Energy security

Saudi oil attacks: Why does the US hide oil underground?

In the wake of the attacks on key Saudi Arabian oil infrastructure, American officials have been talking about drawing on a huge emergency stash of oil kept in the United States.

As oil prices spiked, President Donald Trump tweeted they could use the oil "to keep the markets well-supplied".

The oil he was referring to amounts to more than 640 million barrels which are stored in salt caverns beneath the states of Texas and Louisiana. The idea of holding these "strategic reserves" dates back to the 1970s.

All members of the International Energy Agency have to hold the equivalent of 90 days' worth of petroleum imports, but the US stockpile is the largest emergency store in the world.