Qualification of Reeled Clad SCR Weld Fatigue Performance

Steel Catenary Risers (SCRs) are commonly used in deepwater field developments due to the cost benefits associated with their relatively simple geometry. Installation of SCRs by reel lay is generally the most cost effective approach. One of the major design challenges for SCRs is ensuring adequate fatigue performance at highly stressed regions. Since many deepwater projects require corrosion resistant alloy materials due to sour service requirements, an attractive option is to use metallurgically bonded clad pipes. However, there are very limited full scale fatigue test data available for clad SCR welds to confirm the technical viability of installing clad SCRs using the reel lay method. Thus, a study program was developed to qualify a suitable welding procedure for clad SCRs and to demonstrate that the required fatigue performance can be achieved using reel lay as the method for installation. This paper presents the testing results from the study program, which included full-scale qualification of clad X-65 pipe with alloy 625 welds having undergone reeling simulations. The results from this qualification program demonstrate that the selected welding procedure achieves high quality clad SCR welds with excellent fatigue performance in the reeled condition. This will enable projects using clad SCRs to consider reel lay as an acceptable method of installation. It will also extend the applicability of clad SCRs installed by the reel lay method to more severe environment conditions. This paper also discusses the impact on fatigue performance resulting from different reeling simulation approaches.