Ramform Sovereign is a third generation Ramform-class 3D seismic vessel. The ship, one of the largest and most advanced seismic vessels in the world, was built to participate in operations to discover oil and gas reserves.
PGS awarded the construction of the vessel, worth $85m excluding the cost of seismic equipment, to Aker Yards in April 2006. The ship’s name, Ramform Sovereign, was chosen through a competition conducted by PGS during the same year.
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The vessel completed its first survey in May 2008 in the Norwegian-Danish Basin. In order to get high-resolution data, the vessel pulled along 14 streamers with a separation distance of 50m.
Ramform Sovereign design
Ramform Sovereign was designed with an objective to advance the lead made by PGS in 3D seismic acquisition productivity and efficiency. Apart from introducing several improvements, the vessel’s design was imported from the proven operational capabilities of the previous Ramform fleet.
The length of the vessel is 102m, which is 16m longer than the previous six Ramforms. The extra length accommodates a larger engine room and higher fuel capacity.
The vessel’s moulded breadth is 40m, which is equal to the four previous V-class Ramforms. The draft has been kept at 7.4m. Length between perpendiculars is 95m and depth to gun deck is 8.5m.
The gross tonnage of the vessel is 13,688t, while net tonnage is 6,107t. The vessel was designed for a transit speed of 16.5kt when fully loaded and has 25% longer endurance compared to previous Ramforms.
Ramform Sovereign construction
Planning for the construction of the Ramform Sovereign began as early as November 2005. First steel was cut in September 2006, and the vessel finally christened in March 2008 in Alesund, Norway.
The hull was constructed by about 600 welders and fitters in the Aker Yards in Tulcea, Romania, and the main construction was subsequently carried out in Langsten, Norway. The vessel was launched into water for the first time in June 2007 by a massive synchro-lift, which consisted of a platform with 50 lift points.
In August 2007, the vessel was towed to Stavangar, Norway, for the installation of propellers and thrusters. It was towed back to Langsten in September 2007 for the remaining installation and construction works. Rigging and the installation of maritime and seismic equipment was accomplished there. Heavy machinery, including the main engines and compressors, were fitted out by February 2008.
Facilities and equipment
Ramform Sovereign has 34 single cabins and 17 double berth cabins, and can accommodate around 70 people in total.
The vessel has 26 streamer reels and 22 streamer tow points. Larger paravanes (a form of towed underwater glider) are provided with improved handling system and have the streamer spread width of over 1,300m. The vessel has been fitted with synchronised streamer deployment and recovery system for improved operational efficiency.
The vessel features steerable sources, world’s first roll-compensated helideck for expanded operating windows, digital gun controllers and dual work-boat capacity. It also has a sky lounge for marine mammal observation.
Specialised work boats are available to make operations safer and more efficient.
ODIM supplied the complete aft deck set-up for seismic operations, deck machinery (ODIM Brattvaag Winch) and cranes (ODIM ABAS). The company also supplied two hydraulic-operated anchor winches and five mooring winches. Four remote-controlled knuckle boom deck cranes in three different capacities were supplied by ODIM ABAS.
Propulsion
The Ramform Sovereign is propelled by two 6.5MW (50% more than a V-class Ramform) variable pitch shaft propellers. The vessel is also equipped with forward retractable electric thrusters for smooth manoeuvrability.
In addition to four Bergen Diesel B32:40L9 and two Bergen Diesel B32:40L6 main generator sets, the vessel also has a 350kW, Mitsubishi DPMG 437-S6B3A emergency generator. ABB supplied a high-voltage power plant of 22.16MW (30,000HP) capacity.
