Method of installing a bismuth bridge plug

Abstract

A method of suspending a well comprises the steps of lowering a tool assembly into a into the well, the tool assembly comprising an upper housing including a connection means for lowering the tool, a first heating element, and, a quantity of bismuth disposed in proximity to the heating element, and a lower tool to be left in the well comprising a mandrel and an annular seal connected to the mandrel. The first heating element is actuated to melt the bismuth so that it forms in an annular space defined between the lower tool and the casing of the well above the annular seal to seal the well, releasing the upper housing from the lower tool retrieving the upper housing.

1 . A method of suspending a well comprising the steps of
 lowering a tool assembly into a well,
 the tool assembly comprising:
 an upper housing including a connection for lowering the tool, 
 a first heating element, 
 a quantity of bismuth disposed in proximity to the heating element, and 
 a lower tool to be left in the well comprising:
 a mandrel, and 
 an annular seal connected to the mandrel 
 
 
   actuating the first heating element to melt the bismuth so that it forms in an annular space defined between the lower tool and a casing of the well above the annular seal to seal the well,   releasing the upper housing from the lower tool, and   retrieving the upper housing.   
     
     
         2 . A method according to  claim 1  wherein the first heating element is included in the upper housing. 
     
     
         3 . A method according to  claim 1  wherein the bismuth initially secures the upper housing to the lower tool, and the step of melting the bismuth releases the upper housing from the lower tool, and including the step of retrieving the upper housing. 
     
     
         4 . A method according to  claim 1  wherein the tool assembly is lowered on a wireline. 
     
     
         5 . A method according to  claim 1  wherein the bismuth is cast around first heating element. 
     
     
         6 . A method according to  claim 1 , further comprising
 testing the pressure of the well prior to actuating a second heating element, and   equalising the pressure above and below the annular seal if necessary, and   wherein a pressure sensor is included in the lower tool.   
     
     
         7 . A method according to  claim 1  wherein a pre cast bismuth plug is included in the lower tool. 
     
     
         8 . A method according to  claim 1  wherein the tool assembly includes a brush or brushes which clean a surface of the casing where the bismuth plug is to be cast. 
     
     
         9 . A method according to  claim 1  wherein the annular seal is set against a chamfered surface to allow the seal to flex before it is finally positioned. 
     
     
         10 . A method according to  claim 1  wherein a brush or brushes are set against chamfered surfaces to allow the seal to flex before it is finally positioned. 
     
     
         11 . A method according to  claim 1  wherein tool assembly includes a cavity which can be filled with bismuth in shot form. 
     
     
         12 . A method according to  claim 1  wherein mandrel of the lower tool is secured to the upper housing by a shaped slot, such that the lower tool can move relative to the upper housing when the bismuth is initially melted, and allowing the release of the upper housing from the lower tool. 
     
     
         13 . A method according to  claim 1 , further comprising:
 deploying a retrieval tool in the well to engage with a fishing profile, and   retrieving the lower tool, and   wherein the lower tool comprises the fishing profile.   
     
     
         14 . A method according to  claim 12 , further comprising:
 connecting the retrieval tool to an electrical connection and supplying power to a second heating element,   melting the bismuth above the annular seal and releasing the lower tool for retrieval so that it flows into a container,   releasing the lower tool from the well casing, and   retrieving the lower tool and bismuth, and   wherein the lower tool further comprises
 a second heating element 
 an electrical connection 
 the container. 
   
     
     
         15 . A tool assembly according to  claim 1 . 
     
     
         16 . A lower tool according to  claim 1 . 
     
     
         17 . An upper housing according to  claim 1 . 
     
     
         18 . A retrieval tool according to  claim 1 .