Chuen Hon Cheng and M. Nafi Toksoz
Massachusetts Institute of Technology
Cambridge, Massachusetts
ABSTRACT
The propagation and dispersion characteristics of guided waves in a fluid-filled borehole are studied using dispersion curves and modeling actual full wave acoustic logs by synthetic
seismograms. Theoretical waveforms of seismic waves propagating in a borehole are calculated using the discrete wave number re-presentation. Our results compare favorably with actual well logs from a limestone and a shale formation. Several factors affect the shape of the acoustic logs. The effective radius of a borehole determines the relative significance of the modes generated. Poisson’s ratio of the formation is the primary factor determining the relative prominence of the phases (leaky modes) between the compressional and shear arrivals. Attenuation determines the duration and decay rate of the pseudo-Rayleigh waves.