125 3. Borehole geophysical methods In borehole B1 (Figure 3.6) which is poorly cemented resulting in strong resonances, the short-offset configuration (1 m) only shows refracted P-waves in the 60–70 m depth interval. In contrast, the large offset is less sensitive to resonances, letting clearly appear refracted P-waves along the profile. For both offsets, the differentiation between the refracted P-waves (P) and the Stoneley waves (ST) can be done easily. Figure 3.6 Comparison of short offset (1 m) and large offset (3 m) acoustic sections recorded in borehole B1 (poorly cemented borehole). The different wave trains are identified by letters: C casing resonances, P refracted P-wave, ST Stoneley wave. The acoustic sections are normalized and displayed with a color scale ranging from 0 to 1 (after Mari et al., 2023). Figure 3.7 Comparison of short offset (1 m) and large offset (3 m) acoustic sections recorded in the open hole part of borehole B2. The different wave trains are identified by letters: C casing resonances, P refracted P-wave, S converted refracted S-wave, F fluid wave, ST Stoneley wave, criss-cross. The acoustic sections are normalized and displayed with a color scale ranging from 0 to 1 (after Mari et al., 2023).
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