GRID · STRATEGIC PETROLEUM RESERVE
The Emergency Oil Stockpile
The world’s largest government-owned emergency oil supply sits underground on the Gulf Coast: 714 million barrels of capacity carved into about 60 salt caverns across 4 sites in Texas and Louisiana. The US created it in 1975, after the 1973 oil embargo, as a buffer against supply shocks. Today it tells a dramatic story: it’s drawing down fast and sits at its lowest level in four decades.
How full is it right now
The reserve peaked at 727 million barrels around 2009. It was drawn down hard in 2022 to steady prices after Russia’s invasion of Ukraine, partly refilled, and is now falling again: under a 2026 emergency exchange tied to the war with Iran it has been dropping roughly 8–10 million barrels a week, down to about 331.2 million barrels — near 46.4% of capacity, the lowest since the 1980s. The bar below is the snapshot from 2026-06-19; the live national number is fetched from the EIA on the map.
The four salt-cavern sites
The reserve isn’t one tank — it’s four sites of differing size, each a cluster of giant underground caverns near a major refining centre. On the map the salt-cavern marks are sized by authorized capacity, from Bryan Mound, the largest, down to Bayou Choctaw. Capacities are fixed design figures (the live fill is a national total only).
Why salt caverns
The oil isn’t in tanks — it’s in caverns hollowed out of natural underground salt domes, thousands of feet down. To carve one, engineers drill a well into the salt and pump in fresh water; the water dissolves the salt and the leftover brine is piped away, leaving a cavity of precise shape. It takes about seven barrels of water to make room for one barrel of oil. Salt is close to ideal for the job: it’s impermeable to crude, and at those depths any crack closes itself under pressure, so the store is naturally self-sealing — and far cheaper than building tanks. A typical cavern is a cylinder some 200 feet across and 2,500 feet tall, big enough to swallow a skyscraper, holding around 10 million barrels.
About this data
Site facts — location, authorized capacity, cavern count and year online — come from the U.S. Department of Energy, and the national fill from the U.S. Energy Information Administration’s weekly report (both public domain). Two honest notes. First, the marks are sized by authorized capacity— a fixed design figure — not by how much oil each site holds right now: the EIA publishes only the national SPR total, not a per-site inventory, so the live fill is shown nationally, never split across the caverns. Second, the four site capacities add up slightly above the 714-million-barrel system figure, because those are design capacities and the caverns enlarge naturally over time; 714 million barrels is the official combined authorized total. We show no operator or operational detail. Snapshot taken 2026-06-27.