A study from the International Energy Agency in Paris finds that storing oil in emergency stockpiles does more than support energy security.

The 29 members of the IEA are mandated to hold enough oil in emergency stockpiles to meet 90 days worth of imports. A report published Wednesday finds those stocks not only help support energy security for member states but also save them money.

The review "valued the stockpiles' global benefits over 30 years at about $3.5 trillion."

At the end of March, IEA said member states had about 4.1 billion barrels of oil stored in emergency stockpiles. That represents about 44 days of the total global demand for oil, which IEA said provides a safety valve in the event of a major supply disruption.

IEA found the benefits of storing emergency reserves offset the expense. Member states spend on average $8.5 per barrel of oil stored.

Each barrel of oil stored translates to a net global benefit of $41 per year, after storage costs.

IEA said its estimates were conservative.