Operators planning extended offshore construction or decommissioning campaigns should consider a variety of factors and potential risks. These include regulatory expectations, limited availability of specialised vessels, operational duration uncertainty and the associated cost risk. Offshore operations have a variety of operability limits with adverse weather conditions often producing operational interruptions, resulting in periods of vessel downtime and significant cost, depending on the vessels mobilised. A potential solution for reducing the exposure of extended campaigns to weather-related downtime is separating operations over several independent favourable weather seasons. Grouping preparatory works with low-cost vessels in the first season, and performing operations where large, specialised vessels are required in subsequent seasons is often considered a cost-effective strategy. This paper discusses a quantitative operability assessment estimating the cost-benefit of reduced weather downtime compared to the cost and logistical burden of additional vessel mobilisation and demobilisations and evaluates this trade-off within site-specific metocean conditions for a location offshore Victoria. The example demonstrates how AMOG’s Operability Suite was utilised to assess a decommissioning sequence executed over a single continuous campaign in comparison with multiple short campaigns. Long-term weather patterns and seasonal variability in expected weather downtime are explored. This paper highlights key decision-making parameters, including metocean operability limits, vessel day rates and cost uncertainty, offering an effective approach to planning extended campaigns in highly exposed marine environments.
Lazarides et al. (Thu,) studied this question.
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