Tishreen, Sheikh Mansour and Sheikh Sulaiman are a group of oil and gas fields located in northeast Syria. Of the three, Tishreen is the only one on production, with the others being smaller non-producing discoveries. Tishreen is a large, sour, heavy oil field that has been onstream since the late 1970s. Since 2003, it has been the focus of a major enhanced recovery project. Sinopec became the operator after acquiring Tanganyika Oil in 2008 for a consideration of US$1.88 billion. However, in 2012 a number of Syrian oil fields were seized by armed groups opposed to the government. Although Tishreen is not thought to be under any opposition or militant group control, it is unlikely to be producing as key infrastructure that transports crude from the field is under these groups control.