Interconnector (U.K.) Ltd., the group formed to lay a gas export pipeline from U.K. to Belgium, has begun onshore work related to the £ 450 million ($675 million) project.
The 40-in., 1.9 bcfd Interconnector pipeline will extend 150 miles from a compression plant at Bacton, U.K., to a reception facility at Zeebrugge, Belgium. Once the U.K. becomes a net gas importer, the line could be expanded to deliver as much as 815 MMcfd of gas to Britain.
Interconnector partners are British Gas plc 40%, BP Exploration Operating Co. Ltd. 10%, Conoco (U.K.) Ltd. 10%, Elf U.K. plc 10%, Gazprom 10%, Amerada Hess Ltd. 5%, Distrigaz SA 5%, National Power plc 5%, and Ruhrgas AG 5% (OGJ, Dec. 19, 1994, p. 26).
Of the project partners, only British Gas and Conoco have secured gas sales contracts for U.K. gas within Europe. Both have deals with German gas supplier Wingas GmbH, for a total 3 billion cu m/year.
Onshore work
Tony McEwan, Interconnector's onshore manager, said four redundant transmission lines will be brought back into operation as feeders to carry gas from the U.K. grid to a new compression plant to be built at Bacton.
Four 27-MW compression trains are to be installed within the British Gas site at Bacton. These will raise the gas to 140 bar discharge pressure for transmission to Belgium.
At Zeebrugge, four 3.5-MW water-bath heaters will raise the gas temperature to Belgian grid specifications. The gas will arrive at 83-105 bar, depending on flow rates.
McEwan said engineering work for the two terminals is well in hand, that compression trains are being built, and that procurement has just begun to tender for coolers and pressure vessels.
Work at the two terminals is intended to run in parallel, with construction to begin early next year. Compression trains will be delivered from October 1997 to January 1998.
"Mechanical completion of the pipeline and terminals is scheduled for the end of June 1998," said McEwan. "Then we will have 3 months for testing and commissioning before start-up on Oct. 1, 1998."
McEwan said work on the onshore pipeline section in Belgium has begun, while the onshore stretch at Bacton is slated for installation in mid-1997.
McEwan said the Zeebrugge terminal site covers 10 acres and has enough space to enable relocation of compression facilities from Bacton when Britain needs gas imports: "We don't know when this will be; maybe 10 years, maybe 30 years, depending on future U.K. gas field developments."
Offshore work
Jan Raven, offshore manager at Interconnector, said two lay barges will be required at any one time: one large semisubmersible vessel for the bulk of the offshore pipelaying, starting from Bacton, and a flat-bottomed barge for the shore approach and first 16 km out from Zeebrugge, where water is shallow.
Pipelay contractor European Marine Contractors Ltd., London, will operate Semac I and Castoro Sei vessels for the deeper section, and Castoro Due shallow water barge near to Zeebrugge. The latter will not have the same welding rate as the large vessel but will cut costs by avoiding dredging.
Raven said pipelaying from the Bacton end will begin in March 1997, while the flat-bottomed barge will start pipelaying work from Zeebrugge in April 1997. The two sections will be tied in at a point where water depth is 15 m.
Among obstacles along the pipeline's route are: two major dredging areas near the terminal approaches; sandwaves, which require dredging to enable the pipeline to be laid across them; and four live power cables.
Also, a few weeks after the Interconnector has been laid, the NorFra trunkline from Norway to Dunkirk will be laid above it (OGJ, Aug. 28, 1995, p. 67).
Interconnector will require 130,000 metric tons of line pipe, in 19,700 sections each 12.4 m long. Six thousand anodes will be attached to the pipe, weighing a further total 860 metric tons.
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