* 14 of 24 September Forties cargoes delayed by several days * Another Forties cargo dropped entirely from Sept. schedule * Work on oilfields and pipelines taking longer than expected (Adds detail, comment) By Christopher Johnson LONDON, Sept 2 (Reuters) - Maintenance work has forced delays to as many as 14 of the 24 North Sea Forties crude oil cargoes scheduled to load in September and another cargo has been dropped entirely, trade sources said on Friday. The delays follow problems at Britain's Buzzard oilfield, operated by Canada's Nexen , and maintenance on the BP Plc operated Forties pipeline. Forties shipments have been subject to delays and cancellations since May. Oil supplies from the North Sea, home of the dated Brent benchmark used to price up to 70 percent of the world's physical crude oil cargoes, have tightened sharply, supporting the price of Brent relative to U.S. crude futures. CL-LCO1=R Strong consumer demand for high quality, light oil products has pushed up premiums for physical Brent cargoes to their highest for more than three years this week. "There are all sorts of delays to the September programme," said the head of crude oil trading at a major oil company that actively trades Forties and other grades of North Sea crude. "Work is dragging on longer than expected and most of the programme is affected in one way or another." Premiums for Forties over the "dated Brent" crude oil benchmark have risen to around $2.00 this week, their highest since 2008 after a series of disruptions to supplies from the North Sea, which have coincided with the loss of Libyan crude due to the uprising against former ruler Muammar Gaddafi. VALHALL August also saw a series of deferrals and cancellations of Forties cargoes. As many as 13 of the 16 cargoes planned for loading in August were delayed, according to a Reuters tally. BP said on Wednesday that production at its Valhall oil platform in the North Sea would only resume by mid-September after a fire in July and a well-control problem on Aug. 19, considerably later than previously expected. The July 13 fire at Valhall, in Norway's part of the North Sea, led to the evacuation of hundreds of workers and supported oil prices as the field contributes to a crude oil stream used in the global Brent price benchmark. "All these supply issues have come at the same time," said a crude oil trader with a large U.S. bank. "The market has very little leeway and that is one of the reasons why European crude oil prices are so strong." Demand was also forcing the market higher, traders said. The gap between high-value, light products such as gasoline and diesel has been wide and fairly steady since the beginning of August, despite wild fluctuations in crude markets. The spread between gasoline and Brent, for example, has been close to or exceeded $15 per barrel in northwest Europe for the last month, which is around 50 percent higher than normal for the time of year, traders said. (Reporting by Christopher Johnson; editing by William Hardy)

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