Session: 01-01-02 Offshore Platforms-II

Paper Number: 128336

128336 - Vessel Motion During Side-by-Side Offloading: Comparison of Field Data and Numerical Model 

There are a few floating liquefied natural gas (FLNG) facilities currently in operation, helping unlock offshore stranded natural gas fields. Limited by technology and equipment on existing FLNGs, the side-by-side (SBS) configuration is still the most favourable for offloading liquified cargo from an FLNG to shuttle tankers and may also be useful in future industries like hydrogen export. This operation requires the carrier to be moored alongside the FLNG in a parallel position, and the gap between two vessels can be as small as 4 metres. Operational limiting criteria exist, and a model to accurately predict the relative vessel motion is required to access operability accordingly. This study uses a numerical hydrodynamic model based on the potential flow theory for an FLNG-carrier SBS system, to simulate relative vessel motion under different metocean conditions. To date, there have been no publications comparing such a model with vessel motion (especially carrier) field measurement. This study demonstrates, for the first time, the vessel motion comparison between numerical model and field measurements.

Aspects which are particularly challenging to model and therefore interesting to investigate in the comparison include roll motion, motions coupled to gap resonance, and motions coupled to sloshing. In terms of field data, the FLNG heading and half-hourly averaged directional wave spectrum are measured during actual offloading operations and are used as inputs for the model. The carrier motion during an operation is measured by accelerometers and gyroscopes that are integrated into a portable motion sensor placed onboard. The comparison between numerical results and field data is conducted statistically and spectrally.

Overall, this study unveils the level of agreement between theories and reality, in a more practical sense than laboratory experiments, for predicting vessel motions during FLNG-carrier offloading operations.

Presenting Author: Yutao Wang The University of Western Australia

Presenting Author Biography: Yutao Wang is a Research Associate in Oceans Graduate School of The University of Western Australia. His research topics mainly focus on the fluid structure interaction.

Authors:

Yutao Wang The University of Western Australia
Hugh Wolgamot The Univerisity of Western Australia
Wenhua Zhao The Univerisity of Western Australia
Scott Draper The Univerisity of Western Australia
Phillip Watson The Univerisity of Western Australia