid bores approaches the diameter of the gun body; each gun bore forming a cartridge chamber at its inner end and a bullet passage outwardly therefrom; and a cartridge and bullet for each gun bore and ignition means extending laterally from said gun bore opposite said cartridge.

3. A gun 'perforator for well casing, comprising: a gun body having a plurality of laterally directed gun bores arranged in diametrically opposite sets, the members of said sets arranged in aiternation, said gun bores being closely grouped in parallel planes and extending approximately the diameter 01 said gun body each of said gun bores intersected by ignition ports near its inner end, the axes of said ignition ports likewise arranged in parallel planes; an explosive cartridge for each gun bore occupying a minor portion of its length; a bullet fitting said gun bore; an ignition means for said ignition ports.

4. In a gun perforator having a gun bore of uniform diameter and adapted to receive an explosive cartridge and a bullet, the combination of an expansion delay means comprising: a groove formed in said gun bore; and a split shear ring adapted to be contracted for insertion through said gun bore into said groove, said shear ring, when filling said groove, projecting into said bore for engagement with said bullet.

5. In a gun perforator for well casing: a gun body having a plurality of laterally directed gun bores, ports intersecting said gun bores, conductor passages extending longitudinally of the gun body, and exposedrecesses between said ports and said conductor passages; an explosive cartridge and bullet for each gun bore; ignition means for said ports; and means accessible through said recesses for connecting said igniting means with said conductors.

6. In a gun perforator for well casing: a gun body incorporating integrally a plurality of gun units, each unit including a gun bore, an ignition port intersecting said gun bore near its inner end and exposed at its outer end, said gun body also including passages extending past the several gun units; conductors in said passages terminating at the outer ends of said ignition ports; ignition means filling said ports and accessible from the exterior of the gun body for connection with said conductors; and an explosive cartridge and bullet fitting each of the gun bores.

7. A gun perforator for well casing, comprising: a gun body incorporating a plurality of gun units, each gun unit including a laterally directed gun bore and an intersecting ignition port, said gun bores and ignition ports of the several gun units disposed in parallel planes spaced less than half the diameter of the gun body; a cartridge and bullet for each gun bore and an ignition means for each of said ignition ports.

8. A gun perforator, as set forth in claim '7, wherein said gun body is circular in cross section, said gun bores extend diametrically, their inner ends terminating within the periphery of the gun body a distance approximately equal to the diameter of said gun bores, and said ignition ports are screw-threaded and intersect the peflphery of said gun body and are positioned outwardly from the inner ends of their respective gun bores whereby, by reason of the circular cross section of saidgun body, the lengths of said screw-threads are suflicient to develop the strength of said body member.

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9. A-gun periorator for well casing comprising: a gun body formed from a single piece of material and having drilled therein a. plurality of diametrically extending gun bores and a laterally extending ignition port for each gun bore intersecting said gun bore intermediate its ends; an explosive cartridge fitting the inner end of each bore to a point opposite said ignition port;.

a bullet positioned against said cartridge; an electrical ignition means fitting said ignition port; and a multiple conductor distributing means leading to each ignition means.

10. A gun perforator, as set iorthin claim 9, wherein said ignition means are externally accessible and a separable electrical connector is interposed between each ignition means and said distributing means.

11. In a gun perforator for well casing: a gun body formed from a single cylindrical block of metal and having drilled therein a plurality of parallel disposed gun bores extending almost the entire diameter of the gun body, the gun body thickness remaining at the inner ends of said gun bores being approximately equal to the diameter of said gun bores; an ignition port formed in said gun body opposite each gun bore, said port intersecting said bore intermediate its ends; a cartridge and bullet for each gun bore; and an ignition means for each ignition port.

I GEQRGE I TURECHEK.

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