Shell has completed the $3.8bn sale of a package of North Sea assets to Chrysaor following the approval of regulators and stakeholders.
The package includes Shell's interests in several fields - notably Buzzard, Beryl, Elgin-Franklin and Schiehallion.
Shell is aiming to sell $30bn of assets by 2018 as it seeks to pay off debt following its takeover of BG Group.
More than 250 staff have transferred to Chrysaor as part of the transaction, which was first announced in January.
The deal represents about half of Shell's 2016 North Sea output.
A Shell spokesman said the company "retains a significant, more focused and strengthened presence in the UK North Sea, to which it remains committed".
He added: "Completion of this deal shows the clear momentum behind Shell's $30bn divestment programme and is in line with Shell's drive to simplify the upstream portfolio and re-shape the company into a world class investment."
The sale means Chrysaor has now become the largest independent operator in the North Sea.