The Anglo-Dutch company said in a statement the North Sea deal included an initial consideration of $3 billion and a payment of up to $600 million between 2018-2021 subject to commodity prices, with potential further payments of up to $180 million for future discoveries.
Reuters reported on the nearing deal last week.
The deal is subject to partner and regulatory approvals, with completion expected in the second half of 2017.
Chrysaor, led by veteran North Sea executive Phil Kirk and backed by private equity funds Harbour Energy and EIG Global Energy Partners, will become the largest independent operator in the North Sea after the deal's completion.
"This acquisition reflects Chrysaor's and Harbour's belief that the UK North Sea has material future potential for oil and gas production," Kirk said in a statement.
The package includes Shell's interests in Buzzard, north of Aberdeen, a relatively new field that feeds into the global Brent oil benchmark, as well as a 10 percent stake in the BP-operated Schiehallion oilfield some 110 miles (180 km) west of the Shetland Islands.
Other fields include Beryl, Bressay, Elgin-Franklin, J-Block, the Greater Armada cluster, Everest, Lomond and Erskine, Shell said.
Around 400 staff are expected to transfer to Chrysaor on completion of the deal.
The assets represent some 115,000 barrels of oil equivalent of production per day (boe/d), more than half of Shell's total UK North Sea production of 211,000 boe/d last year.
"This deal shows the clear momentum behind Shell's global, value-driven $30 billion divestment program. It builds on recent upstream divestments in the Gulf of Mexico and Canada," Shell Chief Financial Officer Simon Henry said in a statement.
"It is also consistent with Shell's strategy to high-grade and simplify our portfolio following the acquisition of BG," he added.