A Reuters poll showed analysts expected data to show US crude stocks fell in the week to April 14. US crude futures were down 5 cents at $50.39 a barrel.
More barrels could be on their way to market from US shale fields as financial companies are investing billions in production, a Reuters analysis shows.
A global crude glut has persisted even as the Organisation of the Petroleum Exporting Countries and other producing countries have worked to reduce output under an agreement to cut supplies nearly 1.8 million barrels per day in the first half of 2017.
Gasoline stockpiles, however, edged up by 1.5 million barrels, defying expectations for a decline of 2 million, according to a survey conducted by S&P Global Platts.
US West Texas Intermediate (WTI) crude futures were also down 4 cents at $52.61 a barrel.
Saudi Arabia's oil export in February 2017 has decreased to the lowest level since May 2015, according to the data of the Joint Organizations Data Initiative (JODI). They settled 53c lower at $52,65 a barrel.
"Total inventories of crude and products moved to a deficit versus year-ago levels for the first time since August 2014, despite a build in gasoline stocks following refinery runs rising by 241,000 [barrels per day]", said Troy Vincent, oil analyst at ClipperData.
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Global fuel stocks are well above the five-year average, and Saudi Energy Minister Khalid al-Falih was quoted on Thursday as saying inventories remained elevated in part because traders were selling supplies out of tanker storage.
"Rising oil output in the US remains the predominant bearish factor for prices despite growing anticipation that OPEC will extend a self-imposed cap on its oil production in the upcoming May meeting", said Abhishek Kumar, senior energy analyst at Interfax Energy's Global Gas Analytics in London.
The continued growth in USA production and the rise in stockpiles forced the market to respond bearishly based on the increased inventory outlook.
Oil prices regained some ground on Thursday after steep losses the previous day, with a slight drop in US crude inventories stoking hopes that a global supply overhang might slowly retreat.
USA markets remain heavily oversupplied, data from the American Petroleum Institute showed on Tuesday.
Other geopolitical concerns have supported oil prices.
The United States is working with allies and China on responses to the failed test, U.S. President Donald Trump's national security adviser said on Sunday.