Amos Hochstein, senior energy adviser to former President Joe Biden, told CNBC that the Strategic Petroleum Reserve (SPR) should not fall below 300 million barrels because doing so could damage the underground caverns that store the oil.
What has happened to the reserve?
The Department of Energy reported that the SPR fell under 300 million barrels last week, a level not seen since the 1980s when the reserve was being filled. The reserve is expected to shrink further to about 243 million barrels as the United States releases 172 million barrels to offset supply disruptions linked to the war in Iran.
The oil is kept in 60 salt caverns located at two sites in Texas and two in Louisiana, with a total capacity of 714 million barrels. As oil is withdrawn, water is pumped in to maintain pressure, a process that experts say can erode the salt walls.
Why does it matter?
Critics argue that the physical integrity of the caverns could be compromised, reducing the SPR's ability to respond quickly to emergencies. Siddharth Misra, a professor of petroleum engineering and geophysics at Texas A&M University, explained that the caverns were originally designed for a 25-year lifespan and only five drawdown-refill cycles. In practice, they have endured dozens of releases.
"From an engineering and geomechanical standpoint, these concerns are highly valid," Misra said.
When caverns are drawn down, fresh water is added to keep the total fluid volume at 714 million barrels. The water aggressively dissolves the salt walls, widening the chambers and thinning the partitions between them. The temperature difference between the cool water and the hot cavern can also cause thermal shock, potentially breaking large pieces of salt and damaging extraction pipes.
What do officials say?
The Department of Energy refuted the claim that low inventory threatens cavern stability. Ben Dietderich, a DOE spokesperson, said the caverns are always full and only the oil-to-water ratio changes. He added that the SPR remains a critical national-security asset.
Former Energy Secretary Chris Wright testified that rapid drawdowns after the Biden administration's releases in 2022 and 2023 required costly repairs, but a recent Government Accountability Office report found most caverns to be in "very good condition." The GAO warned, however, that each drawdown expands cavern volume and reduces spacing, which could affect long-term viability.
What happens next?
Misra estimates that at a conservative drawdown rate of 500,000 barrels per day, the SPR will reach its legal minimum of 252 million barrels in about three months. He cautioned that once inventories dip below 300 million barrels, the reserve may lose its ability to pump oil at emergency speeds without risking severe structural damage.
Stakeholders are watching closely to see whether additional repairs will be funded and whether the United States will adjust its release strategy to preserve the caverns for future crises.