Perforating apparatus
United States Patent [191 Cocanower 1 1 PERFORATING APPARATUS [75] Inventor: Robert D. Cocanower, Fort Worth,  
 Tex.  
 1731 Assignee: The Western Company of North America, Fort Worth, Tex.  
 1221 Filed: Aug. 16,1973  
  2| Appl. No; 388,992  
 [52] US. Cl. l75/4.6, 102/20 [51] Int. Cl E2lb 43/117 [58] Field of Search l75/4.5, 4.57, 4.58, 4.59, 175/46; 102/20, 24 HC, 67  
 [56] References Cited UNITED STATES PATENTS 2.067.408 l/l937 Morris 102/20 2.411362 12/1946 Arnold.... 102/67 2.925. 75 2/1960 McKee 175/46 X 3. 68.243 1/1961 Turechek 175/46 [111 3,874,461 14 1 Apr. 1, 1975 3,093,072 6/1967 Pigman l02/7.2 3,346,057 10/1967 Bell.......... 17$/4.6 X 3,366,188 l/1968 Hicks.... 17514.6 3,429,384 2/1969 Shore 175/46 3,580,174 5/1971 Apotheloz et al. 102/72 X 3,739,723 6/1973 Hakala l75/4.6 X  
 Primary Examiner-David H. Brown Attorney, Agent, or Firm-Mason, Kolehmainen, Rathburn &amp; Wyss [57] ABSTRACT A perforating apparatus is provided with a charge receptacle having a groove in the receptacle outer wall. Upon detonation of a shaped charge, the wall portion surrounded by the groove is cleanly sheared away leaving no burr on the receptacle wall. The sheared wall portion serves as a projectile in penetrating a well casing without leaving a burr on the casing wall.  
 10 Claims, 4 Drawing Figures PATENTEB APR 3 874.481  
 FIG. 1  
 PERFURATING APPARATUS This invention relates to perforating apparatus for providing communication between a well bore and fluids in the formations surrounding the well bore so that the fluids can be retrieved More particularly, this inention relates to an improved shaped charge perforating apparatus.  
  in completing a well. for example. an oil or gas well. after the fluid has been drained from a well bore-hole. the bore hole is typically cased and a shaped charge perforating apparatus is lowered into the bore hole. The perforating apparatus contains a series of shaped capsule charges suitably linked to one another to form a chain of charges for perforating the bore hole easing at selected locations. The perforations enable the fluid in the earth formation adjacent the bore hole casing to enter the casing and be retrieved therefrom.  
  The shaped capsule charges for well perforating purposes contain high-brisance detonating explosives. The capsule is shaped with a cavity or hollow. generally of conical shape. and is aligned within a thin metal liner and inserted within a charge receptacle. When detonated. the major proportion of the generated explosive force is concentrated. by virtue of the shape of the hollow and the metal liner. into a relatively narrow gaseous jet of great penetrating force directed at the point to he perforated in the well bore lining. Shaped perfo rating charges normally depend substantially entirely upon the penetrating power of the narrow axially directed gaseous jet to effect the desired degree of perforation. The vertically spaced shaped &#34;capsule&#34; charges are interconnected for detonation by a blasting cord. The blasting cord can he detonated by conventional means such as a blasting cap and an electrical power means.  
  Another type of charge used in perforating apparatus is a bullet gun. A bullet gun employs a projectile such as a steel ball within a torpedo shell for penetrating the charge receptacle wall and the bore-hole casing. An example of this type of charge is found in the Klotz. U.S. Pat. No. 2.779.278.  
  Perforating apparatus may be operated in wells which are filled with hydraulic fluids and for this reason the charges are enclosed in a fluid-tight receptacle. Seep-age of fluid into the charge receptacles will cause misfires and other undesirable damage. The &#34;capsule&#34; charges are fastened in a desired location within the charge receptacle by a suitable fastening means and the thin metal capsule charge receptacle. is positioned within the bore hole.  
  The tubular perforating apparatus used to complete the evacuation of fluid from the area surrounding the bore hole are generally classified as expendable and non-expendable. Nonexpendable perforating apparatus generally has a heavy walled cylindrical housing or receptacle having radially directed ports through which shaped charges can be repeatedly detonated. The ports are sealed after insertion of the shaped charges as by a sealing disc or cap to make the charge receptacle fluidtight.  
  With the expendable type of perforating apparatus, the casing collar or charge receptacle is damaged to an irreparable degree when the capsule charges are detonated. This invention is directed to expendable perforating apparatus. The following U.S. Pat. Nos. disclose \arious non-expendable perforaters: 2.655.619:  
 2.662.474. 2.734.456; 2.750.885; 2,782.7!5; 2.785.631; and 2,953.97].  
  In one prior art form ofexpenclable perforating apparatus. the tubular charge receptacle has not been ma chined and has uniform wall thickness. When the charges are detonated. the tubular carrier is substantially blown outward by the charges and the tubular receptacle may be completely shattered. This type of expendablc perforating apparatus leaves substantial undesirable debris within the well casing.  
  In another prior art type of expendable perforating apparatus. the tubular casing is blown away at wall locations opposite the capsule charges. With this perforating apparatus. a burr an irregular portion of the charge receptacle wall protruding outwardly from its original diameter develops in the casing where the casing has been penetrated by explosive pressures. Burr formation. either on the charge receptacle surface or on the well-bore casing. causes difficulties in removing the perforating apparatus from the bore-hole and in other subsequent operations in the well bore. There have been a number of proposals for solving these two major problems oft l debris in the well casing and (2) the formation of a burr in the charge receptacle after detonation.  
  It has been suggested that a groove or cutout portion be formed in the outer diameter of the tubular charge carrier to reduce the wall thickness at the locations opposite the shaped charges. ln this manner, there is less tubular charge receptacle wall penetrated by the explosive pressures and therefore less debris in the cased bore-hole. Machining of the charge receptacle wall has also been used to prevent the burr formed from the explosive pressure from protruding beyond the maximum outer diameter of the tubular charge receptacle. The following U.S. Pat. Nos. teach machining ofthe tubular charge receptacle at locations corresponding to the positioning of the charges within the carrier: Lebourg- 3.()48,|()2; Christopher-3.128.702; and Shore- 3.429.384.  
  A primary object of the present invention is to provide a perforating apparatus characterized by the absence of a burr on the charge receptacle and well casing and by the elimination of debris in the well casing. Other objects are to provide a perforating apparatus having a tubular charge receptacle with a machined outer wall surface so that detonation causes a defined portion of the tubular wall to be sheared away without leaving a burr; and to provide a perforating apparatus using part ofa charge receptacle wall as a projectile for penetrating a well bore hole easing.  
  ln brief. the above and other objects and advantages of the present invention are achieved through the provision of a charge receptacle having an annular groove in its outer wall surface so that the wall thickness at the groove is less than the wall thickness of the wall portion surrounded by the annular groove. Within the charge receptacle an explosive charge is positioned opposite the wall portion surrounded by the annular groove. Upon detonation of the charge. explosive pressures shear the receptacle wall at the groove and form a clean. burr-free aperture. and drive the sheared wall portion outwardly through the well casing. The perforating apparatus ofthe present invention leaves little or no debris within the well casing since the portion of the tubular wall sheared away is destroyed and/or ejected upon penetration of the well bore casing. The perforating apparatus of the present invention is easily and cheaply manufactured by simply providing an annular groove or ring notch in the outer wall of the tubular charge carrier.  
  The invention together with the above and other objccts and advantages may be best understood from consideration of the following detailed description of an illustrative embodiment of the invention shown in the accompanying drawing wherein:  
  FlGv l is a fragmentary cross sectional view of a perforating apparatus constructed in accordance with the present invention and positioned within a well casing;  
  FIG. 2 is an enlarged fragmentary view of the tubular charge carrier or charge receptacle of the apparatus of FIG. 1;  
  H6. 3 is a cross sectional view of the tubular charge carrier taken along the line 33 of FIG. 2; and  
  FIG. 4 is a view similar to FIG. 3 illustrating the charge carrier after detonation of a shaped charge.  
  Referring now to the drawings, and initially to FIG. 1. there is illustrated perforating apparatus embodying the principles of the present invention and designated as a whole by the reference numeral 10. Apparatus 10 is provided with a tubular charge carrier of novel eon figuration and generally designated by the reference numeral 1]. The apparatus 10 is lowered into the well in accordance with conventional practice for the purpose of perforating a well casing 12 so that oil, gas, water or other fluid within the surrounding earth formation 14 can enter the well bore 16 and be raised to the surface either by pressure existing in the earth formation or by pumping. A positioning device (not shown) such as that shown in U.S. Pat. No. 3,338.3]? or that shown in U.S. Pat. No. 3.l l(l,257 may be em ployed to osition the perforating apparatus 10 within the casing 12.  
  One or more shaped or capsule charges 18 are positioned within the tubular charge carrier 11. The charges [8 are spaced vertically from one another and are connected for detonation by an igniting means 20 such as. for example. a conventional primacord. A detonator or blasting cap (not shown) for the primacord can be connected as by an electrical cable so that the firing of the charges [8 may be electrically initiated at the surface. The shaped charges 18 may be of any conventional type. such as those described in U.S. Pat. Nos. to Christopher-3.128J02; Sweetman-l734.45b or Lebourg-3,(l4ls,l(l2.  
  In accordance with the present invention, the wall of the tubular charge carrier I] immediately in front of each shaped charge 18 is provided with a groove 24 best seen in FlGS. 2 and 3. A thin wall 26 underlies the groove 24 and surrounds a thicker central wall portion 28. Since generally cylindrical charges 18 are normally used. the groove 25 is preferably circular. The diameter of the groove 24 is preferably equal to or larger than the diameter of the axially directed gaseous jet stream resulting from detonation ofthe shaped charge 18. lt is preferred to machine the groove to a substantial depth. for example, approximately half of the receptacle wall thickness. The bottom of the machine groove 24 (the top of the thin wall portion 26) can be flat, but a flat surface is not necessary. For example. a V-notch or other configuration can be provided. The shaped charges 18 should be positioned centrally of the relatively thick wall portions 28 so that the narrow axially directed gaseous jet stream created by the detonation of the shaped charges will create a substantially concentric force on the inner surface of wall portion 28.  
  The explosive pressure against the inner surface of wall portion 28 causes wall portion 28 to be sheared S away from the tubular charge carrier ll in a pattern leaves no irregular protrusion on the inner surface of the wall casing 12 and is therefore more desirable for penetrating the casing than the use of explosive gas pressure only. Moreover due to the fact that wall portion 28 is cleanly sheared and driven into the well cas&#39; ing. the problem of debris within the casing 12 is minimized.  
  Although the present invention has been described by reference to several embodiments thereof, it will be apparent that numerous other modifications and embodiments will be devised by those skilled in the art which fall within the true spirit and scope of the present invention.  
 What is claimed as new and desired to be secured by 3) Letters Patent of the United States is:  
 I. Perforating apparatus comprising:  
 a charge carrier having a shaped charge carried therein, said carrier having in an outer wall surface thereof a groove defining a thin wall area. said groove surrounding a thicker wall area. said surrounded thicker wall area having a thickness greater than the thickness of said thin wall area over substantially the entire surrounded area.  
  2. Perforating apparatus as defined by claim I wherein the thin wall area defined by the groove is approximately half the thickness of the carrier wall portion surrounded by the groove.  
  3. Perforating apparatus as defined by claim I further comprising:  
 the shaped charge is mounted within the charge carrier and positioned substantially centrally of the receptacle wall portion surrounded by said groove.  
  4. Perforating apparatus as defined by claim 1 wherein the lowermost points along the bottom of the groove define an annular ring.  
  5. Perforating apparatus as defined by claim 1 wherein the charge carrier is a tubular cylindrical memher.  
  6. Perforating apparatus as defined by claim 5 wherein said groove is annular, and wherein the bottom of the annular groove lies in substantially a flat plane. said plane being generally parallel to the longitudinal axis of the charge carrier 7. A perforating charge receptacle adapted to receive shaped charges comprising:  
 a tubular member having a shaped charge carried therein and having in an outer wall surface thereof an annular groove defining an annular receptacle wall portion having a thickness less than the thick ness ofthe receptacle wall surrounded by the annular groove over substantially the entire surrounded area.  
 groove in said wall defining a thin wall area. said groove surrounding a thicker wall area, said surrounded thicker wall area having a thickness greater than the thickness of said thin wall area over substantially the entire surrounded area.  
  I0. Perforating apparatus as defined by claim 9 including a plurality of shaped charges and a plurality of continuous grooves carried by said charge carrier each m shaped charge disposed adjacent one of said grooves in said wall.  
 LII