SEOUL/SINGAPORE - Swiss trader Glencore has provisionally booked three supertankers to load 6 million barrels of North Sea Forties crude for South Korea in September, according to shipping data and traders. The volume is larger than usual as low freight rates and wide spot discounts for Forties due to ample supply have encouraged shipments of the crude to Asia, they said.  Typically one to two supertankers head to South Korea each month. If the shipments go through, South Korea’s imports from the United Kingdom in October could surge to the highest since January 2014, when UK crude imports hit 965,815 tonnes (7.1 million barrels), according to customs data.   South Korea has also increased spot crude purchasing to 35.5 percent in the first seven months of the year, up from 26.6 percent in the same period a year ago, data from Korea National Oil Corp showed, due to abundant global supply.   There could be a fourth supertanker of Forties heading to Asia in September, traders said. Swiss trader Trafigura may have sold 2 million barrels to China, they said. Glencore tanker fixtures for Hound Point Tanker Loading Rate date Sara Sept 20 $5.5 million Gener8 Poseidon Sept 5 $6.5 million Houston Sept 10 $6.5 million Source: Eikon