The news comes as BP CEO Bob Dudley told the IHS CERAWeek energy conference in Houston that the UK North Sea faces a "massive" wave of restructuring as part of a "painful readjustment" as low oil prices hit mature fields particularly hard.

While the UK government's decision to cut taxes in last month's Budget would help industry, he said it was unlikely to reverse the effects of the oil price plummet, as the world's biggest oilers have cut spending significantly in the North Sea, axing thousands of jobs.

Royal Dutch Shell said last month it would cut 250 North Sea jobs this year, after insiders said BG Group, Apache and Marathon Oil were looking to sell up to $A38.55 billion worth of UK North Sea assets.

In February, the UK's Oil and Gas Authority CEO Andy Samuel issued a "call to action" on the UK Continental Shelf's falling investment attraction which could lead to premature decommissioning of assets.

The CATS agreement comprises a payment on completion of $453 million and a deferred amount of $33 million, subject to post-closing adjustments.

CATS, which includes a 400km pipeline between the Everest field and a gas terminal at Teesside in England, provides about 8% of the UK's gas needs.

BP North Sea Regional President Trevor Garlick, said: "The North Sea is an important region for BP.

"Our strategy here is to focus our resources and investment to create an efficient, sustainable and competitive business which will contribute to UK energy security for many years to come. Key elements of this are the completion of our major projects in the central North Sea and Shetland area, and continued management of our portfolio.

"CATS has been a great business for BP but, aligned to the recommendations of the Wood Review, we believe securing this new owner will ensure a better long-term future for this key piece of North Sea infrastructure.

"Supporting staff and ensuring continued safe operations will be our priority as we go through this transition period."

The sale of CATS will be as a fully operational business, with staff expected to transfer to the new employer with contractual terms and conditions protected under UK TUPE (transfer of undertakings-protection of employment) regulations.

Subject to the receipt of regulatory and other third party approvals, BP aims to complete the sale and transfer of operatorship before the end of 2015.

BP said the sale would not impact its rights to capacity in CATS.