It sounds like good news for oil importing countries like Australia - the falling price of crude should mean cheaper prices at the bowser, lower transport costs and even food prices could fall.

It is effectively a nationwide tax cut.

But for some of the oil exporting nations, it is a financial disaster. In Russia, it is estimated the falling prices have already cost it $100 billion.

With the economic sanctions imposed on Russia over Ukraine, the decline in oil prices could not have come at a worse time.

The price of this global commodity has declined by nearly 40 per cent this year - below the cost of production in some countries, including Russia.

While the oil pumps keep flowing there, the rivers of revenue gold in reverse have reduced to streams.

As the price goes down, so too does the Russian rouble, which has declined by around 40 per cent this year.

Energy and resources specialist at London's Chatham House Professor Paul Stevens said that could spell deep economic and political trouble.

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"As the price falls, of course revenue falls, which means that the budget deficit in Russia is going to get larger and larger," he explained.

"Because of sanctions, Russia's not really able to go into capital markets to borrow money, so they're going to be in serious trouble."

Russia's central bank spent - some say wasted - billions defending the currency's value, to no avail.

Overnight the rouble hit a fresh low against the US dollar in the biggest one-day fall since the Russian currency crisis of 1998.

Oil price fall 'threatens Putin's power'

Speaking a few days ago, a surprisingly sanguine Russian president Vladimir Putin said he expected by the middle of next year the oil price would restore its balance - in other words, go up.

However, despite controlling vast supplies of oil and gas, Mr Putin cannot do much about it on his own.

OPEC, the global cartel including many major oil producing nations, decided just last week to keep supplies at current levels and, with little growth in the global economy, demand has disappeared.

Dr David Cadier, an international relations expert at the London School of Economics, said the current situation could weaken Vladimir Putin's grip on power.

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"If the energy prices are down, if the oil price is so low, then the economic situation in Russia will be affected and, in other words, you won't be able to bring this economic development that he [Mr Putin] was able to since the old boom," he argued.

"A decrease of oil prices might actually lead to a more nationalist Russian foreign policy, but it also means that Vladimir Putin's personal power might be threatened."

In turn, Dr Cadier predicted that would mean Vladimir Putin might need a diversion, like greater intervention in Ukraine or some other action that will appeal to the high level of nationalist fervour that he has cultivated.

Cheap oil may seem like a great idea, but the consequences in places like Russia are difficult and dangerous to predict.