Method and apparatus for locking charges into a charge holder

Abstract

The invention uses a pair of opposed tabs on the charge holder to engage a groove in the case of the shape charge. The case is generally conical in shape. However, the front opening of the case has both a first and second circumferential ridge separated by a groove. The diameter of the groove generally matches the distance between tabs. The second ridge can have a flat milled thereon to allow case to be inserted until the tabs contact the forward or first ridge. This locates the tabs between the first and second ridges and over the groove. The case is then rotated so that the tabs are captured between the two ridges. Once installed, the detonation cord is attached to the case. The cord helps prevent any rotation of the case, thereby securing it into the charge holder. Thus, the use of easily milled tabs on the charge holder in conjunction with an easily milled groove and flats on the case provide an improved apparatus and method for securing the shape charge into the charge holder of a perforation gun. When the charges are all installed, and the detonation cord is properly linked between each charge, then the charge holder can be placed in a carrier.

We claim:  
     
         1 . A charge holder for accepting an explosive charge in a case, said charge holder comprising: 
 a loading tube including at least one hole disposed through a wall of said loading tube, said hole having a circumference defining at least one tab.    
     
     
         2 . The charge holder of  claim 1  wherein said case comprises a rear ridge.  
     
     
         3 . The charge holder of  claim 1  wherein said case comprises a first and second ridge defining a groove between, and wherein said tab can be captured within said groove.  
     
     
         4 . The charge holder of  claim 3  wherein said case further comprises a flat to allow the at least one tab access to said groove.  
     
     
         5 . The charge holder of  claim 1  wherein said case further defines a cord retainer for retaining a detonation cord.  
     
     
         6 . The charge holder of  claim 3  wherein the circumference has a diameter approximately equal to a diameter of the first ridge.  
     
     
         7  The charge holder of  claim 3  wherein said tab has a length approximately equal to a depth of the groove.  
     
     
         8 . A perforation gun comprising: 
 (a) a charge holder for accepting at least one explosive charge stored in a case;    (b) a cover for use over the charge holder; and    (c) a detonation cord for connecting the at least one explosive charge to a detonation source;    wherein the charge holder comprises a loading tube including at least one hole disposed through a wall of said loading tube, said hole having a circumference defining at least one tab.    
     
     
         9 . The perforation gun of  claim 8  wherein said case has a rear ridge.  
     
     
         10 . The perforation gun of  claim 8  wherein said case comprises a first and second ridge defining a groove between, and wherein said tab can be captured within said groove.  
     
     
         11 . The perforation gun of  claim 10  wherein said case further comprises a flat to allow the at least one tab access to said groove.  
     
     
         12 . The perforation gun of  claim 8  wherein said case further defines a cord retainer for retaining a detonation cord.  
     
     
         13 . The perforation gun of  claim 10  wherein the circumference has a diameter approximately equal to a diameter of the first ridge.  
     
     
         14  The perforation gun of  claim 10  wherein said tab has a length approximately equal to a depth of the groove.  
     
     
         15 . A method of loading a perforation gun comprising the steps of: 
 (a) inserting at least one explosive charge in a case into a charge holder comprises a loading tube including at least one hole disposed through a wall of said loading tube, said hole having a circumference defining at least one tab; and wherein the case has a groove for accepting the tab; and    (b) rotating the case to capture the tab within the groove.    
     
     
         16 . The method of  claim 15  further comprises: 
 (c) attaching a detonation cord to a cord retainer on the case.  
 
     
     
         17 . The method of  claim 15  further comprises: 
 (c) placing a cover over the charge holder.  
 
     
     
         18 . A method of perforating a well comprising the steps of: 
 (a) loading a carrier holder with at least one explosive charge in a case, wherein the charge holder has at least one hole disposed through a wall, said hole having a circumference defining at least one tab; and wherein the case has a groove for accepting the tab;    (b) rotating the case to capture the tab within the groove.    (c) attaching a detonation cord to a cord retainer on the case.    (d) lowering the carrier holder into the well; and    (e) detonating the at least one explosive charge.    
     
     
         19 . The method of  claim 17  further comprises placing a cover over the charge holder before lowering the carrier holder into the well.