A Numerical Study on the Mode Waves Excited by Multipole Sources in the Fluid-Filled Borehole in Radially Layered Transversely Isotropic Porous Medium

The propagating properties of the mode waves excited by multipole sources in a fluid-filled borehole embedded in radially layered transversely isotropic porous formation are investigated. The results show that the propagating characteristics of the mode waves are determined largely by the virgin formation in the low frequency band, and with the frequency increasing the characteristics of the mode waves are controlled by the invaded zone gradually. In the Biot theory the attenuation is easier to be affected by the formation around the borehole wall than the velocity. The frequency-dependent sensitivity coefficients with respect to the parameters of the radial layers are computed quantitatively. Comparing the horizontal permeability with the vertical permeability, the horizontal mobility plays the predominant role over the entire frequency range. The Stoneley wave is more sensitive to the velocity of the horizontally propagating SH wave than the flexural wave. The results of the work also show that the acoustic logging tool with broadband and distributed receiver array is advantageous to image the acoustic parameters in different radial depths.