Changes

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.

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.]]

[[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>

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 />.)]]

[[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]].

==See also==

==See also==