The UK Government's windfall tax is likely to wipe around 20% off the value of North Sea operators on average, according to Wood Mackenzie.
Energy Voice reports that the impact on individual firms is largely dependent on current tax and investment status.
WoodMac research directors Neivan Boroujerdi and Ashley Sherman said the energy profits levy (EPL) was likely to transfer around £15billion of profits of operators to the government over the next three and half years.
Introduced in May, the EPL ups the level of Corporation Tax on North Sea oil and gas producers from 40% to 65%, but also grants them a 91p tax saving for every £1 they invest in offshore projects.
Mr Boroujerdi said: "The impact is really highly dependent on whether you're in harvest mode or whether you're in growth mode, and that's because of the investment allowances that have been introduced.
"For some companies, they've seen a value wipe-out of over 30%, but actually the big spenders like the companies behind Rosebank and Cambo, if they were to proceed with those projects actually the overall value transferred would be quite limited."
Under the WoodMac calculations, operators such as TotalEnergies and Serica Energy stand to see the most value eroded, while Equinor and Ithaca Energy look to benefit most from high reinvestment rates thanks to the above projects.
Fiscal changes
Despite the sizable impact on firms, the research director said that "in theory" the fiscal changes are therefore "achieving what they've been set out to do".
Mr Boroujerdi also said that, despite the current high oil price, there remains hesitance among companies to sanction projects that do not break even at $35 per barrel, with capital discipline "still very much the buzzword".
The economics of EPL rebates are most affected by whether an operator is currently a net taxpayer or not. Without investment allowances, he suggested both Rosebank and Cambo are "fairly marginal" developments but would provide significant benefits to those companies already paying higher levels of tax.
"If we then take these projects, put them into the hands of a full taxpayer, the returns are boosted, the break evens come down, and the payback periods are shorter as well," said Mr Boroujerdi.
"So all of a sudden these projects look super-profitable within these businesses and you think would surely start to creep up the pecking order of an international portfolio."
Mr Boroujerdi suggested the same trend was true for companies looking to claim rebates on new exploration expenses.
"The impact on exploration is really pronounced and there's probably never been a period where it's more attractive to invest in new projects," he said, pointing out this "unprecedented" arrangement beats even Norway's current suite of generous exploration incentives.