Abstract:
Various shaped charges and methods of operation produce multiple jets in various profiles by employing multiple initiation points to address various earthen formations and producing different types of perforations in well bores. The shaped charge device includes a configuration of components wherein multiple detonation tracks are used to allow selective initiation and operation. Dual or quad initiation may be provided to initiate operation.

Description:
STATEMENT OF GOVERNMENT INTEREST 
   The inventions described herein may be manufactured, used and licensed by or for the U.S. Government for U.S. Government purposes. 

   BACKGROUND OF THE INVENTION 
   The invention relates in general to wells and in particular to initiating flow from a well. 
   To initiate the flow of oil and/or other materials in a well, a conventional shaped charge warhead (or perforator) is fired through the well casing, the cement sheath and into the earthen formation. A shaped charge device comprises a shaped charge liner backed by high explosives. When the explosives are detonated, the shaped charge device forms a high velocity forward moving penetrator or “jet” that is capable of deeply penetrating the targeted material. 
   Output of a well is dependent on several factors including the size of the hole made by the perforator, the hole shape and the penetration depth. Fracturing fluids are pumped into the hole to fracture the rock formation and special agents in the fluid hold the fractures open to allow flow. Small diameter holes (as produced by conventional shaped charges) have a tendency to clog with these agents. Well and rock conditions vary at different depths in the same well and in different wells, due to geological differences. 
   A variety of perforators are available for different applications. A disadvantage of conventional perforators is they can only produce one jet profile per design. A single perforator lacks the ability to handle varying well and rock conditions. Most available perforators are designed to produce deep penetration but with a very small diameter hole. To change the jet output and, therefore, the hole profile, a different perforator is required for each desired hole profile. 
   At present, a variety of perforators must be on hand to handle different situations. U.S. Pat. No. 6,925,924 issued on Aug. 9, 2005 and is incorporated by reference herein. The &#39;924 patent shows shaped charge perforators with multiple initiation points. These perforators can produce different jets. However, each perforator is limited to producing a single jet profile. Thus, a need exists for a single perforator that can selectively produce varying jet outputs for different applications. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide an apparatus and method for selectively producing different types of perforations in well bores. 
   A first aspect of the invention is a shaped charge comprising a case having an open front end, a closed rear end, an interior and a longitudinal axis; an explosive material disposed in the interior of the case; and a liner disposed over the explosive material; wherein the case includes a first channel extending from an opening on the rear end of the case along the longitudinal axis to an opening in the interior of the case adjacent the explosive material; and a pair of second channels, the pair of second channels having a common opening on the rear end of the case, the common opening being a different opening than the opening for the first channel, the pair of second channels ending in a pair of diametrically opposed openings in the interior of the case adjacent the explosive material, the pair of openings being disposed on opposite sides of the opening of the first channel. 
   The shaped charge may further comprise a pair of third channels, the pair of third channels having a common opening on the rear end of the case, the common opening for the third channels being a different opening than the opening for the first channel and the common opening for the second channels, the pair of third channels ending in a pair of diametrically opposed openings in the interior of the case adjacent the explosive material, the pair of openings being disposed on opposite sides of the interior case opening of the first channel and further forward than the pair of interior case openings for the second channels. 
   A second aspect of the invention is a method comprising providing a shaped charge according to the first aspect of the invention; and detonating the shaped charge using only one of 1) the opening on the rear end of the case for the first channel; 2) the common opening on the rear end of the case for the second channels; and 3) the common opening on the rear end of the case for the third channels. 
   A third aspect of the invention is a shaped charge comprising a case having an open front end, a closed rear end, an interior and a longitudinal axis; an explosive material disposed in the interior of the case; and a liner disposed over the explosive material; wherein the case includes four channels extending from a common opening on the rear end of the case to four diametrically opposed openings in the interior of the case adjacent the explosive material. 
   The shaped charge may further comprise a fifth channel extending from an opening on the rear end of the case to an opening in the interior of the case adjacent the explosive material, the opening on the rear end of the case being a different opening than the common opening for the four channels, the opening in the interior of the case being centered on the longitudinal axis. 
   A fourth aspect of the invention is a method comprising providing a shaped charge according to the third aspect of the invention; and detonating the shaped charge using only one of the common opening on the rear end of the case for the four channels and the opening on the rear end of the case for the fifth channel. 
   A fifth aspect of the invention is a shaped charge comprising a case having an open front end, a closed rear end, an interior and a longitudinal axis; an explosive material disposed in the interior of the case; and a liner disposed over the explosive material; wherein the case includes a first channel extending from an opening on the rear end of the case along the longitudinal axis to an interior opening in the interior of the case adjacent the explosive material; and a pair of second channels extending from a pair of openings on the rear end of the case to a pair of diametrically opposed interior openings in the interior of the case adjacent the explosive material, the pair of diametrically opposed interior openings of the second channels being disposed on opposite sides of the first channel. 
   The shaped charge may further comprise a pair of third channels extending from a pair of openings on the rear end of the case to a pair of diametrically opposed interior openings in the interior of the case adjacent the explosive material, the pair of diametrically opposed interior openings of the third channels being disposed on opposite sides of the interior opening of the first channel and radially outward from the pair of interior openings of the second channels. 
   The shaped charge may additionally comprise a pair of fourth channels extending from a pair of openings on the rear end of the case to a pair of diametrically opposed interior openings in the interior of the case adjacent the explosive material, the pair of diametrically opposed interior openings of the fourth channels being disposed on opposite sides of the interior opening of the first channel, radially outward from the pair of interior openings of the third channels and axially forward from the pair of interior openings of the third channels. 
   Advantageously, the shaped charge further comprises a pair of fifth channels extending from a pair of openings on the rear end of the case to a pair of diametrically opposed interior openings in the interior of the case adjacent the explosive material, the pair of interior openings for the fifth channels being disposed on opposite sides of the interior opening of the first channel, radially outward from the pair of interior openings of the fourth channels and axially forward from the pair of interior openings of the fourth channels. 
   In one embodiment of the fifth aspect of the invention, the shaped charge further comprises a pair of sixth channels extending from a pair of openings on the rear end of the case to a pair of diametrically opposed interior openings in the interior of the case adjacent the explosive material, the pair of interior openings of the sixth channels being disposed on opposite sides of the interior opening of the first channel, offset circumferentially about ninety degrees from the interior openings of the second pair of channels and disposed radially outward from the interior opening of the first channel about a same distance as the interior openings for the second pair of channels. 
   A sixth aspect of the invention is a method comprising providing the shaped charge of fifth aspect of the invention; and detonating the shaped charge using at least one of the first channel, the pair of second channels, the pair of third channels, the pair of fourth channels, the pair of fifth channels and the pair of sixth channels. The detonating step may include using only one of the first channel, the pair of second channels, the pair of third channels, the pair of fourth channels, the pair of fifth channels and the pairs of second and sixth channels. 
   A seventh aspect of the invention is a method comprising providing a shaped charge having a case having an open front end, a closed rear end, an interior and a longitudinal axis; an explosive material disposed in the interior of the case; and a liner disposed over the explosive material; the shaped charge including a plurality of channels formed therein extending from the rear end to the interior adjacent the explosive material; and detonating the shaped charge using at least one, but not all, of the plurality of channels. 
   The invention will be better understood, and further objects, features, and advantages thereof will become more apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, which are not necessarily to scale, like or corresponding parts are denoted by like or corresponding reference numerals. 
       FIG. 1A  is a rear view of one embodiment of a shaped charge. 
       FIG. 1B  is a sectional view along the line  1 B- 1 B of  FIG. 1A . 
       FIGS. 1C and 1D  are modified sectional views of  FIG. 1A . 
       FIG. 2A  is a rear view of another embodiment of a shaped charge. 
       FIG. 2B  is a sectional view along the line  2 B- 2 B of  FIG. 2A . 
       FIGS. 2C and 2D  are modified sectional views of  FIG. 2A . 
       FIG. 3A  is a rear view of another embodiment of a shaped charge. 
       FIG. 3B  is a sectional view along the line  3 B- 3 B of  FIG. 3A . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Shaped charges that produce a long and narrow jet by axial initiation will produce a fan-like jet if two diametrically opposed detonators are initiated along the side of the warhead. As the detonation points are moved forward along the warhead, the jet output changes. Single point initiation produces a long thin jet for deep penetration. Moving multiple detonation points slightly forward produces a narrow fan-shaped jet followed by a foreshortened round jet. Moving the detonation points even further forward produces a wide fan-shaped jet. 
   The use of four detonation points can produce a variety of effects depending on initiation locations. These locations usually involve a tradeoff between hole depth and hole cross-sectional area. The present invention is a selectable output, shaped charge perforator that can produce various jet profiles. Thus, one perforator may be used to produce jet patterns that can vary depending on well and rock conditions. Multiple sets of dual diametrically-opposed detonation points (or quad detonation points) are included in the shaped charge case to allow for selection of the required jet profile to match required conditions. 
   Commercial well perforators generally use detonation cord (det cord) as the initiation mechanism. In the invention, multiple detonation tracks are fabricated in the shaped charge case to allow selective initiation by choice of det cord placement, or, by rotating or indexing the perforator in its holding fixture. Dual (two point) or quad (four point) initiation may be accomplished from a common point or from multiple points. 
     FIG. 1A  is a rear view of one embodiment of a shaped charge  10 .  FIG. 1B  is a sectional view along the line  1 B- 1 B of  FIG. 1A . Shaped charge  10  includes a case  12  having an open front end  14 , a closed rear end  16 , an interior and a longitudinal axis X-X. An explosive material  18  is disposed in the interior of the case  12 . A liner  20  is disposed over the explosive material  18 . In  FIG. 1A , the dotted lines represent channels within the case  12  and openings into the interior of the case  12 .  FIGS. 1C and 1D  are modified sectional views of  FIG. 1A . In  FIGS. 1C and 1D , only one pair of channels are shown. For purposes of clarity,  FIGS. 1C and 1D  are planar projections of the channels  38 ,  40  and  28 ,  30 , respectively. 
   Case  12  includes a first channel  22  extending from an opening  24  on the rear end of the case along the longitudinal axis X-X to an opening  26  in the interior of the case adjacent the explosive material. A pair of second channels  28 ,  30  have a common opening  32  on the rear end of the case. The common opening  32  is a different opening than the opening  24  for the first channel  22 . The pair of second channels  28 ,  30  end in a pair of diametrically opposed openings  34 ,  36  in the interior of the case adjacent the explosive material. The pair of openings  34 ,  36  are disposed on opposite sides of the opening  26  of the first channel  22 . Preferably, the pair of openings  34 ,  36  are about a same distance from the interior case opening  26  for the first channel  22 . More preferably, the pair of openings  34 ,  36  and the interior case opening  26  for the first channel are substantially collinear. 
   Shaped charge  10  further comprises a pair of third channels  38 ,  40 . The pair of third channels  38 ,  40  having a common opening  42  on the rear end of the case  12 . The common opening  42  for the third channels is a different opening than the opening  24  for the first channel and the common opening  32  for the second channels. The pair of third channels  38 ,  40  end in a pair of diametrically opposed openings  44 ,  46  in the interior of the case adjacent the explosive material. The pair of openings  44 ,  46  are disposed on opposite sides of the interior case opening  26  of the first channel and located axially further forward than the pair of interior case openings  34 ,  36  for the second channels  28 ,  30 . Preferably, the pair of interior case openings  34 ,  36  for the third channels are about a same distance from the interior case opening  26  for the first channel. More preferably, the pair of interior case openings  34 ,  36  for the third channel and the interior case opening  26  for the first channel are substantially collinear. 
     FIG. 2A  is a rear view of another embodiment of a shaped charge  50 .  FIG. 2B  is a sectional view along the line  2 B- 2 B of  FIG. 2A . Shaped charge  50  comprises a case  52  having an open front end  54 , a closed rear end  56 , an interior and a longitudinal axis X-X. Explosive material  58  is disposed in the interior of the case  52 . A liner  60  is disposed over the explosive material  58 . In  FIG. 2A , the dotted lines represent channels within the case  52  and openings into the interior of the case  52 .  FIGS. 2C and 2D  are modified sectional views of  FIG. 2A . For purposes of clarity,  FIGS. 2C and 2D  are planar projections of the channels  62 - 68  and  80 , respectively. 
   Case  52  includes four channels  62 ,  64 ,  66 ,  68  extending from a common opening  70  on the rear end of the case to four diametrically opposed openings  72 ,  74 ,  76 ,  78  in the interior of the case adjacent the explosive material. The common opening  70  on the rear end of the case may be centered on the longitudinal axis X-X. The four openings  72 - 78  in the interior of the case are circumferentially spaced about 90 degrees apart and are equidistant from the longitudinal axis X-X. 
   Case  52  further comprises a fifth channel  80  extending from an opening  82  on the rear end of the case to an opening  84  in the interior of the case adjacent the explosive material. The opening  82  on the rear end of the case is a different opening than the common opening  70  for the four channels  62 - 68 . The opening  84  in the interior of the case is centered on the longitudinal axis X-X. 
   In shaped charges  10  and  50 , each set of channels begins at a common initiation point on the rear end of the case and then forms single or multiple detonation paths to the main explosive in the case. The channels in the case may be filled with an explosive or detonation cord. The desired jet output is produced by selecting and initiating only one of the openings in the rear of the case. One way to do this is to place det cord over the selected openings. As used herein, the “rear” or “rear end” of the case is broadly defined as any portion of the case that is to the rear of the open front end. Thus, the “rear” or “rear end” of the case includes side walls that may be angled, horizontal or curved. 
   In shaped charge  10 , det cord placed only on opening  24  produces a conventional axisymmetric jet for deep penetration. Det cord placed only on opening  32  produces a fan-shaped jet. Det cord placed only on opening  42  produces a wider fan-shaped jet, because the interior openings associated with opening  42  are further forward axially than the interior openings associated with opening  32 . In shaped charge  50 , det cord placed only on opening  82  produces a conventional axisymmetric jet for deep penetration. Det cord placed only on opening  70  produces a cross-shaped or plus sign shaped jet. 
     FIG. 3A  is a rear view of another embodiment of a shaped charge  90 .  FIG. 3B  is a sectional view along the line  3 B- 3 B of  FIG. 3A . Shaped charge  90  comprises a case  92  having an open front end  94 , a closed rear end  96 , an interior and a longitudinal axis X-X. Explosive material  98  is disposed in the interior of the case  92 . A liner  100  is disposed over the explosive material  98 . 
   Case  92  includes a first channel  102  extending from an opening  104  on the rear end of the case  92  along the longitudinal axis X-X to an opening  106  in the interior of the case adjacent the explosive material. A pair of second channels  108 ,  110  extend from a pair of openings  112 ,  114  on the rear end of the case to a pair of diametrically opposed openings  116 ,  118  in the interior of the case adjacent the explosive material. The pair of openings  116 ,  118  are disposed on opposite sides of the opening  106 . 
   Shaped charge  90  further comprises a pair of third channels  120 ,  122  extending from a pair of openings  124 ,  126  on the rear end of the case to a pair of diametrically opposed openings  128 ,  130  in the interior of the case adjacent the explosive material. The pair of openings  128 ,  130  are disposed on opposite sides of the opening  106 , radially outward from the pair of openings  116 ,  118  and axially forward of the openings  116 ,  118 . 
   Additional pairs of channels may be added. Each additional pair of channels ends in diametrically opposed openings in the interior of the case that are radially outward of the preceding pair of interior openings and located axially further forward than the preceding pair of interior openings. For example, a pair of fourth channels  132 ,  134  extends from a pair of openings  136 ,  138  on the rear end of the case to a pair of diametrically opposed openings  140 ,  142  in the interior of the case adjacent the explosive material. Openings  140 ,  142  are disposed on opposite sides of the opening  106 , radially outward from the pair of openings  128 ,  130  and axially forward of the openings  128 ,  130 . 
   Similarly, a pair of fifth channels  144 ,  146  extends from a pair of openings  148 ,  150  on the rear end of the case to a pair of diametrically opposed openings  152 ,  154  in the interior of the case adjacent the explosive material. Openings  152 ,  154  are disposed on opposite sides of the opening  106 , radially outward from the openings  140 ,  142  and axially forward of the openings  140 ,  142 . 
   A pair of sixth channels  156 ,  158  ( FIG. 3A ) extend from a pair of openings  160 ,  162  on the rear end of the case to a pair of diametrically opposed openings (not shown) in the interior of the case adjacent the explosive material. The interior case openings of channels  156 ,  158  have about the same radial and axial position as openings  118 ,  116 , respectively, but are offset circumferentially about ninety degrees from the openings  118 ,  116 . 
   It is the location of the interior openings of the various channels that determine where the explosive  98  will be initiated. Therefore, the precise location of the openings on the rear of the case and the position of the channels is not as important. Preferably, however, for ease of construction, all the channels are substantially parallel to the longitudinal axis X-X with the location of the openings on the rear of the case mirroring the location of the openings in the interior of the case. 
   In shaped charge  90 , each channel begins at an initiation point on the rear and of the case and then forms a single path to the main explosive in the case. The channels may be filled with an explosive or detonation cord. The desired jet output is produced by selecting and initiating certain openings in the rear of the case. One way to do this is to place det cord over the selected openings. 
   In shaped charge  90 , det cord placed on opening  104  produces a conventional axisymmetric jet for deep penetration. Det cord placed on openings  114  and  112  (or  160  and  162 ) produces a fan-shaped jet. Det cord placed on the four openings  114 ,  112 ,  160  and  162  produces a cross-shaped or plus sign shaped jet. Det cord placed on openings  124  and  126  produces a wider fan-shaped jet than openings  114  and  112  (or  160  and  162 ), because the diametrically opposed interior openings associated with openings  124  and  126  are further forward axially than the diametrically opposed interior openings associated with openings  114  and  112  (or  160  and  162 ). Likewise, det cord place on openings  136  and  138  produces a wider fan-shaped jet than openings  124  and  126  and det cord placed on openings  148  and  150  produces a wider fan-shaped jet than openings  136  and  138 . 
   While the invention has been described with reference to certain preferred embodiments, numerous changes, alterations and modifications to the described embodiments are possible without departing from the spirit and scope of the invention as defined in the appended claims, and equivalents thereof.