Sonic to ultrasonic Q of sandstones and limestones: Laboratory measurements at in situ pressures
McCann, Clive and Sothcott, Jeremy (2009) Sonic to ultrasonic Q of sandstones and limestones: Laboratory measurements at in situ pressures. Geophysics, 74, (2), WA93WA101. (doi:10.1190/1.3052112).
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Description/Abstract
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 welllog surveys as well as indicate absorption mechanisms in rocks. Construction and calibration of resonantbar equipment was used to measure velocities and attenuations of standing shear and extensional waves in copperjacketed right cylinders of rocks (Formula in length, Formula in diameter) in the sonic frequency range and at differential pressures up to Formula. We also measured ultrasonic velocities and attenuations of compressional and shear waves in Formuladiameter samples of the rocks at identical pressures. Extensionalmode 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 thesonicfrequency compressionalwave velocities and attenuations from the shear and extensionalmode data. We calculate the bulkmodulus loss. The accuracies of attenuation data (expressed as Formula, where Q is the quality factor) are Formula for compressional and shear waves at ultrasonic frequency, Formula for shear waves, and Formula for compressional waves at sonic frequency. Example sonicfrequency data show that the energy absorption in a limestone is small (Formula greater than 200 and stress independent) and is primarily due to poroelasticity, whereas that in the two sandstones is variable in magnitude (Formula ranges from less than 50 to greater than 300, at reservoir pressures) and arises from a combination of poroelasticity and viscoelasticity. A graph of compressionalwave attenuation versus compressionalwave velocity at reservoir pressures differentiates highpermeability (Formula, Formula) brinesaturated sandstones from lowpermeability (Formula, Formula) sandstones and shales.
Item Type:  Article  

Digital Object Identifier (DOI):  doi:10.1190/1.3052112  
ISSNs:  00168033 (print) 19422156 (electronic) 

Subjects:  Q Science > QE Geology  
Divisions:  National Oceanography Centre (NERC) > Marine Geoscience 

ePrint ID:  207401  
Date : 


Date Deposited:  09 Jan 2012 17:10  
Last Modified:  31 Mar 2016 13:48  
URI:  http://eprints.soton.ac.uk/id/eprint/207401 
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