Abstract:
A perforating gun for use in underground wells where the gun includes a forward guiding element and a rearward conveyancing element. These two elements are interconnected by way of a series of bow springs. In the preferred embodiment, the springs are spirally configured around the central axis of the gun. The spring function in applying pressure to the internal surface of the well shaft and in centering the gun. Additionally, the springs serve in removably carrying a series of explosive charges. The spiral configuration allows perforations to be created in a 360 degree pattern around the central axis of the gun.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to perforating guns for use in forming underground openings, and more particularly to a means for making helical underground openings. 
     2. Description of Related Art 
     Perforating guns are commonly used in underground wells. The guns typically carry charges which perforate the well casing and surrounding earth upon detonating. The resulting perforations facilitate exploitation of mineral and hydrocarbons deposits. 
     One such perforating gun is described in U.S. Pat. No. 5,638,901 to Shirley et al. The gun of Shirely includes an elongated spiral strip to which a series of explosive charges are mounted. 
     U.S. Pat. No. 4,787,458 to Langer discloses a spring bow centralizer. The centralizer of Langer further includes reduction members for affecting the angle of contact between the bow and the adjacent well opening. 
     U.S. Pat. No. 5,542,480 to Owen discloses a perforating gun composed of two or more nonfrangible regions which are connected together by a frangible region. 
     U.S. Pat. No. 4,552,234 to Lowell discloses a perforating gun with a penetration pattern. The pattern is dispersed longitudinally along the gun and rotatively around the circumference. 
     U.S. Pat. No. 4,951,744 to Rytlewski discloses a gun with a charge supporting base strip of an angular cross section. 
     U.S. Pat. No. 4,875,413 to Christopher discloses a gun formed by a wire carriage. The wire carriage functions in supporting various charges. 
     One disadvantage with the majority of the aforementioned known gun designs is that none of them create a multi strand helical perforation pattern, while at the same time using the spring bow staves for containing the charges and centering the gun within the well. Such an arrangement improves the performance of the charges. 
     BRIEF SUMMARY OF THE INVENTION 
     The general purpose of the present invention is to provide a self centering perforating gun which carries charges in a straight or helical configuration. 
     To attain this, the present invention essentially comprises a perforating gun with a guiding element and a rearward conveyancing element. The gun further includes a number of bow springs which extend inbetween and interconnect the guiding element and conveyancing element. Each of the bow springs includes a rearward end secured to the conveyancing element and a forward end secured to the guiding element. Each of the bow springs has a plurality of threaded apertures formed through its thickness, with each successive aperture being in alignment with the adjacent aperture. A plurality of explosive encapsuated perforating charges are included on each of the springs. Each charge, or cap, has a threaded end portion which is threadably secured within one of the threaded openings of the bow spring. 
     It is an object of the present invention to provide a perforation gun with a series charge carrying bow springs. 
     It is another object of the present invention to provide a perforating gun with bow springs with either a right or left handed spiral configuration. 
     It is a further object of the present invention to create a well perforating device which is self centering and which carries charges in a helical configuration. 
     An even further object of the present invention is to provide a perforating system wherein the charges are removably interconnected to a number of bow springs. 
     A further object of this invention is to use several of these bow guns in tandem to perforate a limited length of hydrocarbons or minerals. 
     Further object of this invention to cause each charge to be contacted with the casing to cause the ideal performance from each explosive charge contained on the bow spring stave. 
     Lastly, it is an object of the present invention to provide a perforating gun for use in supporting and detonating explosives within a borehole for the purpose of exploiting hydrocarbons and mineral deposits. The bow gun comprises a guiding element having a lower frustro conical extent and an upper collar. A rearward conveyancing element is included which has an upper extent with a perforation formed therethrough and a lower collar. A plurality of bow springs are included which extend inbetween and interconnect the collar of the guiding element and the collar of the conveyancing element. Each of the bow springs includes a rearward end secured to the collar of the conveyancing element and a forward end secured to the collar of the guiding element. Each of the bow springs is defined by a width and a length. The width of each bow spring is twisted along its length, and each of the bow springs has a plurality of threaded apertures formed through its thickness, with each successive aperture being in alignment with the adjacent aperture. A plurality of explosive encapsulate charges are included with each explosive cap having a threaded end portion and an upper coupling means. Each of the encapsulated charges is threadably secured within one of the threaded openings of the bow springs. Detonating cords are provided with each of the detonating cords positioned along an associated bow spring. Each of the detonating cords is secured to the upper coupling means of the plurality of explosive caps. A bow spring detonation cord is included having a distal end adapted to be interconnected with a detonation means and a proximate end which is adapted to be positioned through the slot of the conveyancing element. The proximate end of the bow spring detonation cord is also interconnected to the detonating cords associated with each of the bow springs. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein: 
     FIG. 1 is an exploded view of the perforation gun of the preferred embodiment. 
     FIG. 2 is a side elevational view of an alternative embodiment of the perforating gun of the present invention. 
     FIG. 3 is a plan view of the embodiment of FIG.  2 . 
     FIG. 4 is a side elevational view of the right handed spiral embodiment of the present invention. 
     FIG. 5 is a plan view of the embodiment of FIG.  4 . 
     FIG. 6 is a side elevational view of the left handed spiral embodiment of the present invention. 
     FIG. 7 is a plan view of the embodiment depicted in FIG.  6 . 
     FIG. 8 is a side elevational view of the gun in position within a well. 
     FIG. 9 is a plan view of the embodiment depicted in FIG.  8 . 
    
    
     The same reference numerals refer to the same parts throughout the various Figures. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention  10  relates to a perforation gun which is designed to removably support explosive charges within a borehole. The gun functions is perforating a well casing and the surrounding earth to enable a user to exploit mineral and/or hydrocarbon deposits. The gun is configured to support the charges in a pre-selected orientation until detonation is desired. In one embodiment, the body of the gun is formed from multiple springs which are oriented into a helix. The components of the present invention, and the manner in which they interrelate, will be described in greater detail hereinafter. 
     Each of the gun embodiments is generally defined by a conveyancing element  20  and a guiding element  22  which are interconnected by a number of bow springs  24 . The guiding element  22  is defined by a lower frustro conical extent  26  and an upper collar  28 . The frustro conical extent  26  allows the gun  10  to penetrate into the interior of a borehole  30  before being detonated. The rearward conveyancing element  20  is defined by an upper extent  34  and a lower collar  36 . The upper extent  34  has a perforated aperture  38  formed through its length. The function of this aperture  38  will be described in greater detail hereinafter. As illustrated in FIG. 1, the upper extent  34  is adapted to be secured to cabling, to thereby enable the gun  10  to be lowered into the into interior of the borehole  30 . It is within the scope of the present invention to position multiple guns in a tandemed or end to end relationship. In this manner, a user can select the desired length to be perforated. Additionally, a detonating cord can be included with the cabling in a manner more fully described herein. 
     The conveyancing and guiding elements,  20  and  22 , together serve to support a series of bow springs  24 . In the preferred embodiment, depicted in FIG. 1, a series of bow springs  24  extend in between, and serve to interconnect, the collar  28  of the guiding element  22  and the collar  36  of the conveyancing element  20 . In one embodiment, four bow springs are included. Each of the series of bow springs  24  is of an identical construction. Consequently, only one such bow spring  24  will be described in detail. 
     The rearward end of each bow spring  24  is secured to the collar  36  of the conveyancing element  20 . Preferably, the bow  24  includes a tab  44  which is welded or otherwise permanently affixed to the collar  36 . In a similar fashion, the forward end of each bow spring  24  is secured to the collar  28  of the guiding element  22 . This interconnection is achieved by tab  45 . Each of the springs  24  is formed from a thin gauge metal and is bowed outwardly intermediate its forward and rearward ends. Furthermore, each of the bow springs  24  is defined by a width and a length. The bowed configuration gives the springs a degree of resilience. Additionally, the cross-sectional area of the straight or spiraled bow springs, or staves, is selected to prevent fragmentation upon detonation of the gun  10 . The resilience, in turn, makes the body of the gun  10  flexible and affords the conveyancing and guiding elements,  20  and  22 , limited movement with respect to one another. Additionally, the bowed springs  24  serve to center the gun  10  within the interior of a borehole  30 . As illustrated in FIG. 8, the central axis  46  of the gun  10  is centered within the shaft of the borehole  30 . Now that the general features of the gun have been described, the specific bow spring geometries employed in the various embodiments will be detailed. 
     The preferred bow spring geometry is that of a helix, depicted in FIGS.  1 - 6 . FIGS. 1 and 4 depict a right handed spiral, while FIG. 6 illustrates a left handed spiral. The spiral, or phased configuration, is achieved by the twisting the width of each spring  24  along its length. The right handed spiral is achieved by twisting the springs in a clockwise orientation. Alternatively, the left handed spiral is achieved by twisting the springs  24  in an anti-clockwise orientation. The top plan views of FIGS. 5 and 7 better illustrate the differences between the right and left handed orientations of the springs. FIGS. 2 and 8 illustrate an alternative embodiment of the present invention, wherein the springs  24  are not formed in to a helix. Rather, the bows remain untwisted along their respective lengths. The function of these bow geometries will be described hereinbelow. 
     In all of the embodiments the springs  24  include threaded apertures  48 . Specifically, each of the bow springs  24  has a plurality of apertures  48  formed through its thickness. Additionally, as illustrated in each of the Figures, the apertures  48  are in alignment with one another, with each successive aperture  48  being aligned with the adjacent aperture  48 . As illustrated in FIG. 1, a plurality of explosive caps  52  are adapted to be removably interconnected to the bow springs  24  by way of the threaded apertures  48 . Each of these caps  52  is defined by a threaded end portion  53  and an upper coupling means  54 . The caps  52  include a cylindrical housing  56  for the storage of an explosive. Thus, as illustrated in FIG. 1, each of the caps  52  is adapted to be threadably secured within one of the threaded openings  48  of the bow springs  24 . Any number of apertures can be included on each spring. However, in the preferred embodiment  7  to  11  apertures are included on each spring. 
     Each of the cap  52  is further interconnected to the gun  10  by way of detonating cords  58 , or prima cords. In the preferred embodiment, each such cords are included, with each cord  58  corresponding to an associated bow spring  24 . Thus, each detonating cord  58  is affixed to the rear of the explosive charge adjacent to, and in series with, the associated bow spring  24 , note FIG.  1 . Each detonating cord  58  is secured to the upper coupling means  54  of the plurality of explosive caps  52  aligned upon the associated bow spring  24 . The coupling means  54  of each cap  52  may take the form of eyelets or threading. In such an embodiment, the associated detonating cord  58  is coupled to the aligned caps  52  by being threaded through the series of eyelets or threading. All of the detonation cords  58  are, in turn, coupled together at their uppermost extents. Furthermore, a master detonation cord  42 , or bow spring detonation cord, has its distal end interconnected with a detonation means  62 . Additionally, the master detonation cord  42  has a proximate end which is positioned through the slot  38  of the conveyancing element  20  and interconnected to the detonating cords  58  associated with the series of bow springs  24 . Thus, when the detonation command is given to the detonation means  62 , which can take the form of a computerized control, electrical impulse, or mechanical means, the signal is passed from the master cord  42  to the individual detonation cords  58 . In this manner, all of the explosive caps  52  are simultaneously detonated. 
     In use, the gun  10  is lowered into a borehole  30 . Support electrical cabling  64  is employed in lowering the gun  10  and controlling its depth with the borehole  30 . Such cabling is interconnected with a spool or other metering means  66  which function in supplying and retrieving the support cabling  64 . The bow springs  24  serve to resiliently contact the inner surface of the borehole  30  to center the gun  10  within the borehole shaft. Once the desired position is achieved the metering means  66  ceases to supply the support cabling  64 . Thereafter, the entire gun  10  can be detonated via the remote detonation device  62 . The remote device  62  is interconnected to the gun  10  via an electrical cable, or major detonation cord,  42  included with the cabling. The major detonation cord  42 , in turn, is interconnected to the detonation cords  58  positioned within the interior of the gun  10 . Specifically, each detonation cord  58  is associated with an individual bow spring  24 , and interconnected to each of the explosive cap  52  secured thereto. Thus, once the remote detonation device  62  is activated, all the explosive caps  52  are simultaneously detonated. Any remaining pieces of the gun  10  can then be retrieved from the borehole. Preferably, the bow  24  are of a strength to withstand the detonation. The detonation, however, causes perforations in the surrounding casing in a pattern which is dictated by the bow springs. Namely, spiral bow springs result in spiraled perforations. The spiral pattern is desirable in that perforations are created in a 360 degree pattern around the central axis of the gun. 
     This detailed description has been provided only for illustrative purposes. It is recognized that other embodiments may be articulated without departing from the objects and scope of the present invention. Any such modifications and variations are meant to be within the scope of the invention as contained within the following claims.