280 Geophysics in Geothermal Exploration In January 2022, a three-day campaign was conducted in the Sénart Forest to drill five holes, each up to 10 meters deep, where copper rods would be placed as injection electrodes. Figure 10.3 shows the location of the drill holes. Figure 10.3 Location of the drilled injection electrodes in the Sénart Forest. We favor the broadside orientation (i.e., perpendicular to the source-to-well shoe axis) of the dipoles, since CSEM modellings indicate this direction to maximize the cold front’s response. Then different tests with different dipole lengths in the broadside direction have been conducted as these directly affect the dipole moment of the emitted signal, thus influencing the amplitude of the detectable signal. Finally, a dipole with a radial, in-line orientation is used to validate modeling results showing weaker coupling compared to the broadside orientation. Between two and five copper rods were inserted into each drilled hole, with bentonite and salt added to enhance coupling between the rods and the ground and lower the grounding resistance. The copper rods were then connected with electrical cable and tape, cut to 10 cm below the surface, and covered with soil, leaves, and stumps to remain inconspicuous and secure. Once the electrodes were prepared, they were connected with electric cables, and grounding resistance was measured to check the dipole’s quality and current injection capacity. With
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