Propellant for fracturing wells

Abstract

An apparatus for fracturing wells employs a propellant charge with a metallic foil to rapidly ignite the surface of the propellant charge. The assembly can be covered with an protective coating to protect against fluids in the well bore.

1 . An apparatus for fracturing wells comprising: 
 a propellant charge for insertion into a well and having at least one surface;    a metallic foil adjacent to the surface of the propellant charge; and    an ignition element for igniting the metallic foil, and thereby rapidly igniting the surface of the propellant charge.    
   
   
       2 . The apparatus of  claim 1  further comprising a protective layer covering at least a portion of the propellant charge.  
   
   
       3 . The apparatus of  claim 2  wherein the protective layer comprises a fluoroelastomeric material.  
   
   
       4 . The apparatus of  claim 1  wherein the ignition element comprises a piece of propellant generating hot combustion gases to ignite the metallic foil.  
   
   
       5 . The apparatus of  claim 1  wherein the metallic foil comprises nickel and aluminum.  
   
   
       6 . The apparatus of  claim 1  wherein the metallic foil comprises nickel and palladium.  
   
   
       7 . The apparatus of  claim 1  wherein the metallic foil comprises nickel and zirconium.  
   
   
       8 . The apparatus of  claim 1  wherein the propellant charge is divided into a plurality of segments with interior surfaces between adjacent segments, and wherein the metallic foil is sandwiched between the interior surfaces.  
   
   
       9 . The apparatus of  claim 1  wherein the propellant charge has a substantially cylindrical exterior surface covered by the metallic foil.  
   
   
       10 . An apparatus for fracturing wells comprising: 
 a propellant charge for insertion into a well, said propellant charge being divided longitudinally into a plurality of segments with interior surfaces between adjacent segments;    a metallic foil between the interior surfaces of the propellant charge; and    an ignition element for igniting the metallic foil, and thereby rapidly igniting the interior surfaces of the propellant charge.    
   
   
       11 . The apparatus of  claim 10  further comprising a protective layer covering at least a portion of the exterior of the propellant charge.  
   
   
       12 . The apparatus of  claim 11  wherein the protective layer comprises a fluoroelastomeric material.  
   
   
       13 . The apparatus of  claim 10  further comprising a longitudinal passageway extending from the ignition element along an interior surface of the propellant charge for propagation of combustion gases along length of the propellant charge.  
   
   
       14 . The apparatus of  claim 13  wherein ignition element comprises a dowel of propellant in the longitudinal passageway.  
   
   
       15 . The apparatus of  claim 10  wherein foil comprises nickel and aluminum.  
   
   
       16 . An apparatus for fracturing wells comprising: 
 a propellant charge for insertion into a well and having an exterior surface;    a metallic foil covering the exterior surface of the surface of the propellant charge;    a protective layer covering the metallic foil and propellant charge; and    an ignition element for igniting the metallic foil, and thereby rapidly igniting the surface of the propellant charge.    
   
   
       17 . The apparatus of  claim 16  wherein the metallic foil comprises nickel and aluminum.  
   
   
       18 . The apparatus of  claim 16  wherein the protective layer comprises a fluoroelastomeric material.  
   
   
       19 . The apparatus of  claim 16  wherein the propellant charge further comprises a groove in the exterior surface of the propellant charge containing the ignition element.