Bermuda-based Teekay Corp has announced that it plans to buy offshore storage equipment from Sevan Marine ASA as part of a deal worth up to $823 million.The oil and gas service company will buy three floating production storage and offloading units The Piranema, The Hummingbird, and The Voyageur for $668 million.It will also pay the remaining cost, estimated at between $100 million and $130 million, to upgrade The Voyageur.In addition, Teekay will buy a $25 million stake in Sevan, equivalent to a 40 percent ownership interest.Teekay has the right to buy future floating storage and offloading projects that were developed by Sevan.The deal is expected to close in the fourth quarter, except for the purchase of The Voyageur, which will be completed in the third quarter of 2012.