Perforating Means For Sand Control

Abstract

1. A perforating gun which comprises: A. a gun barrel provided with a plurality of sets of explosion ports in the wall thereof, with the ports of each set being oriented substantially on a plane which is perpendicular to the axis of the barrel; B. a fuse extending through said barrel; C. a closure member for each of said ports adapted to engage the walls of the explosion port; and D. a tubular casing supported by each said closure member, each said casing of diameter smaller than the diameter of said ports and having a cone shaped end opposite said closure member with length as to extend from said closure member to a location adjacent to the center of said barrel, with said casings forming a structure automatically to position said fuse at the center of said barrel, each said casing including a conical metallic linear and a quantity of an explosive having an inner surface conforming with said metallic liner the apex of which is pointed away from said closure member.

Description

This invention relates to gun perforators for perforating oil well casings, particularly in sand formations, and more particularly relates to apparatus which is readily adapted for loading explosive charges in a perforating gun. In a more specific aspect, the invention relates to an article of manufacture which includes a shaped explosive charge to be inserted into a gun through an explosion port which is maintained liquid-tight by a closure forming part of the article.

Heretofore, shaped detonating charges of the cone type have been employed in an elongated perforating gun barrel. The charges have been loaded into the barrel from one end and have been anchored in position at spaced points along the length of the gun barrel so that the charge faces an explosion port. Such prior structures are of the type illustrated in U.S. Pat. No. 2,844,098. As shown therein, a shaped charge is mounted in fixed position by force applied through a port closing plug which engages the front of a shaped explosive charge. This forces the opposite end of the charge into a well formed in the opposite interior wall of the gun. Loading and positioning the charge in the proper location is time consuming. Further, such charges, employed in accordance with the prior art, are relatively large and in general do not produce optimum results when perforating casing set in sand formations.

In accordance with the present invention, there is provided a gun perforator which includes an elongated gun barrel having a plurality of sets of explosion ports in the wall thereof. The sets are spaced axially along the gun barrel. The ports in each set are positioned in substantially the same plane. Preferably, three or more ports will be formed in each set. Further, in accordance with the invention, the shaped charge units have casings with tapered ends. In each casing the base of a conical explosive charge faces a port closure member whose diameter is larger than the diameter of the casing whereby the unit may be inserted into the gun barrel through the explosion port. An elongated fuse extends through the gun barrel and is centered between and in contact with the ends of each of the units in each set.

For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is an elevation view of a perforating gun having charges supported therein in accordance with the present invention;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1;

FIG. 3 is a partial sectional view taken along the line 3-3 of FIG. 2; and

FIG. 4 illustrates a modification of the invention.

Referring now to FIG. 1, a detonator gun 10, in accordance with the present invention, is of the jet perforating type. The gun is to be lowered into a well bore and, upon energization of an electrical circuit which includes the two conductors 11, a detonator cap 12 fires a fuse 13. The detonation of the fuse 13 proceeds downward through the gun, setting off successive sets of shaped charges located therebelow.

Briefly, the gun system includes a cable adapter head 14 and an intermediate barrel section 15 with a closure member 16 at the lower end. A cable 17 is attached to the head 14 which is employed to lower and raise the gun into and out of a casing (not shown) which is to be perforated. All of the elements of the gun preferably are secured together by means of threaded connections therebetween in order to provide a rigid overall assembly and to facilitate the assembly and disassembly of the structure.

A plurality of sets of explosion ports are formed in the wall of the tube 15. In the embodiment of FIG. 1, each of the sets comprises four ports. The upper set in the lower section includes the ports 21, 22, and 23, and a fourth port 24, not shown in FIG. 1. For the sake of illustration only, the sets of ports in the lower portion of the gun 10 have been shown to be in alignment, i.e., port 21 is directly above port 25 on the next lower set. In the upper portion of the barrel, the ports in the set 28 are offset 45.degree. from the ports in the set 29. It is to be understood that either arrangement may be employed in accordance with the present invention, depending upon the pattern of shots to be produced in the casing walls. It will become apparent from the following description that the in-line relationship shown in the lower portion of the gun 10 will be preferred particularly in connection with the loading of charges in the ports and making certain that they position a detonator fuse.

In FIG. 2, the sectional view illustrates charge units 31--34 in the four explosion ports 21--24. The charges are positioned with their axes at angles of 90.degree. with respect of each other. Shaped charge unit 33, positioned in the explosion port 23, has been shown in section. It includes a cap 33a having an enlarged head 33b and a threaded body 33c. A tubular casing 33d is mounted on a cylindrical extension of the threaded portion 33c . The casing 33d has a cone-shaped end 33e. An explosive charge 33f is formed in the cone-shaped end of the casing 33d. A cone-shaped metallic liner 33g is mounted in the casing 33d to form a particle jet upon detonation of charge 33f.

The fuse 12 is positioned at the center of the barrel 15 and is in contact with the truncated end of the cone-shaped end of casing 33d. A washer 43 of resilient material that is positioned in a countersunk section of the port 23 so that the head 33b may be served into the cylinder 15 to a depth such that the head 33b is approximately flush with the surface of the barrel 15. It will be noted that similar units 31, 32, and 34 of identical construction are mounted in ports 21, 22 and 24 respectively. The charge-containing casings, such as the casing 33d, are each of diameter smaller than the diameter of the threads in the respective explosion ports so that the entire charge closure member may comprise a unitary article for insertion into the gun barrel by way of the ports. By serving the threaded portion of the cap 33a into the opening 23, the truncated end of the tapered section f fis positioned as to be in contact with the fuse 13. The relationship of the units in a set is further understood by reference to FIG. 3 wherein the detonator units 32, 33 and 34 are positioned in the same plane along with unit 31 not shown in FIG. 3. All of the units in each set contact the fuse 13.

The system thus far described will be found to be particularly convenient and advantageous in loading a gun preparatory to firing. More particularly, the fuse 13 will first be loaded into the barrel 15. With the explosion ports in the gun aligned as in the lower section of FIG. 1, the barrel will be placed horizontal. The ports thus located along a line on the top of the horizontal cylinder will first be loaded with the shaped charge units. All of the charge units will be served into the explosion ports so that they are in their final position. The gun will then be rotated to 90.degree. so that the next adjacent line of explosion ports are on top. This line of ports will then be loaded with the shaped charge units so that they are in their final position. The gun is again rotated a quarter turn and the third line of explosion ports will be loaded. The gun will then be rolled a final 90.degree.. In this position, the fuse 13 is readily centered by the sloping surfaces of the ends of the first and third lines of charge units loaded into the gun. When the fourth unit is served into an explosion port in each set, the fuse 13 will be forced into position in the space between four truncated ends and will be placed under some degree of compression between the ends of the four shaped charges. Thus, the fuse is automatically positioned and is maintained in contact with the ends of the shaped charges.

With the gun thus loaded, the gun may be lowered into a borehole to the desired depth. The circuit formed by the conductors 11 will be energized to detonate the cap 12. This initiates denotation of the fuse 13 which sets off the sets of explosive charges mounted at successive points along the length of the barrel 15. The resultant stream of metal particles propelled outwardly through the closure members on each of the shaped charge units, will then perforate the adjacent casing to form sets of holes in the casing.

The use of this type of construction and shaped charges of this nature has been found to be highly desirable, particularly, in connection with production of oil from sand formations. It has been found desirable to shoot relatively small holes in the casing in order to control the sand during producing operations. At the same time a greater number of holes are formed.

In one embodiment of the invention, the gun barrel was about 4 inches outside diameter with about five-eighths inch wall thickness. The diameter of the casing, such as casing 33d, with a conically-shaped end was of the order of about three-fourths inch The length was made such that the truncated end of the cone section 33e was slightly closer to the center of the gun barrel than the radius of the fuse 13. The detonation of such charges produced perforations in the adjacent casing up to about one-eighth inch in diameter. Normally, charges of the type illustrated in the above-identified U.S. Pat. No, 2,844,098 would produce perforations of three-eighths inch to one-half inch in diameter. The use of a greater number of perforations each of small diameter permits production of sand formations while minimizing the sand problem.

As shown, a great number of perforations may be formed in a given length of casing from a single shot by the gun 10. In one embodiment, spacing along the axis of the cylinder 15, as between the centers of ports 21 and 25, was 11/2 inches.

While four charges have been shown as forming each of the sets in FIGS. 1--3, it will be appreciated that different numbers and charges may be employed. It will be preferable that charges would be at least three in number as illustrated in FIG. 4. In this embodiment, charges 41, 42, and 43 are located in the same plane and oriented at angles of 120.degree. between their respective axes. The three element array of FIG. 4, the four element array of FIG. 2, or five or six element arrays might be employed in accordance with the present invention so long as there is room to include them in the circumference of the gun barrel and cone-shaped ends are appropriately shaped. From FIG. 2 it would appear that eight charges could be mounted in the same plane. Closer axial spacing could be employed by staggering the elements as shown in FIG. 1. Further, it would not be necessary that all charges be centered precisely on the same plane. They should be close enough to each other as to assure contact with the fuse 13.

It will be apparent that the closure member and the casing in which the charge is placed may be maintained separate one from the other until immediately prior to loading in the gun. The casing may be a metallic or plastic cup. In either case the casing may frictionally engage a tubular extension of the closure member. The end of the casing will be beveled or cone-shaped subtending an angle which is dependent upon the number of units to be employed in each set. In general, the angle will not exceed 2.pi./n, where n is the number of units in a given set.

Having described the invention in connection with certain specific embodiments thereof, it is to be understood that further modifications may now suggest themselves to those skilled in the art and it is intended to cover such modifications as fall within the scope of the appended claims.

Claims

I claim:

1. A perforating gun which comprises: a. a gun barrel provided with a plurality of sets of explosion ports in the wall thereof, with the ports of each set being oriented substantially on a plane which is perpendicular to the axis of the barrel; b. a fuse extending through said barrel; c. a closure member for each of said ports adapted to engage the walls of the explosion port; and d. a tubular casing supported by each said closure member, each said casing of diameter smaller than the diameter of said ports and having a cone shaped end opposite said closure member with length as to extend from said closure member to a location adjacent to the center of said barrel, with said casings forming a structure automatically to position said fuse at the center of said barrel, each said casing including a conical metallic liner and a quantity of an explosive having an inner surface conforming with said metallic liner the apex of which is pointed away from said closure member.

2. The combination set forth in claim 1 in which each said closure member is provided with sealing means to form a fluid-tight seal in one of said ports.

3. The combination set forth in claim 1 in which said closure member and said casing form a unitary charge assembly.

4. The combination set forth in claim 1 in which the closed end of said casings are in the form of truncated cones where the angle subtended by each cone is approximately equal to 2.pi./n, where n is the number of ports in a given set.

5. The combination set forth in claim 4 in which the height of the cone that would be removed by truncation is about equal to the radius of said fuse.