Ocean Systems Engineering

Techno-Press (테크노프레스)
권호 표지
DOI QR코드

DOI QR Code

Mooring chain fatigue analysis of a deep draft semi-submersible platform in central Gulf of Mexico

  • Jun Zou (Floating and Green Energy Consulting, LLC)
  • Received : 2024.04.23
  • Accepted : 2024.06.20
  • Published : 2024.06.25
⟨ Previous Next ⟩

Abstract

This paper focuses on the rigorous and holistic fatigue analysis of mooring chains for a deep draft semi-submersible platform in the challenging environment of the central Gulf of Mexico (GoM). Known for severe hurricanes and strong loop/eddy currents, this region significantly impacts offshore structures and their mooring systems, necessitating robust designs capable of withstanding extreme wind, wave and current conditions. Wave scatter and current bin diagrams are utilized to assess the probabilistic distribution of waves and currents, crucial for calculating mooring chain fatigue. The study evaluates the effects of Vortex Induced Motion (VIM), Out-of-Plane-Bending (OPB), and In-Plane-Bending (IPB) on mooring fatigue, alongside extreme single events such as 100-year hurricanes and loop/eddy currents including ramp-up and ramp-down phases, to ensure resilient mooring design. A detailed case study of a deep draft semi-submersible platform with 16 semi-taut moorings in 2,500 meters of water depth in the central GoM provides insights into the relative contributions of wave scatter diagram, VIMs from current bin diagram, the combined stresses of OPB/IPB/TT and extreme single events. By comparing these factors, the study aims to enhance understanding and optimize mooring system design for safety, reliability, and cost-effectiveness in offshore operations within the central GoM. The paper addresses a research gap by proposing a holistic approach that integrates findings from various contributions to advance current practices in mooring design. It presents a comprehensive framework for fatigue analysis and design optimization of mooring systems in the central GoM, emphasizing the critical importance of considering environmental conditions, OPB/IPB moments, and extreme single events to ensure the safety and reliability of mooring systems for offshore platforms.

Keywords

Acknowledgement

The research presented in this paper received financial support from Floating and Green Energy Consulting, LLC. This organization is committed to advancing fundamental research and development initiatives aimed at both the oil and gas industry and renewable energies sectors. Their support facilitated the comprehensive analysis and findings detailed in this study, contributing to advancements in understanding mooring chain fatigue.

References

  1. ABS Guidance Notes (2021), The Application of Fiber Rope for Offshore Mooring, American Bureau of Shipping, Spring, TX, USA.
  2. ABS Guide (2023), Position Mooring Systems, American Bureau of Shipping, Spring, TX, USA.
  3. API RP 2MET (2021), Derivation of Metocean Design and Operating Conditions, American Petroleum Institute, USA.
  4. API RP 2SK (2008), Design and Analysis of Stationkeeping Systems for Floating Structures, American Petroleum Institute, USA.
  5. API RP 2SM (2001), Recommended Practice for the Design, Manufacture, Installation and Maintenance of Synthetic Fiber Ropes for Offshore Moorings, American Petroleum Institute, USA.
  6. API RP 2T (2010), Recommended Practice for Planning, Designing and Constructing Tension Leg Platforms, American Petroleum Institute, USA.
  7. Bureau Veritas Guidance Note NI 604 DT R00 E (2014), Fatigue of Top Chain of Mooring Lines due to In-plane and Out of-plane Bendings, Marine & Offshore Division, 92571 Neuilly sur Seine Cedex, France. 
  8. Chung, W.C., Kang, H.Y. and Kim, M.H. (2020), "Multi-scale approach of a chain-mooring OPB-induced failure considering time-varying interlink bending stiffness and fairlead condition", Appl. Ocean Res., 98, 102128. https://doi.org/10.1016/j.apor.2020.102128.
  9. Das, S. and Zou, J. (2015), "Characteristic responses of a dry tree paired-column and dDeep draft semisubmersible in central Gulf of Mexico", Proceedings of the 20th SNAME Texas Section Offshore Symposium, Houston, USA, February.
  10. DNV-OS-E301 (2021), Position Mooring, Det norske Veritas, Hovik, Norway.
  11. DNV-RP-C203 (2016), Fatigue Design of Offshore Steel Structures, Det norske Veritas, Hovik, Norway.
  12. D'Souza, R.B., Basu, S., Bhaumik, T. and Sharples, M. (2019), "The Semisubmersible Floating Production System: A 25-Year Technical and Historic Retrospective", Proceedings of the SNAME Maritime Convention 2019, Tacoma, Washington, USA, October.
  13. D'Souza, R.B.; Zou, J., Jatar, S.M. and Andersen, D.B. (2024), "Gulf of Mexico Deepwater Mooring Experience Applied to Floating Offshore Wind Turbines", Accepted and will be published in SNAME Maritime Convention 2024, Norfolk, VA, USA, October.
  14. Finnigan, T. and Roddier, D. (2007). "Spar VIM model tests at supercritical reynolds numbers", Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering, San Diego, California, USA.
  15. Goncalves, R., Rosetti, G., Fujarra, A.C. and Oliveira, A. (2012), "Experimental study on vortex-induced motions of a semi-submersible platform with four square columns, Part I: Effects of current incidence angle and hull appendages", Ocean Eng., 54(4), 150-169. https://doi.org/10.1016/j.oceaneng.2012.06.032.
  16. Gordon, R.B., Brown, M.G. and Allen, E.M. (2014), "Mooring integrity management: A state-of-the-art review", Proceedings of the Offshore Technology Conference, Houston, TX, USA, May.
  17. Izadparast, A., Heyl, C., Ma, KT; Vergas, P. and Zou, J. (2018), "Guidance for assessing out-of-plane bending fatigue on chain used in permanent mooring systems", Proceedings of the 23rd SNAME Texas Section Offshore Symposium, Houston, USA, February.
  18. Koop, A., Leverette, S., Bangs, A., Withall, T., Castillo Valverde, F., Zanden, J.V.D., Heerink, R. and Wilde, J.D. (2024), "Investigating the effect of damping originating from mooring and risers on the VIM response of a semi-submersible floater using coupled CFD-time-domain simulations", Proceedings of the Offshore Technology Conference, Houston, TX, USA, May.
  19. Kvitrud, A. (2013), "Failures in anchor lines and methods for improving the safety level", Proceedings of the Normoor Conference, Hovik, Norway, November.
  20. Ma, K.T., Duggal, A., Smedley, P., L'Hostis, D. and Shu, H. (2013), "A historical review on integrity issues of permanent mooring systems", Proceedings of the Offshore Technology Conference, Houston, TX, USA, May.
  21. Ma, W., Wu, G., Thompson, H., Prislin, I. and Maroju, S. (2013), "Vortex induced motions of a column stabilized floater", Proceedings of the Deep Offshore Technology International Conference, Houston, TX, USA.
  22. Melis, C., Jean, P. and Vargas, P. (2005), "Out of plane bending testing of chain links", Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering, Halkidiki, Greece.
  23. Rampi, L., Bignonnet, A., Le Cunff, C., Bourgin, F. and Vargas, P. (2016a), "Chain out of plane (OPB) fatigue joint industry project (JIP) FEA results and multiaxiality study results", Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering, Busan, South Korea.
  24. Rampi, L., Gerthoffert, A., Francois, A., Bignonnet, A. and Vargas, P. (2016b), "Chain out of plane (OPB) fatigue joint industry project (JIP) fatigue test program results and methodology", Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering, Busan, South Korea.
  25. Rampi, L., Dewi, F., Francois, M., Gerthoffert, A. and Vargas, P. (2016c), "Chain out of plane (OPB) fatigue joint industry project (JIP) static test program and OPB interlink stiffness", Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering, Busan, South Korea.
  26. Rampi, L., Dewi, F. and Vargas, P. (2015), "Chain out of plane bending (OPB) joint industry project (JIP) summary and main results", Proceedings of the Offshore Technology Conference, Houston, TX, USA, May. 
  27. Rampi, L. and Vargas, P. (2006), "Fatigue testing of out of plane bending mechanism of chain links", Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering, Hamburg, Germany.
  28. Roddier, D., Finnigan, T. and Liapis, S. (2009), "Influence of the reynolds number on spar vortex induced motions (VIM): Multiple scale model test comparisons", Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering, Honolulu, HI, USA.
  29. Sai, M. and D'Souza, R.B. (2013), "Application of lessons learned from field experience to design, installation and maintenance of FPS moorings", Proceedings of the Offshore Technology Conference, Houston, TX, USA, May.
  30. Sterenborg, J., Koop, A., de Wilde, J., Vinayan, V., Antony, A. and Halkyard, J. (2016), "Model test investigation of the influence of damping on the vortex induced motions of deep draft semisubmersibles using a novel active damping device", Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering, Busan, Korea.
  31. Zou, J. (2008), "Dynamic responses of a dry tree semi-submersible platform with ram style tensioners in the post-Katrina irregular seas", Proceedings of the International Society of Offshore and Polar Engineering Conference, Vancouver, Canada.
  32. Zou, J. (2014), "VIM response of a dry tree pair-column semisubmersible platform and its effects on mooring fatigue", Proceedings of the 19th SNAME Texas Section Offshore Symposium, Houston, USA, February.
  33. Zou, J., Poll, P., Antony, A., Das, S., Padmanabhan, P., Vinayan, V. and Parambath, A. (2014), "VIM Mmodel testing and VIM induced mooring fatigue of a dry tree paired-column semisubmersible platform", Proceedings of the Offshore Technology Conference, Houston, TX, USA, May.
  34. Zou, J., Poll, P., Park, Y.C., Converse, R., Antony, A. and Moideen, H. (2011), "The gulfstar standard floater and its vortex induced motion model tests", Proceedings of the International Society of Offshore and Polar Engineering Conference, Maui, HI, USA.
  35. Zou, J., Poll, P., Roddier, D., Tom, N. and Peiffer, A. (2013), "VIM Testing of a Paired Column Semisubmersible", Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering, Rotterdam, Nantes, France.