Page 52 - Acquisition and Processing of Marine Seismic Data

2.1 COMPONENTS OF MARINE SEISMIC ACQUISITION 43

range between 90 and 120 m and they provide Fig. 2.4A shows the stern photo of the Sanco
accommodations for 50–60 people onboard, Sword seismic vessel of Dolphin Geophysical.
including ship’s crew, seismic team, and client The Sanco Sword can handle up to 16 streamers,
representatives. When it is taken into account each of which is deployed through its own fair-
that a survey may take several months, depend- leads at the towpoints (Fig. 2.4B). Gun decks
ing on the size of the working area, the vessels host the air gun arrays (Fig. 2.4C). 2D vessels
must also contain some recreational facilities have one single array while 3D vessels generally
such as a TV room, a sauna, gym and sometimes have two identical source arrays for flip-flop
a swimming pool, or even a basketball court. acquisition. There are also a gun shack and an
These vessels have a unique back deck design air gun control room in the gun deck. Back decks
to accommodate all required in-sea equipment also involve the tail and head buoys with their
such as guns, streamers, birds, etc. 2D and 3D specific rGPS navigation equipment mounted.
seismic vessels have two separate back decks: Both 2D and 3D vessels also have a central
the streamer deck (which is the upper deck used hydraulic system and several different winches
to store and deploy the streamers and related and reels to store, deploy and retrieve the
devices such as tail buoys or birds), and the streamers, buoys, gun umbilicals, paravanes
gun deck (which is the lower deck used to store and other necessary towing ropes and cables.
and deploy the guns and their peripherals). Streamer decks also have a shack for birds and

FIG. 2.4 (A) Stern photo of Sanco Sword 3D seismic vessel of Dolphin Geophysical, (B) fairleads used to deploy the
streamers, (C) gun deck, (D) streamer deck, and (E) instrument room of R/V Marcus Langseth operated by Columbia
University.