The U.S. oil industry pumps more than 3 billion barrels of crude per year. Oil crosses continents in pipelines like the Keystone, which moves 1.3 million barrels per day. It travels between them on tanker ships, the largest of which can carry 3.7 million barrels. When oil leaks, the disaster is quantified in barrels spilled—more than 250,000 from the Exxon Valdez, and at least 3 million from Deepwater Horizon. When oil sells, it is priced per barrel, and when it burns, its energy output is measured in “barrel-of-oil equivalents” (5.8 × 106 BTUs). The world of oil is a world of barrels.
And yet less and less of the oil trade requires actual barrels. In the movies they make good historical set pieces and symbols of future apocalypse. But there aren’t any barrels in the Dakota Access Pipeline. No barrels rolled off the Exxon Valdez. And the oil that spewed from Deepwater Horizon never had a chance to reach a barrel in the first place.
So why do people still talk about barrels when they talk about oil? Because the oil barrel became a concept rather than a physical thing.
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The oil barrel almost didn’t survive the 19th century. Oil companies hated them: Barrels were leaky, costly, and cumbersome. But they were also necessary. When the first Pennsylvania wells began gushing in the late 1850s, prospectors scrambled to catch the erupting crude. Any container would do—whiskey or ale jugs, salt or turpentine vats. The best option was an old one: the casks still used today to age wines and whiskies. They dated to the Romans and Celts, who designed them to replace clay pots for moving wine and olive oil. In the first Pennsylvania oil fields, demand for those barrels rose so quickly that at times their price exceeded the value of oil itself.