PGS has exercised the option following its original order for two similar vessels, signed in April 2011.
The two vessels will be capable of gathering 3D seismic data for sea bottom resource exploration, and will support PGS in its deepwater natural prospecting services.
Each of the Ramform Titan-class vessels will be 104m long and 70m wide, and equipped with advanced 3D seismic data acquisition / analysis capability.
For quiet operation, the vessels will be powered by a diesel electric propulsion system, and will be capable of receiving supplies at sea to help achieve long-term exploration work over large areas.
The Ramform Titan-class vessels to be built by MHI will have a wider stern than existing vessels, which will enable the vessels to deploy up to 24 streamer cables to explore a wider area at one time.
Sensors fitted in the cables detect echoes of sound waves nounced back from the seabed and stratum boundaries.
The new vessels are scheduled to be delivered in the first and second half of 2015.
MHI is currently building the two originally-ordered Ramform vessels at its Nagasaki Shipyard & Machinery Works.
Image: The Ramform Titan-class vessel will have a wider stern, allowing them to deploy up to 24 streamer cables for marine seismic exploration. Photo: Mitsubishi Heavy Industries.