Exxon Neftegas tops off Sakhalin-1 platform GBS installation
Exxon Mobil Corp.’s Exxon Neftegas Limited (ENL), the operator of the Sakhalin-1 Project has completed the installation of gravity-based structure (GBS) for its new offshore platform on the third field of the Project Arkutun-Dagi, the company press release said.
The platform named Berkut (which means “golden eagle” in Russian) is designed to withstand harsh subarctic conditions with waves up to 18 meters, ice two meters thick, and temperatures minus 44 degrees Celsius. It will comprise the specially designed concrete GBS and topsides with drilling and production facilities mounted on it. Once mating of the topsides with the GBS is completed in 2013, Berkut will become the largest offshore platform in Russia.
“The successful completion and installation of the GBS highlights a significant milestone to the scheduled 2014 production start-up from Arkutun-Dagi field,” said Jim Flood, Exxon Neftegas Limited chairman. “ The project’s outstanding safety and operational performance is a testament to our skilled offshore installation staff and the successful collaboration developed with local port authorities and our Russian marine transportation contractors.”
The GBS was constructed in dry dock of port Vostochny near Nakhodka, Russian Far East. The total weight of the structure is approximately 160 thousand tons, including over 52,000 cbm of concrete, and 27,000 tons of steel rebar, pre-stressed cables and internal outfitting. Nearly 4,000 Russian specialists were involved in the GBS construction, which was completed in two years.
Upon completion, the GBS was towed 1,024 nm (1,870 km) from the construction site to the Arkutun-Dagi field across two seas, Sea of Japan and Sea of Okhotsk, and LaPerouse Strait. The towing operation took approximately two weeks with average speed 3.5 knots (approximately 5.5 km / h). To ensure safe transportation, climate history data had been thoroughly researched to select a window of opportunity with the most favorable navigation conditions. Five vessels, including three ocean class tugs, a command vessel and an operation support vessel, were involved in towing of the structure.
The GBS was set down on the sea floor at its permanent location approximately 25 kilometers off of Sakhalin at water depth of about 35 meters. The ballasting was controlled remotely from a support vessel with no personnel on board the GBS. The installation operation was followed up by grouting, rock dumping and connection to Sakhalin-1 production infrastructure.
The Sakhalin-1 Consortium includes Exxon Neftegas Ltd (operator, 30 percent interest); Japanese Consortium Sakhalin Oil and Gas Development Co. Ltd., (30 percent); affiliates of Rosneft, the Russian state-owned oil company, RN-Astra (8.5 percent), SakhalinmorneftegasShelf (11.5 percent); and Indian ONGC Videsh Ltd. (20 percent).
