Indonesia is located at the meeting point of the Australian, Pacific and South-East Asian tectonic plates. Most major petroleum discoveries in Indonesia were associated with Tertiary sediments or, locally, with either basement or Tertiary volcanics.
Indonesia has 60 sedimentary basins, of which 36, located in the mature west, have been well explored, and 14 of which are producing oil and gas. In the under-explored east, 39 Tertiary and Pre-Tertiary basins show rich promise in hydrocarbons.
About 75% of exploration and production is located in western Indonesia. There are four oil-producing regions: Sumatra, the Java Sea, East Kalimantan and Natuna. There are four main gas-producing regions: East Kalimantan, Arun (North Sumatra), South Sumatra and Natuna.