During conceptual engineering for a deepwater Gulf of Mexico field development project, the option of a long distance dual flowline tie-back to a semi-submersible platform was assessed. Pipe-in-pipe (PIP) steel cantenary risers (SCRs) were considered for connecting the PIP flowlines to the platform, to satisfy stringent thermal insulation requirements. Preliminary analysis results for the PIP SCRs based on an equivalent single pipe finite element (FE) model and use of generic correction factors to account for PIP behavior indicated marginal performance for both fatigue and extreme hurricane loading conditions. Therefore, to improve response prediction accuracy, application-specific correction factors were established by comparing results from the single pipe model and a detailed PIP model, for selected static and dynamic load cases. This paper describes the analysis models and methodology, the load cases assessed, and summarizes the results and conclusions.
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