Oil edges up after big OPEC-driven weekly rally

By Devika Krishna Kumar NEW YORK (Reuters) - Oil prices edged higher on Friday above $51 a barrel with Brent crude on track for its biggest weekly rally since 2009 following OPEC's decision to cut crude output in order to rein in a global glut. After the deal was announced on Wednesday, the market focussed on the implementation and impact of OPEC's first output cuts since 2008, to be joined by Russia and possibly other non-OPEC producers. Crude prices were pressured by data showing oil output in