Flow tested between 5027 and 5102 metres total depth, Jeruk-2 ST5 was flowing at a stabilised rate with a gas oil ratio of 137 cubic metres per barrel through a 22/64 inch choke. This raises hopes that Jeruk could be bigger than the pre-drill estimate of 170 million barrels.

Santos said the flow rate was restricted by surface facility limitations and the need to keep a stable rate for evaluation.

This latest test could restore confidence in Santos’ prediction that Jeruk would be larger than its initial estimate of 170 million barrels. But by how much will be determined when four more appraisal wells, Jeruk 3-6, are drilled later this year, using 3D seismic tests to determine their positions.

Despite Jeruk-2 being close to Jeruk-1, the appraisal wells will be spread further afield on the Jeruk structure.

Suggestions of it being a 500 million barrel find came during early enthusiasm for Jeruk-2 results. But Santos said that any upgrade to its estimates would wait until the results of Jeruk 3-6 were known.

Participants in Jeruk and the Sampang PSC are: Santos (operator - 45%); Singapore Petroleum Sampang (40%); and Cue Sampang (15%).