**The Strategic Petroleum Reserve management office is located in New Orleans, Louisiana.
The reserve is stored at four sites on the Gulf of Mexico, each located near a major center of petrochemical refining and processing. Each site contains a number of artificial caverns created in salt domes below the surface.
Individual caverns within a site can be up to 1000 m below the surface, average dimensions are 60 m wide and 600 m deep, and capacity ranges from 6 to 37 million barrels (1 to 4.3 million m³). Almost $4 billion was spent on the facilities. The decision to store in caverns was taken to reduce costs; the Department of Energy claims it is roughly 10 times cheaper to store oil below surface with the added advantages of no leaks and a constant natural churn of the oil due to a temperature gradient in the caverns. The caverns were created by drilling down and then dissolving the salt with water.**
I can't understand why they're pumping it up, and then pumping it back down again.