Method and apparatus for well casing shoe seal

Abstract

A method and apparatus is disclosed to seal and prevent fluidic communication in the annulus between a cemented and drilled through casing float shoe and a well-bore formation. The present invention provides a component that installs as a coupling unit between a well casing shoe track and a float shoe which integrates a fusible metal alloy. After the well casing is cemented into the well-bore according to conventional procedures, the metal alloy may be melted using a downhole heating device deployed within the casing to a location adjacent to the alloy, thereby causing the alloy to flow, infill, plug and seal any incompetent cracks or micro-annulus conditions within and about the cured cement and well-bore formation.

1 . A method to plug and seal leaking channels occurring in cured well casing cement within the annulus between the wellbore and casing in proximity to a float shoe due to hydrostatic pressure, the method comprising the process steps including:
 a) Installation of a seal coupling component between a first casing section shoe track and a float shoe;   b) Heating of a zone in proximity about said seal coupling including said cement infilling the well-bore and an extent of well-bore formation wherein a fusible alloy material provided about said seal coupling is caused to melt;   c) Progression of molten alloy material through porous channels within said cement and well-bore formations wherein materials surrounding porous channels are heated to a temperature at or above the melting temperature of said alloy material; and   d) Re-solidification of said alloy material to thereby plug and seal leakage channels.   
     
     
         2 . The method of  claim 1 , wherein said metal is a fusible alloy comprising Bismuth, Lead or other compositions suitable for controllable melting by selective heating and re-solidification. 
     
     
         3 . The method of  claim 1 , whereby said coupling component is attached to and between a first section of well casing shoe track and a float shoe. 
     
     
         4 . The method of  claim 1 , wherein said coupling component includes an amount of said fusible alloy precast circumferentially on the outward surface. 
     
     
         5 . The method of  claim 1 , whereby said coupling component incorporates guide rings to protect said precast alloy from scraping against the well casing bore during deployment. 
     
     
         6 . The method of  claim 1 , whereby the heat for melting of said fusible alloy is provided by an electric resistance type heater or inductance type heater. 
     
     
         7 . The method of  claim 1 , whereby the heat for melting said fusible alloy is provided by an exothermal-chemical reaction within said seal coupling component. 
     
     
         8 . The method of  claim 1 , whereby said alloy may be subsequently re-melted. 
     
     
         9 . A seal coupling apparatus attached to and between a conventional shoe track and a float shoe, wherein said apparatus includes the following components:
 a) A threaded coupling at the top end for attachment to the bottom of said shoe track;   b) A threaded coupling at the bottom end for attachment to a conventional float shoe;   c) A center tubular section about which an amount of fusible alloy is provided to be melted;   d) Guide rings located above and below said alloy to prevent scraping said alloy material against the well-bore formation during installation   
     
     
         10 . The apparatus of  claim 8  wherein said guide rings incorporate slot features to facilitate the flow of molten alloy into micro-annulus channels. 
     
     
         11 . The apparatus of  claim 8  wherein said alloy material is cast about said center tubular section. 
     
     
         12 . The apparatus of  claim 8  wherein said alloy material cast into tubular shape and assembled as a component about said center tubular section. 
     
     
         13 . An apparatus to be attached to the bottom section of a well casing, wherein said apparatus includes the following components:
 a) A coupling at the top end for attachment to said well casing,   b) A tubular section to serve as a shoe track,   c) A section of fusible alloy provided about the circumference of a tubular section to serve as a shoe seal component,   d) A float shoe component made part of or coupled to the bottom of the shoe seal component.   
     
     
         14 . A method to plug and seal leaking channels occurring in cured well casing annulus cement in proximity to a seal coupling due to hydrostatic pressure, the method comprising the process steps including:
 e) Installation of one or more seal coupling components between a first and a second casing section;   f) Heating of a zone in proximity about said seal coupling including said cement infilling the well-bore and an extent of well-bore formation wherein a fusible alloy material provided about said seal coupling is caused to melt;   g) Progression of molten alloy material through porous channels within said cement and well-bore formations wherein materials surrounding porous channels are heated to a temperature at or above the melting temperature of said alloy material; and   h) Re-solidification of said alloy material to thereby plug and seal leakage channels.