Saudi Arabia and its OPEC allies’ firm stand against cutting crude output to slow the plunge in oil prices has set the energy world on a painful course that will leave the weakest behind, from governments to U.S. wildcatters.

Opec threw down the gauntlet to US shale oil producers by deciding not to cut its production, in a move that sent the oil price tumbling by more than 8 per cent to a four-year low.

Oil anchors world financial markets, and Opec has just decided to raise its anchor. The consequences could be profound, and go far beyond the power game between the traditional oil producers in the Middle East and the new generation of shale producers in North America.

Shares in the world’s biggest energy groups have tumbled in a market rout as plunging oil prices put at risk billions of dollars of investment and jeopardised future supplies of crude.

Even as Western sanctions over Ukraine bite, crashing oil prices are hitting Russia's economy and government finances.

Brent and West Texas Intermediate crudes fell to the lowest level in more than four years after OPEC failed to cut its output in response to a glut.

The International Energy Agency’s chief economist on Friday urged oil producers to boost investment in new projects to meet an anticipated rise in demand, a move that he said may avoid oil price spikes in coming years.

OPEC 166th Meeting concludes

Crude Rises as China Rate Cut Spurs Optimism About Demand

Iran will protect its share of global crude sales under all circumstances, Oil Minister Bijan Namdar Zanganeh said, as OPEC members prepare to meet next week to review production levels.