One of the North Sea's billion barrel fields is to cease production due to “challenging” market conditions.
CNR said that the Ninian field is no longer economically sustainable due to "projected cost burdens" and will be decommissioned.
The company did not reference the UK windfall tax in its statement, but industry body OEUK said the decision showed how much international investor confidence has been rocked.
The Ninian field was discovered in 1974 and started production in 1978.
Ninian became just the third field in the sector to surpass one billion barrels of oil equivalent produced, after Brent and Forties.
No further drilling
In a statement to Energy Voice, CNR said it had “no further drilling activity planned” and was proceeding with the shutdown of the south and central platforms, along with the field’s wider hub infrastructure.
It added: “The company has made the decision following a detailed review of Ninian opportunities and projected cost burdens, concluding the field is economically unsustainable.
“The cessation of production and decommissioning of these platforms is likely to take several years and lead to fewer jobs long-term in the North Sea.”
CNR underlined that it will continue to operate its Tiffany platform in the UK North Sea, as well as manage its offshore Africa operations out of Aberdeen.
“As a result, no job losses are currently planned,” it added.
Confidence rocked
Mike Tholen, sustainability director at trade body Offshore Energies UK, told the Press & Journal: ”This news is a stark example of how confidence to invest in UK energy security is being rocked by the UK’s current fiscal regime.
“The Ninian platforms are iconic assets that have contributed thousands of jobs and millions of pounds to the UK.”
He added: “We have written to Chancellor Jeremy Hunt urging him to focus on creating a long-term competitive regime that supports investment across the energy sector.
“We also continue to warn that the windfall taxes introduced last year have rocked investor confidence and companies’ investment plans.
“Two windfall taxes on the oil and gas sector plus a windfall tax on the electricity generators have significantly undermined the appetite of companies and international investors to invest in the UK.
“The Spring Budget must address energy security where the offshore energy sector has a vital role to play, whilst supporting the energy transition.”
The UK Government declined to comment.