US strategic oil reserve nears levels that could damage salt caverns

U.S. Strategic Petroleum Reserve (SPR) levels have fallen to lows not seen since the early 1980s, and experts say the rapid drawdowns responding to the war with Iran are approaching volumes that could damage the salt caverns used to store the oil.

The reserve is held in roughly 60 salt caverns thousands of feet underground at four coastal sites in Louisiana and Texas, including the Bryan Mound complex in Brazoria County, Texas. Department of Energy data released on Monday show SPR inventories have dropped below 300 million barrels for the first time since the stockpile was first filled in the early 1980s.

U.S. authorities have released roughly 172 million barrels in recent months because of supply disruptions linked to the conflict with Iran; after the current program of releases finishes the SPR is projected to sit at about 243 million barrels.

Why experts are alarmed

Senior Biden administration energy adviser Amos Hochstein has been outspoken about physical limits. He warned that the frequently cited 70 million-barrel figure for a safe minimum is unrealistic: "Don't trust people outside the government who say the SPR can climb to 70 million barrels. That's nonsense." He added that at that level the reserve would be depleted to "a point that would never come back."

Engineers and geologists note that the caverns are filled and emptied by pumping water into the bottom to force oil upward and out through wells and pipelines. Sidart Misra, a petroleum engineering professor at Texas A&M University, said the strict physical minimum at the top of the caverns is 70 million barrels to keep extraction tubing submerged in oil rather than water. But, he added, "the practical operational floor for crude stocks is between 250 million and 300 million barrels." At current inventory levels, "the integrity of the caverns and overall operational capability are at increased risk," Misra said.

The Government Accountability Office cautioned that repeated partial releases followed by refills can leach parts of a cavern and create undesirable shapes. While GAO said most caverns were in "very good condition" after the 2022 drawdown, the office warned that every release cycle expands cavern volume and reduces the rock separation between adjacent caverns, ultimately hurting long-term sustainability.

The Department of Energy rejected claims that the drawdowns would cause imminent collapse. DOE spokesperson Ben Ditterich said the caverns remain full and "all that changes is the ratio of oil and water that fill them." DOE officials have acknowledged using temporary repairs to hold infrastructure together, telling GAO they keep parts of the SPR patched with what they called "band-aids," and that it is uncertain how long such measures will last. GAO reported that more than a quarter of SPR inventory had been unavailable for withdrawal as of December 2025 because of construction outages and cavern disruptions.

Private analysts at Rapidan Energy estimate the SPR has a "soft bottom" around 170 million barrels, below which cavern integrity and pump infrastructure constrain further withdrawals. Hochstein also warned that a large hurricane hitting Florida or Louisiana while reserves are at current levels would leave the United States in a precarious position: "Below 300 million, where we are now, it's not that we can't do it, it slows the flow and puts us at risk."

Photo: press material from the event