MTECHTIPS- Oil futures fell for the first time in three sessions on Friday, but still scored their third weekly gain in a row as market players awaited details of a planned output cut by the Organization of the Petroleum Exporting Countries. On the ICE Futures Exchange in London, Brent oil for December delivery slipped 58 cents, or 1.1%, on Friday to settle at $51.93 a barrel by close of trade. The contract rallied to $52.84 earlier in the day, the most since June 9. For the week, London-traded Brent futures surged $1.74, or 3.35%, the third straight weekly gain. Crude prices have been on a bullish trend ever since OPEC members surprised the market late last month by agreeing to a framework to cut production for the first time in eight years in talks held on the sidelines of an energy conference in Algeria. The oil cartel reached an agreement to limit production to a range of 32.5 million to 33.0 million barrels per day, a reduction of 0.7%-to-2.2% from its current output of 33.2 million barrels. However, market analysts remained skeptical of the deal, pondering how such a plan would be implemented. OPEC oil producers plan an informal meeting with non-OPEC member Russia on the sidelines of the World Energy Congress in Istanbul, Turkey, which runs from October 9-13 to discuss how to implement such a deal. No decision however is expected to be taken in Istanbul, OPEC sources said. The 14-member oil group said it won’t finalize details or complete its production agreement until the group’s next official meeting in Vienna on November 30. Elsewhere, on the New York Mercantile Exchange, crude oil for delivery in November slumped 63 cents, or 1.25%, to end the week at $49.81 a barrel. Prices touched a four-month peak of $50.74 earlier Friday.