The Adelaide-based oil and gas producer said the resource potential was between 200 billion and 450 billion cubic feet. Maleo-1 is about 140km east of Surabaya in 58m of water.
The discovery is about 7km from an existing gas pipeline to Surabaya, which is Indonesia's second largest city.
Participants in the Madura Offshore PSC are Santos (operator) 75% and Talisman (Madura) 25%.