Abstract:
An initiator device, comprising an explosive foil initiator; an initiator shaped charge that is activated by the explosive foil initiator; the initiator shaped charge comprising an outer casing having an opening therein defining a volume, an explosive located inside the opening, the explosive defining a concave cavity therein; a metal liner lining the concave cavity; and a detonation cord that is activated by the initiator shaped charge.

Description:
PRIORITY 
       [0001]    The present application clams priority to U.S. Provisional Patent Application No. 61/140,949 filed on Dec. 27, 2008, such being incorporated by references in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present application relates to shaped charges, and more particularly to a shaped charge explosive pellet used in conjunction with an initiation design. 
       BACKGROUND 
       [0003]    Hydrocarbons and other desirable fluids are located below the earth&#39;s surface and/or below the seafloor. To gain access to the hydrocarbons a well is drilled into the earth. The well is normally cased with a metal casing that is secured in place by cement. To produce the hydrocarbons it is often advantageous to perforate portions of the casing to allow hydrocarbons and other reservoir fluids to flow from the formation through the perforations and into the casing. Once the hydrocarbons are inside the casing they can be produced to the surface. 
         [0004]    The perforations are commonly created using shaped charges. Shaped charges have a case, explosive material, and an inverted conical liner. The internal shaped charge geometry is arranged such that when the explosive initiates, the case confines the detonation, and the inverted conical liner collapses to produce a high-pressure jet of liner material. When a shaped charge is used in an oil well, the jet that is produced penetrates the casing, cement, and reservoir rock. 
         [0005]    Shaped charges are generally delivered into an oil well using a perforating gun, which is a specially designed longitudinally extending tubular device. Shaped charges are commonly arranged in a perforating gun such that each charge is located in close proximity to a detonating cord. The detonating cord extends along the perforating gun and may be initiated in a variety of ways depending on the situation. 
         [0006]    The present application relates to and describes a design for advantageously initiating the detonation cord by utilizing a miniature shaped charge. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a cross-sectional schematic of a miniature shaped charge initiator device according to an embodiment. 
           [0008]      FIG. 2  is a cross-sectional schematic relating to manufacture of the device shown in  FIG. 1 . 
           [0009]      FIG. 3  is a schematic showing an embodiment of an initiation design whereby the detonation cord is initiated from its end. 
           [0010]      FIG. 4  is a schematic showing an embodiment of an initiation design whereby the detonation cord is initiated with the aid of an explosive booster. 
           [0011]      FIG. 5  is a schematic showing an embodiment of an initiation design whereby the detonation cord is initiated via a perpendicular miniature shaped charge. 
           [0012]      FIG. 6  is a schematic showing the low-resistance bridge used in an explosive foil initiator. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The following description concerns a number of embodiments and is meant to provide an understanding of the embodiments. The description is not in any way meant to limit the scope of any present or subsequent related claims. 
         [0014]    As used here, the terms “above” and “below”; “up” and “down”; “upper” and “lower”; “upwardly” and “downwardly”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or diagonal relationship as appropriate. 
         [0015]      FIG. 1  shows an embodiment of a miniature initiator shaped charge  1  according to an embodiment. The initiator shaped charge  1  includes a casing  10  that has an opening therein that contains explosive  12 . Preferably the explosive  12  is high explosive, e.g., Nonanitroterphenyl (abbreviated Nona) or hexanitrostilbene (abbreviated HNS). Nona and HNS are commercially available and therefore not described in excessive detail in the present application. The explosive  12  defines an indentation that is preferably conical in shape. A liner  14  is located in the indentation and adjacent to the explosive  12 . Preferably the shape of the liner  14  conforms to the shape of the indentation, e.g., conical, and is directly against the explosive  12 .  FIG. 1  shows that the explosive  12  is exposed on one side of the opening in the casing  10  and is covered by the liner  14  on the opposite side. Preferably the liner  14  is metal. 
         [0016]    The initiator shaped charge  1  is made by a process according to an embodiment involving locating, e.g., pressing, a metal cone  16  made from a first metal having a coating (liner material) of a second metal  14 , into the explosive  12 . The metal cone  16  of the first metal should have different solubility characteristics than the liner  14 . A preferable embodiment includes using a solid copper cone  16  coated with a second metal liner part  14  that is not soluble in nitric acid (i.e. gold, etc.). The bottom of the cone  16  is not coated with the liner  14  material so that immersion in a solvent, e.g., nitric acid, results in removal of the copper cone  16  leaving the coating behind to form the liner. In this manner, a miniature shaped charge is produced having a metal liner  14  in the shape of an inverted cone. 
         [0017]    Several embodiments are capable of accomplishing coating of the cone  16  with a liner  14  material. One is sputter coating, which involves the cone  16  being placed on a cathode plate beneath a sputtering target of the desired coating material in a vacuum chamber. When a voltage is applied to the sputtering target under vacuum, metal ions are produced within the chamber and are attracted to the cathode plate (i.e., cone  16 ) thereby creating a coating on any exposed surface of the copper cone  16 . In this scenario, the cone  16  should be placed on its base to avoid coating with the liner  14  material in that region. Electroplating is another possible manner for producing the coating. 
         [0018]      FIG. 2  shows an embodiment relating to the manufacturing description above including a cone  16 . 
         [0019]      FIGS. 3 ,  4 , and  5  shows schematics of initiation designs according to the present application. An explosive foil initiator device  3  (depicted in  FIGS. 3 ,  4 , and  5 ) is shown in  FIG. 6  from a front-on view. A capacitor  9  is connected electrically with a low-resistance electric bridge  7 . When the capacitor  9  is charged and that energy released, the low electrical resistance of the bridge results in a high flow of current that causes the bridge to explode, propelling material at a high velocity into the exposed portion of the explosive  12  in the initiator shaped charge  1 . The explosive then initiates, collapsing the liner  14  and forming a high-pressure jet. In  FIGS. 3 and 5 , the jet directly impacts the detonating cord  18  causing the detonating cord  18  to initiate. As shown in  FIG. 4 , the jet impacts and initiates an explosive-loaded booster  19 , which in turn initiates the detonating cord  18 . It is, however, preferable to remove the requirement for a booster, as the miniature shaped charge is capable of directly initiating detonating cord. Later in the explosive train, the detonating cord  18  is located near a shaped charge  20  and initiates the shaped charge  20 . The shaped charge  20  can include a case  22 , a liner  24 , explosive between the case  22  and the liner  24 , and an explosive primer region  28 . 
         [0020]    The detonating cord  18  leads to a shaped charge  20 . The shaped charge  20  has a cuplike shaped case  22 , a liner  24 , and explosive  26  located between the case  22  and the liner  24 . An explosive primer region  28  is integrated within the case  22  thereby assisting in the detonation of the explosive  26 . 
         [0021]    Advantageous aspects of the device are, for example, its simplicity, potential to use less explosive  12  by elimination of the explosive-loaded booster that exists in the current state-of-the-art, capability to directly initiate detonation cord  18  by way of the initiator shaped charge  1 , and capability to initiate detonation cord from any location along its length within a perforating gun. 
         [0022]    The embodiments described herein are meant to provide a full understanding of the embodiments, and are not meant in any way to limit the claims herein, or any subsequent related claims.