Combined well plug/chemical heater assemblies for use in down-hole operations and associated heater cartridges
The present invention provides a cartridge ( 1 ) for a chemical heater used in down-hole operations. The cartridge ( 1 ) comprises a quantity of a chemical reaction heat source ( 2 ) wrapped in a temporary coating ( 3 ) that is capable of maintaining the shape of the cartridge ( 1 ) prior to use but which is consumed during the burn of the heater. The present invention also provides a eutectic/bismuth based alloy well plugging/sealing tool ( 5 ). The tool ( 5 ) having a tubular heater body ( 6 ) with an internal cavity ( 8 ) capable of receiving a chemical heat source and a quantity of eutectic/bismuth based alloy ( 7 ) provided in thermal communication with the heater body ( 6 ) around an outer surface of the heater body ( 6 ). The tool has a sleeve ( 10 ) provided around an outer surface of the alloy ( 7 ), which insulates and/or mechanically protects the alloy ( 7 ) down-hole. In this way the sleeve ( 10 ) enables the diameter of tool ( 5 ) to be reduced whilst maintaining its functionality. In further aspect, the present invention also discloses the provision of a refractory lining ( 20 ) on the inner walls of the tubular heater body of chemical heaters, such as the heater ( 6 ) used in the eutectic/bismuth based alloy well plugging/sealing tool ( 5 ).
1. A cartridge for a chemical heater used in down-hole operations, the cartridge comprising a plurality of chemical reaction heat sources, wherein the plurality of chemical reaction heat sources are configured to define a shape of the cartridge, and wherein the plurality of chemical reaction heat sources are wrapped and completely surrounded in a temporary coating; whereby the temporary coating maintains the shape of the cartridge during insertion into a well, and whereby the temporary coating is consumed during the burn of the heater.
2. The cartridge of claim 1 , wherein the heat source is wrapped in a plastic film.
3. The cartridge of claim 1 or 2 , wherein the wrapped heat source is held within a flexible elongate surround member.
4. The cartridge of claim 1 or 2 , comprising a flexible surround member, wherein the flexible surround is formed from one or more of the following: fibre glass, thin steel, carbon fibre, and synthetic fibre of a high tensile strength (e.g. Kevlar®).
5. The cartridge of claim 1 or 2 , wherein the chemical reaction heat source is provided in the form of one or more blocks.