London - The International Energy Agency says the world has saved $3.5trn over the last 30 years by maintaining emergency oil stocks to offset supply shocks and curb price surges.
The West's energy watchdog said on Wednesday that emergency oil stocks held by member and non-member states had acted as "insurance" against oil supply disruptions.
Spiralling violence in key oil producer Iraq in recent weeks has pushed global oil prices to nine-month highs, reviving speculation of a release of strategic stocks in case of severe supply disruptions.
Market outcomes
The IEA said: "Significant economic benefits are derived primarily from offsetting oil supply losses and reducing potentially significant oil price increases.
"These consist of reduced GDP losses and reduced import costs."
Using a model to simulate tens of thousands of possible oil supply disruption scenarios and market outcomes, the report estimated global net benefits derived from existing emergency stocks amount to $41 per barrel per year after storage costs.
The report said the 29 IEA member states must hold stocks equivalent to at least 90 days of net imports. At the end of March 2014, member countries' stores totalled 4.1 billion barrels, equivalent to about 44 days of total global demand.
By the end of 2013, 60% of oil stocks in IEA member countries were crude oil and 40% refined products such as gasoline and diesel.
Supply shock
Limiting oil consumption, particularly within the transport sector which accounts for more than half of all oil use in IEA members, was another way to offset supply disruptions, it said.
The IEA was created in 1974 by 16 Western countries in the wake of the 1973 oil supply shock in an effort to limit the impact of future crisis.
The IEA estimated the cost of stockpiling at $7-$10 per barrel per year, depending on the size and type of storage.
Holding reserves in underground caverns is about 30% cheaper than in above ground storage facilities, it said.
The last major supply disruption occurred in 2011 when output from OPEC member Libya dropped sharply due to civil war.