A Simulation Model for Analysing Weather Impact on Upstream Supply Chain Service Performance
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- Institutt for marin teknikk 
In the oil and gas industry, the upstream logistics are defined as the delivery and retrieving of products, and services at offshore installations. In order to maintain a continuous production, offshore installations are dependent on frequent deliveries and pickups of cargo. Shortages may hold up production or delay operations causing economic loss for the oil companies in charge. The nature of the upstream supply chain is highly stochastic. The largest uncertainties relate to voyage durations and demand. Because the transportation costs for supply vessel operations adds up to one of the largest costs in the upstream logistics, good planning and utilisation of supply vessels is important. Wave height is considered by planners to be the most critical factor when planning weekly supply vessel schedules. It affects both sailing and service time. The aim of the thesis is to create a simulation model to analyse the impact of weather conditions to the upstream supply chain. Discrete-event simulation (DES) is the chosen approach. The weather conditions are represented by four different weather states, each describing different occurrences of wave height, and the impact it will have on sailing and service time. The model that has been created is flexible, and can be adjusted to small- or large-scale scenarios at any geographical location. It is limited to only have one supply base, but can include n offshore installations and supply vessels. The cases that have been run and is presented in this thesis focus on observing the different components of the supply chain, and record durations of service, sailing, waiting on weather and idle time. Cost and capacity of supply vessels and offshore installations have not been included in the current model. The results that are found from the different cases show that the duration of each voyage is highly dependent on weather conditions. Waiting on weather before service can potentially delay voyages for several days, and is the largest uncertainty in regards to voyage durations. The alternative approach where an offshore supply base is used, reduces sailing time, which will give lower transportation costs. It must still be assumed that an offshore base introduce new uncertainties in regards to turnaround time, as it will be more exposed to the weather conditions.