A Numerical Simulation for Predicting Sea Waves Characteristics and Downtime for Marine and Offshore Structures Installation Operations

In this paper, a numerical simulation of sea wave characteristics and operation downtimes of offshore structures is presented. The simulation was based on available wind data and seawater temperature recorded by an oceanography buoy installed in the Caspian Sea. Wave characteristics were simulated for deepwater parts of the Caspian Sea by applying the Bretschneider spectrum and equations using following recorded data: wind velocity, wind duration, fetch length, and water/air temperature differences. Since recorded wave data were only available for a one-year period, they were solely used for validation of the simulation results with recorded data but for not the simulation itself. Some practically established thresholds for wave velocity, wave period, and wind velocity were considered as constrains, limiting the operation of offshore installations. The numerical simulation model revealed that it is possible to operate offshore installations for 250 days per year in the southern parts of the Caspian Sea. A worst-case scenario showed that the maximum waiting time for restarting the offshore installations is 17 days. Considering the swell parameter, it was concluded that the annual downtime period of offshore installation operations in southern parts of the Caspian Sea is about one third of a year and the maximum waiting time for this operation is about two third of a month.