Freshfields Bruckhaus Deringer, Macfarlanes and Bredin Prat have won roles as Neptune Oil & Gas agrees to buy French utility Engie's oil and gas unit for $3.9bn (£3bn).

Freshfields is advising Neptune on the deal, fielding a team led by London corporate partners Sam Newhouse, Tim Wilmot, Charles Hayes and oil and gas partner Graham Watson. Paris corporate partner Alan Mason, who also co-manages the firm's continental Europe business, is leading on French law matters.

It is understood Neptune's management sought independent advice from Macfarlanes, instructing M&A group head Ian Martin.

French law firm Bredin Prat is representing Engie on the deal. Its Paris-based team includes corporate partners Patrick Dziewolski and Kate Romain alongside employment partner Laetitia Tombarello.

Neptune was founded in 2015 and is chaired by Sam Laidlaw, the former chief executive of Centrica. The company is backed by US private equity houses Carlyle Group and CVC Capital Partners.

Engie's upstream oil and gas business, EPI, includes 319 exploration and production licences in 12 countries across the UK and globally. Neptune is buying a 70% stake in EPI.

Engie said in a statement that the total value of the deal was €4.7bn  (£3.7bn), which includes €1.1bn (£0.9bn) of decommissioning liabilities.

Other energy deals announced this year include Shell's £3bn disposal of North Sea assets to Chrysaor Holdings.

CC is advising Shell alongside the oil major's 650-lawyer in-house team, which is headed by group general counsel Donny Ching.

Dechert is acting for UK-headquartered exploration and production company Chrysaor, which is being funded on this deal by Harbour Energy.