PetroChina, the mainland's no. 1 oil producer, has discovered oil and gas reserves off southern Sumatra in Indonesia. The find coincides with Amerada Hess Corp discovering oil and gas reserves off Java. Indonesia's regulatory agency said the size of the reserves had yet to be determined. Indonesia has put out the welcome mat for foreign producers. Purnomo Yusgiantoro, the country's energy and mineral resources minister, has warned that national oil output could fall by 15% a year without more production investment.