It suggests that crude oil could be entering a more stable trading range of $50-$70/barrel rather than falling back below $50 again for a significant period.

Iraq, which depends on oil sales for 95 percent of its public spending, appears set to continue boosting production, which currently stands at around 4.6 million barrels per day.

Iran sent a letter to members of the Organization of the Petroleum Exporting Countries saying it would attend the group’s informal talks in Algeria in September, OPEC delegates told The Wall Street Journal. An Iranian oil-ministry press official couldn’t confirm the letter had been sent late Tuesday.

Saudi Arabia has traditionally accounted for most of the crude imports by Asia, the world's biggest oil-consuming region. But recently OPEC's top producer has lost ground in a number of major markets including Russia and China, and faces a further threat from Iran, which is ramping up exports after the removal of Western sanctions.

International Brent crude oil futures were trading at $48.86 per barrel at 0644 GMT (0244 ET), down 30 cents, or 0.61 percent, from their last close. U.S. West Texas Intermediate (WTI) crude was down 40 cents, or 0.84 percent, at $47.01 per barrel.

Brent crude futures LCOc1 were trading at $49.39 per barrel at 1028 GMT, down $1.49 from their last close. U.S. West Texas Intermediate (WTI) crude Clc1 was down $1.27 at $47.25 a barrel.

This summer the U.S. oil price has whipsawed from more than $50 a barrel in June to below $40 earlier this month. In the past two weeks it has risen more than 20%, to a recent $48.22 a barrel.

Customs data showed on Monday that diesel exports rose 181.8 percent to a record 1.53 million tonnes, almost tripling China's average monthly export volume in 2015.

Brent ended the session up 2.09 percent at $50.89. The session high of $51.05 was its highest since June 23. U.S. crude settled at $48.22, up 3.06 percent after touching a session high of $48.38, the highest since July 5.

Prices have struggled to go much higher than $50 a barrel. After the longest run of gains since March, Brent crude, the international benchmark, traded 0.9 percent higher at $51.17 at 7:13 a.m. in London on Friday.

Nigeria's crude oil production disruptions are concentrated in the Niger Delta region, an oil-rich area bordering the Gulf of Guinea that is the mainstay of the country's crude oil production. Since the beginning of 2016, the Niger Delta Avengers (NDA) have conducted many attacks on oil and natural gas infrastructure throughout the region. Although not the only militant group conducting attacks in the region, the NDA is currently the most active.

The U.S. Energy Information Administration said Wednesday that crude stockpiles fell by 2.5 million barrels in the week ended Friday. Analysts surveyed by The Wall Street Journal had expected a 500,000-barrel addition. Gasoline stockpiles fell by 2.7 million barrels. That helped the oil markets recover from losses tied to estimates from the American Petroleum Institute, an industry group, showing gasoline stockpiles rose by 2.2 million barrels.

OPEC revenue has fallen in step with the steep decline in crude oil prices. The monthly average Brent spot price dropped from $112 per barrel in June 2014 to $38/b in December 2015. OPEC revenue is expected to fall further in 2016 to $341 billion before rising to $427 billion in 2017.

The world's fifth-largest crude importer has continued to buy more crude oil from Iran since sanctions were lifted in January. Shipments of Iranian crude more than doubled to 7.22 million tonnes, or 248,616 bpd, in the January-July period of 2016 from a year earlier, according to its customs office data.

The Russian government has issued the license for the Central Oil and Gas Company – a joint venture between Lukoil (25%), Gazprom (25%) and Kazakhstan’s KazMunaiGaz (50% ) – to develop the Central field.