Method for interconnecting adjacent expandable pipes

1. A method for interconnecting adjacent expandable pipes, wherein the pipes are circumferentially welded together by laser beam welding; wherein the laser beam welding further comprises using a tool which is transformed into a downhole laser beam cutting tool to cut off a partially expanded pipe string below an expansion mandrel or roller that is stuck downhole, and which laser beam cutting tool passes through an orifice in the expansion mandrel or roller.

2. The method of claim 1 , wherein an Nd:YAG laser or CO 2 laser is used.

3. The method of claim 1 , wherein the pipes are interconnected in a welding station on a rig near the bore hole.

4. The method of claim 3 , wherein the laser energy is transmitted through a fibre optical cord from a laser source that is up to 200 meters removed from the welding station.

5. The expandable pipe strings prepared in accordance with the method of claim 1 .

6. The expandable pipe strings of claim 5 , that are made of a malleable steel, selected from the group consisting of carbon steel, duplex stainless steel and martensitic stainless steel, including 13 Cr and super 13 Cr oilfield grades.

7. A method for preparing expanded pipes wherein an expandable pipe as claimed in claim 5 is expanded.

8. The method of claim 7 , wherein the expandable pipe is expanded by moving a mandrel and/or a roller through the pipe.

9. The method of claim 7 , for the production of a casing, a production tubing or protective cladding in wellbore operations.

10. The method of claim 9 , comprising the steps of: lowering an expandable pipe into a well until the upper end thereof is located near the entrance of the well:

a) aligning and fixing a second expandable pipe in axial direction with the first pipe;

b) interconnecting the first pipe and second pipe by circumferential laser beam welding;

c) lowering the interconnected pipes into the well; and

d) expanding the interconnected pipes with a mandrel and/or a roller.

11. The method of claim 1 , wherein the interconnected ends of the expandable pipes are equipped with complementary screw threads and are screwed together such that ring-shaped gaps are formed adjacent to the interconnected ends of the expandable pipes, and wherein at least one ring-shaped gap at the outer or inner surface of the interconnected ends of the expandable pipes is circumferentially welded by laser beam welding.

12. The method of claim 1 , wherein the laser beam welding comprises a tool which is transformed into a laser beam cutting tool in case a weld made by laser beam welding is rejected.

13. The method of claim 1 , wherein the laser beam welding comprises a tool which is transformed into a downhole laser beam welding tool to weld a leaking expanded pipe connection and/or other well component downhole.

14. The method of claim 1 , wherein the laser beam welding comprises a tool which is equipped with an optical tracking system for guiding the laser beam at a predetermined distance relative to the pipe ends during the laser beam welding process. relative to the pipe ends during the LBW process.