Page 51 - Acquisition and Processing of Marine Seismic Data

42 2. MARINE SEISMIC DATA ACQUISITION

FIG. 2.3 Plan view of general in-sea equipment for (A) 2D and (B) 3D conventional towed streamer seismic survey.

long, the vessels used to manage this equipment acquisition without any interruption of data
must have very specific characteristics. recording. All modern seismic vessels have a heli-
Although some fishing ships were converted copter deck to use for emergency situations and
into 2D seismic vessels after the 1980s, seismic crew change. In addition, acquisition is accom-
acquisition is maintained by operating modern panied by at least one chase boat, which provides
3D seismic vessels dedicated to acquire seismic connection to the land for transferring data or
data all over the world. They are commonly replenishing supplies and tries to keep all the
designed as powerful diesel-electric vessels with spreadsafefromshippingactivitiesofothernearby
at least two drivelines to operate on a 24/7 basis vessels. Even bunkering is done as the vessel tows
for the acquisition of 2D and 3D seismic data. the streamers. Damaged or defective streamer
Sincethedeployment and recovery of the in-sea sections are repaired or replaced by work boats
equipment, especially the streamers, are quite when thestreamers arestillin thewater.
time-consumingprocesses,allshippingoperations Although 2D seismic vessels may be smaller,
as well as crew changes are done during the overall lengths of contemporary seismic vessels