Unocal said the potential of the discovery is in the order of two to three trillion cubic feet of gas equivalent, with flows in excess of 100m ft of gas a day and 5,000 barrels of condensate a day per well.
If confirmed, the size of the discovery means it would be able to supply the Bontang liquefied natural gas plant.
The Ganal block is one of Indonesia's first deepwater exploration zones and is close to other concessions operated by Unocal including Ranggas and West Seno.
Indonesian officials also recently stated that Unocal is currently producing 10,000bopd of crude at the West Seno field in the Makassar Strait, with output expected to reach 30,000 bopd by year end.
Unocal holds an 80% stake in the Ganal block with the remaining 20% held by Eni.
Indonesia oil production is at its lowest in over a decade and needs fresh investment. Production now stands at barely 1.1m bpd compared with a peak of over 1.6m bpd in the mid 1990s.
