Shear Acquisition by LWD Quadrupole Tools : Case Histories

The measurement of shear wave velocity in slow formations always offered difficulties to acoustics logging industry. Wireline tools used successfully dipole sources, however in the logging-while-drilling environment (LWD) the presence of the collar doesn’t make feasible the option. Quadrupole sources were developed to solve the needs for this information. Quadrupole waves are dispersive and guided waves, demanding special care in the acquisition and processing. This paper presents some case histories were the shear acquired by quadrupole sources doesn’t fit with the shear acquired by dipole and monopole sources and discuss the presumable reasons for the differences.