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Petrobras used the world's first gimbaled J-lay tower from Houston's Radoil Inc. to install its P26/P18 subsea pipeline and connect the steel catenary riser to a P18 floating production system.
The job, completed early in 1999, was the first use of the Radoil tower. This gimbaled tower is a decided departure from the usual J-lay barge. The tower was proposed to Petrobras and designed as a fast-track project with installation and engineering going on concurrently.
Unlike prior J-lay tower builders whose backgrounds were in pipeline construction, Radoil's principals had experience mostly with drilling rigs and towers. Radoil President Benton Baugh said this led to a fundamental approach based on what could be done with a derrick, rather than a conventional pipeline S-lay setup.
Working with pipeline contractor Oil States International, Radoil designed a far lighter tower than the S-Lay derivatives with an ability to gimbal 15° in any direction and continue to lay pipe off a semisubmersible or other vessel that would have to turn into the wind in rising weather.
One of the results of the Radoil design was an extremely light rig that could be installed in many lightweight vessels yet deliver very high capacity. For example, Radoil's gimbaling J-lay can handle 90% of the weight of the largest pipelay vessel, the Saipem 7000, yet it weighs only 350 tons compared to 5,000 tons for the larger ship. The Saipem can handle quad joints of pipe and the J-lay only doubles. However, with a separate coating station below the stinger, the smaller tower may very well approach the speed of the larger tower, Baugh said.
From the rear of the Sedco Amethyst for the Petrobras pipeline, the J-lay installation began with the tower upright and then tilted to 15° as the vessel moved along its route, laying the line at 3,000ft of water. During the job, weather forced pipe-laying operations to take place with the Amethyst traveling sideways down the route of the pipeline. At the end of the line, the tower lifted and installed the world's first catenary riser.