Estimated to contain more than 36 billion barrels of proven oil reserves and boasting the largest natural gas reserves in Africa, OPEC-member Nigeria is a bustling hub for deepwater and ultra-deepwater exploration. The West African nation is an important supplier of light, sweet crude oil to the U.S., and disruptions in Nigerian production due to instability in the region can affect global oil prices. Nigeria is dependent on its oil sector, primarily located in the Niger Delta, which barrels in more than 95% of export earnings and some 85% of government revenues. Major producers in the region include Nigerian National Petroleum Corporation (NNPC), Shell, Chevron, ExxonMobil, Total and Eni/Agip.