Numerical Study of Mode Waves in a Deviated Borehole Penetrating a Transversely Isotropic Formation

A 2.5 dimensional method is developed to investigate the mode waves in a deviated borehole penetrating a transversely isotropic formation. The phase velocity dispersion curves of the fast and slow flexural mode waves excited by a dipole source are computed accurately at different deviation angles for both hard and soft formation. The sensitivity of flexural waves to all the five elastic constants are calculated. Numerical results show that for a soft formation, the fast flexural mode wave is dominated by C66 at high deviation angles and low frequencies, the slow flexural mode wave is dominated by C44 at the same condition. An inversion procedure is presented to prove the sensitivity analysis.