In early March, the appraisal well intersected a 184m gross gas zone.
In subsequent weeks the P'nyang South ST1 well drilled through the gas-water contact as planned.
"Based on the preliminary interpretation of data collected in both P'nyang South 1 and P'nyang South 1 ST1, the gas zone is interpreted to extend approximately 200 metres deeper than the lowest known gas in P'nyang South 1, indicating an increase in the total gas column to approximately 380 metres," Oil Search said.
"Seismic interpretation and structural mapping suggests additional up-dip potential above P'nyang South 1 and indicates a potential vertical gas column in the P'nyang South field of over 650 metres."
The sidetrack well will be plugged once an evaluation program is complete but it is already clear the goal of at least doubling resources to 2 trillion cubic feet of gas in the wider P'nyang area has been achieved.
The rig will then move east to spud the ExxonMobil-operated Trapia-1 exploration well in the Southern Highlands.
Oil Search did the P'nyang South drilling on behalf field operator ExxonMobil.
Exxon has a 49% stake in P'nyang South-1, Oil Search owns 38.5% while JX Nippon owns 12.5%.