(Adds context on infrastructure challenges in UK North Sea)
LONDON, June 17 (Reuters) - Britain's BG Group has sold a majority stake in one of Europe's biggest gas pipelines to Antin Infrastructure Partners for nearly $1 billion, the firm's first major asset sale since announcing a portfolio review to beef up its finances.
The deal, set to close in the second half of the year, is expected to generate a post-tax profit for BG of around $700 million at a time when it is under pressure to return value to shareholders disappointed by a string of production downgrades.
"At a time when its balance sheet remains under some pressure, the divestment ... represents a sensible release of capital," said Lucas Herrmann, an analyst at Deutsche Bank.
Shares in BG were up 0.3 percent at 0811 GMT.
BG will retain its right to access gas transport capacity on the CATS pipeline, a 404-kilometre subsea link that pumps up to 1.7 billion cubic metres of gas a day from UK North Sea fields, more than eight times Britain's average daily gas demand.
Attracting infrastructure specialists to the UK North Sea was one of the recommendations made by Sir Ian Wood in his strategic review of the UK's oil and gas industry, published in February this year.
He noted that the Netherlands already has a number of infrastructure companies, whose business model is solely to operate offshore pipeline and onshore processing facilities.
Industry experts say this approach would help resolve some of the problems relating to infrastructure access in the UK North Sea by removing conflicts of interest. It is also expected to help improve efficiency by allowing oil and gas companies to focus on production rather than midstream issues.
The BG deal also includes the takeover of a platform linked to the Everest oil and gas platform and an onshore gas processing terminal at Teesside.
Antin Infrastructure Partners is a Paris- and London-based fund investing in energy, transport and telecoms projects in Europe. Its portfolio includes stakes in solar plants in Spain and an interest in northern French midstream oil company Pisto.
Reporting by Karolin Schaps; additional reporting by Claire Milhench; editing by Jason Neely and David Evans