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.

A theory of compressional wave attenuation in noncohesive sediments

Geophysics ◽  
1985 ◽  
Vol 50 (8) ◽  
pp. 1311-1317 ◽  
Author(s):  
C. McCann ◽  
D. M. McCann
Keyword(s):  
Wave Attenuation ◽  
Compressional Wave ◽  
Solid Particles ◽  
Biot’S Theory ◽  
Attenuation Coefficients ◽  
Low Frequencies ◽  
Biot's Theory ◽  
Compressional Waves ◽  
High Frequencies ◽  
Water Saturated

Published reviews indicate that attenuation coefficients of compressional waves in noncohesive, water‐saturated sediments vary linearly with frequency. Biot’s theory, which accounts for attenuation in terms of the viscous interaction between the solid particles and pore fluid, predicts in its presently published form variation proportional to [Formula: see text] at low frequencies and [Formula: see text] at high frequencies. A modification of Biot’s theory which incorporates a distribution of pore sizes is presented and shown to give excellent agreement with new and published attenuation data in the frequency range 10 kHz to 2.25 MHz. In particular, a linear variation of attenuation with frequency is predicted in that range.

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.

Pore fluid effects on S-wave attenuation caused by wave-induced fluid flow

Geophysics ◽  
2012 ◽  
Vol 77 (3) ◽  
pp. L13-L23 ◽  
Author(s):  
Beatriz Quintal ◽  
Holger Steeb ◽  
Marcel Frehner ◽  
Stefan M. Schmalholz ◽  
Erik H. Saenger
Keyword(s):  
Fluid Flow ◽  
Wave Attenuation ◽  
Pore Space ◽  
Seismic Attenuation ◽  
P Wave ◽  
S Wave ◽  
Hydrocarbon Reservoir ◽  
Saturated Media ◽  
Water Saturated ◽  
Wave Induced

We studied seismic attenuation of P- and S-waves caused by the physical mechanism of wave-induced fluid flow at the mesoscopic scale. Stress relaxation experiments were numerically simulated by solving Biot’s equations for consolidation of 2D poroelastic media with finite-element modeling. The experiments yielded time-dependent stress-strain relations that were used to calculate the complex moduli from which frequency-dependent attenuation was determined. Our model consisted of periodically distributed circular or elliptical heterogeneities with much lower porosity and permeability than the background media, which contained 80% of the total pore space of the media. This model can represent a hydrocarbon reservoir, where the porous background is fully saturated with oil or gas and the low-porosity regions are always saturated with water. Three different saturation scenarios were considered: oil-saturated (80% oil, 20% water), gas-saturated (80% gas, 20% water), and fully water-saturated media. Varying the dry bulk and shear moduli in the background and in the heterogeneities, a consistent tendency was observed in the relative behavior of the S-wave attenuation among the different saturation scenarios. First, in the gas-saturated media the S-wave attenuation was very low and much lower than in the oil-saturated or in the fully water-saturated media. Second, at low frequencies the S-wave attenuation was significantly higher in the oil-saturated media than in the fully water-saturated media. The P-wave attenuation exhibited a more variable relative behavior among the different saturation degrees. Based on the mechanism of wave-induced fluid flow and on our numerical results, we suggest that S-wave attenuation could be used as an indicator of fluid content in a reservoir. Additionally, we observed that impermeable barriers in the background can cause a significant increase in S-wave attenuation. This suggests that S-wave attenuation could also be an indicator of permeability changes in a reservoir due to, for example, fracturing operations.

Spatio-temporal variation of Anaelastic and Scattering Seismic Attenuation during the 2016-2017 Central Italy Seismic Sequence

2021 ◽  
Author(s):  
Simona Gabrielli ◽  
Aybige Akinci ◽  
Ferdinando Napolitano ◽  
Luca De Siena ◽  
Edoardo Del Pezzo ◽  
...  
Keyword(s):  
Wave Attenuation ◽  
Central Italy ◽  
Temporal Variations ◽  
Seismic Attenuation ◽  
Coda Wave ◽  
Seismic Sequence ◽  
Rock Fracturing ◽  
Low Frequencies ◽  
Main Shocks ◽  
Stress Changes

<p>Between August and October 2016, the Central Apennines in Italy have been struck by a long-lasting seismic sequence, known as the Amatrice (Mw 6.0) - Visso (Mw 5.9) - Norcia (Mw 6.5) sequence. The cascading ruptures occurred in this sequence have been considered connected to the fluid migration in the fault network, as suggested by previous studies. The behaviour of fluids in the crust is crucial to understand earthquakes occurrence and stress changes since fluids reduce fault stability. It has long been understood that the seismic attenuation is strongly controlled by the structural irregularity and heterogeneities; micro-cracks and cavities, either fluid-filled or dry, temperature and pressure variations cause a decrease in seismic wave amplitude and pulse broadening. Hence seismic attenuation imagining is a powerful tool to be a relevant provenance of information about the influence and abundance of fluids in a seismic sequence.</p><p>The aim of this work is to separate scattering and absorption contributions to the total attenuation of coda waves and to provide their spatial and temporal variations at different frequency bands of these quantities using two datasets: the first one comprising 592 earthquakes occurred before the sequence (March 2013-August 2016) and the second one comprising 763 events (ML > 2.8) from the Amatrice-Visso-Norcia sequence. Scattering and absorption have been measured through peak-delay and coda-wave attenuation parameters (the latter inverted using frequency-dependent sensitivity kernels).</p><p>The preliminary results show a clear difference between the pre-sequence and sequence images, mainly at low frequencies (1.5 Hz), where we can define a spatial increase of scattering with time attributed to rock fracturing and fluid circulation. The coda attenuation tomography also demonstrates a clear variation between the pre-sequence and the sequence over series of time windows being before and after the largest main shocks of the seismic sequence, with an increase of the attenuation in space with decreasing time. The peak delay indicates a high scattering area corresponding to the Gran Sasso massif and L’Aquila zone, where an important seismic sequence (Mw 6.3) occurred in 2009.</p>

scholarly journals Modeling nonlinear compressional waves in marine sediments

2009 ◽  
Vol 16 (1) ◽  
pp. 151-157 ◽  
Author(s):  
B. E. McDonald
Keyword(s):  
Marine Sediments ◽  
Plane Waves ◽  
High Stress ◽  
Nonlinear Behavior ◽  
Analytic Solutions ◽  
Compressional Waves ◽  
Series Of Experiments ◽  
Model Equations ◽  
The Time Domain ◽  
Water Saturated

Abstract. A computational model is presented which will help guide and interpret an upcoming series of experiments on nonlinear compressional waves in marine sediments. The model includes propagation physics of nonlinear acoustics augmented with granular Hertzian stress of order 3/2 in the strain rate. The model is a variant of the time domain NPE (McDonald and Kuperman, 1987) supplemented with a causal algorithm for frequency-linear attenuation. When attenuation is absent, the model equations are used to construct analytic solutions for nonlinear plane waves. The results imply that Hertzian stress causes a unique nonlinear behavior near zero stress. A fluid, in contrast, exhibits nonlinear behavior under high stress. A numerical experiment with nominal values for attenuation coefficient implies that in a water saturated Hertzian chain, the nonlinearity near zero stress may be experimentally observable.

Experimental measurements of solitary wave attenuation over shallow and intermediate submerged canopy

2016 ◽  
Vol 30 (3) ◽  
pp. 375-392 ◽  
Author(s):  
Qian Wang ◽  
Xiao-yu Guo ◽  
Ben-long Wang ◽  
Yong-liu Fang ◽  
Hua Liu
Keyword(s):  
Solitary Wave ◽  
Wave Attenuation ◽  
Experimental Measurements

Laboratory experiments on compressional ultrasonic wave attenuation in partially frozen brines

Geophysics ◽  
2008 ◽  
Vol 73 (2) ◽  
pp. N9-N18 ◽  
Author(s):  
Jun Matsushima ◽  
Makoto Suzuki ◽  
Yoshibumi Kato ◽  
Takao Nibe ◽  
Shuichi Rokugawa
Keyword(s):  
Ultrasonic Wave ◽  
Laboratory Experiments ◽  
Wave Attenuation ◽  
Ultrasonic Attenuation ◽  
Liquid System ◽  
Seismic Attenuation ◽  
Ultrasonic Waves ◽  
Frequency Range ◽  
Pore Microstructure ◽  
Solid Liquid

Often, the loss mechanisms responsible for seismic attenuation are unclear and controversial. We used partially frozen brine as a solid-liquid coexistence system to investigate attenuation phenomena. Ultrasonic wave-transmission measurements on an ice-brine coexisting system were conducted to examine the influence of unfrozen brine in the pore microstructure on ultrasonic waves. We observed the variations of a 150–1000 kHz wave transmitted through a liquid system to a solid-liquid coexistence system, changing its temperature from [Formula: see text] to –[Formula: see text]. We quantitatively estimated attenuation in a frequency range of [Formula: see text] by considering different distances between the source and receiver transducers. We also estimated the total amount of frozen brine at each temperature by using the pulsed nuclear magnetic resonance (NMR) technique and related those results to attenuation results. The waveform analyses indicate that ultrasonic attenuation in an ice-brine coexisting system reaches its peak at [Formula: see text], at which the ratio of the liquid phase to the total volume in an ice-brine coexisting system is maximal. Finally, we obtained a highly positive correlation between the attenuation of ultrasonic waves and the total amount of unfrozen brine. Thus, laboratory experiments demonstrate that ultrasonic waves within this frequency range are affected significantly by the existence of unfrozen brine in the pore microstructure.

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