Cooper Energy finds new offshore gas field off Peterborough

Cooper Energy's Ocean Monarch rig began an $80 million shared exploration with Mitsui in mid-July in search of gas at two new fields, Annie and Elanora, named after nearby historic shipwrecks.

The companies announced on Friday they had discovered a gas supply at Annie, about nine kilometres offshore.

The exact amount is yet to be announced, but Cooper Energy managing director David Maxwell said it was "consistent with our expectations".

"It's a risky business, and when you find something it's exciting. It is something to be pleased about," he said.

Mr Maxwell said the company had preliminary plans to extract gas from Annie in the latter half of 2021.

Up to 150 people live and work on the Ocean Monarch rig during exploration, but gas production would not require a manned platform and the site would connect underwater to a gas plant.

"Once it's in production, there is nobody," Mr Maxwell said.

Cooper Energy will takeover BHP's Minerva gas plant in Port Campbell in the next four months. Mr Maxwell said there would be no reduction in staff at the plant, which employed about 20 people.

"Our wish would be to retain them. When they leave BHP and transfer to us, there are issues we have to work out. But we will have those jobs available in the community," Mr Maxwell said.

He said the company was spending about $25 million connecting the Minerva plant to existing Henry and Casino gas fields, in use since 2007, and estimated it could now spend $120 million connecting the plant to Annie.

A depletion of gas from existing nearby Bass Strait fields and an increase in gas prices has driven the search for new gas supplies for south-east Australia.

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The rig will now plug the well at Annie before travelling further seaward to explore at Elanora until early October.

"We fly people by plane from Essendon to Warrnambool and then helicopter them from Warrnambool out to the rig," Mr Maxwell said.

"Separately, we are running a supply base from Portland, that's where the food, equipment and fuel go out from."

Mr Maxwell said new gas fields were costly because most low-cost gas fields were now developed.

"Most of the gas goes into the industrial sector with minerals and manufacturing. That's a market that is going to be around for a long time," he said of the future.

"The amount of gas going into electricity has been declining, and some of that has been because of renewables. But there are times where gas is needed to keep the electricity stable as well."

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