The paper presents the design and analysis of a spread mooring system for the Delta House Floating Offshore Installation (FOI), which is a production semi-submersible installed in Mississippi Canyon 254 in the Gulf of Mexico in 1350 m water depth. The unit was designed by Exmar Offshore Company (EOC) and owned and operated by LLOG Exploration LLC.

In the design and analysis of the mooring system, one major challenge is modeling polyester rope change-in-length characteristics. Conventional method to envelope maximum vessel offset and maximum line tension using lower and upper bound stiffness is compared to results based on nonlinear change-in-length characteristics from full scale sub-rope tests. Mooring chain fatigue analysis considering vessel Vortex Induced Motion (VIM) and tension Root Mean Square (RMS) amplification due to Out-of-Plane bending (OPB) are performed. Significant effects of VIM and OPB on chain fatigue are found.

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