105 5. Geophysical methods The attribute, called the VSP flow index, which is defined as the product of the ambient noise factor by the body-wave to Stoneley-wave conversion factor, was used to detect both karstic bodies and flow (Fig. 15b). In the same way as for the calculation of the acoustic flow log, a VSP flow rate is calculated from the VSP flow index. (a) (b) Figure 14 Borehole M20: VSP with Hydrophones – Stoneley wave separations and conversion factor estimate. (a) Down-going Stoneley waves, (b) Up-going Stoneley waves.
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