Indonesia currently holds proven Oil reserves of 4.7 billion barrels, down 13% since 1994. Much of Indonesias proven oil reserve base is located onshore. Central Sumatra is the countrys largest oil producing province and the location of the large Duri and Minas oil fields. Other significant oil field development and production is located in accessible areas such as offshore northwestern Java, East Kalimantan, and the Natuna Sea. Indonesian Crude Oil varies widely in quality, with most streams having gravities in the 22o to 37 o API range. Indonesias two main export crudes are Sumatra Light, or Minas, with a 35 o API Gravity, and the heavier, 22o API Duri crude.