Saudi Arabia’s state oil group has agreed to pay almost £500 million to Royal Dutch Shell to buy it out of an oil refinery joint venture on the Gulf.

Saudi Aramco will buy Shell’s 50 per cent stake in the plant, ending a 30-year joint venture, as it expands its refining and petrochemical operations in a drive to become the world’s largest energy company.

Saudi Aramco is the world’s biggest oil company, pumping more than 10 million barrels per day last year. The acquisition, for $631 million, is due to complete later this year.

The disposal by Shell is part of a move by the Anglo-Dutch group to shift its focus from oil to lower-carbon products such as natural gas. It has sold more than…