Oil prices ticked higher on Tuesday, lifted by indications that supply is gradually tightening, especially in the United States.
Benchmark Brent crude oil was up 24 cents at $51.90 a barrel by 2:30 a.m. ET (1830 GMT). U.S. light crude ended Tuesday's session 27 cents higher at $47.64.
Both contracts fell more than a dollar on Monday, wiping out most of the gains they accrued during a rally on Friday.
U.S. commercial crude inventories have fallen by almost 13 percent from their March peaks, to 466.5 million barrels.
"U.S. crude oil stocks have been falling consistently in recent weeks," said Fawad Razaqzada, market analyst at futures brokerage Forex.com.
"If the downtrend in oil inventories is maintained, then a bullish case can be made for oil, especially given the ongoing supply restrictions from OPEC and Russia," he added.
The weekly rollout of data on U.S. inventories starts later on Tuesday, giving the market a chance to see if the recent downward trend in U.S. crude stocks is continuing.
Industry group the American Petroleum Institute will publish statistics on crude inventories and refinery operations for last week at 4:30 p.m. EDT (2030 GMT).
On Wednesday, it will be the turn of the U.S. government's Energy Information Administration.
U.S. crude inventories are expected to have fallen for an eighth straight week and drop by 3.4 million barrels, a Reuters poll shows.
"Another decline in U.S. crude stocks may push prices somewhat higher again, but the upside may be limited — especially if U.S. crude production ticks higher again," said Hans van Cleef, senior energy economist at ABN AMRO Bank N.V. in Amsterdam.
The Organization of the Petroleum Exporting Countries and non-OPEC producers including Russia have pledged to hold back around 1.8 million bpd of output between January this year and March 2018 in order to tighten supplies and prop up prices.
Oil prices found extra support from news that Libya's Sharara oilfield, the country's largest, shut on Tuesday just hours after reopening following a three-day pipeline blockade.
But oil production elsewhere has been rising, blunting the impact of output cuts by OPEC and its allies.
U.S. crude production has broken through 9.5 million barrels per day (bpd), its highest since July 2015.
Some analysts say U.S. oil output growth will slow as energy firms cut the number of rigs drilling for oil.
So far, however, the increase in U.S. production has been relentless with increasing volumes from shale, particularly from the giant Permian basin in Texas and New Mexico.
"With U.S. shale oil production proving more than resilient, the autumn period presents a lot of downside risk to oil prices," Harry Tchilinguirian, chief oil market strategist at French bank BNP Paribas, told Reuters Global Oil Forum.
— CNBC's Tom DiChristopher contributed to this report.