By OGJ editors
HOUSTON, May 7 -- Petroleo Brasiliero SA (Petrobras) Monday claimed a world record in ultradeep waters for the installation of a subsea natural gas lift manifold at a depth of 1,885 m (6,184 ft.) in Roncador field in the Campos basin off Brazil.
Speaking at the Offshore Technology Conference, Petrobras Pres. and CEO Francisco Gros said the installation was unique for subsea equipment at this depth because of its size and weight: 10 x 7.5 x 4 m (32.8 x 24.6 x 13.1 ft.) and 191 tons (including installation equipment).
This marked the first time the installation of such heavy equipment surpassed waters deeper than 1,000 m. The manifold was installed with steel cables and support vessels. It was designed to reduce gas lift costs by distributing gas coming from the production unit via a single gas line for injection into six wells, Petrobras said.
The manifold is scheduled to go on stream by Dec. 31 following the interconnection of the wells to the manifold and the manifold to the Brasil floating production storage and offloading vessel.
The installation was carried out jointly by the Amethyst-1 (SS-47) semisubmersible drilling rig and the Asso 23 anchor-handling supply tug, as well as various supply boats.
The manifold was loaded on the deck of the Amethyst-1 and lowered into 90 m of waterwith the semi's lateral crane. Beyond that depth, the weight of the manifold was transferred to a 4-in. cable that was connected simultaneously to the Asso 23 tug winch and the semi's drilling tower.
With the objective of minimizing dynamic amplification, when lowered to the 900-m depth, the rig compensator and the riser tensioners were activated. The manifold was placed on the seabed only 2.3 m from the target location.
Aside from the cost savings of $4 million, the installation method also freed for service the the SS-51 semisubmersible that was originally scheduled for manifold installation, Petrobras said. The SS-51 is rated to work in 2,000 m of water, while the Amethyst-1 is rated to work in only 1,000 m.
Over the past 15 years, Petrobras has set a series of deepwater records in the Campos basin, including the world record set 2 years ago for deepwater oil production, 1,853 m (6,079 ft) in Roncador field. Although the well has since been shut in, the record has yet to be surpassed.
Meanwhile, Petrobras already has wells completed in waters up to 1,886 m (6,187 ft) deep that are waiting to be brought on stream.