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SAFE OFFSHORE VESSEL POSITIONING PRACTICE

SAFE OFFSHORE VESSEL POSITIONING PRACTICE. MOORING ANALYSIS. Orcaflex Workshop, 23 rd Jun 2012 IDEC, Intercontinental, Mumbai. AGENDA. Challenges in present Station Keeping Mooring Analysis … A glance Mooring Analysis – Usage Mooring Analysis – Stages, Categories

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SAFE OFFSHORE VESSEL POSITIONING PRACTICE

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  1. SAFE OFFSHORE VESSEL POSITIONING PRACTICE MOORING ANALYSIS Orcaflex Workshop, 23rd Jun 2012 IDEC, Intercontinental, Mumbai

  2. AGENDA Challenges in present Station Keeping Mooring Analysis … A glance Mooring Analysis – Usage Mooring Analysis – Stages, Categories Advantage with FUGRO-Vedam collaboration

  3. Challenges in Present Station Keeping • Complex platform and sub-sea infrastructure • Vessel positioning in close proximity to assets • Stringent safety requirement • Longer mooring durations • Operational requirement: gangway connections, helicopter operations • Vessel response under accidental damage of a line • Support vessel’s movement in close proximity to barge • Unconventional requirements: Connection to Jacket leg, DP buoys etc.. MOORING ANALYSIS IS A TOOL TO SIMULATE COMPLEX NATURE OF STATION KEEPING TO ENSURE SAFETY AND REDUCE RISK DURING OFFSHORE OPERATION

  4. Global Standards…

  5. POSITIONING SERVICE – way ahead… CLIENT/MWS

  6. Mooring Analysis – An Overview...

  7. Mooring Analysis – An Overview... • Motion analysis & determining RAO • Modelling of mooring pattern • Quasi-static Mooring Analysis (equilibrium position) • Rule Check as per API/ISO/DNV Standards

  8. Mooring Analysis … An Overview • Catenary shape & positioning of mooring buoy • Safe vertical distance from sub-sea pipelines • Limiting anchor loads • Chain lengths for DP buoys • One line Damage analysis • Limiting line tensions • Limiting vessel excursions

  9. Mooring Analysis … An Overview • Transient analysis • Vessel trajectory after breakage of a line • Maximum vessel offsets from platform/assets. • Detailed Report and Anchor Pattern with catenary diagrams,

  10. Usage of Mooring Analysis … • Derivation of exact catenary shapes • Correct estimation of distance between subsea structure and mooring lines/anchors. • Mooring optimization to meet stringent safety requirement • Stabilisation of vessel motion, excursion • Clash Check • Usage of Damage Prevention Buoys • Derivation of limiting weather • Vessel Relocation Capability

  11. Mooring Analysis… Catenary Shape • Deployed wire length • Initial tension in the wire • Load on Anchor • Location and size of DP buoys • Load on vessel’s mooring fittings • Safe navigation zone around moored vessel

  12. Mooring Analysis… Complex Field Layout • Limiting Vessel excursion • Distance from pipe lines • Distance from floating bodies • Uneven distribution of spread mooring • Support from Jacket Leg

  13. Mooring Analysis… Stringent Safety Criteria • Effect of different directional weather • Effect of extreme weather condition • Effect of one line damage condition • Limitation to excursion • Factor of Safety of anchor, line & mooring fittings

  14. Mooring Analysis… Vessel Stabilisation • Limiting vessel roll & pitch motion • Limiting vessel’s heave motion for • Better habitability • Safe operation of gangway, crane etc • Safe platform repair work • Limiting vessel excursion • For position keeping for subsea repair work

  15. Mooring Analysis… Clash Check • Platform to barge safe distance • Anchor to pipe line distance • Across the pipe • Along the pipe • Mooring line to subsea pipe distance • Line to line distance in cross mooring • Distance from platform helideck or flare

  16. Mooring Analysis… Usage of DP Buoys • DP Buoy parameters for effective lifting of mooring line • Location • Capacity or size • Buoy chain length • Catenary shape with effect of DP buoys • Optimum usage of DP buoys

  17. Mooring Analysis… Limiting Weather • Analysis with extreme weather condition • Derivation limiting weather condition for safe working condition • Contingency plan beyond limiting weather

  18. Mooring Analysis… Relocation Analysis • Transient Analysis for relocating the vessel • Line tension and catenary for relocation operation • Weather condition for safe relocation operation

  19. THANK YOU vedam@vedamindia.com @linkd.in/VedamDes @VedamDesign

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