Petrofac, the international oil and gas facility service provider, is to acquire a 20% interest in the Gateway Storage Company.
It is involved in developing the Gateway gas storage project in the east Irish Sea.
Petrofac said the deal, which involves it joining Gateway as technical project operator and taking a place on its board, could cost up to £33million.
It said the front-end engineering and design (Feed) phase of the Gateway project was nearing completion.
The focus is now on taking the project to its final stages and in finding others to invest in it before a final decision is made on it in 2011.
Gateway, once completed, would add nearly 30% to the current gas storage capacity in the UK market.
It is expected to enter service in 2016.
Petrofac Energy Developments managing director Rob Jewkes said: “Petrofac is pleased to join with Gateway to progress this strategically important and well advanced storage project.
“With Feed activities largely complete, we are entering the project at this stage to bring confidence to the investor group that execution and delivery objectives for the complete facilities can be met, and will utilise the full capabilities of our group to optimise the facility design and deliver the project.”
Gateway chairman George Grant said the project was the most advanced gas storage project in the UK that has not yet committed to construction.
He added: “We are delighted to have an organisation with the execution and operational track record of Petrofac to take the project forward through to financing and into construction.”