110 Seismic Imaging The data were sorted in common midpoint (CMP) gathers. NMO corrections were carried out with a stacking velocity model obtained by velocity analysis. Surface consistent residual statics were calculated to enhance the signal to noise ratio and preserve the high resolution of the data in the CMP stack procedure. Figure 4.17 CMP stacked sections. The high-resolution 3D cube revealed near-surface seismic horizons between 50 and 200 ms. The 3D block is composed of 13 in-line sections 1 m apart. Each section is composed of 44 CMP points 1 m apart. Figure 4.17 shows an example of in-line and cross-line seismic sections extracted from the 3D block. The two sections presented (section 6 in the in-line direction, and section 23 in the cross-line direction) intersect in the middle of the 3D block. They have been filtered in the 15-150 Hz bandwidth, which provides an excellent signal-to-noise ratio. The CMP point located at the intersection of the in-line seismic section No. 3 and cross-line No. 6 is located about twenty meters from a borehole in which a vertical seismic profile (VSP) was recorded. The VSP (Figure 4.18, top) was used to obtain an interval velocity model and a time versus depth law, which was used to perform the time to depth conversion of the 3D block (Figure 4.18, bottom).
RkJQdWJsaXNoZXIy NjA3NzQ=