Russian tycoon Roman Abramovich is in talks with Western petroleum firms over the sale of his Sibneft oil company, the Financial Times has reported.
Mr Abramovich has been steadily withdrawing from Russia
Shell, ChevronTexaco and France's Total are said to be the likely bidders.
Sibneft is currently being unwound from a merger with larger rival Yukos, a deal which was called off in December.
Mr Abramovich, whose fortune has been estimated at $13bn (£7.2bn), owns UK football club Chelsea and has sold off most of his Russian assets.
Selling Sibneft could prove trickier, however, since large oil firms are highly politically sensitive in Russia.
According to the FT report, which Sibneft refuses to confirm or deny, half of Mr Abramovich's 92% stake in Sibneft is up for grabs.
The shares had already been bought by Yukos when their merger was torpedoed, and now must be extricated.
Sibneft shareholders were made wary of Yukos after its boss, Mikhail Khodorkovsky, was jailed last year on charges of fraud and tax evasion.
Sibneft has until recently been left alone by the Russian authorities, but earlier this month was hit by surprise tax bill of more than $1.4bn.
Retaining the support of the Kremlin will be crucial in any change of ownership at Sibneft.
Suitors line up
The reported likely Sibneft bidders are all known to have an interest in Russia.
The Russian oil sector has become far more attractive in the past couple of years, after sustained high crude prices and an improvement in the operating environment under President Vladimir Putin.
BP has already invested heavily in Russia, and ExxonMobil was in talks to buy into a merged Yukos-Sibneft.
Of the three firms mentioned in the FT story, the keenest bidder is likely to be ChevronTexaco, another Yukos suitor which has made no secret of its ambitions to buy a Russian firm.
Any serious bidder is likely to want a majority stake in the firm, however, since minority shareholders have often had problems in Russian ventures.