What is the Strategic Petroleum Reserve?

The Strategic Petroleum Reserve (SPR) is an emergency stockpile of petroleum maintained by the United States Department of Energy (DOE), and it is the world's largest supply of emergency crude oil.

The federally-owned oil stocks are stored in huge underground salt caverns at four sites along the Gulf Coast, with an authorized storage capacity of 714 million barrels.

The SPR is intended to protect the economy and strengthen national security during major oil supply disruptions.

Key Points

- The SPR was created in 1975 following the 1973-1974 oil embargo to mitigate future supply disruptions.

- Emergency crude oil is stored at four major facilities in the Gulf Coast region—two sites in Texas (Bryan Mound and Big Hill) and two sites in Louisiana (West Hackberry and Bayou Choctaw)—with the reserve containing 60 huge underground caverns.

- Oil can begin flowing to U.S. refineries within about 13 days after a presidential order to release it.

- Historically, the President has authorized emergency releases from the SPR on four occasions.

• The reserve serves as both a physical supply buffer and a market stabilization tool during energy crises.

Understanding the Strategic Petroleum Reserve

The SPR was conceived in response to the 1973 oil embargo by the Organization of Petroleum Exporting Countries (OPEC), imposed in retaliation for the United States' support of Israel during the Fourth Arab-Israeli War. The Energy Policy and Conservation Act (EPCA), signed into law by President Gerald R. Ford in 1975, authorized the creation of a strategic oil reserve to shield the U.S. economy from future supply shocks.

A number of existing storage sites were acquired in 1977, construction of the first surface facilities began in June 1977, and on July 21, 1977, the first oil—approximately 412,000 barrels of Saudi Arabian light crude—was delivered to the SPR.

The SPR was originally intended to hold at least 750 million barrels of crude oil as an insurance policy against future supply cutoffs, though today's design capacity is 714 million barrels.

The reserve represents a critical component of U.S. energy security infrastructure. The sheer size of the SPR makes it a significant deterrent to oil import cutoffs and a key tool in foreign policy.

The U.S. holds about one-third of the emergency oil reserves that are maintained by members of the International Energy Agency, a global forum of dozens of countries that helps members deal with major oil disruptions, with IEA members collectively holding over 1.2 billion barrels of emergency oil reserves.

How It Works

The SPR operates through a sophisticated system of underground storage and distribution infrastructure designed for rapid deployment during emergencies.

1. Storage in Salt Caverns

Besides being the lowest cost way to store oil for long periods of time, the use of deep salt caverns is also one of the most environmentally secure. Rock salt exhibits extremely low porosity and permeability, plastic deformation characteristics, and self-healing characteristics at the subsurface depths that the caverns are located, and these self-healing characteristics will almost instantly close any microcracks should they develop in the walls of the salt caverns.

Strategic Petroleum Reserve caverns range in size from 6 to 37 million barrels in capacity; a typical cavern holds 10 million barrels and is cylindrical in shape with a diameter of 200 feet and a height of 2,500 feet, and the Reserve contains 60 of these huge underground caverns.

The process of creating caverns involves drilling a well into a salt formation, then injecting massive amounts of fresh water. The water dissolves the salt, and in creating the SPR caverns, the dissolved salt was removed as brine and either reinjected into disposal wells or piped several miles offshore into the Gulf of America. By carefully controlling the freshwater injection process, salt caverns of very precise dimensions can be created.

2. Withdrawal Process

The fact that oil floats on water is the underlying mechanism used to move oil in and out of the SPR caverns. To withdraw crude oil, fresh water is pumped into the bottom of a cavern, and the water displaces the crude oil to the surface. After the oil is removed from the SPR caverns, pipelines send it to various terminals and refineries around the nation.

As of March 2025, the four SPR storage sites were connected by SPR owned pipelines and commercially owned pipelines and terminals, to 24 Gulf Coast area refineries and six refineries located in Michigan, Ohio, and Kentucky.

3. Authorization and Distribution

SPR oil is sold competitively when the President finds, pursuant to the conditions set forth in the Energy Policy and Conservation Act (EPCA), that a sale is required.

The US president can authorize emergency drawdowns, and the DOE then sells the oil to the highest bidders, typically major refining, trading and oil companies.

The secretary of energy can authorize test sales or temporary exchanges with private oil companies during localized disruptions, like when Hurricane Katrina cut off domestic supply chains in 2005.

This authority allows the SPR to negotiate exchanges where the SPR ultimately receives more oil than it released, thereby acquiring additional oil.

Why It Matters

The Strategic Petroleum Reserve serves multiple critical functions for U.S. energy security and economic stability. During supply disruptions—whether caused by natural disasters, geopolitical conflicts, or infrastructure failures—the reserve provides a buffer that can help stabilize markets and ensure continued access to crude oil for domestic refineries.

The whole purpose of the SPR is to stabilize prices, so the government must time its release and replenishment according to supply and demand. The reserve functions both as a physical supply of oil and as a psychological signal to markets. When releases are announced, they can help calm market fears and moderate price spikes even before the oil physically reaches refineries.

The SPR also fulfills international obligations. On November 18, 1974, the United States became a signatory to the Agreement on an International Energy Program (IEP) and a founding member of the International Energy Agency that the IEP established, and one of the key commitments made by the treaty's signatories is to maintain oil stocks of no less than 90 days of net imports. This international coordination allows member nations to respond collectively to global supply disruptions.

Related Terms

• International Energy Agency (IEA): A global forum of countries that coordinates emergency oil releases among member nations during supply disruptions.

• Salt Dome: A geological formation created when ancient salt deposits are forced upward, providing ideal conditions for creating underground storage caverns due to salt's impermeability and self-healing properties.

• Emergency Drawdown: A presidential authorization to release oil from the SPR in response to severe energy supply interruptions, as defined by the Energy Policy and Conservation Act.

Frequently Asked Questions

How much oil is currently in the Strategic Petroleum Reserve?

Inventory levels fluctuate based on releases and refills. At the end of calendar year 2025 (as of December 31, 2025), the SPR's crude oil inventory was 411 million barrels, equivalent to approximately 125 days (more than 4 months) of U.S. crude oil net imports. The reserve has experienced significant drawdowns in recent years, particularly following major releases in 2022 in response to supply disruptions.

What types of oil does the SPR store?

The SPR stores both sour crude—meaning the oil contains more than 0.5 percent but less than 2 percent sulfur by weight—and sweet crude—oil with sulfur content less than 0.5 percent by weight. Sweet crude oil is more frequently requested from the SPR, as it can be processed by nearly all refiners; the same is not true of sour.

How quickly can oil from the SPR reach the market?

According to the Department of Energy, oil can enter the U.S. market 13 days from a Presidential decision. This timeline includes the physical process of displacing oil from the caverns, transporting it through pipelines, and delivering it to refineries or marine terminals for distribution.

Has the SPR been used before?

Yes, the reserve has been tapped multiple times throughout its history. Five of the sales have been emergency drawdowns: in 1991, during the Gulf War; in 2005, in response to Hurricane Katrina; in 2011, during the conflict in Libya; and twice in 2022, both in response to Russia's invasion of Ukraine.

In 2022, the Biden administration sold 180 million barrels of oil from the Strategic Petroleum Reserve over 6 months, which lowered the SPR to its lowest levels in 40 years and was the largest ever release of oil from the SPR.

Last updated: June 12, 2026. For the latest energy news and analysis, visit stakeandpaper.com.