282 Geophysics in Geothermal Exploration Figure 10.4 Different parts of the LBNL sensors (left) and the probe connected to the logging cable (center), wireline instrument ready to go down into the well (right). 10.4 Survey The survey took place at two sites: the boiler plant site, where the GEV3 borehole (cross-section shown in Figure 10.5) is located and where the logging truck operated the probe (Figure 10.4, right), and the Sénart Forest, where the source (CSEM transmitter) was located. The measurements were carried out on March 1st, 2022, preceded the previous day by the setup of the source equipment and current injection tests to validate proper coupling of the poles. These tests showed improved contact resistance (after pole installation), allowing approximately 15 A of current to be injected. The measurement campaign initially planned to lower the probe into the uncased section of the borehole and perform measurements while raising it, sampling at a minimum of four different depths (Table 10.1). For a given depth, the source emitted the frequency sequence shown in Table 10.2 for a given dipole. This sequence was repeated successively for the four possible dipoles. Once all four dipoles were activated, the probe was raised to the next level, and the operation was repeated.
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