Data from the Energy Information Administration showed that inventories jumped by 10.4 million barrels, much more than the forecast for 3.604 million according to Investing.com.
On Tuesday, the American Petroleum Institute's data also showed a big build, by 9.9 million barrels, which was more than expected.
There are now 518 million barrels of oil in storage, which the EIA describes as a "historically high" level.
Stockpiles at Cushing, a key delivery point for crude, jumped 1.2 million barrels to a record 66.2 million barrels. That's now near operational limits, according to Bloomberg's Javier Blas.
Last week, crude production fell by 25,000 barrels per day.
After the data release, crude oil fell, with West Texas Intermediate crude futures dropping as much as 2% to as low as $33.69 per barrel before storming back into the green.
Here's a chart of the weekly builds in oil inventories:
Investing.com
And this was the reaction in crude prices right after the data dropped:
Investing.com