Development of the Adriatic LNG Terminal Deep Casting Basin Construction Site
- Bryan Wesselink (ExxonMobil) | Bora Tokyay (ExxonMobil Development Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Projects, Facilities & Construction
- Publication Date
- December 2008
- Document Type
- Journal Paper
- 1 - 6
- 2008. Society of Petroleum Engineers
- 4.2 Pipelines, Flowlines and Risers, 4.1.9 Heavy Oil Upgrading, 4.3.4 Scale, 4.5 Offshore Facilities and Subsea Systems, 4.6 Natural Gas, 2.4.3 Sand/Solids Control, 4.8.3 Onshore Construction Management, 4.6.2 Liquified Natural Gas (LNG)
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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.
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.
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