Liquefied Natural Gas (LNG) trades are expected to increase rapidly over the coming years and the gas industry is preparing itself by planning facilities for import and export of LNG. In the USA alone, dozens of prospective import sites have been identified of which many are planned offshore due to security concerns and public opposition against onshore facilities.
Amongst the terminal concepts developed and promoted, floating terminals attract the attention of the industry, offering the combination of use of proven technology with attractive cost and schedule.
A key issue for any offshore LNG import terminal is the safe and reliable transfer of LNG from LNG Carriers (LNGCs) to the terminal with sufficient availability. For floating terminals such transfer is typically performed in a side-by-side mooring arrangement.
The safety and availability of the offshore LNG offloading operation is governed by many elements, including the performance of the assisting tugs, the general sea state conditions, the mooring line and fender arrangement, the loading arm design and its operational envelope, emergency conditions, LNGC maneuverability, but also tugboat and mooring master competency and the amount of specialist training.
This paper addresses how SBM - the company with the worlds longest track record in offshore offloading of hydrocarbons, and operating the largest fleet of floating production systems in the world - has combined results from numerical analyses and model tests with feedback from marine operational practice to define how offshore LNG transfer can be done safely and with sufficient uptime.
The paper will present a step-by-step insight into the offloading operations supported by practical examples of sideby- side offloading operations from the worldâ??s largest LPG FPSO, and give typical availability figures for side-by-side LNG offloading for various locations in the world. In addition, alternative offshore LNG offloading solutions will be discussed for those locations where higher uptime will be required.
The technologic solutions for cryogenic liquefaction or regasification of LNG on an offshore floating platform are available. However, the safe and reliable transfer of this LNG in open sea conditions, possibly harsh environment has not been performed in practice yet. SBM has almost 50 years experience in the development, design, supply, installation and operation of Single Point Mooring (SPM) terminals for mooring large crude oil tankers without having to build complex and expensive port facilities. Furthermore, SBM owns and operates the largest fleet of Floating Production, Storage and Offloading (FPSO) units. Based on this track record and operational experience, SBM is able to grasp all major aspects that are relevant for defining and optimizing offloading availability.
One of the most important criteria for a continuous gas supply from a new-build (Figure B-1) or conversion (Figure B-2) Floating Storage and Re-gasification Unit (FSRU) to shore, is the ability of an LNGC to carry out a successful side-by-side LNG offloading operation alongside the FSRU. Similarly, the availability of the side-by-side LNG loading operation is very relevant in the design of the LNG F(P)SO used as an offshore LNG storage and export facility (Figure B-3).