Multipole Dispersion Tracking for Accurate Slow Shear Determination in LWD Sonic Data

Slow shear determination from LWD sonic data is considerably complicated by the substantial presence of the drill collar in the well bore. Within the industry, monopole, dipole, and quadrupole modes are used to derive shear in slow formations, with a variety of dispersion correction techniques. A multipole slow shear inversion method is described here, which makes use of multiple borehole modes simultaneously both to characterise the tool/collar influence on the dispersion characteristics of the modes and to reduce the uncertainty in the inversion parameters.