Study says floating liquefaction plants are viable

April 9, 2001
Higher natural gas prices and improving technology have combined to move the use of a floating LNG plant closer to reality.

Higher natural gas prices and improving technology have combined to move the use of a floating LNG plant closer to reality.

A group led by France's Bouygues Offshore SA released a study of the concept last month that made the case for the future viability of a fully floating liquefied natural gas chain.

Bouygues said the 18-month Azure R&D project, underwritten by the European Union's Thermie program, investigated designing floating liquefaction plants, floating LNG terminals, and offshore LNG transfer systems, and included "thorough testing" of all the key components of the chain.

The study concluded that "a fully floating LNG chain, from gas well to gas distribution network, is a safe and viable industrial proposal."

Consortium

Bouygues headed a nine-company consortium made up of M.W. Kellogg Ltd., Chantiers de l'Atlantique SA, Fincantieri SPA, FMC Europe, Gaz Transport & Technigaz SA, the Institut de Recherches de la Construction Navale, and classification societies Bureau Vééritas SA and Registro Italiano Navale.

Oil and gas companies RoyalDutch/Shell Group, TotalFinaElf SA, Chevron Corp., Texaco Inc., and Conoco Inc. gave "technical and financial support" to the project:

  • M W Kellogg developed two scenarios for the liquefaction barge, a stand-alone gas field in southeast Asia, involving a 3 million tonnes/year (tpy) capacity, based on a dual mixed-refrigerant process cycle; and a single processing train in West Africa, with a capacity of 1 million tpy with a nitrogen expander cycle for the liquefaction of the associated gas for a deepwater oil field.
  • Fincantieri formulated a design for a floating receiving terminal in southern Europe, while SN Technigaz's regasification process was designed around submerged combustion vaporizers with LNG storage capacity of 200,000 cu m.

Bouygues said the study found that the transfer of LNG in open seas "can be performed safely in a tandem loading configuration," using the boom-to-tanker designed by FMC.

"A large scale model of this device was successfully tested, using motion data from basin tests," the company noted.

The Azure project looked at both steel and concrete hull designs for the LNG FPSO, with Chantiers de l'Atlantique developing the steel hull options, and Bouygues designing the concrete hull alternative.

Safety assessment of the various facilities linking the proposed floating LNG chain was conducted under the supervision of BV and RINA.

Here is a concept for large-scale, floating-LNG-barge design. (OGJ, Mar. 9, 1998, p. 67; courtesy Mobil E&P Technology Co., Dallas)
Click here to enlarge image

The study found that by combining engineering practices from the offshore industry with those of onshore LNG terminals, the necessary safety criteria could be met, said Bouygues.

Advanced computer tools, developed by IRCN to address the liquid motion of the slack LNG storage tanks, found "sloshing" was not an issue, a fact confirmed by Gaz Transport & Technigaz via liquid motion tests and impact testing on membranes.

Australian LNG coming to California

Phillips Petroleum Co. and El Paso Corp. plan to deliver Timor Sea LNG to southern California and Mexico's Baja California.

The two companies' subsidiaries signed a letter of intent last month for El Paso's long-term purchase of LNG from a plant to be built by Phillips near Darwin.

A definitive agreement, expected by midyear, will outline terms for sales beginning in 2005. El Paso will market the 680 MMcfd of gas.

Estimated cost of the project, including the LNG plant, ships, and a West Coast receiving terminal, is between $3 and $3.5 billion, depending upon the size of the LNG plant, said Phillips.

The Darwin LNG facility, using Phillips' LNG technology, will be supplied from the Greater Sunrise fields with reserves of 9 tcf.

Phillips and El Paso plan to develop LNG shipping and the receiving terminal jointly. They are working with Mexican and US authorities to select the site for the terminal and acquire permits for the terminal, slated to go on stream in 2005. Existing pipelines will transport the gas to customers.

The Phillips-El Paso announcement followed the increase of Phillips' interest in the Greater Sunrise fields to 30% and finalization with Shell Development Australia Pty. Ltd. and Woodside Petroleum Ltd. of terms for development of Timor Sea gas resources (OGJ Online, Feb. 23, 2001).

Gas production from the Woodside-operated Greater Sunrise fields could begin as early as mid-2006. Until then, Phillips-owned reserves in Bayu-Undan will be used.