U.S. oil stockpiles surged dramatically last recent week, with crude inventories jumping by more than 15 million barrels as imports surged and exports plunged, the Energy Information Administration (EIA) said on Dec. 9.

Crude inventories rose by 15.2 million barrels in the week to Dec. 4 to 503.2 million barrels, the largest build in crude inventories since April, compared with analysts' expectations in a Reuters poll for a 1.4 million-barrel drop.

U.S. net crude imports contributed heavily to the gain in inventories, as imports rose by a record high of 2.7 million barrels per day, EIA said. That boosted U.S. Gulf Coast stocks up 11.8 million barrels, most in one week ever, according to EIA data.

U.S. gross crude exports plunged by 1.6 million bbl/d to just 1.8 million bbl/d, the lowest since 2018, while gross imports surged, rising 1.08 million bbl/d.

"It defies the math that is in the market, for sure," said Bob Yawger, director of Energy Futures at Mizuho in New York. "Do U.S. refiners at a time when they're closing refineries need to increase imports by a million barrels a day? That's ridiculous."

Crude markets reacted immediately to the news, with U.S. crude and global benchmark Brent changing course to trade lower on the day. U.S. crude traded 40 cents lower, or 0.9%, at $45.20 by 11:02 a.m. EST (1502 GMT).

Gasoline and distillate stocks were also markedly higher, causing U.S. gasoline futures to pare gains as heating oil futures turned negative.

Gasoline stockpiles rose by 4.2 million barrels in the week to 237.9 million barrels, the EIA said, compared with expectations for a 2.3 million-barrel rise.​

Distillate stockpiles, which include diesel and heating oil, rose by 5.2 million barrels in the week to 151.1 million barrels, versus expectations for a 1.4 million-barrel rise, the EIA data showed.

Crude stocks at the Cushing, Okla., delivery hub fell by 1.4 million barrels in the last week, EIA said.

Refinery crude runs rose by 424,000 bbl/d, as refinery utilization rates rose by 1.7 percentage points, the EIA said.