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March 9, 2004

ABS to class first offshore LNG port buoy

ABS has contracted with Advanced Production and Loading AS of Norway (APL) to provide classification services for APL's Submerged Turret Loading (STLTM) system, a single-point mooring system (SPM) and an integral component of the industry's first offshore LNG terminal, destined for the Gulf of Mexico, some 116 miles offshore Louisiana.

APL is applying well-proven buoy technology to facilitate innovative gas transfer in marine environment. The accompanying photograph shows one of two submerged turret loading buoys (STLTM) installed on the Heidrun Field in the Norwegian North Sea.

The project will create industry's first offshore LNG deepwater port terminal in the United States and will be the first of its kind in the world, says William J. Sember, ABS vice president of Energy Development.

"ABS is supporting a safe and cost-effective regional development that will create the first offshore LNG receiving terminal in the world. This effort is aiding industry operators to reach new thresholds of LNG capability while addressing escalating gas demand, particularly in the U.S. market," said Sember.

Dubbed the Energy Bridge Deepwater Port, the terminal system, planned for installation on West Cameron Block 603 in 280 feet of water, incorporates APL's STL technology commonly used in the offloading of oil in regions including the North Sea, offshore China and offshore Western Australia. First cargo for the Energy Bridge Deepwater Port is scheduled for January 2005.

ABS, which has classed some 40 SPMs, is leveraging its worldwide expertise with buoy mooring technology to assist industry in the delivery of this gas transport innovation, says Sember.

The project, he adds, provides an industry model for taking traditional, land-based LNG receiving terminals offshore to achieve environmental advantages and economies of scale to global gas trading.

"Offshore gas ports, such as the Energy Bridge Deepwater Port, will avoid many of the challenges associated with building or expanding conventional terminals in environmentally sensitive or populated areas while facilitating the delivery of re-gasified LNG directly into pipeline grids," said Sember.

The terminal will consist of the STL system, a new-build piled platform to support a gas-custody transfer metering station and associated pipelines connecting the STL system to two pipeline grids.

To be classed by ABS as XA1 Single-Point Mooring (SPM), the (STL) buoy is under construction with Junoverken AB at Uddevalla, Sweden, and will be transported to U.S. waters this November. The 186-ton unit will allow specially built LNG carriers fitted with onboard re-gasification equipment to transfer gas through the buoy, which is connected to a pipeline end manifold (PLEM) on the seafloor.

The new carriers, known as Energy Bridge re-gasification vessels or EBRVs, are equipped with a small moonpool to accommodate the STL buoy connection but retain the flexibility to trade as conventional LNG carriers. Two EBRVs are under construction at Daewoo Shipbuilding & Marine Engineering in South Korea, the first of which is due for delivery this November with the second due in April 2005.

The STL buoy, planned for 298 feet of water, will float at a submerged depth of 90 feet at the top of buoy and is the receiving point for the Energy Bridge concept as developed by Excelerate Energy and El Paso Corporation. Instead of supplying natural gas as a liquid to a shoreside re-gasification plant, the two proposed Energy Bridge carriers, equipped with vaporizers to convert LNG to gas, are intended to supply regasified product directly to the deepwater port facility.
irst offshore LNG deepwater port buoy

"Because of the inherent mobility of the Energy Bridge concept incorporating the novel use of the STL mooring and loading buoy, the system can be deployed virtually anywhere in the world to meet incremental demand for natural gas," said Sember.

The plan for product transfer calls for one of these dedicated carriers to connect to the underwater buoy and export gas through the buoy to the PLEM. The gas then transports to a 20-inch diameter, 1.9-mile pipeline to the platform metering station. From the platform, the gas routes into an existing network of underwater high-pressure pipelines to shore.

The Energy Bridge Deepwater Port project, with planned capacity to deliver base load gas volumes in excess of 500 million cubic feet per day, is scheduled to complete in January 2005. ABS' scope of work in this effort encompasses the submerged turret loading buoy; the mooring system for the buoy; and the riser to take the gas from the buoy to the PLEM.

Ian Simpson, ABS manager of Energy Project Development, advises that ABS classification services to APL are designed to facilitate an on-time start-up for the project.

The ABS services include:

  • Technical review of the STL buoy and associated moorings, riser and PLEM for site-specific location in accordance with ABS Rules for Building and Classing Single Point Moorings, 1996.

  • Survey of the STL buoy during construction.

  • Survey of the mooring piles and PLEM during construction.

  • Survey of the components and materials for the single point mooring system at the manufacturer's shop for certification purposes and as required by the ABS SPM Rules.
  • Survey of the offshore installation of the piles, moorings, PLEM and STL buoy together with gas riser.

Upon satisfactory completion of the above, the attending ABS surveyor may issue an Interim Class Certificate to allow the STL system, as part of a Deepwater Port, to proceed with gas transfer operations.

Founded in 1862, ABS is a leading international classification society devoted to promoting the security of life, property and the marine environment through the development and verification of standards for the design, construction and operational maintenance of marine-related facilities.


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