Oil prices traded mixed Thursday amid a stronger dollar and persistent worries about a global oversupply of crude.

US benchmark West Texas Intermediate for delivery in August fell 50 cents to $50.91 a barrel on the New York Mercantile Exchange.

Brent North Sea crude for August delivery rose to $57.51 a barrel in London trade, up 46 cents from Wednesday's settlement.

Both contracts had shed more than $1.50 on Wednesday.

"There are conflicting forces keeping the market in check," said Phil Flynn of Price Futures Group.

"Among the bearish elements, there are concerns about rising interest rates with (Federal Reserve Chair) Janet Yellen," he said, referring to her testimony in Congress this week reaffirming a rate hike by the end of the year.

"There are still concerns about an oversupply of oil," he added.

On the positive side, the analyst said, was the "record pace" of crude oil used by US refineries. The Department of Energy reported Wednesday that US refineries operated at 95.3 percent of capacity in the week ending July 10.

"We keep talking about weak demand and oversupply but refiners don't seem to mind," Flynn said. "If demand is so bad, why are refiners running at 95 percent of their capacity?"

The dollar hit a seven-week high against the euro and its highest level against the yen in three weeks. A stronger greenback makes dollar-priced oil more expensive for buyers using weaker currencies.