Page 89 - Acquisition and Processing of Marine Seismic Data

80 2. MARINE SEISMIC DATA ACQUISITION

TABLE 2.2 Example Gun Array Specifications of Modern 3D Survey Vessels

R/V Marcus M/V Pacific M/V Geo M/V Bergen
Langseth (NSF) Explorer (PGS) Challenger (CGG) Surveyor (CGG)
Gun type 1500LL and 1900LL 1900LL G gun II 1500LL and 1900LL
3
Array volume (in ) 6600 3090 4480 4100
Pressure (psi) 2000 2000 2000 2000
Number of strings 2 2 2 3 2 3 2 3
Tow depth (m) 6 6 7 6
String separation (m) 8 10 10 8
Array length (m) 16 14 17 16
Gun separation (m) 2.4 (inner) 2 (inner) 3 (inner) 3 (inner)
3.2 (outer) 3 (outer) 3 (outer) 3 (outer)
P-P amplitude (bar-m) 177.1 122.7 125.8 111.1
PBR value 28.5 34 28.3 21.9

FIG. 2.37 Example source directivity of an air gun array. Amplitude distributions for (A) inline and (B) crossline directions
(top) and schematic illustration of emitted signal signatures with respect to the radiation angle (bottom).