IN the 21st century, Russia's Kara Sea off the coast of Siberia could supply Asia's so-called ``tiger economies'' with low-cost natural gas, likely to last for at least the next 250 years. The technical journal Offshore claims that Arctic Russia's massive Rusanovskaya, Leningradskaya, and Zapadno-Sharasovskaya fields could replace both the Gulf of Mexico and the North Sea as the world's primary source of natural gas ``for the first half of the 21st century''.

But until recently, hopes of actually obtaining Arctic Russia's gas have been daunted by the fact that the Kara Sea, Barents Sea, and Arctic Ocean are icebound approximately 10 months of the year and are only accessible to icebreakers.

Offshore energy operators have previously put forward various proposals to exploit Russia's Arctic offshore energy fields, but studies foundered on the inability of conventional offshore installations to withstand Arctic ice. Now, a US-based company has signed a joint venture agreement with the Russian government to exploit the Rusa-novskaya and Leningradskaya fields - using underwater technology culled from Nazi Germany's methods of supporting its U-boat fleets during the Battle of the Atlantic in World War Two.

Then, modified U-boats, known as Milch Kuhs (Milk Cows), each carrying more than 200 tonnes of diesel fuel, lurked under the polar ice until needed to resupply U-boat packs harrying Allied convoys. The Second World War refuelling submarines were 67 metres long and 9.35 metres wide. They carried crews of about 60 men.

Former U-boat commander Herbert Werner, now head of US-based Werner Offshore, plans a fleet of 22 submarine tankers to be completed by the year 2013 at a new shipyard in Vladivostok. Construction could begin during 1997. The yard will be jointly operated by Werner Offshore and its Russian partners. The new tankers - 1300ft long with a capacity of 170,000 cubic metres of liquid natural gas - would make 11-day journeys east under the Arctic ice, eventually unloading their cargos at St Matthew in Alaska. Thereafter, the gas would be taken by conventional surface tankers to ready markets in China, Japan, Taiwan, and Korea.

Offshore-related journals suggest the first underwater voyage from the Kara Sea to the North Pacific, could take place as early as the year 2004. Each giant submarine would have a crew of 14 and would be powered by an air-independent, closed-cycle diesel system. The power units are tipped to be sourced from UK companies.

This potentially massive energy boost for Asia's already booming economies could stem from ``undersea mining'' techniques first envisaged in 1870 by science fiction writer Jules Verne. In his classic 20 Thousand Leagues Under the Sea, Verne described Captain Nemo and his submarine Nautilus mining the floor of the Arctic Ocean, at depths of 3000 feet beneath 4000ft of ice. Real-life fully automated sub-sea production systems extracting oil and gas from the Kara Sea would have to operate at a depth of only 50 metres. Gas would be piped to liquefaction plants on Russia's Novaya Zemlya Island, where it would be processed into liquid natural gas and transferred to the 21st century Milch Kuhs for transport to industrial Asia.

Ironically, the first sub-sea traverses of the Arctic ice cap, via the Northwest Passage from the Atlantic to the Pacific, were made in 1958 by the US nuclear submarine Nautilus. That expedition was primarily mounted for military purposes.

Now, with Russia's submarine-building expertise wedded to the 1939-45 experience of that nation's former deadly enemies, submarine technology could fuel post-millennium economic wars predicted by some analysts between the West and emerging Asian economies.

First reports suggest that when peak production is reached in the Kara Sea, Asian economies could receive more than 21 million tonnes of natural gas per year. Europe might obtain some supplies of offshore oil from Nemoesque offshore undersea wells likely to be created in the Barents Sea, to the west of the Kara Sea gas sources. But the already highly competitive economies of Asia could take the lion's share of offshore Siberia's natural gas. The heritage of Admiral Karl Doenitz's Second World War ``wolf-packs'' could yet give a whole new meaning to that slogan about putting a tiger in the tank.

Submarine tankers will be built to carry tomorrow's fuel