NEW YORK, Dec. 22 (Xinhua) -- Oil prices settled slightly higher Friday as data showed the number of U.S. oil rigs remained steady this week.

The number of rigs operating in U.S. oil fields was unchanged at a total of 747 rigs this week, oilfield service firm Baker Hughes said in its weekly report on Friday.

Investors kept a close eye on the count amid concerns that shale producers could move to ramp up production next year in response to higher prices.

Market trade volumes were very thin as traders closed positions ahead of the Christmas and New Year holidays.

Meanwhile, traders closely watched the North Sea pipeline outage. Operator Ineos said Thursday it expects to bring oil flowing through the pipeline progressively back to normal rates in early January.

The West Texas Intermediate for February delivery increased 0.11 U.S. dollar to settle at 58.47 dollars a barrel on the New York Mercantile Exchange, while Brent crude for February delivery added 0.35 dollar to close at 65.25 dollars a barrel on the London ICE Futures Exchange.