Multi-layer loading tube for perforating gun

Abstract

A perforating gun for perforating a casing of a well includes one or more shaped charges configured to perforate the casing; a loading tube configured to hold the one or more shaped charges; a housing having a cylindrical shape and configured to receive inside the loading tube and the one or more shaped charges; and a protective tube located in an annulus formed between the housing and the loading tube.

What is claimed is: 
     
         1 . A perforating gun for perforating a casing of a well, the perforating gun comprising:
 one or more shaped charges configured to perforate the casing;   a loading tube configured to hold the one or more shaped charges;   a housing having a cylindrical shape and configured to receive inside the loading tube and the one or more shaped charges; and   a protective tube located in an annulus formed between the housing and the loading tube.   
     
     
         2 . The perforating gun of  claim 1 , wherein the loading tube, the protective tube, and the housing are concentric to each other. 
     
     
         3 . The perforating gun of  claim 1 , wherein the protective tube fully encircles the loading tube. 
     
     
         4 . The perforating gun of  claim 1 , wherein the protective tube includes plural discrete sections, each section fully enclosing a corresponding portion of the loading tube. 
     
     
         5 . The perforating gun of  claim 1 , wherein the protective tube has plural holes, each hole being configured to receive a corresponding shaped charge of the one or more shaped charges. 
     
     
         6 . The perforating gun of  claim 1 , wherein the housing has plural scallops, and the protective tube has plural holes, and each hole is radially aligned with a corresponding scallop. 
     
     
         7 . The perforating gun of  claim 1 , wherein the protective tube is located so that there is a first annulus between the loading tube and the protective tube and a second annulus between the protective tube and the housing. 
     
     
         8 . The perforating gun of  claim 1 , further comprising:
 plural legs that extend throughout an entire wall of the protective tube to contact the loading tube,   wherein the plural legs maintain the protective tube centered around the loading tube.   
     
     
         9 . The perforating gun of  claim 1 , further comprising:
 end plates that attach to the loading tube, the end plates having one or more slots so that tabs of the protective tube enter the one or more slots and the protective tube is maintained around the loading tube without touching the loading tube.   
     
     
         10 . The perforating gun of  claim 1 , wherein only the one or more shaped charges holds the protective tube around the loading tube. 
     
     
         11 . The perforating gun of  claim 1 , wherein the protective tube includes two or more concentric tubes having different thicknesses or made of different materials. 
     
     
         12 . The perforating gun of  claim 1 , further comprising:
 a detonator cord that connects to the one or more shaped charges; and   a detonator configured to ignite the detonation cord,   wherein the detonator is located inside the housing but outside the protective tube.   
     
     
         13 . The perforating gun of  claim 1 , wherein the protective tube is configured to not interfere with a melted jet produced by the one or more shaped charges. 
     
     
         14 . A perforating gun for perforating a casing of a well, the perforating gun comprising:
 one or more shaped charges configured to perforate the casing;   a loading tube configured to hold the one or more shaped charges;   a protective tube located around the loading tube and configured to receive the one or more shaped charges in corresponding holes; and   a housing located around the protective tube.   
     
     
         15 . The perforating gun of  claim 14 , wherein the loading tube, the protective tube, and the housing are concentric to each other. 
     
     
         16 . The perforating gun of  claim 14 , wherein the protective tube is located so that there is a first annulus between the loading tube and the protective tube and a second annulus between the protective tube and the housing. 
     
     
         17 . The perforating gun of  claim 14 , further comprising:
 plural legs that extend throughout an entire wall of the protective tube to contact the loading tube,   wherein the plural legs maintain the protective tube centered around and radially distanced from the loading tube.   
     
     
         18 . The perforating gun of  claim 14 , further comprising:
 end plates that attach to the loading tube, the end plates having one or more slots so that tabs of the protective tube enter the one or more slots and the protective tube is maintained around the loading tube without touching the loading tube.   
     
     
         19 . A method for protecting a housing of a perforating gun from excessive damage, the method comprising:
 placing one or more shaped charges into a loading tube of a perforating gun;   covering the loading tube with a protective tube; and   loading the loading tube with the protective tube into a housing of the perforating gun,   wherein the protective tube is located in an annulus formed between the loading tube and the housing.   
     
     
         20 . The method of  claim 19 , further comprising:
 centering the protective tube around the loading tube.