NEW YORK, Dec. 21 (Xinhua) -- Oil prices continued to rally Thursday after official data showed a larger-than-expected drop in U.S. crude stockpiles.

U.S. crude inventories decreased by 6.5 million barrels to 436.5 million barrels last week, touching the lowest level since October, 2015, the U.S. Energy Information Administration (EIA) said in its weekly report Wednesday.

Meanwhile, traders kept a close eye on the North Sea pipeline outage. Operator Ineos said Thursday it expects to complete repair work around Christmas and bring oil flowing through the pipeline progressively back to normal rates early in the New Year, according to MarketWatch.

The Forties Pipeline System was shut down on Dec. 11 after Ineos discovered a crack in a pipe. The outage has stopped the flow of 450,000 barrels of oil a day, with the result of tightening supply in the region and propping up the price of Brent.

The West Texas Intermediate for February delivery increased 0.27 U.S. dollar to settle at 58.36 dollars a barrel on the New York Mercantile Exchange, while Brent crude for February delivery added 0.34 dollar to close at 64.90 dollars a barrel on the London ICE Futures Exchange.