168 Seismic Imaging 6 receiver lines. The source lines are perpendicular to the receiver lines. The receiver and source line spacings are respectively 80 m and 120 m. The receiver and source point spacings are 20 m. The receiver is an array of 12 geophones. The length of the array equals the receiver interval (20 m). The source is a vibroseis source generating a signal in the 14-140 Hz frequency bandwidth. The bin size is 10 x 10 m2. The nominal fold is 60. The in-line IL 405 is composed of 544 CMP points. The crossline XL 217 is composed of 772 CMP points. For the 2D seismic acquisition, the shot point is located at the centre of the receiver spread composed of 120 stations. The receiver and source point spacings are 25 m. The source is a vibroseis source generating a signal in the 14-140 Hz frequency bandwidth. The bin size is 12.5 m. The nominal fold is 60. The selected part of the 2D line 07EST10 is composed of 727 CMP points. The main aim of the processing was to apply an amplitude preserving sequence and to accurately image the target zone. Frequencies above 100 Hz were also present in the final data volumes. Andra supplied a geological model (distribution of velocities in depth), which was used to compute a first set of static corrections (Figure 7.4). An up-hole survey consisting of 20 wells was used to calibrate the static correction model. The use of the statics model and a consistent processing approach for both the 2D seismic lines and the 3D seismic volume ensured a good match between them. Figure 7.4 Map of basic static corrections (Andra document). Although the area was generally rural, there were high levels of ambient noise, both linear and random. The 3D survey is located in forest and rural areas. In land seismic the variability of receivers is related to geophone coupling with the ground and
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