19 1. Shear velocity measurement in boreholes Figure 1.1 Illustration of a Full wave sonic log used as a CBL-VDL to evaluate the quality of the cementation (LIM Logging acquisition for EDF). This logging can be carried out with an acoustic tool of the sonic full waveform type. This is a necessity for a crosshole through an unstable formation (sandygravelly). Indeed, depending on the results, the allocation of emitting and receiving boreholes may be reviewed. 1.2 Vs measurements by borehole seismic method Borehole transmission seismic surveying can be illustrated as a special type of Vertical Seismic Profiling (VSP, see Chapter 2) where the focus of interest is not the waves reflected at the interfaces, but the time of first arrival of the transmitted wave free pipe good cimentation waves of formation
RkJQdWJsaXNoZXIy NjA3NzQ=