Kurnia-1’s primary target in the block is the Kujung limestones, with a secondary target in the shallower Ngrayong sandstones.

A 120 square kilometre structure has been identified in the eastern part of the block on reprocessed seismic data.

Proven and probable undiscovered reserves are estimated to be 200 million barrels of oil in the Kujung, and 256 billion cubic feet of gas in the Ngrayong, Cooper said.

“The drilling break resulted in gas concentrations in the mud rising from a background level of 30 units to 224 units before the gas-cut mud was circulated through the rig degasser with an increase in pressure on the choke manifold,” the company said.

“The mud weight was increased to control any further gas influx. A maximum gas reading of 3132 units was recorded when normal circulation was resumed.”

The sandstone samples also exhibited oil stain and increasing fluorescence with depth (100% fluorescence at 1791m) and oil was observed on the mud surface.

The rig is conditioning the drilling mud before drilling ahead and on Friday morning was at a depth of 1793m.

“The significance of these gas and oil shows will be evaluated by wireline logs after the well has reached total depth of this section at 2500 metres,” Cooper said.