134 Geophysics in Geothermal Exploration Figure 3.14 Wave attenuation versus heating profiles (after Mari et al., 2024). The picked times of the first arrivals (downgoing P-waves) are used to compute the time versus depth law and the P-wave interval velocity log (Figure 3.15b). The upgoing and downgoing P-waves are separated by an f-k filter (Figures 3.15c and 3.15d). After deconvolution, the upgoing wave field is flattened (Figure 3.16a), a stacking corridor section is designed and a corridor stacked trace is computed (Figure 3.16b). The VSP trace stacked in a corridor (corridor stacked trace or VSP stacked trace), which represents the reflectivity function filtered in the seismic bandwidth and associated with the geological medium crossed by the borehole, is used to calibrate seismic sections located in the vicinity of borehole B1. The corridor stacked trace is used to identify primary reflections on surface seismic sections. For that purpose, the corridor stacked trace duplicated several times is inserted in a seismic section at the location of borehole B1 (Figures 3.16c and 3.16d). In the example, the seismic section is extracted from the 3D block, obtained by a 3D survey conducted on the site (Mari and Mendes, 2019: see Figures 2.27 to 2.29, chapter 2). Another approach is to use both velocity log obtained by acoustic logging (Figure 3.7, right side) and density log to compute synthetic seismograms (SS). The VSP stacked traces (indicated by a red rectangle) and the synthetic seismograms (indicated by a blue rectangle) are inserted in the 3D seismic section. The results are
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