Hungry Western oil majors, hunting for a of slice Russia's energy booming output and improving economy, may only get the crumbs left by domestic firms, analysts say.
Seeking to escape volatile OPEC supplies and impress shareholders with double digit reserves growth, Western companies are rushing to join every potentially lucrative project in Russia, but will probably have to wait for decades before they produce their first oil.
"Russian firms have enough money to tap the most lucrative fields, so they invite Western partners only in the most tough projects and regions, where investment risks are extremely high," said oil analyst Valery Nesterov from Troika Dialog.
The world's top four oil firms ExxonMobil, Royal Dutch Shell, BP and TotalFinaElf have all recently said they were counting on Russia for long-term strategic growth.
BP said this week that it was holding talks with Russia's number two oil firm Yukos to jointly explore huge and untapped fields in eastern Siberia, which might yield reserves comparable to the vast oil riches of Western Siberia.
TotalFinaElf joined Yukos last month in oil exploration on the Black Sea and bought a controlling stake in the Vankor oilfield in Eastern Siberia. BP and Shell have also said they were looking to expand outside the remote eastern island of Sakhalin, where they have been working for years.
"These projects require billions of dollars to complete exploration, confirm reserves, build infrastructure and link them to markets with extremely long and expensive pipelines," said Alfa Bank oil analyst Konstantin Reznikov.
Ivan Mazalov from London's Commerzbank agreed that Western majors were joining extremely costly and risky projects but added they expected new pipelines to be at least partly independent from the state monopoly Transneft, which currently unilaterally decides how and where ship the crude.
Analysts said French major TotalFinaElf looked like it was gambling more than its peers.
"Black Sea offshore exploration is a very doubtful idea as nobody has ever discovered oil there over the last century," said Nesterov. Sources in Yukos have said experts from both firms see the Black Sea offshore structure as similar to the North Sea and the Gulf of Mexico.
"Yukos will at least get some offshore exploration experience from this project," said Reznikov, who added that the Black Sea deal was probably only the first step helping the two firms to attack bigger projects, including in the Caspian Sea.
Reznikov also said he was not impressed by Total's acquisition of the Vankor oilfield: "This is a very tough project, which is hundreds of miles away not only from the markets but even from the existing pipelines."
Royal Dutch Shell pulled out of Vankor two years ago. The field, situated in the far north of eastern Siberia, contains up to one billion barrels of potential reserves, but Shell said it would focus on Sakhalin instead.
Analysts said BP's possible decision to join Yukos in Eastern Siberia would also require huge investments, but made sense as Yukos's fields are situated in the region's south, focussed on the vast Chinese market.
Yukos plans to build a pipeline to China and has said it is considering linking it to eastern Siberia fields, currently hundreds of miles away from the country's major pipelines.
BP holds a major stake in the Russia Petroleum group, which plans to build a gas link to China from the giant Kovykta gas field in eastern Siberia's south. "Merging two pipelines could have a positive cost-cutting synergy effect," said Reznikov.
Experts agreed that the excitement about Russian oil reserves was set to subside and Western oil majors would start analysing projects more realistically.
"I would say the Barents Sea is a good place to invest billions. It is closer to Europe and allows building an independent export infrastructure," said Nesterov.
Russian gas giant Gazprom and top oil firm Lukoil hold huge, untapped onshore and offshore oil and gas fields in the Barents Sea.
Reznikov said Sakhalin island, where Shell and Exxon Mobil are already operating, was also a very attractive region with huge oil and gas reserves potential and direct routes to Asian markets.