LNG Floating Regasification Unit (FRU) Side-by-Side Mooring Analysis

Abstract

This paper presents a newly developed Floating Regasification Unit (FRU) concept for LNG import in the US Golf of Mexico (GOM) region. The FRU can be converted from a Suezmax tanker and has a turret mooring system. One of the key technologies of the FRU concept is the Side-By-Side (SBS) mooring between the FRU and the LNG Carrier (LNGC) for offloading. The mooring lines and pneumatic fenders between the two vessels should be able to restrain the relative motions to ensure the safe transfer of LNG. Advanced hydrodynamics modeling techniques have been applied, which include full hydrodynamic interactions between the FRU and the LNGC with full QTFs considering the shallow water effect. The anchor legs are modeled as dynamically, fully coupled to the turret and the FRU. The feasibility of the FRU concept is established for LNG import in the GOM, with a variety of workable water depths ranging from 40 meters to more than 100 meters with an uptime exceeding 98%. Analysis results demonstrate the significance of hydrodynamic interactions between the two vessels in close proximity arrangement.

Time Domain Simulations of Side-by-Side Moored Vessels: Lessons Learnt From a Benchmark Test

“…A Floating Storage and Regasification Unit (FSRU) is a new promising concept for offshore LNG import. Locations are envisaged in the Gulf of Mexico (see Ye et al (2005)), US East Coast, California or the US West Coast. The FSRU will receive regular shipments of LNG from LNG carriers, transfer it to the onboard storage tanks and send it to shore in gaseous phase through a sub sea pipeline.…”

Hydrodynamic Forces and Reactions of Two Floating Bodies in Close Proximity

“…The first fact clearly highlights the problem of floating bodies in the close proximity i.e. the emergence of hydrodynamic coupling, which must be taken into account when designing a mooring or anchoring system, [2]. Coupling is manifested through hydrodynamic reactions and wave forces.…”

“…In fact, a particular situation that occurs when the terminal is used i.e. the transhipment of liquefied gas from the LNG carrier to FRSU, [2], is considered. This is done for a side-by-side configuration so that the LNG and FSRU are in close proximity, [3].…”

“…For such system an assumption of harmonic body motions can be used. The harmonic motions then can be represented in complex form as (2) where ω is the wave frequency and is the complex amplitudes vector of the body motions. Whit such assumption the motion equation takes a form a complex algebraic system…”