The caverns holding the American emergency oil reserve are completely full right now. They are always full. The Strategic Petroleum Reserve dropped below 300 million barrels this month for the first time since the early 1980s, and the 172-million-barrel release tied to the Iran war will leave it around 243 million, against a design capacity of about 714 million. The caverns are still full. The rest of what is in them is water.
That is how the oil comes out. Raw water is pumped down into the bottom of a salt cavern to float the crude up and out through the well. Salt dissolves in water. Every release widens the chamber and thins the pillar of salt standing between one cavern and the next, which is why the reserve was designed for about five full emptyings and has been drawn on dozens of times.
Asked about the risk, the Energy Department told Fortune that "the caverns are always full," and that only the ratio of oil to water inside them changes. The reassurance and the mechanism are the same sentence.
So the government keeps a second ledger. Sandia National Laboratories, the reserve's geotechnical adviser for decades, reports each year how many drawdowns every individual cavern has left. Its May 2025 count found 47 of the 60 with at least four remaining at the end of 2024. At Bayou Choctaw in Louisiana, three of six had one, and two of those may have developed a pathway between them.
And the caverns are mostly holding. Sandia found the record 2022 release left most of them in very good condition, and that draining some fully improved their shape by clearing out salt bridges left by decades of partial draws.
The Energy Department puts the operating floor at 70 million barrels, well under where the reserve is headed. What the Government Accountability Office flagged in May was not the caverns at all. It was the wells — the straws.
The second-newest well in the system is 38 years old. More than 70 percent of the wells at Big Hill show moderate to severe casing deformation. One at Bryan Mound ruptured in May 2024 with no warning, and as much as 400,000 barrels went somewhere underground.
The reserve was built to empty roughly six times faster than it fills, which is the number that matters now. Refilling to peak capacity would cost about $20 billion by the department's own estimate. Congress has appropriated $171 million toward it, enough for roughly two million barrels.
In December the department put effective drawdown capability at 61 percent of design, and more than a quarter of the oil then in the ground could not be drawn at all.
The reserve has never really been a tank of oil. It is sixty holes with a countable number of emptyings left in them, and the emptyings are what is being spent.
The reassurance and the mechanism are the same sentence.
