Subsidiaries Engie Fabricom and Tractebel have formed a joint venture and partnered with Iemants. The companies will be responsible for completing the project's offshore substation and jacket foundation.
The topside will be manufactured at Fabricom's yard in Antwerp, Belgium. It is due for completion in 2017, according to Engie.
The 22-turbine Merkur project reached financial close in August 2016.
It will be the first commercial European offshore project to use GE's Haliade 6MW turbine. Project completion is expected in 2019.
The development consortium is led by investment managers Partners Group, which holds a 50% stake. GE Energy Financial Services holds 6.25% of the shares.