Shell and Esso have announced they are putting their joint interests in a number of North Sea oilfields up for sale.
Included in the sale are interests in the Tern oilfield
These include the Cormorant Alpha and Cormorant North, Tern, Eider, Kestrel and Pelican fields.
Shell said "many" of its 400 onshore and offshore staff affected were expected to transfer to the new buyers.
But local politicians have raised concerns about the sale and the future of employees.
A planned expansion of Shell's Aberdeen operational headquarters has also been abandoned as a result of the decision.
Aberdeen University oil economist Professor Alex Kemp said Shell appeared to be selling its mature fields, which are not producing a lot of oil, to companies which specialise in late oilfield life.
A similar strategy has been adopted by BP on several occasions.
Shell and Esso have also confirmed they are in negotiations with Fairfield Energy for the sale of their interests in the Dunlin cluster of fields.
Tom Botts, executive vice-president of Shell Exploration and Production in Europe, said the assets it is selling are not "core" to the future of the business.
"These are relatively high cost assets within our European portfolio, where other operators might be better placed to add value," he said.
"At Shell, we are committed to focus on where we can best use our people, capital and technologies, for competitive long-term returns and on a global basis."
Mr Botts said Shell remained committed to Europe and the North Sea.
He said in 2006, the assets which the firm are selling represented less than 3% of Shell's European production.
Anne Begg, Aberdeen South MP, and Richard Baker, North East Scotland MSP, are to meet executives at Shell's Aberdeen headquarters on Friday.
Miss Begg, who recently visited the building at Altens to view the expansion plans, said she was disappointed with Shell's decision.
"This announcement has left 400 Shell employees uncertain about their future," she said.
"The priority of Shell and local politicians is to do whatever we can to get their jobs secured.
"But we have to ask why Shell have decided, quite suddenly, to sell these interests and stop the extension of their headquarters."
Graham Tran from the Unite Amicus union, which represents oil workers, said if Shell was no longer committed to the North Sea then it should sell up the rest of its assets.
However, Aberdeen City and Shire Economic Forum development manager Rita Stephen said Shell had committed to locating its "global energy hub" in Aberdeen.
"Shell is confident these assets will be sold, as has happened in the past, bringing new investment which will ensure the prolonged operational life of North Sea exploration and production," she said.