New Delhi, Oct. 2 -- The world is preparing to tap another vast pool of emergency oil. On 2 October, G7 countries agreed to release 100 million barrels of crude and diesel from emergency reserves over four months, with a substantial diesel component expected within 20 days. The move, coordinated through the International Energy Agency (IEA), comes as Middle East disruptions squeeze energy supplies and push fuel prices higher.

But the oil is not held in one global reserve. It sits in government caverns, commercial storage facilities and mandatory industry stockpiles. The IEA can coordinate countries, but it does not own the oil.

So who controls the world's emergency oil reserves, and who decides when those barrels are released?

The US E...