To reduce the cost of weather waiting without compromising the requirement for safe operations, it is essential to determine accurate limiting criteria, and response forecasting allows us to significantly improve the accuracy of the modelled wave spectrum used in the underlying calculations.

Offshore installation work is sensitive to weather conditions and progress is frequently delayed when conditions are outside workable limits. While weather waiting is costly due to the high cost of installation vessels and delayed completion of projects, it is necessary in order to prevent damage on the installed products, the installation vessel, and to ensure safety of personnel.

Wave spectra based on generic models (such as JONSWAP or Torsethaugen) are often used, even though forecasted wave spectra are available at the time of execution. To make use of the forecasted wave spectrum, it is necessary to perform calculations during the execution phase and translate it into responses that actually limit the operation, namely a ‘Response Forecast’. In this context, a response is used as a general term and not limited to vessel motion.

This presentation describes the challenges and savings experienced during practical implementation of response forecasting on pipelay projects performed by Subsea 7.