This project began as a consequence of the DeepStar-sponsored workshop held October 29-30, 1998. OTRC conducted this workshop entitled ‘Deepwater Mooring and Riser Analytical Capabilities’ for the purpose of assessing industry capabilities and technology needs in the deepwater vessel motions, mooring system and riser analysis area. Results of the workshop indicated the top priority need to be comparative analyses of “theme structures” in 3,000 to 10,000 ft water depth and benchmarking these with model data. DeepStar Phase IV funded a comparative analysis study to be managed by OTRC.
In order to obtain the broadest possible sampling of industry analysis capabilities, the community of contractors/consultants known to work in the floating production systems field was invited to participate by contributing their analyses for one or more of the theme structures. System specifications and environmental conditions were developed and sent to all participants. Later the analysis results of the participants were sent to OTRC in spreadsheet format for review and intercomparison. Eleven entities contributed analyses of one or two of the systems specified; none analyzed all three. They are ABB Lummus, American Bureau of Shipping, Aker Maritime (including Spars International), Boston Marine, Chevron, Det Norske Veritas, Imodco, Marnitek, Mentor Subsea, SOFEC and Zentech.
The project also sponsored M. H. Kim for hull/mooring/riser fully-coupled time domain analyses of the SPAR and TLP systems, and Dr. Johan Wichers for the fully-coupled analyses of the FPSO systems. These efforts provided DeepStar with completely documented results for all aspects of the specified systems, for which the methodology used is also known in detail.
A time domain, coupled analysis method that can simultaneously represent the dynamic response of a floating structure and its mooring and riser systems is generally regarded as the most physically realistic analysis of deepwater structures. The importance of coupling was being recognized as this project was initiated. Most contractors now have this (or in kind) analysis capability, although some analysis packages have been only recently completed. Most of the analyses contributed to this project used a time domain, coupled approach. An attempt was made to understand the relationship between differences in results and differences in analytical methodologies.
Related Publcations: Kim, M.H., Ward, E.G., Haring, R. (2001). “Comparison of Numerical Models for the Capability of Hull/Mooring/Riser Coupled Dynamic Analysis for Spars and TLPs in the Deep and Ultra-Deep Waters,” Proc., 11th International Offshore and Polar Engineering Conf., ISOPE, Vol. III, Stranger, Norway, June. pp 474-479.