the SPR was created for...see the attached link...or if that's too troublesome, here's the opening paragraph...
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• Why is there a Strategic Petroleum Reserve?
Established in the aftermath of the 1973-74 oil embargo, the SPR was established to counter a disruption in commercial oil supplies which could threaten the U.S. economy. It is also the critical component for the United States to meet its International Energy Agency obligation to maintain emergency oil stocks.
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Link: https://www.energy.gov/ceser/spr-faqs