Amplitude Energy has determined that the Isabella gas discovery in the VIC/L24 permit in the Otway Basin offshore Victoria is not commercially viable.
This follows the completion of a flow test and pressure build-up analysis on the ST-1 sidetrack well.
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Pressure depletion recorded during the testing period does not support commercial development of the Isabella field at its current location.
The ST-1 well, drilled as a sidetrack from the earlier Elanora-1 well within permit VIC/L24 in Commonwealth waters, intersected gas in the Waarre C reservoir.
The well was subsequently cased and completed on 8–21 March, before undergoing a flow test to estimate resource volumes.
Flow testing recorded a peak surface-constrained flow rate of 60 million standard cubic feet per day (mscf/d) through a 64/64in choke.
Over two flowing periods with a combined duration of approximately 22 hours, a total gas volume of 40.2mscf and 22.3 barrels of condensate were produced.
The main flow period of eight hours averaged a stabilised gas rate of 46.4mscf/d at an average flowing bottom hole pressure of 2,639 pounds per square inch absolute.
Amplitude Energy, which holds a 50% operating interest in VIC/L24, is set to plug and abandon the ST-1 well over the coming days.
Once that activity is complete, the company will release the Transocean Equinox rig to the next member of the offshore Otway Basin rig consortium. O.G. Energy holds the remaining 50% interest in the joint venture.
Amplitude Energy managing director and CEO Jane Norman said: “The result at Isabella is disappointing but geological data from this well will help inform our future exploration prospects. Isabella was a large and prospective target for the East Coast Supply Project (ECSP); however, its size also corresponded with reservoir complexity, meaning it will require time to interpret the drilling information received.
“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 confirmed there is no change to the ECSP drilling programme, project budget or the first gas target of 2028.
A final investment decision for the ECSP development phase will be deferred until after subsequent wells are drilled, which is expected in the second half of 2026. The Elanora-1/ST-1 well programme has remained within budget.
Amplitude Energy will analyse drilling and flow test data from both the Elanora and Isabella wells over the coming months. The Isabella field is situated approximately 6km south-west of the producing Casino gas field.
The Waarre C formation sands were tested between depths of 1,905.6m and 1,916.3m, with approximately 11m of gross pay and 8m of net pay recorded.
The company operates offshore gas fields in Commonwealth waters and onshore processing plants in the Otway and Gippsland Basins, and holds non-operated oil production in the Cooper Basin.
Its portfolio includes undeveloped discovered resources such as the Annie and Manta gas fields.
