Russo-British energy giant TNK-BP has said that a subsidiary firm which controls the huge Kovykta gas field in Russia has filed for bankruptcy.
It said RUSIA Petroleum, in which it owns a 62.9% stake, could not repay its loans to the TNK-BP Group.
Russian officials have threatened to withdraw the Kovykta licence because of low production volumes.
In 2007, TNK-BP agreed to sell the licence to Russian gas monopoly Gazprom, but the talks stalled.
Alexander Burgansky, an analyst at Renaissance Capital, said: "Following the bankruptcy of RUSIA Petroleum, we expect the Kovykta licence to be reclaimed by TNK-BP Ltd in lieu of debts, which should simplify the negotiation process for its disposal and maximise the sales proceeds for TNK-BP."
BP owns 50% of TNK-BP, while the other 50% belongs to a consortium of Russian billionaires.
The Kovykta field is estimated to contain more than 2 trillion cubic metres of natural gas.
Under the agreement reached in 1997, 9bn cubic metres of gas should have been produced in Kovykta annually since 2006, but the actual figure is about 34m cubic metres.
TNK-BP has said that the local region does not require much gas, and it cannot export surplus gas to China as Gazprom has monopoly rights to export gas.
Kovykta, one of the biggest undeveloped gas fields in the world, is strategically important to Russia, which is trying to diversify its gas supplies.
Russia, which satisfies more than a quarter of Europe's gas needs, hopes to become a major supplier of gas to China.