Oil prices declined on concerns over the global oil glut. The oil driller Baker Hughes reported on Thursday that the number of active U.S. rigs climbed by 12 rigs to 640 last week. It was the first rise since December 5, 2014.
Combined oil and gas rigs rose by 2 to 859.
News that Chinese regulators opened an investigation into suspected stock market manipulation also weighed on oil prices.
Traders expect the results of talks on the Iranian nuclear program. Talks will continue until July 07. The head of the International Atomic Energy Agency (IAEA) said on Friday that Iran and the agency have worked out "some ways forward".
WTI crude oil for August delivery decreased to $55.69 a barrel on the New York Mercantile Exchange.
Brent crude oil for August fell to $60.44 a barrel on ICE Futures Europe.