Frozen seas and earthquake zone
Ice poses serious technical challenges too. From December to May, a thick layer of ice surrounds the platforms in the Sea of Okhotsk, preventing tankers from reaching them to load oil and gas. Instead, a 300-kilometre network of underwater pipelines takes the hydrocarbons ashore year-round.
Two major earthquakes of 6.4 and 7.6 on the Richter scale have struck the Sakhalin region in the past 15 years. The platforms are designed therefore to resist the kind of enormous earthquake that occurs perhaps once in 3,000 years. The topsides, or upper parts, of two of the platforms are connected to their concrete legs by sliding joints. If an earthquake strikes, they can move independently from the legs in a pendulum motion, preventing damage.
Ridges of compressed ice can carve deep gashes in the seabed and could damage pipelines. A thick concrete coating protects them, however, and they are buried five metres beneath the seabed wherever the sea is less than 30 metres deep. As an extra safeguard, electronic leak-detection systems including valves halt the flow of oil and gas if the pressure drops.
Protecting western gray whales
Western gray whales, a species brought to near extinction by commercial whaling early in the 20th century, feed in the waters off Sakhalin Island. Sakhalin Energy rerouted the offshore pipelines 20 kilometres to the south to avoid the feeding grounds, following advice from an independent panel of scientists set up under the International Union for Conservation of Nature (IUCN). In recognition of its western gray whale protection programme, Sakhalin Energy won the 2008 Environmental Project of the Year award from Russia’s Ministry of Environment and Natural Resources.
To protect the whales, sound levels in the area are constantly monitored. During construction, work such as drilling and pipelaying was suspended when the noise exceeded levels recommended by scientists. Buoys with acoustic monitors positioned along the edge of the feeding grounds track sound levels. The large-scale research programme is jointly financed by Sakhalin Energy and ExxonMobil, the operator of the Sakhalin-1 project. In 2012 nine calves and several adult whales were registered for the first time in the waters off north-east Sakhalin.
Pipelines crossing seismic faults and salmon rivers
Once the hydrocarbons are pumped ashore, a processing plant treats gas and condensate, a natural gas liquid, from the Lunskoye-A platform, along with oil and some gas produced by the Molikpaq and Piltun Astokhskoye-B platforms. From there, the gas is sent through two parallel 800-kilometre pipelines to the Prigorodnoye complex at Aniva Bay in the south of the island, which includes an LNG plant, an oil export terminal and a port which is virtually ice-free during winter.
As long as the distance from Paris to Berlin, the pipelines cross seismic faultlines at 19 places and more than 1,000 of Sakhalin Island’s 60,000 rivers and streams. The 8,000 construction workers who built them could only start work after unexploded munitions from World War II had been cleared.
Engineers planned the onshore pipeline route to avoid most of the active faults, where even low levels of seismic activity could cause ruptures. If no alternative route existed, they used pipeline segments made of steel that can bend up to four metres without breaking.
Sakhalin Energy planned the route to create the least disturbance to vulnerable species, such as the Steller’s sea eagle and Siberian spruce grouse, and to the island’s rich vegetation. Laying the pipelines beneath streams where salmon spawn — a highly sensitive operation — mainly took place in winter when the water was frozen.