Norway-based ship design and building firm Ulstein Verft will develop two platform supply vessels (PSVs) for Nordic American Offshore (NAO).
The two new vessels will feature Ulstein's PX121 design and are expected to be delivered in January 2015.
PSVs are medium-sized ships that offer fuel efficiency and optimum deadweight capacities.
They have the capability to perform like large PSVs, but at lower operating and investment costs.
The two vessels with hull numbers 303 and 304 will be the seventh and eight vessels to be purchased by NAO, from Ulstein.
In December 2013, NAO purchased six PSVs with PX121 design from Ulstein Verft, which are on firm contracts in the North Sea.
The total value of all the eight PSVs is more than Nkr2bn ($328.1m).
Ulstein Group CEO Gunvor Ulstein said the company is pleased that NAO has chosen Ulstein to expand its fleet of PSVs.
Ulstein Verft has sold 18 vessels of PX121 design to date. The company currently has five vessels on order, and a further ten vessels that are constructed or under construction at yards in China and South East Asia.