The Energy Department on Friday announced it was buying up to five million barrels of oil for the U.S. strategic petroleum reserve, a federally owned stockpile of oil that is available in case of an emergency or sudden disruption in oil supply. In March 2014, the Energy Department announced it was selling five million barrels of sour crude oil in what the government described then as a “test sale.” Friday’s announcement to buy back that amount of oil is required by law within one year, according to Energy Department spokeswoman Lindsey Geisler. The Energy Department will be able to buy five million barrels of light, sweet oil at roughly half the price they earned for the same amount of sour crude last year. The benchmark U.S. oil price fell 4.7% Friday to $44.84 a barrel on the New York Mercantile Exchange. The price for light, sweet oil averaged right around $100 a barrel in March 2014. Sour crude typically costs less than light, sweet crude because it is considered lower-quality by refiners.