Oil refinery 1

Oil prices briefly fell below $30 a barrel for the first time since April 2004 on Thursday, before settling above the mark.

Brent crude oil fell to as low as $29.96 before bouncing back somewhat to $30.22.

Prices are down 70% over the past 18 months, and oil has fallen by more than 20% since the start of the year alone.

Earlier, Russia warned that it may be forced to revise its budget for the year, if prices continue to fall. With oil and gas accounting for around half of Russia's state revenue, Prime Minister, Dmitry Medvedev said the country had to be prepared for a "worst case".

Russia's current economic budget was based on prices being close to $50 per barrel. And finance minister Anton Siluanov said the country will only be able to balance the books if oil prices were around $82 a barrel. He recommended the government revise its budget based on prices of $40 per barrel.

"Our task is to adapt our budget to the new realities," Mr Siluanov said.

But economy minister Alexei Ulyukayev has warned that those 'new realities' could be oil prices falling as low as $15-20 per barrel.

"The biggest risk is that there will be low prices for a long time - that is, for years, for decades," he said.