Eversheds Sutherland and Herbert Smith Freehills (HSF) have advised two Chinese energy companies on their combined $2.6bn (£2.1bn) investment in a joint venture with state-owned Abu Dhabi National Oil Company (ADNOC).

In a deal announced on 19 February, state-owned China National Petroleum Corp (CNPC) – one of the three top oil producers in China – agreed to pay $1.76bn (£1.4bn) for an 8% stake in the $22bn (£17.5bn) Abu Dhabi Company for Onshore Petroleum Operations concession.

On the following day, Shanghai-based CEFC China Energy, a non-state-owned energy company, agreed to take a 4% stake for $888m (£708m).

CNPC and CEFC now join a consortium of global energy companies that hold a 40% stake in Abu Dhabi's largest oil concession, while ADNOC holds the remaining 60%. Among the investors, BP and France's Total each hold 10%, while Japan's Inpex and Korea's GS Energy hold 5% and 3% respectively.

The concession consists of 15 oil fields and is responsible for producing more than half of the Middle Eastern emirate's 3.1 million barrel-per-day production, according to Abu Dhabi-based newspaper The National.

Eversheds represented CNPC on the deal with a team led by Beijing managing partner Wenying Zhu-Clark, Abu Dhabi managing partner Tim Armsby and London partner Greg Hammond. They were supported by Abu Dhabi partners Geraldine Ahern and Dani Kabbani and London partners Paul Fontes, Adrian Toutoungi and Alex Doughty.

HSF acted for CEFC with a team led by Beijing partner Monica Sun, with help from Dubai partner Joanna Addison.

Advising ADNOC is the company's regular counsel on the project, Shearman & Sterling. Abu Dhabi partner Matthew Powell led the US firm's team. Powell also advised the state-owned oil company in December, when it awarded BP a 10% interest.