Topsides nearly 24,000 tons
Several world records and “firsts” were accomplished to mate the Lunskoye-A topsides to its concrete gravity base offshore Sakhalin Island, eastern Russia, in the Sea of Okhotsk.
One record was set when the topsides, at 23,980 tons (21,800 metric tons), were installed using the “float-over” method. The installation barge was towed between the four legs of the base and lowered onto the concrete gravity base structure (CGBS) by ballasting down the barge, which was built for the purpose. Leg mating units weighing 143 tons (130 metric tons) each were pre-installed to centralize the topsides during lowering and to act as shock absorbers upon initial contact of the topsides with the legs.
The concrete gravity base is towed onto the site in preparation of the topsides arrival.
The topsides were part of an onshore lift record at Samsung Heavy Industries’ Geoje Island, South Korea, fabrication facility. The topsides were raised to 95 ft (29 m) so the load out support frame could slide underneath.
The tow also set a record, arriving in 11 days, five days ahead of schedule. The unique “T” shaped transport barge was accompanied by three tugs. The barge itself was 623 ft (190 m) long and 312 ft (95 m) wide. The transport covered 1,500 nm (2,831 km).
Several days’ preparation was required in order to settle the topsides atop the CGBS. This preparation included mooring of the installation barge and topsides in front of the CGBS, testing of the barge ballasting equipment, and cutting of the sea fastenings. The actual installation required nine hours and involved coordination of the topsides, its transport barge, the SaipemCastoro-8 installation support vessel, plus five tugs and anchor handling vessels.
Following installation of the topsides onto the CGBS, hook-up began.
“A crew of over 500 people weld the topside legs to make it structurally sound, hook-up all the systems that interlink the topsides and CGBS, and commission all of the topsides’ habitation, utility, drilling, and production systems,” says Bill Luyties, Lunskoye project manager.
Lunskoye-A will be home to 120 drilling and operations staff personnel who expect to begin work by the end of 2006. Lunskoye-A is a drilling and production platform which incorporates equipment for both, plus hydrocarbon liquids separation and living quarters. The structure has 27 well slots for directional drilling. The platform’s production capacity will exceed 1,800 MMcf/d (50 MMcm/d) of gas and 50,000 b/d of condensate. It will supply most of the gas for Russia’s first LNG plant being built in south Sakhalin Island. Final separation and treatment of Lunskoye gas and condensate will be onshore. That facility also will supply power to the platform via subsea cables.
Lunskoye-A is 9.3 mi (15 km) off the northeast coast of Sakhalin Island on the Lunskoye gas field in a water depth of 157 ft (48 m).
In another first, the platform also has special sliding connections called “friction pendulum bearings” between the CGBS and the topsides. These allow the topsides and base to move independently in the event of an earthquake to help protect the topsides from damage. This is the first time these bearings have been used in the oil and gas industry.
The base was the first such built in the port of Vostochnoye in the Primorsky Krai, Russia. It consists of a base caisson and four shafts topped by cylindrical steel deck connector legs which support the topsides. It has a total dry weight of 113,300 tons (103,000 metric tons) and measures 344 ft (105 m) by 287 ft (88 m) and 44 ft (13.5 m) in height. Each shaft is more than 65 ft (20 m) in diameter and is 184 ft (56 m) long. Total height of the structure is 228 ft (69.5 m) before installation of the topsides.
“This operation is a great example of professional engineering and marine mastery,” says David Greer, Sakhalin Energy Phase II project director. “The marine team not only safely towed the giant topsides all the way from Korea to Lunskoye, they then successfully placed it atop the concrete legs.
“The ‘silent elegance’ of the docking and mating of these two structures was a wonderful piece of engineering and a new world record. The top of the Lunskoye-A platform, which will become Russia’s first offshore gas production platform, now stands proudly some 360 ft (110 m) above the Sea of Okhotsk.”
