Falling water levels in the Caspian Sea owing to climate change threaten Kazakhstan's giant Kashagan oil field, its operator said Wednesday.
Kashagan is one of the world's largest offshore fields, with estimated reserves of 13 billion barrels of oil.
Its operator, the North Caspian Operating Company, is an international consortium that includes Eni, Shell, Total ExxonMobil, Inpex, the China National Petroleum Company (CNPC) and Kazakhstan's KazMunayGas.
"The falling Caspian Sea level followed by the sea's shallowing in the area of Kashagan offshore facilities have limited the use of sea vessels," the operator said in a statement.
"It is posing a threat towards the safe operation of offshore production facilities that may lead to the complete shutdown of one of the largest fields in Kazakhstan."
The Caspian, which is shared by Russia, Iran, Azerbaijan, Kazakhstan and Turkmenistan, is the world's largest inland lake.
Water levels there fell by around 1.4 metres (4.6 feet) between 1996 and 2015 as air temperatures rose, according to a study published in 2017 by the American Geophysical Union.
Scientists have predicted that water levels could fall by a further nine to 18 metres (30-60 feet) before the end of this century.
The Northern Caspian, where the Kashagan oil field is situated, is the shallowest part of the lake.
Discovered in 2000, the oil field has faced endless delays owing to technical problems.
Predictions of the drying up of swathes of the Caspian in the coming decades are foreshadowed by the disaster that befell the Aral Sea, once the world's fourth largest lake and shared by Central Asian neighbours Kazakhstan and Uzbekistan.
By 2000, the Aral had shrunk to just a tenth of its size in 1960, when Soviet authorities embarked on a giant expansion of water-intensive cotton farming in arid Uzbekistan.
Dust storms occurring in the Aral's former seabed that carry salt and chemicals have become regular events, and threaten harvests in the region.