Concerns about US strategic oil reserve damage are mounting as inventories fall below 300 million barrels for the first time since the reserve was filled in the early 1980s, with experts warning that the pace of releases could permanently impair the underground caverns where the oil is stored.
The Strategic Petroleum Reserve (SPR) holds crude oil in 60 salt caverns thousands of feet underground at four major sites along the Gulf Coast in Louisiana and Texas. Those caverns are now under strain. According to Wikipedia’s account of the Strategic Petroleum Reserve, the SPR plunged to its lowest level since 1983 on 15 June 2026, as a government-ordered drawdown continued to drain stocks.
How the drawdown began
The release was set in motion on 11 March 2026, when US Secretary of Energy Chris Wright announced a drawdown of 172 million barrels over approximately 120 days, in response to rising oil prices following US attacks on Iran. Once complete, the SPR is expected to sit at around 243 million barrels, well below the level many experts consider safe for the caverns’ long-term health.
The Department of Energy has stated that at least 70 million barrels must remain in the reserve to safely manage the caverns. Amos Hochstein, a senior energy advisor to President Joe Biden, challenged that figure. Speaking on CNBC’s ‘Squawk Box’, he said: ‘Don’t believe the people out of the government that are saying the SPR can go to 70 million barrels. It’s nonsense.’ At that level, he warned, the reserve would be depleted to ‘the point of never resurrecting it.’
Hochstein had sounded the alarm earlier, too. ‘I don’t know anyone who believes we can go below 300,’ he told CNBC’s Brian Sullivan at an Atlantic Council event in June. ‘I know plenty of people who think we can’t get near 300 because physically you will damage the caverns where the oil is stored.’
US strategic oil reserve damage: what the engineers say
Siddharth Misra, a petroleum engineering professor at Texas A&M University, put the practical operational floor at between 250 million and 300 million barrels. Below 300 million, he told CNBC, the SPR loses the ability to pump oil quickly enough to address emergencies. Pipes and pumps could also be damaged as the oil layer thins and sludge rises toward the extraction intake at the cavern ceiling.
Fresh water pumped in during rapid drawdowns dissolves the salt walls, Misra explained. This ‘creates flatter, less stable roof and severely thins the critical salt pillars that separate adjacent caverns, greatly increasing the geological risk of a structural cave-in,’ he said. The SPR was originally designed for five full drawdowns. Instead, Misra said, it has executed dozens of large and small releases over the past 40 years, causing ‘severe cavern deformation, accelerated the rate of massive salt falls from the ceilings, and significantly weakened the overall structural integrity of the aging reserve.’
At current inventory levels, Misra said, ‘cavern integrity and overall operational capability are at an elevated risk.’
Energy Department spokesman Ben Dietderich pushed back on claims that the caverns face collapse. ‘The caverns are always full. All that changes is the ratio of oil and water that is filling them,’ he told CNBC. The Trump administration is ‘responsibly managing the SPR as the critical national security asset it was designed to be,’ he said.
Bipartisan unease and the government’s own admissions
Concern over the caverns is not confined to one side of politics. Republican lawmakers raised similar worries when the Biden administration released a record 180 million barrels following Russia’s invasion of Ukraine in 2022. The SPR fell below 350 million barrels in 2023 under Biden before being refilled to around 415 million barrels ahead of the Iran war.
A May report from the Government Accountability Office (GAO) found that ‘repeated partial drawdowns followed by refill can leach a single part of a cavern repeatedly, leading to undesirable shapes.’ While the majority of caverns were in ‘very good condition’ after the 2022 drawdown, the GAO cautioned that ‘every drawdown cycle expands cavern volume and reduces the spacing between caverns within the salt dome, which ultimately reduces their long-term viability.’
The GAO also reported that Energy Department officials described themselves as ‘holding the SPR infrastructure together with “Band-Aids”‘, with uncertainty about how long those fixes would hold. More than a quarter of SPR inventory was unavailable for drawdown as of December 2025, due to construction and cavern outages.
Analysts at Rapidan Energy estimated the SPR has a ‘soft-ish floor’ of around 170 million barrels, below which ‘cavern integrity and pumping infrastructure limitations argue against further draws.’ Hochstein pointed to a more immediate risk: a hurricane striking Florida or Louisiana. ‘Below 300 million, which is where we are now, it is not that we can’t do it, but it slows the flow and puts us in danger,’ he said.
