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| The most direct use of FWAL is the measurement of formation shear wave velocity. Together with P wave velocity and density, one can obtain the shear modulus and compressibility of the formation, which are very important in engineering applications. P wave to S wave velocity ratio is a good indicator for lithology, and borehole S wave velocity information is necessary for tie-in with shear wave reflection profiles, amplitude versus offset studies, and elastic wave equation migrations, among many other uses. | | The most direct use of FWAL is the measurement of formation shear wave velocity. Together with P wave velocity and density, one can obtain the shear modulus and compressibility of the formation, which are very important in engineering applications. P wave to S wave velocity ratio is a good indicator for lithology, and borehole S wave velocity information is necessary for tie-in with shear wave reflection profiles, amplitude versus offset studies, and elastic wave equation migrations, among many other uses. |
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− | The FWAL is also commonly used to identify and characterize fractures. Fractures are easily identified by a significant attenuation in all the wave modes—P, S, and Stoneley. An example of data across a fracture zone is shown in Figure 2. Various models are available to estimate the permeability of the fracture from the Stoneley wave attenuation across a fracture<ref name=pt07r44>Paillet, F. L., 1983, Acoustic characterization of fracture permeability at Chalk River, Ontario, Canada: Canadian Geotechnical Journal, v. 20, p. 468–476., 10., 1139/t83-055</ref>; <ref name=pt07r57>Tang, X. M., Cheng, C. H., 1989, A dynamic model for fluid flow in open borehole fractures: Journal of Geophysical Research, v. 94, p. 7567–7576., 10., 1029/JB094iB06p07567</ref> and reflection from a fracture<ref name=pt07r21>Hornby, B. E., Johnson, D. L., Winkler, K. W., Plumb, R. A., 1989, Fracture evaluation using reflected Stoneley wave arrivals: Geophysics, v. 54, p. 1274–2188., 10., 1190/1., 1442587</ref>.
| + | [[file:full-waveform-acoustic-logging_fig2.png|thumb|{{figure number|2}}FWAL microseismograms across a fracture zone.]] |
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− | [[file:full-waveform-acoustic-logging_fig2.png|thumb|{{figure number|2}}FWAL microseismograms across a fracture zone.]] | + | The FWAL is also commonly used to identify and characterize fractures. Fractures are easily identified by a significant attenuation in all the wave modes—P, S, and Stoneley. An example of data across a fracture zone is shown in [[:file:full-waveform-acoustic-logging_fig2.png|Figure 2]]. Various models are available to estimate the permeability of the fracture from the Stoneley wave attenuation across a fracture<ref name=pt07r44>Paillet, F. L., 1983, Acoustic characterization of fracture permeability at Chalk River, Ontario, Canada: Canadian Geotechnical Journal, v. 20, p. 468–476., 10., 1139/t83-055</ref> <ref name=pt07r57>Tang, X. M., Cheng, C. H., 1989, A dynamic model for fluid flow in open borehole fractures: Journal of Geophysical Research, v. 94, p. 7567–7576., 10., 1029/JB094iB06p07567</ref> and reflection from a fracture.<ref name=pt07r21>Hornby, B. E., Johnson, D. L., Winkler, K. W., Plumb, R. A., 1989, Fracture evaluation using reflected Stoneley wave arrivals: Geophysics, v. 54, p. 1274–2188., 10., 1190/1., 1442587</ref> |
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− | Similar to fractures, the FWAL can also be used to identify and characterize permeable zones<ref name=pt07r62 />; <ref name=pt07r3 />). Stoneley wave velocity decreases and attenuation increases with formation permeability. These changes can be attributed to the interaction between the pore fluid and borehole fluid (<ref name=pt07r50>Rosenbaum, J. H., 1974, Synthetic microseismograms— logging in porous formations: Geophysics, v. 39, p. 14–32., 10., 1190/1., 1440407</ref>. A correlation between core measured permeability and change in Stoneley wave slowness for two different formations is shown in Figure 3.
| + | [[file:full-waveform-acoustic-logging_fig3.png|thumb|left|{{figure number|3}}Plot of the difference between the measured slowness and the predicted elastic slowness (ΔΔT) against the core measured permeability values for both the limestone-dolomite and the sand-shale examples. (After <ref name=pt07r3 />.)]] |
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− | [[file:full-waveform-acoustic-logging_fig3.png|thumb|{{figure number|3}}Plot of the difference between the measured slowness and the predicted elastic slowness (ΔΔT) against the core measured permeability values for both the limestone-dolomite and the sand-shale examples. (After <ref name=pt07r3 />.)]] | + | Similar to fractures, the FWAL can also be used to identify and characterize permeable zones<ref name=pt07r62 />; <ref name=pt07r3 />). Stoneley wave velocity decreases and attenuation increases with formation permeability. These changes can be attributed to the interaction between the pore fluid and borehole fluid.<ref name=pt07r50>Rosenbaum, J. H., 1974, Synthetic microseismograms— logging in porous formations: Geophysics, v. 39, p. 14–32., 10., 1190/1., 1440407</ref> A correlation between core measured permeability and change in Stoneley wave slowness for two different formations is shown in [[:file:full-waveform-acoustic-logging_fig3.png|Figure 3]]. |
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| ==See also== | | ==See also== |