 The Chevron Corporation discovered the Adar Yale field in 1981, shortly before the start of the Second Sudanese Civil War (1983 – 2005). Four exploratory wells had flow rates that exceeded 1,500 barrels (240 m3) a day. The oil is held in the Yabus Formation sandstone from the Paleogene age. The field has an area of about 20 square kilometres (7.7 sq mi) but the average pay zone is only 2.9 square kilometres (1.1 sq mi). Initially the field was estimated to hold 168 million barrels (26,700,000 m3), but Seismic data acquired in 2000 pushed that up to 276 million barrels (43,900,000 m3). Also, three small oil pools were discovered south of Adar-Yale with another 129 million barrels (20,500,000 m3). Chevron started to pull out of Sudan in 1984 when three of its employees were killed, finally selling all of its Sudanese interests in 1992.
