Effects of fluid viscosity on shear‐wave attenuation in saturated sandstones

Geophysics ◽  
1990 ◽  
Vol 55 (6) ◽  
pp. 712-722 ◽  
Author(s):  
D. Vo‐Thanh
Keyword(s):  
Shear Wave ◽  
Wave Attenuation ◽  
Crack Density ◽  
Viscoelastic Model ◽  
Fluid Viscosity ◽  
Partially Saturated ◽  
Aspect Ratios ◽  
Viscous Shear ◽  
Shear Relaxation ◽  
Water Saturated

Measurements of shear wave velocity and attenuation as a function of temperature were made in the kilohertz frequency range in sandstones saturated with various liquids. For sandstones partially saturated with glycerol, two attenuation peaks are observed between −80°C and 100°C; they are attributed to viscous shear relaxation and squirt flow. For fully water‐saturated Berea sandstone, the attenuation decreases as the crack density increases. The displacement of the squirt peak, caused by the increase of the central aspect ratio of cracks, is at the origin of this decrease. A simple viscoelastic model, based on the model of O’Connell and Budiansky using a Cole‐Cole distribution of cracks, is proposed for calculation of the shear modulus of fluid‐saturated rocks. This model interprets the experimental data satisfactorily. The data suggest that the shear attenuation and velocity are controlled by the distribution of crack aspect ratios.

Effects of fluid viscosity on shear‐wave attenuation in partially saturated sandstone

Geophysics ◽  
1991 ◽  
Vol 56 (8) ◽  
pp. 1252-1258 ◽  
Author(s):  
Dung Vo‐Thanh
Keyword(s):  
Shear Wave ◽  
Velocity Dispersion ◽  
Wave Attenuation ◽  
Pore Space ◽  
Viscoelastic Model ◽  
Fluid Viscosity ◽  
Berea Sandstone ◽  
Frequency Range ◽  
Partially Saturated ◽  
Viscous Shear

Shear‐wave attenuation and velocity have been measured in the kiloHertz frequency range at temperatures varying from −80°C to 80°C in a sample of Berea sandstone partially saturated with glycerol. I investigated 7 saturation states ranging from 0 to 62 percent of the pore space. Plots of attenuation versus temperature show squirt and viscous shear peaks, even at low saturation. Their amplitudes and half‐widths increase with increasing saturation. The maxima of the peaks progressively move to higher temperatures (about 4°C for viscous shear peak and 30°C for squirt peak) with increasing saturation from 7 to 62 percent. The velocity dispersion between −80°C and 80°C progressively increases from 700 to 1200 m/s with increasing saturation from 7 to 62 percent. By introducing the crack saturation parameter, a simple viscoelastic model based on O’Connell and Budiansky and using a Cole‐Cole distribution of cracks, is proposed for calculating the shear modulus in partially saturated rocks. This model partially interprets the experimental data.

Experimental measurements of seismic attenuation In microfractured sedimentary rock

Geophysics ◽  
1994 ◽  
Vol 59 (9) ◽  
pp. 1342-1351 ◽  
Author(s):  
Sheila Peacock ◽  
Clive McCann ◽  
Jeremy Sothcott ◽  
Timothy R. Astin
Keyword(s):  
Sedimentary Rock ◽  
Wave Attenuation ◽  
Crack Density ◽  
Seismic Attenuation ◽  
Experimental Measurements ◽  
Effective Pressure ◽  
Carrara Marble ◽  
Compressional Waves ◽  
Linear Relationships ◽  
Water Saturated

Ultrasonic compressional‐ and shear‐wave attenuation in water‐saturated Carrara Marble increase with increasing crack density and decreasing effective pressure. Between 0.4 and 1.0 MHz, empirical linear relationships between 1/Q and crack density CD were found to be: CD = 1.96 ± 0.63 × 1/Q, for compressional waves and CD = 6.7 ± 1.5 × 1/Q, for shear waves.

COMPRESSIONAL‐WAVE ATTENUATION IN MARINE SEDIMENTS

Geophysics ◽  
1972 ◽  
Vol 37 (4) ◽  
pp. 620-646 ◽  
Author(s):  
Edwin L. Hamilton
Keyword(s):  
Marine Sediments ◽  
Wave Attenuation ◽  
Unit Length ◽  
Viscoelastic Model ◽  
Compressional Wave ◽  
Coarse Sand ◽  
Sediment Types ◽  
Viscous Losses ◽  
Clayey Silt ◽  
Water Saturated

In‐situ measurements of compressional (sound) velocity and attenuation were made in the sea floor off San Diego in water depths between 4 and 1100 m; frequencies were between 3.5 and 100 khz. Sediment types ranged from coarse sand to clayey silt. These measurements, and others from the literature, allowed analyses of the relationships between attenuation and frequency and other physical properties. This permitted the study of appropriate viscoelastic models which can be applied to saturated sediments. Some conclusions are: (1) attenuation in db/unit length is approximately dependent on the first power of frequency, (2) velocity dispersion is negligible, or absent, in water‐saturated sediments, (3) intergrain friction appears to be, by far, the dominant cause of wave‐energy damping in marine sediments; viscous losses due to relative movement of pore water and mineral structure are probably negligible, (4) a particular viscoelastic model (and concomitant equations) is recommended; the model appears to apply to both water‐saturated rocks and sediments, and (5) a method is derived which allows prediction of compressional‐wave attenuation, given sediment‐mean‐grain size or porosity.

Wave attenuation in partially saturated rocks

Geophysics ◽  
1979 ◽  
Vol 44 (2) ◽  
pp. 161-178 ◽  
Author(s):  
Gerald M. Mavko ◽  
Amos Nur
Keyword(s):  
Crack Width ◽  
Seismic Waves ◽  
Liquid Drop ◽  
Wave Attenuation ◽  
Pore Shape ◽  
Liquid Droplets ◽  
Wave Excitation ◽  
Partially Saturated ◽  
Aspect Ratios ◽  
Complete Saturation

A model is presented to describe the attenuation of seismic waves in rocks with partially liquid‐saturated flat cracks or pores. The presence of at least a small fraction of a free gaseous phase permits the fluid to flow freely when the pore is compressed under wave excitation. The resulting attenuation is much higher than with complete saturation as treated by Biot. In general, the attenuation increases with increasing liquid concentration, but is much more sensitive to the aspect ratios of the pores and the liquid droplets occupying the pores, with flatter pores resulting in higher attenuation. Details of pore shape other than aspect ratio appear to have little effect on the general behavior provided the crack width is slowly varying over the length of the liquid drop.

scholarly journals Lorentz force induced shear waves for magnetic resonance elastography applications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Guillaume Flé ◽  
Guillaume Gilbert ◽  
Pol Grasland-Mongrain ◽  
Guy Cloutier
Keyword(s):  
Magnetic Resonance ◽  
Shear Wave ◽  
Lorentz Force ◽  
Wave Attenuation ◽  
Shear Waves ◽  
Estimation Method ◽  
Biological Tissues ◽  
Magnetic Resonance Elastography ◽  
Motion Generation ◽  
Wave Source

AbstractQuantitative mechanical properties of biological tissues can be mapped using the shear wave elastography technique. This technology has demonstrated a great potential in various organs but shows a limit due to wave attenuation in biological tissues. An option to overcome the inherent loss in shear wave magnitude along the propagation pathway may be to stimulate tissues closer to regions of interest using alternative motion generation techniques. The present study investigated the feasibility of generating shear waves by applying a Lorentz force directly to tissue mimicking samples for magnetic resonance elastography applications. This was done by combining an electrical current with the strong magnetic field of a clinical MRI scanner. The Local Frequency Estimation method was used to assess the real value of the shear modulus of tested phantoms from Lorentz force induced motion. Finite elements modeling of reported experiments showed a consistent behavior but featured wavelengths larger than measured ones. Results suggest the feasibility of a magnetic resonance elastography technique based on the Lorentz force to produce an shear wave source.

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