Low Frequency Motions of LNG carriers Moored in Shallow Water

With the LNG market booming, the need for reliable and safe means of transferring LNG from a producing, floating facility to an LNG carrier and from this carrier to a near-shore terminal is becoming acute. The Soft Yoke Mooring and Offloading (SYMO© ) system has recently been model tested in MARIN’s offshore basin. Results of these tests are presented.
Insight has been gained, from these model tests and from the calibration of numerical tools performed thereafter, on the following issues:
• The inherent weakly damped nature of a moored LNG carrier,
• Shallow water effects in wave drift forces,
• The effect of current on drift forces,
• The structure of low frequency long waves in a shallow water basin.

These issues will be discussed and guidance regarding their importance will be provided. Consequences in terms of system design, mooring analysis methodology and model test program will be discussed.