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.

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.

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.

In our view, crude prices in the next few months are likely to exhibit a sideways-to-bearish trend, mostly trading in the $35-$45 per barrel range. As North American supply remains strong and demand looks underwhelming, we are likely to experience pressure to the price of a barrel of oil.

Brent crude futures were trading at $48.35 per barrel at 0737 GMT (3:37 a.m. ET), flat from their last close, but over 15 percent higher than the $41.51 low for the month on Aug. 2. U.S. West Texas Intermediate crude was trading at $45.76 a barrel, up 2 cents from its previous close, and still over 16 percent above its $39.19 monthly low from Aug. 3.