WOOD Group has underlined its belief in the potential of a scheme to use unmanned buoys to produce oil and gas from the North Sea, which champions believe could result in a host of so-called stranded fields being brought into production.

The Scottish oil services giant has taken an option to expand its participation in an initiative launched by Enegi Oil and AB Technology to develop buoys they believe could be used to slash the cost of developing North Sea fields.

With 261 undeveloped fields on the United Kingdom Continental Shelf estimated to contain around five billion barrels oil and gas, Enegi and ABT think there could be a huge market for the buoys.

Their belief that buoys could be used to transform the economics of many fields too small or isolated for conventional development appears to be shared by Wood Group, under chief executive Bob Keiller.

"ABT's buoy solution offers an exceptional opportunity to develop a significant proportion of reserves that would otherwise remain untapped," said Aberdeen-based Wood Group.

The option move raises the stakes in a competition that pits Enegi and ABT against a Scottish rival called Unmanned Production Buoy. The Aberdeenshire firm has teamed up with Wood Group's rival, AMEC.

Alan Minty, the former Scottish squash international who runs Enegi and owns ABT, said Wood Group's decision could pave the way for a major advance.

"The execution of the option with Wood Group is further evidence of the attractiveness of the marginal field business model. The option represents the first step in securing independent investment into this initiative," said Mr Minty.

He added: "Successful conclusion of negotiations would see stronger links with a leading, global engineering services company providing access to the engineering manpower and expertise that will be needed to deliver on the many projects that it expects to secure and fulfil the potential of the marginal field initiative."

Analysts at Enegi's joint house broker, Shore Capital, told clients: "With the possibility of direct investment or participation by a major oil services company, this is highly encouraging news, in our opinion."

Wood Group said it looked forward to strengthening its ­partnership with Enegi and ABT without elaborating.

AB Technology formed a ­strategic partnership with Wood Group in May 2011 to ­commercialise buoy technology.

The buoys under development would have a price tag of £60m to £80m. They are designed to sit just below the surface of the water, with an access tower protruding, and be attached to wells on the seabed. They include facilities to separate oil from gas and to store the output.

Enegi did not say how many fields the buoys could be used on.

It noted the IHS consultancy calculated there are 261 ­undeveloped fields on the UK Continental Shelf containing five billion barrels oil equivalent.

In July, Enegi and ABT signed their first development deal in the North Sea by agreeing to acquire a 50% stake in the 10 million barrel Fyne field off eastern Scotland from Antrim Energy.

They expect to start production using a buoy in November 2016.

Enegi was awarded two licences in the UK North Sea last year.

Owned by Richard Selwa, Unmanned Production Buoy signed a memorandum of understanding with AMEC in October, covering the supply of engineering and construction management services for three unmanned platforms in the North Sea.

The company was awarded licences covering three fields in the latest UK offshore licensing round. Last month, Unmanned Production Buoy signed a memorandum of understanding with Offshore Oil Engineering (Zuhai) Co under which the Chinese firm will make 100 platform shells and other components.

The shells will be ­transported to a Scottish fabrication yard for assembly. The company said the 10-year agreement had an anticipated contract value of £2.5 billion.