Brent crude rose on uncertainty over Saudi oil output following the death of King Abdullah, while U.S. crude prices fell, with traders citing a reported build at the Cushing, Oklahoma storage hub and the partial shutdown of an Indiana refinery.
Salman, the late king's brother and successor to the throne, is expected to continue OPEC's policy of keeping oil output steady to protect market share. Still, the transition should be bullish for Brent, said Bob Yawger of Mizuho Securities USA.
"Any time there's uncertainty in the market, you tend to have support," he said.
Brent was up 47 cents to trade at $48.99 by 12:50 p.m. EST (1750 GMT). It rose as high as $49.80 after reports of the Saudi king's death.
U.S. crude fell 49 cents to trade at $45.83. A trader said energy data provider Genscape estimated that U.S. crude stockpiles in Cushing, Oklahoma, rose 2.7 million barrels in the week ending Tuesday.
The spread between WTI and Brent should keep widening, said Walter Zimmerman, chief technical analyst at United-ICAP. "There's substantial downside to that," Zimmerman said.
Reports of a partial shutdown at BP's oil refinery in Whiting, Indiana, weighed further on U.S. crude. Sources familiar with the plant's operations said they did not know when the 90,000-barrel-per-day (bpd) crude distillation unit would be restarted.
Mizuho's Yawger said the refinery disruption would exacerbate the U.S.'s oversupply woes. "That story even trumps the death of the king of the biggest oil producing country basically in the world," he said.
WTI pared some losses as the National Association of Realtors said U.S. home sales rose in December, which may indicate a recovering housing market. .
On Thursday, U.S. government data showed domestic oil inventories are at an 80-year high for this time of the year.
Booming U.S. production has turned the United States from the world's biggest oil importer into one of the top producers, pumping more than 9 million barrels per day.
Some oil exporters, such as Venezuela, want the 12-member Organization of the Petroleum Exporting Countries (OPEC) to cut output to support prices and revenues.
Yet, led by Saudi Arabia, OPEC announced last November it would keep output steady at 30 million barrels per day.