High Density Perforating Gun System Producing Reduced Debris

Abstract

A perforating system has a perforating module comprising a unitary body of explosive. The explosive is contained within a non-explosive casing, or liner, having formed indentations and a cover thereover. The indentations, which will transform into explosively formed penetrators (EFP's) upon detonation, have a perimeter shape that allows for improved packing density, e.g., a hexagonal perimeter, which results in relatively little “dead space” wherein no perforating penetrators are generated. In operation, the module provides a relatively dense shot pattern and substantially reduced amount of post-detonation debris that could clog the perforations and/or require remedial clean-up or repeat perforation.

1 . A method for perforating a subterranean formation, comprising:
 lowering a plurality of perforating modules in a wellbore,
 wherein each of the plurality of perforating modules comprises:
 a central rod,
 wherein the central rod comprises: 
  an exterior load bearing portion, and 
  an interior detonation portion including a first explosive, 
 
 a second explosive at least partially surrounding the central rod, and 
 a liner surrounding the second explosive,
 wherein the liner has a plurality of shallow concave surface indentations; and 
 
 
   detonating the plurality of perforating modules in the wellbore.   
   
   
       2 . The method of  claim 1 , wherein the central rod further comprises:
 an axial passage.   
   
   
       3 . The method of  claim 2 , wherein the central rod further comprises:
 a conducting wire disposed within the axial passage.   
   
   
       4 . The method of  claim 2 , wherein the axial passage is adapted to receive a hydraulic fluid. 
   
   
       5 . The method of  claim 1 , wherein the plurality of shallow concave surface indentations each have a cavity, the cavity being defined by a diameter and a depth, and wherein the diameter to depth ratio is approximately not less than two to one. 
   
   
       6 . The method of  claim 5 , wherein the diameter to depth ratio is not less than six to one. 
   
   
       7 . The method of  claim 1  wherein the plurality of shallow concave surface indentations each have a cavity, the cavity being defined by a depth, wherein the depth is no greater than a thickness of the liner. 
   
   
       8 . The method of  claim 1 , wherein the plurality of shallow concave surface indentations each have a cavity, and further comprising: forming a plurality of perforations in a region adjacent to the perforating modules, wherein the plurality of perforations extend substantially through a cement layer into a formation a distance from a cement face that is no greater than a diameter of the cavity. 
   
   
       9 . The method of  claim 8 , wherein the distance is no greater than one-half of the diameter of the cavity. 
   
   
       10 . The method of  claim 8 , further comprising at least partially lining the plurality of perforations in the cement layer with a liner material. 
   
   
       11 . The method of  claim 1 , wherein the exterior load bearing portion comprises a frangible material. 
   
   
       12 . The method of  claim 1 , wherein each of the plurality of shallow concave surface indentations is linearly contiguous with at least another of the plurality of shallow concave surface indentations. 
   
   
       13 . The method of  claim 1 , wherein the shallow concave surface indentations are arcuate. 
   
   
       14 . A method for perforating a subterranean formation, comprising:
 lowering a plurality of perforating modules in a wellbore,
 wherein at least one of the plurality of perforating modules is separated from another of the plurality of perforating modules by a spacer, and 
 wherein each of the plurality of perforating modules comprises:
 a central rod,
 wherein the central rod comprises: 
  an exterior load bearing portion comprised of a frangible material, 
  an axial passage adapted to receive hydraulic fluid disposed along the length of the interior load bearing portion, 
  a wire disposed within the axial passage, and 
  an interior detonation portion including a first explosive, 
 
 a second explosive adapted to at least partially surround the central rod, 
 a liner disposed to surround the second explosive,
 wherein the liner is made of a non-explosive material, and 
 wherein the liner has a plurality of shallow concave arcuate surface indentations, 
  wherein each of the plurality of shallow concave arcuate surface indentation is polygonal, 
  wherein each of the plurality of shallow concave arcuate surface indentations is configured to face substantially perpendicular to the longitudinal axis of the wellbore, and 
  wherein each of the plurality of concave arcuate surface is linearly contiguous with at least another of the plurality of shallow concave arcuate surface indentations, and 
 
 
 a cover disposed about the liner; and 
   detonating the plurality of perforating modules in the wellbore.   
   
   
       15 . A method for perforating a subterranean formation, comprising:
 lowering a perforating module into a wellbore having a casing incased in cement, the perforating module having at least one explosively formed penetrator forming charge and liner;   positioning the plurality of perforating modules in the wellbore and adjacent to a substantially unconsolidated formation;   perforating the casing and cement; and   perforating the formation to a distance no greater than a diameter of the at least one explosively formed penetrator forming charge and liner, wherein the distance measured from a boundary between the cement and the formation.