The large oil reserves in Sudan, which are located almost entirely in the southern third of the country, make it potentially a producer in the Brunei/Colombia range. It is not considered a potential megaproducer on the level of Saudi Arabia or Iraq.2 But, if properly managed, its oil resources could be a godsend to a country as poor as Sudan, where the annual per capita gross domestic product is an estimated U.S. $ 424.
The main area of oil exploration and production in Sudan to date, the Muglad Basin, stretches southeast down across the midsection of the country, from El Muglad in Western Kordofan through Bentiu and Western Upper Nile, known by the government as Unity (al Wihda) State, to Juba on the White Nile and Eastern Equatoria.3
The Western Upper Nile/Unity State area was traditionally the homeland of the Nuer people. Oil exploitation in southern Sudan began north of Bentiu, in Western Upper Nile/Unity State—in Blocks 1, 2, and the southernmost parts of Block 4, the sites of Unity and Heglig oilfields. (See Map B.) The oil history and development of Block 5A, which is a continuation of the Muglad Basin to the south east of Blocks 1 and 4, has been controlled by the developments in these blocks. Blocks 1, 2, and 4 total nearly 19,500 square miles (50,500 square kilometers or 12.5 million acres). 4 Block 5A totals 8,076 square miles (20,917 square kilometers or 5.2 million acres), and Block 5B totals 7,768 square miles (20,119 square kilometers or 5 million acres).5
Petroleum exploration in Sudan began in the early 1960s. Activity was originally concentrated offshore in the Red Sea. In 1974, two years after the peace accord that ended the first civil war (1955-72), the Sudanese government granted the Chevron Oil Company (U.S.) large oil concessions in Sudan. Chevron discovered and named the Muglad and Melut basins. It drilled for and found oil near Bentiu town in 1978. The government named the oilfield “Unity.” It was located in Block 1, inside Upper Nile province, part of the autonomous Southern Region. Soon after, Chevron discovered the Heglig field, in Block 2. Chevron spent about U.S. $ 1 billion on exploration but never recovered it costs. It suspended activities in southern Sudan in 1984 due to a rebel attack that killed three expatriate oil workers and other security concerns. The French firm Total, which acquired various oil concessions around 1980, also suspended its onshore exploration activities, but retained its rights, including to Block 5, which, at 120,000 square kilometers, is larger than the size of Blocks 1, 2, 4, 5A, and 5B combined.
http://www.hrw.org/reports/2003/sudan1103/8.htm#_Toc54492556http://www.hrw.org/reports/2003/sudan1103/