President George W. Bush plans to double the size of the country’s emergency oil reserves to 1.5 billion barrels by 2027, Energy Secretary Samuel Bodman said.

The government this spring will start buying 100,000 barrels of oil a day to fill the stockpile to its current capacity of 727 million barrels, Bodman said in a conference call with reporters. Crude oil prices had their biggest gain since the aftermath of Hurricane Katrina in September 2005 on concerns that the purchases will stretch global supplies.

“U.S. demand continues to grow, and our strategic stocks need to keep up that same pace at least,” said Mark Routt, an analyst at Energy Security Analysis Inc. in Wakefield, Mass. “It’s obviously a wise decision in terms of economic and political security.”

Congress established the emergency reserve in 1975, after the Middle East oil embargo, to make up for global supply disruptions. The U.S. tapped the stockpile in 1991 after Iraq invaded Kuwait and in 2005 after Hurricanes Katrina and Rita disrupted pipelines, refineries and Gulf of Mexico production.

“Expanding the strategic petroleum reserve is a wise and prudent policy decision that will provide an additional layer of protection for our nation’s energy security,” Bodman said. The expanded reserve, stored in salt caverns along the U.S. Gulf Coast, would be equal to about 97 days of U.S. oil imports. It will cost about $65 billion, including $10 billion to build new storage facilities and $55 billion for the extra crude, according to Energy Department spokesman Craig Stevens.