Mahmoud Ahmadinejad, the Iranian president, will sign the investments during a state visit to the Southeast Asian nation next month.
Yuri Thamrin, an Indonesian foreign ministry spokesman said on Friday: "Iran wants to invest $200 million to fix offshore refinery platforms in Indonesia and also to invest $400 million in building a gas pipeline from South Sumatra to Batam."
The pipeline would have to be at least 400km long to connect South Sumatra, one of Indonesia's gas-rich provinces, with Batam industrial island, which is located just 16km from Singapore, the region's shipping hub.
Thamrin did not provide additional details about the pending investment, which would provide Indonesia's gas and oil sector with a greatly needed cash injection.
Indonesia is the sole Southeast Asian member of the Organisation of Petroleum Exporting Countries (Opec), but it was a net oil importer in 2005.
Its oil industry has suffered and foreign investors have been scared away amid perceptions of rampant corruption, poor infrastructure and judicial unpredictability.
Ahmadinejad will be in Indonesia from May 9-13 for the fifth conference of a group of eight predominantly Muslim countries known as the D-8.
The group comprises Iran, Indonesia, Pakistan, Malaysia, Bangladesh, Turkey, Egypt and Nigeria.