Russia's biggest independent oil producer OAO Lukoil Holdings (LKOH.RS) said Wednesday it started commercial production at the Caspian offshore field Yuriy Korchagin, which could reach annual output of 2.5 million metric tons of oil at peak.

Lukoil, 20%-owned by
U.S. oil major ConocoPhillips (COP), plans to produce 343,000 tons of oil at the field this year. At peak, annual output will reach 2.5 million tons of oil and 1 billion cubic meters of natural gas.

Between 2004 and 2009, Lukoil invested 34.4 billion rubles [$1.18 billion] in the field, which holds estimated reserves of 270 million barrels of oil equivalent.