Mitsubishi Heavy Industries Technical Review Vol. 50 No. 2 (June 2013)18

Building the 5th Generation Ramform
Titan-class Seismic Vessel

Shipbuilding & Ocean Development
Ship & Ocean Engineering Division
Nagasaki Ship & Ocean Engineering Department

Global primary energy demand has been increasing year by year, and exploration markets ofmain energy sources (oil and natural gas) continue to expand. Petroleum Geo-Services ASA (PGS),
which is a major natural resource survey company in Norway specializing in offshore oil and gas
fields, have developed and built uniquely-shaped seismic vessels called Ramform in Europe, andhas operated the fleet to gather geological data correctly and efficiently. Mitsubishi Heavy
Industries, Ltd. had received an order to build 2 Ramform vessels from PGS and has recently
delivered the first vessel, which will form the state-of-the-art 5th generation Ramform Titan-classfleet. This report outlines these vessels.

|1. General description of seismic survey
Seismic survey is a form of geophysical prospecting method to collect and analyze
information on geological structures and properties underground by releasing acoustic waves (alsoreferred to as seismic waves) into the underground and receiving reflected or refracted waves
traveling back from discontinuous geological layers. For example, seismic survey is used to detect
oil or gas deposits.
Seismic vessels tow both air sources that release seismic waves and streamers that havehydrophones (receivers) embedded at a regular interval. The hydrophones receive both thereflection waves from beneath the seabed and GPS data, simultaneously. Towing several streamersin parallel enables a 3D survey by gathering stereographic geological data beneath the seabed.
Figure 1 is a schematic view of 3D seismic survey.

Figure 1 Schematic view of 3D seismic survey

Mitsubishi Heavy Industries Technical Review Vol. 50 No. 2 (June 2013)19|2. Features of the Ramform Titan-class
Table 1 and Figure 2 are the principal particulars and appearance of the Titan-class,respectively. This version of the Ramform provides significantly denser streamer spreads than theprevious fleet because it has a broader breadth and more streamers.
This version of the Ramform has the following features.
Table1Registry
Vessel Classification
LengthBreadth
Full draft in summer
Transit and towing speed
Propulsion typeEngine plant
Bow thruster
Accommodations

Figure 2

2.1

Main specifications of the Titan-class Ramform
BahamasDNV +1A1, SPS, ICE C, E0, HELDK, RP, CLEAN DESIGN,TMON, BIS, NAUT-OSV(A), VIBR, COMF-C(3)V(3)
About 104.2 m
70.00 m6.42 mAbout 15.5 and 5.0 knots
Electric, triple CP propeller plant with nozzle and propeller shaft,total 3 x 6,000 kW
6 x 3,840 kW
1 x 2,200 kW
80 persons (60 single and 10 double cabins)

As-built drawing of the Titan-class RamformRamform hull

The greater number of longer streamers that receive seismic waves enables a wider fieldsurvey in a single operation. PGS has used Ramform hull forms, with each hull widest at the aftend section, since the early 1990s, aiming for more efficient operations and safer deployment andrecovery of air guns and streamers. The 1st to 4th generation Ramforms are about 40 m in breadthand tow up to 22 streamers at most, while the 5th generation Titan-class Ramform has a wider
breadth of 70 m and deploys and recovers up to 24 streamers more efficiently and safely.

2.2

Survey equipment and relevant machinery・ Streamer winches (left of Figure 3)
Deck 3 (open two levels to Deck 5) is equipped with 24 streamer winches to wind up to12,000 m streamers and other winches, etc., to deploy and recover the streamers efficiently andsafely.
・ Gun arrays (upper right of Figure 3)
Deck 1 (open two levels to Deck 3) is equipped with a system to deploy and store six gun
arrays that have air guns linked with buoys, and a winch to wind cables of compressed air andcontrol signals from the ship. Three air compressors are installed under Deck 1 to supply thecompressed air during operations.
・ Work boats
Work boats are used to repair and replace damaged or defective equipment such asstreamers on the spot during operations. This approach is more efficient than bringing damaged
equipment back to the main ship each time. Deck 1 is equipped with two work boats andsystems to launch and recover the boats safely while the main ship is underway.
・ Paravanes (middle of Figure 3)
A pair of paravanes forms a plate-like towing system to deploy multiple streamers at
regular intervals. A shock absorber is placed between the paravane and the winch to mitigate
large loads on the ropes during towing.

Mitsubishi Heavy Industries Technical Review Vol. 50 No. 2 (June 2013)
20・ Instrument room (lower right of Figure 3)
The instrument room has a computer system to monitor and acquire the observation data
and GPS data of the deployed streamers around the clock.

Figure 3

2.3

Survey equipment

Special Purpose Ship Code (SPS Code)The Special Purpose Ship Code (SPS Code), adopted by the International Maritime
Organization (IMO), is a set of rules for the safe operation and equipment of special purpose ships
including seismic vessels, which carry special personnel who are not passengers or crew members.
The 5th generation Ramform applies the 2008 edition of SPS Code, which applies the passenger
vessel rules mutatis mutandis and has severer requirements than cargo vessels.

2.4

Accommodations

Offshore seismic surveys are conducted around the clock, and if a survey field is extensive ittakes several months. For crew comfort, the Ramform series are fully equipped with recreational
facilities including a lounge, a TV room, a sauna and an outdoor pool, as well as living facilities
including a living room and a dining room. The Titan Class, in particular, is equipped with anindoor ball game court, the most outstanding facility where crews can play full-scale basketballgames.
The Titan Class is also equipped with a helicopter deck to shift crews or replenish supplies
without mooring and interrupting observations. Bunkering by a bunker ship is also possible while
the seismic vessel tows streamers.

|3. Future vision
Mitsubishi Heavy Industries Ltd. has an ample track record in building ships for various
special purposes (e.g., offshore resource surveys, marine research, training and submarine cableinstallation), as well as conventional merchant ships. Our ship design and building knowledge, as
well as our comprehensive skills, are supporting this version of the Ramform. We have concluded
an agreement with PGS to build another 2 vessels with revised specifications. The demand forseismic vessels is likely to increase. Based on this version of the Ramform, we hope to attain aposition in the domestic and international markets for survey vessel building.