Estimations of formation velocity, permeability, and shear-wave anisotropy using acoustic logs
- Massachusetts Inst. of Technology, Cambridge, MA (United States)
Field data sets collected by an array monopole acoustic logging tool and a shear wave logging tool are processed and interpreted. The P- and S-wave velocities of the formation are determined by threshold detection with cross-correlation correction from the full waveform and the shear-wave log, respectively. The array monopole acoustic logging data are also processed using the extended Prony`s method to estimate the borehole Stoneley wave phase velocity and attenuation as a function of frequency. The well formation between depths of 2,950 and 3,150 ft (899 and 960 m) can be described as an isotropic elastic medium. The inverted V{sub S} from the Stoneley wave phase velocity is in excellent agreement with the shear-wave log results in this section. The well formation between the depths of 3,715 and 3,780 ft (1,132 and 1,152 m) can be described as a porous medium with shear-wave velocity anisotropy about 10% to 20% and with the symmetry axis perpendicular to the borehole axis. The disagreement between the shear-wave velocity from the Stoneley wave inversion and the direct shear-wave log velocity in this section is beyond the errors in the measurements. Estimated permeabilities from low-frequency Stoneley wave velocity and attenuation data are in good agreement with the core measurements. Also it is proven that the formation permeability is not the cause of the discrepancy. From the estimated ``shear/pseudo-Rayleigh`` phase velocities in the array monopole log and the 3-D finite-difference synthetics in the anisotropic formation, the discrepancy can best be explained as shear-wave anisotropy.
- DOE Contract Number:
- FG02-86ER13636
- OSTI ID:
- 218396
- Journal Information:
- Geophysics, Vol. 61, Issue 2; Other Information: PBD: Mar-Apr 1996
- Country of Publication:
- United States
- Language:
- English
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