The Strategic Petroleum Reserve (SPR) is an emergency oil store maintained by the United States Department of Energy. It is the largest emergency supply in the world with the capacity to hold up to 700 million barrels (111 billion liters) of crude oil.
The reserve is stored at four sites on the Gulf of Mexico. The sites are Big Hill and Bryan Mound in Texas, and West Hackberry and Bayou Choctaw in Louisiana. Each site contains a number of artificial caverns created in salt domes below the surface.
Individual caverns can be up to 1000m below the surface, average dimensions are 60m wide and 600m deep, and capacity ranges from 6 to 30 million barrels. Almost $4 billion was spent on the facilities. The decision to store in caverns was taken to reduce costs; the Dept. 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.
On November 13, 2001, President George W. Bush announced that the SPR would be filled to capacity, saying, "The Strategic Petroleum Reserve is an important element of our Nation's energy security. To maximize long-term protection against oil supply disruptions, I am directing...the Secretary of Energy to fill the SPR up to its 700 million barrel capacity." The highest prior level was reached in 1994 with 592 million barrels. By redirecting a certain amount of imported crude oil to the reserve, some think this effective raised oil prices by 28 cents per gallon.
Access to the reserve is determined by the conditions written into the 1975 Energy Policy and Conservation Act (EPCA), primarily to counter a severe supply interruption. The maximum removal rate, by physical constraints, is 4.1 million barrels per day. Oil could begin entering the marketplace 15 days after a Presidential order. The Dept. of Energy says that it has roughly 7-8 weeks worth of inventory protection in the SPR. This, combined with private sector inventory protection, is estimated to total 150 days worth of emergency supply.
The SPR was created following the 1973 energy crisis. The EPCA of December 22, 1975, made it policy for the US to establish a billion barrel reserve. A number of existing storage sites were acquired in 1977 with the first oil arriving in July of that year. Oil has been removed under emergency conditions only once, in 1991. The current SPR sites are expected to be usable until around 2025.
The US consumes around 20 million barrels of oil every day, about 26% of world daily consumption.