Amplitude Energy Ltd. has confirmed that its Isabella gas discovery in the offshore Otway Basin is not commercially viable, following the completion of a critical flow test.
The Isabella sidetrack well (ST-1), located in Commonwealth waters south-west of the producing Casino field, will now be plugged and abandoned.
While the well successfully intersected gas in the primary Waarre C reservoir target earlier this month, technical data gathered during a subsequent pressure build-up period told a less favourable story.
Amplitude said significant pressure depletion observed during the testing phase indicated that the field cannot support a commercial development in its current location.
Despite the setback, the joint venture, comprising Amplitude Energy and O.G. Energy, confirmed that the drilling programme remains within budget.
The Transocean Equinox rig, which has been executing the programme, will be released in the coming days to the next member of the offshore Otway Basin rig consortium.
While Isabella was a key prospect for the company’s East Coast Supply Project (ECSP), Amplitude remains committed to its broader 2028 target for first gas.
Amplitude CEO Jane Norman described the result as disappointing but noted that the geological data would be invaluable for future exploration.
“Isabella was a large and prospective target, however its size also corresponded with reservoir complexity, meaning it will require time to interpret the drilling information received,” the CEO said.
“The result at Isabella does not impact our view on the probability of success of other Otway Basin exploration prospects, which have simpler geology.”
The company has opted to defer a final investment decision (FID) for the ECSP development phase until after the drilling of subsequent wells, which are scheduled for the second half of 2026.
Amplitude will assess Elanora and Isabella drilling and flow test data over coming months.
