The U.S. Strategic Petroleum Reserve has fallen below 300 million barrels for the first time since it was filled in the early 1980s, hitting 298.7 million barrels as of early August 2026, according to Department of Energy data. The sharp depletion—driven by 172 million barrels of authorized releases to address the Iran war supply disruption—is now raising alarms among energy experts about the structural integrity of the salt caverns that store the nation’s emergency oil stockpile.
The reserve’s collapse to a four-decade low marks a critical threshold that experts say poses mounting risks to the caverns themselves. Siddharth Misra, a petroleum engineering professor at Texas A&M University, warned that the practical operational floor for the reserve is between 250 million and 300 million barrels, and that current inventory levels mean “cavern integrity and overall operational capability are at an elevated risk.”
The 60 salt caverns that comprise the SPR, located thousands of feet underground at four major sites along the Gulf Coast in Louisiana and Texas, were designed for five full drawdowns over the reserve’s operational life. Instead, the system has executed dozens of large and small releases over the past 40 years, according to Misra. Energy Secretary Chris Wright told Congress in June 2025 that rapid SPR drawdowns under the Biden administration resulted in structural damage to facilities, with more than $100 million of repairs needed to restore full capacity.
When the SPR inventory drops below 300 million barrels, the system loses its ability to pump oil at rapid speeds during emergencies, and the pipes and pumps face damage as the oil layer thins at the top and sludge rises toward the extraction intake, Misra said. Additionally, fresh water is often pumped into the caverns during rapid drawdowns to displace the crude, and this water dissolves the salt walls—creating flatter, less stable roofs and severely thinning the critical salt pillars that separate adjacent caverns, greatly increasing the geological risk of a structural cave-in.
Cavern Integrity at Risk
The Government Accountability Office reported in May 2026 that “repeated partial drawdowns followed by refill can leach a single part of a cavern repeatedly, leading to undesirable shapes.” The majority of SPR caverns were found to be in “very good condition” after the 2022 drawdown, but the GAO warned that “every drawdown cycle expands cavern volume and reduces the spacing between caverns within the salt dome, which ultimately reduces their long-term viability.”
Energy Department officials told the GAO that they are “holding the SPR infrastructure together with ‘Band-Aids,’ and that it is uncertain how long they will hold.” More than a quarter of the SPR inventory was “not available for drawdown due to a combination of construction outages and cavern outages” as of December 2025, the GAO found. Amos Hochstein, a senior energy advisor, warned that depleting the reserve below 300 million barrels risks damage that would make it more difficult to respond to future energy emergencies. “I don’t know anyone who believes we can go below 300,” Hochstein told CNBC in June 2026, adding that the reserve would reach “the point of never resurrecting it” if depleted to 70 million barrels, the Energy Department’s stated physical minimum.
The Energy Department disputed concerns about cavern integrity, with spokesman Ben Dietderich stating that “the caverns are always full. All that changes is the ratio of oil and water that is filling them.” Analysts at Rapidan Energy, however, 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. The reserve will sit at around 243 million barrels after the current Iran war drawdown is completed.
Sources
- CNBC — SPR falling below 300M barrels, cavern damage risks, expert commentary from Siddharth Misra and Amos Hochstein on operational floors and cavern integrity
- E&E News by POLITICO — Energy Secretary Chris Wright testimony on structural damage from Biden-era drawdowns, repair costs exceeding $100 million, cavern deformation mechanism
- Fox Business — SPR inventory level at 298.7M barrels as of Aug 7-10, 2026, lowest since 1983
- Government Accountability Office (via CNBC) — Cavern condition assessment, repeated drawdown effects on cavern shape and spacing, infrastructure maintenance backlog
- Wall Street Journal — Historical context on frequent oil draws and aging infrastructure strain on the reserve system
