Method and apparatus for plugging perforations

Abstract

Apparatus and method for plugging perforations in an oil or gas well. A bridge plug is formed in the casing below the perforations. A heating tool and a fusible alloy adjacent the heating tool is lowered into the well to a position above the bridge plug and adjacent the perforations. Heat is applied to melt the fusible alloy and pressure is applied to the molten material to force it through the perforations. The heating operation is terminated to allow the molten material to solidify and plug the perforations.

1 . A heating tool for use in plugging perforations in an oil or gas well, said tool comprising a heating element, a circumferential tube surrounding said heating element, a fusible alloy adjacent to and outside said circumferential tube and means for releasably connecting said circumferential tube and said fusible alloy to said heating element.  
   
   
       2 . A heating tool as in  claim 1  wherein said circumferential tube is a thermally conductive metal material.  
   
   
       3 . A heating tool as in  claim 2  wherein said fusible alloy is formed around said heating tube.  
   
   
       4 . A heating tool as in  claim 1  wherein said means for releasably connecting said circumferential tube and said fusible alloy to said heating element is a latching means which in its closed position retains said tube and which opens to release said circumferential tube and said fusible alloy.  
   
   
       5 . A heating tool as in  claim 2  wherein said fusible alloy is formed in segments which are mounted around said circumferential tube.  
   
   
       6 . Method of plugging perforations in the casing of an oil or gas well comprising the steps of forming a bridge plug in said casing at a position lower than the lowermost perforation sought to be plugged, lowering a heating tool and a fusible metal alloy to a position above said bridge plug and adjacent said perforations sought to be plugged, melting said alloy and applying pressure to said molten alloy to force said molten alloy through said perforations in said casing, lowering the temperature of said heating tool to allow said molten alloy to solidify within said perforations, removing said pressure from said molten alloy and withdrawing said heating tool from said oil or gas well.  
   
   
       7 . Method as in  claim 6  wherein said fusible alloy surrounds said heating tool.  
   
   
       8 . Method as in  claim 7  wherein said fusible alloy is formed on the circumference of said heating tool.  
   
   
       9 . Method as in  claim 7  wherein said fusible alloy is formed in segments and said segments are fitted around said heating tool.  
   
   
       10 . Method as in  claim 9  wherein the quantity of fusible alloy surrounding said heating is sufficient to fill said perforations in said oil or gas well.  
   
   
       11 . Method as in  claim 10  wherein said fusible alloy is a bismuth-tin alloy.  
   
   
       12 . Method as in  claim 11  wherein said heating tool further comprises a heating tube and said fusible alloy extends around the circumference of said heating tube.  
   
   
       13 . Method as in  claim 12  wherein said heating tube is made from aluminum.  
   
   
       14 . Method as in  claim 13  wherein said heating tool is a resistive type heating tool.  
   
   
       15 . Method as in  claim 13  wherein said heating tool is an inductive type heating tool.  
   
   
       16 . Method as in  claim 6  and further comprising depositing a layer of sand on top of said bridge plug.