54 Well seismic surveying and acoustic logging geophone is sited near the wellhead. Several seismic shots are carried out to verify the proper functioning of the entire acquisition system (recorder, probe, reference geophone, source) and good data repeatability. The probe is then raised to the surface. After setting the zero (probe reference) according to a reference plane (raft, rotary table...) or on the ground surface, the probe is lowered to the bottom of the well and anchored to the well wall. Prior to this step, it is important to verify that the probe anchorage is sufficient to make measurements with the loose cable. The VSP operation at a given depth involves: 1. Checking the depth of the well receiver or probe, 2. Anchoring the probe (if the probe type allows the anchor arms to be opened and closed), 3. Slackening the cable, 4. Recording seismic data and checking them using the visualization system, 5. Verifying the repeatability of the source on the seismic channel dedicated to the reference geophone, 6. Tightening the cable, 7. Unattaching the probe (if the probe type allows the anchor arms to be opened and closed), 8. Positioning the probe at the next depth. This procedure can be repeated several times at the same depth to evaluate the variations in coupling and the signal-to-noise ratio. Well seismic operations can be carried out in vertical, deviated or horizontal wells, in open or cased holes. 2.2.2.2 Well probes • In the petroleum industry, most receiver systems are multi-sensor probes for the purpose of reducing well seismic data acquisition time and thus the costs of well downtime. These systems are array probes that include a master unit and satellite tools. They allow simultaneous recording at several depths and are particularly useful for seismic walkaway operations. The master tool includes a telemetry system that transfers data from the bottom to the surface. Each tool includes an anchoring system and a seismic module. In geotechnics, the drilling probe is usually a single-sensor probe. • The receiver can be a single-component geophone (vertical geophone) or a three-component geophone (a vertical component and two orthogonal horizontal components). The receiver can also be a hydrophone, or even have four components: a three-component geophone and a hydrophone. In geotechnics, a geophone-type single-sensor probe with 1 or 3 components is conventionally used. The anchoring system can be hydraulic or mechanical, with or without
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