The United States' Strategic Petroleum Reserve (SPR) has dropped below 300 million barrels for the first time since it was originally filled in the early 1980s, and energy experts are warning that continuing to draw it down could permanently damage the underground storage caverns that hold the nation's emergency oil supply.
The oil sits in 60 man-made salt caverns buried thousands of feet underground across four major storage sites along the Gulf Coast in Texas and Louisiana. These caverns were engineered decades ago to be tapped only occasionally, during genuine emergencies — not repeatedly drained and refilled the way they have been in recent years.
The Department of Energy disputes that the caverns are at risk of collapsing, saying they remain physically full at all times — what changes as oil is withdrawn is simply the ratio of oil to water inside them.
Independent experts, however, point to a more nuanced reality. According to a Texas A&M petroleum engineering professor, while 70 million barrels is the bare technical minimum needed to keep the extraction pipes submerged in oil rather than water, the practical safe operating threshold is closer to 250–300 million barrels. Below that point, both cavern integrity and the system's ability to pump oil quickly during emergencies become increasingly compromised.
A government watchdog agency has echoed these concerns, noting in a recent report that repeated partial drawdowns followed by refills can reshape parts of the caverns in ways that aren't ideal, and that every cycle expands cavern volume while shrinking the buffer space between caverns — gradually undermining their long-term durability. The same report found that more than a quarter of the SPR's total capacity was unavailable for use as of the end of last year due to ongoing construction and operational outages, and that Energy Department officials described current maintenance efforts as barely holding the aging infrastructure together.
For now, the reserve continues to serve its purpose as an emergency buffer. But the growing chorus of warnings from former officials, engineers, and government auditors alike suggests that how much further it can be drawn down without lasting damage is becoming an urgent open question.
Source: Reporting based on CNBC coverage, August 2026.
Why the Reserve Is Shrinking
The SPR is being emptied rapidly as the U.S. government releases roughly 172 million barrels to soften the supply shock triggered by the ongoing conflict involving Iran. Once that release is complete, the reserve is expected to settle at around 243 million barrels — a level not seen in more than four decades.The oil sits in 60 man-made salt caverns buried thousands of feet underground across four major storage sites along the Gulf Coast in Texas and Louisiana. These caverns were engineered decades ago to be tapped only occasionally, during genuine emergencies — not repeatedly drained and refilled the way they have been in recent years.
A Fight Over the "Safe" Floor
Officials at the Department of Energy maintain that at least 70 million barrels must stay in the reserve to keep operations safe. But that figure is being publicly challenged by energy veterans, including Amos Hochstein, who advised the Biden administration on energy policy. Hochstein argues that dropping anywhere near that level would effectively destroy the reserve's usefulness for good, and that few serious analysts believe the system can safely go much below 300 million barrels without risking structural harm to the caverns.The Department of Energy disputes that the caverns are at risk of collapsing, saying they remain physically full at all times — what changes as oil is withdrawn is simply the ratio of oil to water inside them.
Independent experts, however, point to a more nuanced reality. According to a Texas A&M petroleum engineering professor, while 70 million barrels is the bare technical minimum needed to keep the extraction pipes submerged in oil rather than water, the practical safe operating threshold is closer to 250–300 million barrels. Below that point, both cavern integrity and the system's ability to pump oil quickly during emergencies become increasingly compromised.
How the Drawdown Process Can Damage the Caverns
To extract oil, operators pump fresh water into the base of each cavern, which pushes crude oil up and out through wells into pipelines. That same freshwater injection gradually dissolves the surrounding salt walls. Over repeated drawdown cycles, this process can:- Flatten and weaken cavern ceilings
- Erode the salt "pillars" that separate neighboring caverns
- Increase the risk of a structural cave-in
- Cause sludge to build up near the extraction points as the oil layer thins
A government watchdog agency has echoed these concerns, noting in a recent report that repeated partial drawdowns followed by refills can reshape parts of the caverns in ways that aren't ideal, and that every cycle expands cavern volume while shrinking the buffer space between caverns — gradually undermining their long-term durability. The same report found that more than a quarter of the SPR's total capacity was unavailable for use as of the end of last year due to ongoing construction and operational outages, and that Energy Department officials described current maintenance efforts as barely holding the aging infrastructure together.
A Bipartisan Concern
Worries about cavern integrity aren't new or one-sided. Similar alarms were raised by Republican lawmakers back in 2022, when the Biden administration authorized a record release of 180 million barrels in response to Russia's invasion of Ukraine. That drawdown pushed the reserve below 350 million barrels by 2023, before it was slowly rebuilt to around 415 million barrels ahead of the current crisis.What's at Stake
Analysts caution that the practical risks go beyond long-term geology. With inventories now below 300 million barrels, the reserve's ability to respond quickly to a second emergency such as a Gulf Coast hurricane is diminished. Some estimate a "hard floor" exists much lower, around 170 million barrels, below which both pumping infrastructure and cavern integrity would make further releases especially risky.For now, the reserve continues to serve its purpose as an emergency buffer. But the growing chorus of warnings from former officials, engineers, and government auditors alike suggests that how much further it can be drawn down without lasting damage is becoming an urgent open question.
Source: Reporting based on CNBC coverage, August 2026.