Tool for metal plugging or sealing of casing

1. A device for sealing perforations or leaks in a well, comprising:

a) a generally cylindrical sleeve having sides and an open top and a closed bottom and a cylindrical oversleeve made of meltable plugging material molded around an outside surface of said sleeve, said oversleeve covering said sides and bottom of said sleeve;

b) a heater located inside the sleeve, the heater comprising a thermite mixture;

c) an ignition mechanism that ignites said thermite mixture upon actuation, said ignition mechanism inside said sleeve and contacting said thermite; and

d) a line detachably connected to said sleeve and said line connected to said ignition mechanism, such that said sleeve can be detached and left behind to form a sealed casing with said sleeve bonded to said plugging material when said ignition mechanism is retrieved from a subterranean well.

2. The device of claim 1 , wherein said sleeve plus oversleeve has an outer diameter smaller than an inner diameter of the well casing.

3. The device of claim 1 , wherein the thermite is nano-thermite.

4. The device of claim 1 , wherein said ignition/heater mechanism is a drop bar ignition, a pressure ignition, or a wireline ignition.

5. The device of claim 4 , wherein said line is tubing string.

6. The device of claim 4 , wherein said line is wireline.

7. The device of claim 4 , wherein said line is coiled tubing.

8. A system for sealing perforations or leaks in a well casing or tubular in a subterranean well, comprising:

a) a generally cylindrical sleeve having sides and an open top and a closed bottom;

b) a heater located inside the sleeve, the heater comprising a thermite mixture;

c) an ignition mechanism that ignites the thermite mixture upon actuation;

d) an oversleeve of meltable plugging material molded over an outside surface of said sleeve, said oversleeve being cylindrical and covering said sides and bottom of said sleeve;

e) a line connected to said ignition mechanism and said line detachably engaging said sleeve, such that said sleeve can be detached and left in said well to form a sealed casing with said sleeve bonded to said plugging material, thereby reducing an amount of molten plugging material needed to seal said well between a well wall and said sleeve, as compared to a system that removes the sleeve; and

f) a blocking device at or below a bottom end of said zone to be sealed.

9. The system of claim 8 , wherein the sleeve plus said oversleeve has an outer diameter smaller than the inner diameter of the well casing.

10. The system of claim 8 , wherein the thermite is nano-thermite.

11. The system of claim 8 , wherein the ignition mechanism is a drop bar ignition, a pressure ignition, or a wireline ignition.

12. The system of claim 8 , further comprising a leak detector selected from an infrared detector, an acoustic energy detector, or a camera.

13. The system of claim 8 , wherein the oversleeve of meltable plugging material is an expandable bismuth alloy.

14. A method for sealing a well casing in a subterranean well, comprising:

a) lowering a blocking device into a well casing to block a bottom of a zone of a well to be sealed, unless said zone is already blocked with a blocking device;

b) lowering a body or pellets of a meltable plugging material into said well casing to rest on said blocking device;

c) lowering a plugging tool into the well casing before or after step b), the plugging tool comprising a generally cylindrical sleeve having an open top and a closed bottom, a heater located inside the sleeve, the heater comprising a thermite mixture and an ignition mechanism that ignites the thermite mixture upon actuation, and a line connected to said ignition mechanism and said line detachably connected to said sleeve;

d) melting the meltable plugging material by igniting the thermite thereby transferring heat to the meltable plugging material;

e) cooling the plugging tool and the plugging material until the melted plugging material solidifies in a space between a wall of said well and an exterior of said sleeve, wherein an amount of plugging material deployed in step b is less than would be required by a system that removes said sleeve;

f) disengaging said line from said sleeve and retrieving said line with the ignition mechanism.

15. The method of claim 14 , further comprising g) drilling out or milling out said sleeve.

16. The method of claim 15 , further comprising, after step g):

h) evaluating a sealed section of the well casing to determine whether sealing is complete.

17. The method of claim 14 , wherein the sleeve has an outer diameter smaller than an inner diameter of the well casing.

18. The method of claim 14 , wherein the thermite is nano-thermite.

19. The method of claim 14 , wherein the ignition mechanism is a drop bar ignition, a pressure ignition, or a wireline ignition.

20. The method of claim 14 , wherein the plugging tool further comprises a leak detector selected from an infrared detector, an acoustic energy detector, and a camera.

21. The method of claim 20 , further comprising, after step c):

c-1) determining an optimal location to place the plugging tool by detecting an actual leakage on the well casing.

22. The method of claim 14 , wherein the meltable plugging material is an expandable bismuth alloy.

23. The method of claim 14 , further comprising the step of plugging the sleeve with a meltable alloy.

24. The method of claim 14 , further comprising drilling out or milling out the sleeve, and plugging a remaining volume with a meltable alloy.

25. A method for sealing a well casing in a subterranean well, comprising:

a) lowering a blocking device into a well casing to block a bottom of a zone of a well to be sealed;

b) lowering a plugging tool into the well casing immediately on top of the blocking device, the plugging tool comprising a generally cylindrical sleeve having sides and an open top and a closed bottom, a heater located inside the sleeve, the heater comprising a thermite mixture and an ignition mechanism that ignites the thermite mixture upon actuation, and a line connected to said ignition mechanism and said line detachably connected to said sleeve, an oversleeve of a meltable plugging material molded on an outside of the sleeve, said oversleeve being cylindrical and covering said sides and bottom of said sleeve;

c) melting the meltable plugging material by igniting the thermite thereby transferring heat to the meltable plugging material;

d) cooling the melted plugging material until the plugging material re-solidifies in a space between a wall of said well and said sleeve with a reduced amount of plugging material as compared to a system that removes said sleeve;

e) disengaging said line from said sleeve and retrieving said line with the ignition mechanism and exhausted thermite residue.

26. The method of claim 25 , further comprising drilling out or milling out said sleeve.

27. The method of claim 25 , further comprising the step of plugging the sleeve with a meltable alloy.

28. The method of claim 25 , further comprising drilling out or milling out the sleeve, and plugging a remaining volume with a meltable alloy.