Petroleum industry in Chad  Chad maintains sizable reserves of crude oil which, alongside agriculture, makes up the largest share of the landlocked former French colony's export revenue. Producing around 100,000 barrels of oil a day, most of Chad's crude comes from its reserves in the Doba Basin in southern Chad where oil was discovered in the early 1970s by foreign drillers. There is an estimated one billion barrels of oil in Chad, most of it being exploited by hundreds of rigs operated by Western companies such as Exxon-Mobil and Royal Dutch Shell. However, many challenges exist to Chad's petroleum industry including but not limited to corruption, internal conflict, and geography. Since Chad is landlocked, most of Chad's oil exports are transported out of the country by a pipeline that leads to the Cameroonian port city of Kribi. This pipeline, owned by a consortium, has come under fire due to allegations of exploitation by international corruption watchdogs, and Chadian politicians. In addition, environmentalists have voiced their concerns over the pipeline's impact on the natural environment, citing several spills. Oil exploration in Chad began in the 1950s while the country was still under French colonial administration. At least three oil rich areas were discovered in the country, however due to the high cost that would have been incurred in exploiting the finds, the French opted not to develop them. At the time the bulk of France's petroleum was being imported from Algeria and the Middle East. In 1960, Chad achieved its independence from France, and François Tombalbaye took over the country as its first president. Tombalbaye enlisted Conoco, an American oil and gas company to search for oil reserves. The company found oil in several areas in 1973-1975, notably the Doba Basin in the Central African Rift system, and the Sedigui area of Lake Chad. In 1975, Tombalbaye was killed by soldiers in a coup d'état and he was replaced with a military junta. This further intensified an already ongoing civil war between the government led by Goukouni Oueddei who became head of state of Chad in 1979, and Hissène Habré, the French and U.S.-backed former defense minister. During this period of especially heavy fighting, Conoco and other foreign oil companies suspended their oil exploitation efforts and left the country. Throughout the 1980s, very little was done to cultivate the petroleum industry owing to political instability, internal conflict, and the Chadian–Libyan conflict. In 1990, Idriss Déby came to power in a coup changing the dynamics of oil and power in the country.