• journal_title：Geophysics
• Contributor：Clive McCann ; Jeremy Sothcott
• Publisher：Society of Exploration Geophysicists
• Date：2009-
• Format：text/html
• Language：en
• Identifier：10.1190/1.3052112
• journal_abbrev：Geophysics
• issn：0016-8033
• volume：74
• issue：2
• firstpage：WA93
• section：LABORATORY MEASUREMENTS

Laboratory measurements of the attenuation and velocity dispersion of compressional and shear waves at appropriate frequencies, pressures, and temperatures can aid interpretation of seismic and well-log surveys as well as indicate absorption mechanisms in rocks. Construction and calibration of resonant-bar equipment was used to measure velocities and attenuations of standing shear and extensional waves in copper-jacketed right cylinders of rocks ( in length, in diameter) in the sonic frequency range and at differential pressures up to . We also measured ultrasonic velocities and attenuations of compressional and shear waves in -diameter samples of the rocks at identical pressures. Extensional-mode velocities determined from the resonant bar are systematically too low, yielding unreliable Poisson's ratios. Poisson's ratios determined from the ultrasonic data are frequency corrected and used to calculate thesonic-frequency compressional-wave velocities and attenuations from the shear- and extensional-mode data. We calculate the bulk-modulus loss. The accuracies of attenuation data (expressed as , where Q is the quality factor) are for compressional and shear waves at ultrasonic frequency, for shear waves, and for compressional waves at sonic frequency. Example sonic-frequency data show that the energy absorption in a limestone is small ( greater than 200 and stress independent) and is primarily due to poroelasticity, whereas that in the two sandstones is variable in magnitude ( ranges from less than 50 to greater than 300, at reservoir pressures) and arises from a combination of poroelasticity and viscoelasticity. A graph of compressional-wave attenuation versus compressional-wave velocity at reservoir pressures differentiates high-permeability (, ) brine-saturated sandstones from low-permeability (, ) sandstones and shales.