ExxonMobil puts Gippsland Basin assets, including oil and gas platforms and Longford plants, on the market.

SHOCKWAVES have been reverberating across Esso's Gippsland facilities after workers were told on Wednesday morning that the company had all of its Gippsland Basin assets on the market.

Work was halted on sites at 11am as the company's lead country manger, Nathan Fay, made the announcement to workers via Skype.

The sites up for sale include offshore oil and gas platforms, the Longford Gas Plants and Long Island Point facilities.

It is understood ExxonMobil will maintain its interests in the huge Gorgon gas project in Western Australia, and its interests in Papua New Guinea.

After the announcement was made, the Longford carpark was reportedly peppered with workers on phones making calls to family members and colleagues.

In a statement to the Gippsland Times, an ExxonMobil spokesperson said the company would be "testing market interest for a number of assets worldwide".

This included its "operated producing assets in Australia, as part of an ongoing evaluation of its assets".

"No agreements have been reached and no buyer has been identified.

"ExxonMobil continually reviews its assets for their contribution toward meeting the company's operating needs, financial objectives and their potential value to others.

"Operations will continue as normal throughout the effort to sell the assets.

"Our priorities continue to be effectively meeting the expectations of our customers, employees and business partners, while maintaining a consistent focus on safe and efficient operations," the statement read.

Australian Workers' Union Victorian vice president Ben Davis said everyone was assuming ExxonMobil had a buyer lined up.

"I'm not assuming that," he said.

"This announcement doesn't change that our members will get up and go to work tomorrow.

"If ExxonMobil finds a buyer, it's probably a good thing.

"Otherwise they'll continue to manage it the way they have for decades.

"We just need to wait and see what happens."

In June the Gippsland Times noted speculation was again growing as to whether the company would dispose of its Gippsland Basin oil and gas assets, but at the time an ExxonMobil spokesperson said the company did "not comment on rumours and speculation".

In March US-based ExxonMobil chairman and chief executive Darren Woods confirmed plans to sell billions of dollars in assets, the energy giant forecasting it could generate $15 billion in cash through to 2025 by selling assets.

Mr Woods said Exxon was reviewing its global portfolio for divestment opportunities, and would prune assets that didn't fit its strategic priorities, adding the company would look for tactical opportunities to offload assets at good value.

Back in June 2016, joint venture partners ExxonMobil and BHP confirmed they had their stakes in Bass Strait crude oil up for sale.

At the time the offshore fields being offered for sale included Perch, Dolphin, Seahorse, Tarwhine, Kingfish A, Kingfish B, West Kingfish, Fortescue, Halibut, Cobia, Mackerel, Blackback and Flounder, and associated platforms.

With declining oil reserves, the joint venturers were planning to divest much of their crude oil interests in Bass Strait, saying they would focus on the substantial reserves of gas.

They had planned to retain all the major gas production operations, both the offshore fields and the onshore production plant at Longford.

However in February last year there was a change of heart, following a jump in oil prices.

BHP and ExxonMobil said they would hold onto their ageing oil platforms and fields in Bass Strait, an ExxonMobil spokesman saying "we are committed to our Australian operations and ensuring the safe and reliable delivery of oil and gas to our customers".

Then with new ExxonMobil Australia chief Nathan Fay in the chair, speculation again arose that ExxonMobil would not just sell off its share of Gippsland Basin oil assets, but gas as well.

In June The Australian speculated the Gippsland assets were a clear target for Beach Energy, the assets possibly fetching up to $3.2 billion.

"Speculation is emerging in the market that its 50 per cent stake in the asset it owns with BHP Billiton will soon be placed on the market following the investment banker discussions, with an adviser likely to be appointed soon," the article stated at the time.

"Some believe BHP may also sell its interest in the project, with the resources powerhouse viewing the project as too old and too small to retain in its portfolio."

Local workers now fear an uncertain future, with the possibility that a new operator may reduce the workforce.

The joint venturers have operated oil fields in Bass Strait since the 1960s after they drilled the country's first offshore well in 1965, reaching peak production of about 500,000 barrels a day in the 1980s.

This year is the 50th anniversary of the Gippsland Basin Joint Venture.

The joint venture supplies between 40 and 50 per cent of the east coast's domestic gas demand.

BHP was approached for comment.