Innovative Architectures for LNG Transfer at Sea Studied
Authors: Lanquetin Bertrand , Lanteri-Minet Pierre Luc , Dupont Bernard 
Published: October 2008

Jetties for LNG transfer are traditionally based on the same design: a loading platform, several dolphins and a trestle linking the jetty to the shore. They require a sheltered area, ample facilities for ship navigation and manoeuvring including a navigation channel and a turning basin and the assistance of four tugs. The construction of such facilities usually necessitates a lot of civil works (piling, dredging, sometimes a breakwater) and their overall cost becomes rapidely prohibitive as soon as the distance from the coast increases.

As a result the liquefaction (or the vaporizing) plant and the jetty have to be very close together, adding difficulties in the siting of plants and jetties. Today the new LNG plants and new projects are more widely dispersed in the world. In most cases the siting constraints (such as soil occupancy, congested or shallow waters) and the economic constraints impose the jetties to be located at more remote areas and in more weather exposed locations.

For this reason TotalFinaElf, Gaz de France, Eurodim and several other French companies, have carried out, since 1999, an extensive programme of studies of new and more compliant architectures for LNG transfer together with an ambitious programme of development and test of the main cryogenic components like sub-sea lines, transfer hoses and connecting and disconnecting systems. This programme is now nearing completion and offers attractive solutions to LNG transfer at sea (like tandem offloading).

This paper therefore is organized in three sections:Section 1 explains the historical background of the design of traditional LNG jetties and their limits.Section 2 explains the specific and inter-related siting constraints of LNG plants and jetties and how some of the most important constraints can be removed through more compliant LNG transfer architectures.Section 3 presents these new innovative architectures for LNG transfer at sea and gives their performances. This technology now allows to propose and built compliant cryogenic transfer systems similar in principle to the ones used in the oil industry. Priority in these developments has been given to non-dedicated ships and to safety levels equal to or above those of the traditional jetties.

Section 1: design of traditional LNG jetties and their Limits

An artist view of a loading jetty is given on figure 1 (source, see reference [1]).

Figure 1: artist view of a traditional LNG jetty(AVAILABLE IN FULL PAPER)

All the loading/unloading jetties for liquefied gases today (mainly LNG - Liquefied Natural Gas and LPG - Liquefied Petroleum Gas) use very similar designs including:A fixed orientation.A trestle between the jetty and the shore, which supports the liquid and vapour lines and very often an access road.A loading (or unloading) platform often with two or three levels, which supports the loading (unloading) arms and the fire protection.Two to four breasting dolphins for berthing the ships.Six to eight mooring dolphins for mooring the ships. These jetties necessitate a very large number of piles and a lot of civil and marine works, the cost of which becomes rapidly prohibitive when the distance to the coast increases.