Global Wave Persistence Study for Offshore Operation and Planning

Abstract

This paper describes the guidelines for preliminary workability analysis for offshore operation and planning using global wave persistence study. In offshore engineering, the weather information has to be studied to select the appropriate path for the project during the concept design, the detail design and the operation plan. The workability analysis is part of the weather study for various offshore operations and this study is used as a guide for the operation schedule, the selection of the operation method, the design of the equipment and the supporting structures. The detailed workability analysis is based on response based simulations which are only available after or during detail system design. On the other hand, preliminary workability can be calculated based on hindcast data with statistical methods before the detail design and this study can lead the project on the appropriate path at the beginning stages. The wave persistence analysis with thresholds on time and wave heights is used for the preliminary workability calculation and can also be used for route planning during offshore transportation. The objective of this paper is to provide global wave persistence analysis data to guide offshore operation and planning and makes the transition to workability with the required working wave period easier. For the global wave persistence analysis, the National Center for Environmental Prediction (NCEP) Climate Forecast System Reanalysis Reforecast (CFSRR) system data was used which has 35-year numerical wave hindcast. Data resolution is 0.5°×0.5° grid size with a temporal resolution of 3 hours for the period from 1979 to 2013, and this database covers most offshore locations except the Caspian Sea, and the North and South Pole areas. The persistence analysis was calculated with 0.5m, 1.0m, 1.5m and 2m wave thresholds, and each wave threshold is categorized as 24 hours, 48 hours and 72 hours persistency.