Australian offshore operator Cooper Energy is progressing two all-subsea gas developments off the south-east coast in tandem as it eyes domestic gas market opportunities in local gas-hungry states.

The two projects - Otway phase three (OP3D) and Manta - are in the select engineering phase and moving towards final investment decisions in in 2022, said Cooper in an Investor Day presentation.

Cooper is looking to exploit 120 petajoules (113 billion cubic feet) of best estimate contingent gas resource from each project; Manta also has more than 3 million barrels of liquids.

Appraisal of the field by the Manta-3 well is being planned in 2023, and Cooper believes the field can provide 18 petajoules (17 Bcf) per year of new gas supply into south-east Australia and 500,000 barrels of condensate "at a cost that sits at the low end of the cost curve", said the operator.

Manta will be a two-well subsea tieback in 130 metres of water in the Gippsland basin. The wells receiving power via a 33-kilometre umbilical to Cooper's Sole subsea field, and connecting to the Patricia-Baleen pipeline 35 kilometres away.

Otway phase three in the Otway basin will develop gas from the Henry-3 and Annie-2 fields into Cooper's Athena gas plant.

Cooper is aiming to drill production wells in 2023 and bring gas to market in 2024, subject to FID and rig availability.

Field Development

Subsea projects moving ahead in tandem off SE Australia