Abstract It is still argued whether we measure phase or group velocities using acoustic logging tools. In this paper, three kinds of models are used to investigate this problem by theoretical analyses and numerical simulations. First, we use the plane-wave superposition model containing two plane waves with different velocities and able to change the values of phase velocity and group velocity. The numerical results show that whether phase velocity is higher or lower than group velocity, using the slowness-time coherence (STC) method we can only get phase velocities. Second, according to the results of the dispersion analysis and branch-cut integration, in a rigid boundary borehole model the results of dispersion curves and the waveforms of the fi rst-order mode show that the velocities obtained by the STC method are phase velocities while group velocities obtained by arrival time picking. Finally, dipole logging in a slow formation model is investigated using dispersion analysis and real-axis integration. The results of dispersion curves and full wave trains show similar conclusions as the borehole model with rigid boundary conditions.
*This work was supported by the National Natural Science Foundation of China (Grant No. 40774099, 10874202 and 11134011) and the National 863 Program of China (Grant No. 2008AA06Z205).
Cite this article:
WANG Jing,CHEN De-Hua,ZHANG Hai-Lan et al. Studies on phase and group velocities from acoustic logging*[J]. APPLIED GEOPHYSICS, 2012, 9(1): 108-113.
[1]
Cheng, C. H., and Toksoz, M. N., 1981, Elastic wave propagation in a fluid-filled borehole and synthetic
[2]
acoustic logs: Geophysics, 46(7), 1042 - 1053.
[3]
Hornby, B., Wang, X. M., and Dodds, K., 2003, Do we measure phase or group velocity with dipole sonic tools:
[4]
th EAGE Conference and Exhibition, Norway, F - 29.
[5]
Kim, K. Y., and Sachse, W., 1993, Determination of all elastic-constants of transversely isotropic media with a
[6]
cusp around the symmetrical axis by use of elastic pulses propagating in 2 principal directions: Physical Review B,
[7]
(17), 10993 - 11000.
[8]
Kimball, C. V., and Marzetta, T. L., 1984, Semblance processing of borehole acoustic array data: Geophysics,
[9]
(3), 274 - 281.
[10]
Sinha, B. K., Simsek, E., and Liu, Q. H., 2006, Elasticwave propagation in deviated wells in anisotropic
[11]
formations: Geophysics, 71(6), D191 - D202.
[12]
Tang, X. M., and Cheng, A., 2004, Quantitative borehole acoustic methods: Elsevier, Amsterdam, Boston.
[13]
Wang, X. M., Hornby, B., and Dodds, K., 2002, Dipole sonic response in deviated boreholes penetrating an
2012, Vol. 9 
