The contracts relate to the use of a diving support vessel (DSV) and a remotely operated vehicle support vessel (ROVSV) to provide subsea construction, inspection, repair, maintenance and decommissioning services for Shell's collective UK offshore fields and facilities.
The DSV contract will deliver on a 24-hour, year round basis, while the ROVSV will only operate for 100 vessel days per year through to the second quarter of 2018.
Subsea 7's North Sea fleet will take part in the contracts, while associated project management and engineering support will be executed from Shell's and Subsea 7's offices in Aberdeen.
"We are proud to have received these contract extensions," Subsea 7 vice president UK Phil Simons said.
"An award of this importance recognises our strong track record in providing life of field expertise and high quality vessels and safe and efficient operations to Shell since our support of their subsea operations began in 1984."
According to Shell's website, it has interests in more than 50 fields in the UK, operating more than 30 offshore installations, 30 subsea installations, two floating production storage and offloading vessels, three onshore gas plants and a marine terminal for distribution of natural gas liquids globally.
Shell said it produces about 11% of oil and gas in the region along with its joint venture partners.
