With inventories reaching a 40-year low, experts warned this week that the caverns storing America’s strategic oil reserves could be damaged by rapid stockpiling releases in response to the Iran war.
Experts said damage to the cave would make it more difficult to respond to future energy emergencies. The Strategic Petroleum Reserve (SPR) oil is stored in 60 salt caverns thousands of feet underground at four major locations along the Gulf Coast in Louisiana and Texas.
The SPR has fallen below 300 million barrels for the first time since it was reclaimed in the early 1980s, according to data released Monday by the Department of Energy. Stockpiles are dwindling as the US releases 172 million barrels in response to supply disruptions caused by the Iran war. After the drawdown, SPR will be approximately 243 million barrels.
The Department of Energy said at least 70 million barrels must remain in reserves to safely manage the cave. President Joe Biden’s senior energy adviser, Amos Hochstein, disputed that number this week.
“Don’t believe any government official who says SPR can increase to 70 million barrels. It’s nonsense,” Hochstein told CNBC’s “Squawk Box” on Thursday. Once that level is reached, reserves will be depleted “to the point where they can never be revived,” he said.
The caves are at risk of damage if reserves fall below 300 million barrels, a former Biden administration official warned in June.
“I don’t know of anyone who believes it could be less than 300,” Hochstein told CNBC’s Brian Sullivan at an Atlantic Council event. “I know a lot of people who think it’s impossible to get close to 300 because you would physically damage the caverns where the oil is stored.”
Department of Energy spokesman Ben Diederich said claims that SPR’s storage caverns are at risk of collapse due to oil extraction are false.
“The cave is always full. The only thing that changes is the ratio of oil and water filling the cave,” Dietderich told CNBC in a statement. The Trump administration said it is “responsibly managing the SPR, which was designed as a critical national security asset.”
Both sides of the political spectrum have expressed concern about the integrity of the salt caves. Republican lawmakers expressed these concerns when the Biden administration released a record 180 million barrels in response to Russia’s 2022 invasion of Ukraine. In 2023 under the Biden administration, the SPR fell below 350 million barrels. Before the Iran war, it had been replenished to about 415 million barrels.
The Strategic Petroleum Reserve Brian Mound Storage Facility in Brazoria County, Texas, is one of four locations that make up the nation’s oil reserves.
New |Reuters
“Repeated partial drawdowns and subsequent backfilling can cause a single section of the cavity to repeatedly seep out, resulting in an undesirable shape,” the Government Accountability Office said in a May report.
Most of the SPR caves were found to be in “very good condition” after depletion in 2022, GAO said.
“However, with each drawdown cycle, the volume of the cavities expands and the spacing between cavities within the salt dome narrows, ultimately reducing long-term survivability,” the study says.
operation floor
To release oil from an SPR, operators pump water to the bottom of the cavity to move the oil to the surface and pump it through a well and into a pipeline.
Siddharth Misra, a professor of petroleum engineering at Texas A&M University, said 70 million barrels is the minimum physical requirement at the top of the cave to safely submerge the extraction pipe in oil rather than water.
But Misra said in an email to CNBC that “the effective operating floor for crude oil inventories is between 250 million barrels and 300 million barrels.” At current inventory levels, “the integrity of the cave and its overall operational capacity are at high risk,” he said.
If stocks fall below 300 million barrels, SPR will lose the ability to pump oil at high speeds to deal with emergencies, Misra said. He said the oil layer at the top could also become thinner, causing sludge to rise toward the water intake in the cavern ceiling, potentially damaging the system’s pipes and pumps.
Misra said fresh water is often pumped into the cave during rapid water levels, melting the salt walls. This, he said, would “make the roof flatter and less stable, significantly thinning the critical salt columns separating adjacent caves, and greatly increasing the geological risk of structural cave-ins.”
SPR was originally designed for five full drawdowns. Instead, Misra said it has carried out dozens of releases, both large and small, over the past 40 years.
He said: “The system was not designed for so many cycles, and the repeated injection of water and extraction of oil caused severe deformation of the cave, accelerating the rate of fall of large amounts of salt from the ceiling, and significantly weakening the overall structural integrity of the aging reserve.”
Department of Energy officials told GAO, “SPR infrastructure is being stored with ‘band-aids,’ but it is unclear how long it will be stored.” According to the GAO study, as of December 2025, more than one-quarter of the SPR inventory “cannot be withdrawn due to a combination of construction halts and caving halts.”
Analysts at Rapidan Energy estimated that SPR’s “soft bottom” is around 170 million barrels, below which “cave integrity and pumping infrastructure limitations would argue against further pumping.”
Hochstein said a hurricane in Florida or Louisiana could put the U.S. in a difficult position at current SPR levels. “With less than 300 million people, where we are now, that doesn’t mean we can’t do that, but it will slow the flow and put us at risk,” he said.
