Improvements relating to downhole heater assemblies and methods of operating such

Abstract

The present invention relates to a downhole heater assembly comprising at least one heating tool with a delivery support connection point, by which the heating tool is connectable to delivery means via a delivery support such that said heating tool can be delivered to and retrieved from a downhole target region of a borehole. The assembly is provided with a baffle that is configured to be positionable in the borehole at a location between said heater tool and said delivery means. When in position said baffle acts to restrict the movement of heated fluids produced during the operation of the heating tool so as to at least partially replicate the fluid flow conditions found in the test vessel in which the heating tool's configuration was originally tested. The present invention also provides associated methods that employ a baffle between a heating tool and the above ground delivery means used to deploy the heating tool downhole.

1 . A method of heating a downhole target region of a borehole using a downhole heater assembly, said method comprising:
 a) delivering a heating tool to the target region of the borehole using a delivery support connected to above-ground delivery means;   b) positioning a baffle in the borehole at a location between the heating tool and the delivery means, wherein the baffle is configured to at least partially restrict the flow of fluids within the borehole;   c) operating the heating tool so as to generate heat within the target region of the borehole; and   d) retrieving the baffle and the heating tool from the borehole.   
     
     
         2 . The method of  claim 1 , comprising providing the baffle on the delivery line/pipe. 
     
     
         3 . The method of  claim 1  or  2 , wherein the baffle and the heater are delivered downhole at the same time. 
     
     
         4 . The method of  claim 1  or  2 , wherein the baffle is positioned downhole after the heating tool has been delivered to the target region. 
     
     
         5 . The method of  claim 1 ,  2 ,  3  or  4 , said method further comprising the step of delivering the baffle downhole in an unexpanded state and then expanding the baffle towards the walls of the borehole so as to increase the extent to which the baffle restricts the flow of fluids within the borehole. 
     
     
         6 . The method of  claim 5 , wherein the expansion of the baffle is co-ordinated with the operation of heating tool. 
     
     
         7 . The method of  claim 5  or  6 , wherein the expansion of the baffle is controlled by the heating tool. 
     
     
         8 . The method of any of the preceding claims, wherein the baffle is positioned up to 20 m (approx. 70 feet) above the heating tool, and preferably between 0.3 to 1.0 m (approx. 1 to 3 feet). 
     
     
         9 . The method of any of the preceding claims, wherein operating the heating tool comprises the use of a chemical reaction heat source, such as a thermite based material, to generate the heat within the target region. 
     
     
         10 . A downhole heater assembly comprising at least one heating tool with a delivery support connection point, by which the heating tool is connectable to delivery means via a delivery support such that said heating tool can be delivered to and retrieved from a downhole target region of a borehole; and
 wherein the assembly further comprises a baffle configured to be positionable in the borehole at a location between said heater tool and said delivery means, said baffle being configured to restrict the movement of heated fluids produced during the operation of the heating tool.   
     
     
         11 . The downhole heater assembly of  claim 10 , wherein the baffle is located between the heating tool and the delivery support connection point. 
     
     
         12 . The downhole heater assembly of  claim 10 , further comprising a delivery support connected to the delivery support connection point and wherein the baffle is located on the delivery support. 
     
     
         13 . The downhole heater assembly of  claim 10 ,  11  or  12 , wherein the baffle is configured to be expandable towards the walls of the borehole so as to increase the extent to which the baffle restricts fluid movement within the borehole. 
     
     
         14 . The downhole heater assembly of  claim 13 , wherein the mechanism by which the expansion of the baffle is achieved is selected from hydraulic means, pneumatic means, mechanical means and combinations thereof. 
     
     
         15 . The downhole heater assembly of  claim 13  or  14 , wherein the assembly comprises control means that co-ordinate the operation of the heating tool and the expansion of the baffle. 
     
     
         16 . The downhole heater assembly of any of  claims 13 ,  14 , or  15 , wherein the control means that control the expansion of the baffle are provided on the heating tool. 
     
     
         17 . The downhole heater assembly of any of  claims 13  to  16 , wherein the baffle is urged to expand and/or contract by way of one or more resilient biasing means. 
     
     
         18 . The downhole heater assembly of  claim 17 , wherein the baffle comprises a canopy of flexible material connected to an umbrella spring mechanism. 
     
     
         19 . The downhole heater assembly of any of  claims 10  to  18 , wherein the baffle is positioned a distance of up to 6 m (approx. 20 feet) from the heating tool, and preferably between 0.3 to 1.0 m (approx. 1 to 3 feet). 
     
     
         20 . The downhole heater assembly of any of  claims 10  to  19 , wherein said at least one heating tool employs a chemical reaction based heat source. 
     
     
         21 . The downhole heater assembly of any of  claims 10  to  20 , wherein the baffle comprises insulating means. 
     
     
         22 . A method of deploying a eutectic/bismuth based alloy based tool in a downhole target region, said method comprising:
 delivering the eutectic/bismuth based alloy based tool to the downhole target region,   heating the tool using the heating method of any of  claims 1  to  9 .   
     
     
         23 . A method of clearing an underground conduit from a borehole, wherein the underground conduit is melted using the heating method of any of  claims 1  to  9 .