The contract forms part of a series of awards made to Aberdeen-based Wood Group and Stork Technical Services worth around £300 million in total, which underline gas producer BG's commitment to the North Sea.
BG said it expects to invest £1 billion in North Sea facilities over the next three years in support of an active exploration and development programme.
The company said it has signed contracts with Wood Group and Stork to provide a range of specialist engineering and maintenance support over the next five years to its Armada, Everest and Lomond assets in the central North Sea. These include three production platforms that lie around 160 miles east of Aberdeen.
The Wood Group PSN unit, which specialises in helping firms boost production from existing assets, is taking over work done by another contractor. BG did not name the company.
Dave Stewart, UK managing director of Wood Group PSN, said: "This is a significant win in terms of size, value and the number of jobs it will support."
Wood Group expects to create 150 jobs offshore and 150 in Aberdeen to support the contract.
Renowned for its activities in areas like offshore Brazil, BG also has a big North Sea business. It has a stake in the giant Buzzard field.
The contracts extend the scope of existing agreements between BG and Holland-based Stork.
Separately, Wood Group's Mustang engineering business has won a contract to work on a development off Newfoundland in Canada in what is understood to be a multi-million dollar deal.
The company will complete design and engineering work on the White Rose Extension Project.
Wood Group did not name the client. The White Rose Extension is operated by Husky Energy.
Wood Group disclosed that its chairman Allister Langlands had exercised 40,000 share options granted in 2009 under a long-term retention plan at a price of 3.33p per share.
The shares were worth £267,400 in total at yesterday's closing price of 668.5p.
Mr Langlands transferred 40,000 shares to his children at no cost. Chief financial officer Alan Semple also exercised options to acquire 40,000 shares at 3.33p each under the retention plan.