Swiss chemicals company Ineos has bought all the UK North Sea gas fields owned by the DEA Group, which is in turn owned by Russian billionaire Mikhail Fridman's investment fund LetterOne, the companies said on Oct. 11.

In April, Britain's Energy Ministry gave Fridman six months to dispose of oil and gas fields LetterOne bought from German utility RWE, or see their licences revoked as the West tightened sanctions against Moscow over its role in the Ukraine.

"INEOS has been very open about its intention to make strategic investments in the North Sea and this acquisition is our first step in fulfilling this goal. It will also help our UK petrochemical assets to have ongoing access to competitive energy," INEOS Chairman Jim Ratcliffe said in a statement.

Ineos announced plans last year to make a $1 billion investment in British shale gas exploration with an ambition to become the country's biggest shale gas player.

A LetterOne spokemsan confirmed the sale.

"DEA will now use the proceeds from the sale to invest in its core growth areas in Europe and North Africa," he said.

Neither company gave financial details of the sale.

The sale process attracted interest from several buyers, including private equity funds which have built up resources over the past year for acquisitions in the sector, banking sources have said.

The intial offers submitted in July fell far short of LetterOne's target price of up to $1.2 billion, with the highest offers coming in at around $750 million, several sources close to the process have said.

Offshore