Summary
The world’s first bottom-founded offshore liquefied natural gas (LNG)
storage and regasification terminal is under development by affiliates of Qatar
Terminal Limited, ExxonMobil, and Edison for installation in the Northern
Adriatic, 15 km east of Porto Levante, Italy. This paper will describe the
unique challenges faced and effort undertaken to locate and transform a casting
basin to a world-class construction and integration site, including removal of
the earthen wall prior to tow-out of the terminal.
The concrete gravity-based structure (GBS) terminal enclosing two
125,000-m3 LNG tanks and supporting 8 GSCM regasification facilities
will measure 180 m by 88 m and be located in 29 m of water. These dimensions,
as well as proximity to Porto Levante, led to selection of the casting basin in
the Spanish Bay of Algeciras as the construction and integration site. The site
is under development by the Algeciras Port Authority for use as a container
port, and therefore did not have the infrastructure needed to build the
terminal. This paper will provide the basis for how parameters such as size,
depth, layout, water and electricity supply, accessibility, dredging
requirements, lease requirements, availability of workforce, and capacity for
growth were established to result in an effective construction and integration
site. Some of the execution technologies used for this terminal, such as
removal of the earthen wall, installation of regasification facilities, and
installation of the LNG tanks will also be described.
The conclusions drawn in this paper can be utilized for upgrading of an
existing construction site, or development of a Greenfield site into an
effective facility for future GBSs, floating structures, or large-scale
construction and integration projects.
Background
Adriatic LNG Terminal, the world’s first offshore liquefied natural gas
(LNG) receiving, storage and regasification terminal, is under development by
affiliates of Qatar Terminal Limited, ExxonMobil, and Edison for installation
in the Northern Adriatic, 15 km offshore just east of Porto Levante, Italy in
29 m of water.
The substructure of the terminal consists of a concrete GBS with dimensions
of 180 m × 88 m × 47 m. Two 125,000-m3 modular LNG tanks are housed
inside the GBS, while the topsides facilities with 8 GSCM/year send-out
capacity are located on the top. The export pipeline has a 30-in. diameter with
a metering station near Cavarzere, Italy, tying into the Italian grid at
Minerbio through a 36-in. line. The terminal will provide a berthing facility
for 65,000- to 152,000-m3 LNG carriers. Fig. 1 shows a rendering of
the terminal.
The major components of the Adriatic LNG (ALNG) Terminal built by Terminale
GNL Adriatico srl are the GBS substructure constructed in the bay of Algeciras,
Spain; the LNG tanks fabricated in South Korea; topsides modules being
fabricated in Cadiz, Singapore, and Sweden; and the mooring dolphins being
constructed in Venice, Italy. Figs. 2a through 2d show photos taken at various
stages of construction of these major components.
The execution plan for the ALNG terminal consists of building the GBS at the
deep casting basin site in Algeciras Bay, Spain, transporting the LNG tanks
from South Korea to install into the GBS, transporting all the topsides modules
and installing them on top of the GBS, removing the existing levee that keeps
the basin dry and towing the fully integrated terminal to offshore Venice,
where the mooring dolphins will be installed as well.
Construction and Integration Site Selection
One of the most important decisions during the execution planning of the
ALNG Terminal Project was selecting the construction and integration site. In
order to select the most appropriate location, more than 15 sites from western
Europe through the Mediterranean to the Black Sea were evaluated based on
particular criteria.
All of the evaluated sites presented some advantages and challenges. For
example, some of the sites were not selected because of their limited size or
lack of adequate skilled labor to support a project of this magnitude. Others
that were large enough and provided access to adequate labor required extensive
dredging works to obtain the draft required for the execution plan (all
installation and construction activities to be completed onshore). While some
of the sites met the space and infrastructure requirements, because of the
tow-route to offshore Venice, the available tow window was considered too
restrictive. Another important criterion that led to elimination of some of the
sites was the difficulty in obtaining the necessary permits for the development
of the project. Last, but not least, the lease fee and availability of the site
were other criteria that were evaluated before making the final decision to
select the Algeciras Bay site. These criteria and how the Algeciras Bay site
satisfied them are summarized in Table 1.
The Algeciras Bay deep casting basin site is owned by the Algeciras Port
Authority (APBA). APBA manages the 11th largest container port in Europe.
Although the site is leased from APBA for construction and integration of the
terminal, the Andalusian regional government and the San Roque local government
also have jurisdiction over the site for regulatory purposes.
The site is located in an industrial area with a refinery and chemical plant
in the vicinity. The perimeter of the casting basin consists of mass concrete
quay walls. The natural material behind these walls is very impermeable
overconsolidated clay, which minimizes the amount of seepage into the basin.
The basin was previously used for the construction of a concrete breakwater
structure for Monaco and is included in APBA’s plans for use as a container
port. Figs. 3a and 3b show the Algeciras Bay site in November of 2003, before
the ALNG Terminal Project and March 2007 after the arrival of the LNG tanks
from South Korea.
© 2008. Society of Petroleum Engineers
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History
- Original manuscript received:
26 July 2007
- Meeting paper published:
4 December 2007
- Revised manuscript received:
28 May 2008
- Manuscript approved:
17 June 2008
- Version of record:
15 December 2008
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