Drilling of Thebe-1 began in the first week of July in block WA-346-P using the semi-submersible rig Atwood Eagle.
Evaluation has confirmed Thebe-1 encountered a 73m gas column, BHP said.
“The Thebe discovery is an excellent addition to our global portfolio,” BHP Petroleum’s global exploration president Steve O’Rourke said.
“The results are encouraging and we will now proceed with further data gathering and evaluation.”
BHP is operator and holds a 100% stake in the field, which represents the company’s second significant gas discovery in the basin after Scarborough, about 50km south and shared 50-50 with ExxonMobil.
The Thebe discovery well is 300km off the north-west coast in about 1173m of water.
The well was abandoned after the reservoir core was collected.
