Brent oil headed for the longest run of weekly declines since January as ample inventories and an accord to ease sanctions on Iran suggested global markets will remain oversupplied. Futures gained 0.4 percent in London, paring their third weekly drop to 2.8 percent. U.S. crude stockpiles remain almost 100 million barrels above the five-year average for this time of the year, Energy Information Administration data show. The prospect of increasing Iranian output may still weigh on prices even if the gain is gradual, according to Barclays Plc and Australia & New Zealand Banking Group Ltd. Oil’s recovery from a six-year low has faltered amid speculation the surplus will be prolonged as U.S. drillers return rigs to fields and Iran seeks to regain market share. The full impact of higher Iranian exports won’t be felt until 2016 as the nuclear deal is implemented, banks including Goldman Sachs Group Inc. predict. […]