Kjell Inge Rokke's offshore vessel company Akastor has taken a stake in Odfjell Drilling through an investment of $75m.
It has been issued with preference shares and warrants in return for the cash at a special general meeting of the drilling company.
The deal was mooted in April, when Odfjell said it was planning to buy the Stena Midmax rig, a Moss CS60E semisubmersible.