Abstract
Butt welding of coiled tubing performed routinely in both new and used tubing extends life or increases application versatility of existing strings. Welds are commonly made to replace overly fatigued sections, remove mechanical damage, extend string length, and attach special application strings or tools to work reels and repair tubing imperfections. Properly designed and executed butt welds provide the same load bearing properties of the surrounding tubing. The weld integrity is verified by non-destructive testing, insuring sound joints. The fatigue properties of the weld must be understood and properly managed. This has resulted in an extremely successful record for butt welds placed in coiled tubing for field application.
The paper documents the steps required to insure the best weld quality is being placed into a string of coiled tubing. Data on properties of welds from manual and machine welds, in both new and used tubing verify the load carrying capability of the welds. The down rating of fatigue life and potential corrosion implications are handled through continuous string management. The field experience of butt welds performed in both factory and field environments are reviewed. Results indicate the clear cost effectiveness of currently available, properly installed butt welds combined with systematic monitoring by the relevant service companies.
