QGC Pty. Ltd. simultaneously laid two 1-m gas pipelines across Gladstone Harbor, using the same trench to connect the Queensland Curtis LNG project and Australia Pacific LNG project—both on Curtis Island—to the mainland. The segments will connect each project’s main pipelines from Surat basin gas fields, about 300 km inland, to the Curtis Island LNG plants.
Pipelay entailed winching the lines 2.3 km from the mainland to Curtis Island in what QGC described as Australia’s longest large-diameter underwater pipe pull. The harbor crossing involved construction of temporary facilities including a 2-km road, two bridges, and a railway line to move the pipes across two creeks, marshes, and mud flats. A temporary 450-tonne capacity winch on Curtis Island pulled the pipes—which together weigh 8,000 tonnes—through the subsea trench, which will now be filled with gravel and rock to protect the pipelines.
Co-locating the pipelines and installing them concurrently minimized environmental and boating disruption, QGC said. The crossing follows raising the roof on Queensland’s first LNG storage tank, completed Feb. 8.
QGC, a BG Group company, managed the project, with lay work completed by MCJV, a joint venture of McConnell Dowell Constructors (Aus.) Pty. Ltd. and Consolidated Contracting Co. Australia Pty. Ltd. BG agreed last year to sell a stake in Queensland Curtis LNG to China National Offshore Oil Corp. (OGJ Online, Oct. 31, 2012).
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