What is the Strategic Petroleum Reserve?

In a move that some economists are calling rare and unprecedented, President Joe Biden on Tuesday ordered the release of 50 million barrels of oil from the Strategic Petroleum Reserve located along the Gulf of Mexico. 

Biden's move is in response to the soaring gas prices Americans have experienced this fall. The Biden administration said it hopes the 50 million barrels from the nation's stockpile will help lower the cost of fuel at a time when people are expected to travel in droves to reunite with family members for the Thanksgiving and Christmas holidays. 

"Today's announcement reflects the president's commitment to do everything in his power to bring down costs for the American people and continue our strong economic recovery," the White House said in a statement Tuesday. 

For anyone wondering what exactly the Strategic Petroleum Reserve is, here's an explainer. 

What is the Strategic Petroleum Reserve?

The Strategic Petroleum Reserve is what the U.S. government calls a collection of 60 underground salt caverns where millions of gallons of crude oil are stored in barrels. Known as the largest supply of emergency crude oil in the world, the federally owned SPR is managed on a day-to-day basis by the U.S. Department of Energy. Whoever is the current U.S. president can decide to tap the reserve, but only under a set list of parameters. 

Where is the reserve located?

The massive 60 underground salt caverns that constitute the reserve are found at four different sites along the coastlines of Louisiana and Texas. The Bryan Mound site is just outside of Freeport, Texas. The Big Hill site is approximately 26 miles outside of Beaumont, Texas. The West Hackberry site is about half an hour from Lake Charles, Louisiana, and the Bayou Choctaw site is about 10 minutes away from Baton Rouge, Louisiana. 

How big is the reserve?

The four sites vary in size, with a combined authorized storage capacity of 714 million barrels, according to the Energy Department. Bryan Mound, the largest of the four, is a 500-acre location with 19 storage caverns that can hold 230.1 million barrels. Big Hill is 271 acres, with 14 storage caverns and an inventory of 143.7 million barrels. Bayou Choctaw, on 356 acres, has six storage caverns and and an inventory of 70.9 million barrels. West Hackberry is 405 acres with 21 storage caverns that currently hold 192.3 million barrels. 

When was the reserve created?

The reserve was created in December 1975, when former President Gerald Ford signed the Energy Policy and Conservation Act. About 30 years prior to that, in 1944, then-Secretary of the Interior Harold Ickes introduced the idea of storing oil reserves in case of an emergency. The idea sat dormant for decades until 1973, when the Organization of Petroleum Exporting Countries (OPEC) placed an embargo on oil and the U.S. decided to revisit Ickes' proposal. 

What is the reserve used for?

Having a massive supply of crude oil ready to deploy helps keep the price of gasoline or the price of home heating oil somewhat predictable and stable for U.S. consumers. When the U.S. decides to pull barrels of crude oil from the reserve, it is known as an emergency drawdown or an emergency release. During a drawdown, the U.S. selects an amount of crude oil to sell, then auctions it off to the highest bidder — which is typically an oil company.  

How has the reserve oil been used in the past?

Drawdowns of the SPR reserves have been relatively rare in its 45-year existence. Since 1975, presidents have called just three emergency drawdowns, according the the Energy Department.

In 1991, for example, President George H. W. Bush ordered a drawdown of 33.7 million barrels soon after Operation Desert Storm began in an effort to minimize the war's effect on oil markets. George W. Bush pulled out 30 million barrels in 2005 after Hurricane Katrina pummeled the Gulf Coast. The Obama administration also puled out 30 million barrels of oil in 2011, when the war in Libya reduced that country's oil production.

It's more common for the government to release oil under exchange agreements, which act like a loan — more than a dozen exchanges have taken place, usually after hurricanes. In 2000, former President Bill Clinton released 30 million barrels to combat a rise in heating oil prices, in a move that was criticized at the time as a political ploy to help his vice president, Al Gore, who was running for the presidency. 

The government has also released oil in non-emergency situatios, such as to raise money or plug a budget deficit.

Is the reserve being used in a way we've never seen before?

The U.S. government very rarely plucks from the reserve, and when it does, it's often right after a natural disaster or to fend off a prolonged economic downturn. Some economists say what Mr. Biden is doing this week doesn't fit either of those criteria. 

Carl Weinberg, chief economist at research firm High Frequency Economics, said that calling on the SPR is really a power play against OPEC. Weinberg called Biden's move "an unprecedented overt effort to thwart OPEC's price maximizing strategy" in a research note Tuesday. 

Troy Vincent, analyst at market research firm DTN, told CBS MoneyWatch that Biden's move is rare and doesn't fit with the common understanding of an emergency.

"It's been understood for decades that we don't really use this stuff unless something really bad and disruptive is going on," Vincent said. "You're not actually seeing this [now]. There's not a current crisis of any type of supply; this is just trying to pull prices down."

CBS News' Irina Ivanova contributed to this report.