The Otway Basin, offshore Victoria and Tasmania, is undergoing a significant drilling campaign, using the Transocean Equinox semi-submersible rig, aimed at bolstering Australia’s domestic gas supply. This initiative seeks to address the anticipated gas shortfall on the East Coast by 2029. An initial seven exploration wells are planned by Beach Energy, ConocoPhillips and Amplitude Energy, with a contingency for at least an additional four wells.
Geological context and reservoir targets
The Otway Basin’s gas reserves are primarily found in the Cretaceous-aged Waarre and Pretty Hill sandstones. These reservoirs, part of major fluvial and alluvial depositionary systems in the Cenomanian and Valanginian, are characterised by their high porosity and permeability, making them ideal targets for gas exploration.
Hercules-1 Fails to do the Heavy Lifting
Beach Energy kicked off the drilling campaign with the Hercules-1 exploration well in September-October 2025. Situated approximately 5km south of the Artisan gas discovery in the VIC/P43 permit, Hercules-1 targeted a three-way fault-bound structure in the Waarre C reservoir. The prospect was considered to be medium to high risk and was ultimately proved to be, with the well plugged and abandoned dry at 2,350m.
ConocoPhillips: Essington-1 Success with Charlemont-1 to Follow
ConocoPhillips, in partnership with 3D Energi and Korea National Oil Corporation (KNOC), will drill two exploration wells in VIC/P79. The wells will aim to explore the potential of the Waarre A and C reservoirs, which have historically been prolific gas producers in the basin. Essington-1 started the campaign as a success, discovering gas in mid-November from both reservoirs. Wireline logs interpreted 58.5 m of net gas pay in the primary Waarre A reservoir at 2,515 m measured depth (MD) and 31.5 m of net gas pay in the secondary Waarre C reservoir at 2,265 mMD.
Reservoir quality is reported to be consistent with pre-drill predictions. Essington-1 was targeting a combined 262 Bcf gross mean prospective resource from two stacked reservoirs. The Waarre C reservoir has a potential resource of 76 Bcf. The Waarre A reservoir has a potential resource of 186 Bcf. While results are encouraging, flow rates, recoverability, and commercial significance will be assessed using SLB’s Ora wireline formation testing platform.
Charlemont-1 will target the Charlemont B prospect (previously known as Rosetta), located within the La Bella Complex — a series of tilted fault blocks that progressively step down into the basin, extending from the nearby 1993 La Bella gas discovery. Prospective resource at Charlemont-1 is 93 Bcf. Should these wells prove to be successful, a further four optional exploration wells could be drilled within ConocoPhillips-operated VIC/P79 and T/49P permits in 2026-28, which are adjacent to existing natural gas developments in the Otway Basin, such as the Casino and Thylacine fields.
Amplitude Energy: Tuning the Basin
Amplitude Energy, in collaboration with O.G. Energy, plans to drill an initial three wells in Licence VIC/L24 in 2026: Elanora-1, Elanora-1 ST1 (sidetrack targeting the neighbouring Isabella prospect), and Juliet-1. However, the low-risk Nestor-1, in the neighbouring VIC/P76, could be added to the roster in Q1 2026 with a view to drilling in late 2026 or early 2027 to utilise the Transocean Equinox. These wells, part of Amplitude’s East Coast Supply Project, are located approximately 25–40 km offshore from Peterborough, in water depths ranging from 65-74 m. The Elanora-1 well is targeting up to 161 Bcf of gas, while the sidetrack is targeting 149 Bcf from the Isabella prospect. Juliet-1 and Nestor-1 aim to tap into an additional 49 Bcf and 64 Bcf of gas, respectively. Amplitude’s campaign benefits from its proximity to existing infrastructure in the Otway Basin and ability to utilise available gas processing ullage at the Athena Gas Plant near Port Campbell.
Strategic Implications for Gas Supply
Victoria’s gas supply is under pressure due to declining output from legacy fields, high winter demand, and political resistance to new gas developments. The Otway Basin drilling campaign is a strategic response to these challenges, aiming to secure a reliable and affordable gas supply for the region. A successful outcome could reduce dependence on potentially costly LNG imports and support the state’s energy security.
In summary, the Otway Basin drilling campaign represents a concerted effort by key industry players to address the looming gas supply challenges in southeastern Australia. With encouraging signs from Essington-1, promising geological targets and strategic partnerships, the campaign holds the potential to significantly impact the region’s energy landscape.
