(Sharecast News) - Shell is reportedly preparing to launch the sale of its stakes in two clusters of gas fields in the southern British North Sea, part of an ongoing retreat of long-time producers from the ageing basin.

Reuters cited industry sources as saying that the oil giant is planning to offer its 50% stake in a cluster of fields in the Clipper hub, as well as the Leman Alpha complex. It was understood the assets could fetch up to $1bn in total.

Reuters said a Shell spokesperson declined to comment on its plans for the fields, which both supply natural gas via a pipeline to the onshore Bacton gas processing plant in eastern England.

Shell has in recent years sold a number of stakes in ageing fields in the North Sea, including a $3.8bn package of assets to Harbour Energy in 2017.

The company owns a 50% stake in the Clipper and Leman Alpha fields which were part of a large joint venture with Exxon Mobil dating back to the 1960s. Exxon sold its British North Sea assets last year to private equity-backed Neo.