Oil prices dipped slightly in choppy, thin trade on Friday as traders weighed concerns about Middle East unrest and Libya's conflict as well as demand for oil in quake-hit Japan and debt-laden Europe.

Investors eyed the threat to oil demand from Japan, where radiation fears escalated.

Concerns about euro zone debt woes continued and while U.S. fourth quarter economic growth rate was revised higher, a Thomson Reuters/University of Michigan survey showed consumer sentiment fell this month to its lowest since November 2009.

Protests in Yemen, Syria, Bahrain and by Shi'ites in Saudi Arabia kept concerns about unrest and the threat to supply from region in focus.

Rebel forces and those loyal to Libyan leader Muammar Gaddafi clashed as Western warplanes struck at armor used by the government to crush the revolt.

Brent crude futures for May delivery dipped 30 cents to $115.42 a barrel by 1:55 p.m. EDT, having seesawed between $115.20 and $116.13.

U.S. May crude futures fell 26 cents to $105.34 a barrel, swinging between $104.50 and $105.95.

We've had a good run this week and for today we are seeing some pre-weekend profit-taking. While there is a lot of turmoil in the Middle East, none of the ongoing unrest affects big oil producers, said Ed Meir, senior commodities analyst at MF Global in New York.

And on balance we are not short of physical supply. Libya's outage due to the fighting there has been offset by Saudi production and the demand in Japan is down. So there's no real tightness in supply at the moment.

BRENT/WTI SPREAD ALSO SEESAWS

Brent's premium to the U.S. benchmark West Texas Intermediate crude, down 23 cents at $10.11 a barrel, was choppy on Friday, swinging from $9.83 to $11.24, but remaining well off its March 1 record above $17.

Brent and U.S. crude have stalled ahead of 2011 peaks. The May Brent may run into resistance ahead of its contract peak of $118.42, before approaching the 2011 front-month intraday high of $119.79 struck on February 24.

U.S. crude has been unable to move above its 2011 high of $106.95 reached on March 7 and several recent moves above $106 have stalled.

Total U.S. crude trading volume, at just over 321,000 lots traded, continued to track well below the 30-day average. Brent trading volume also remained anemic at just above 208,000 lots.

The U.S. volume was on track to be one of the lowest weekly volumes in 2011.

PRICE SPIKE EXPECTED

With an expected summer driving demand boost and continuing supply uncertainty, J.P. Morgan analysts headed by Lawrence Eagles raised oil price forecasts for 2011 for Brent and U.S. crude.

So long as ongoing problems in the Middle East continue to elevate risks of a further supply disruption, there is a strong likelihood of a price spike in the second quarter as the market demands additional oil to meet summer demand, J.P. Morgan said in a research note.

Analysts polled by Reuters this week forecast oil prices will hold over $100 a barrel through 2013, due to tensions in the Middle East, with average forecasts for 2011 raised by $12 to over $104 a barrel.

(Additional reporting by Gene Ramos in New York, Christopher Johnson in London and Alejandro Barbajosa in Singapore; Editing by Marguerita Choy)

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