Observations of wave velocity and attenuation in two‐phase media

Geophysics ◽  
1986 ◽  
Vol 51 (12) ◽  
pp. 2193-2199 ◽  
Author(s):  
G. W. Purnell
Keyword(s):  
Physical Model ◽  
Wave Velocity ◽  
Wave Attenuation ◽  
P Wave ◽  
Rubber Matrix ◽  
Two Phase ◽  
P Wave Velocity ◽  
Porosity And Permeability ◽  
Dispersion And Attenuation ◽  
Scattering Losses

The velocity and attenuation of a wave transmitted through a two‐phase material are functions of the material’s composition. In physical model experiments, I used suspensions of grains in a silicone rubber matrix to reduce or avoid uncertainties about framework elastic constants, porosity, and permeability that result from using fluid‐saturated grain frameworks. I varied the composition to produce materials that are useful in physical seismic modeling. In the tested suspensions, ultrasonic P-wave velocity, velocity dispersion, and attenuation all increase with grain concentration and frequency. I compared seven published mathematical models for wave propagation in two‐phase media. One given by Mehta most closely agrees with the P-wave velocities I observed. The agreement is sufficiently close to merit use of Mehta’s model in the design of physical model materials. The observed P-wave attenuation generally increases approximately linearly with frequency. This approximate linearity leads to reliable constant-Q estimates, ranging from 187 to 16 for grain concentrations from 0 to 0.49. I conclude that relative motion between the grains and the rubber matrix contributes most of the observed attenuation at lower concentrations, whereas scattering losses become much more important at higher concentrations and frequencies.

scholarly journals 2-D multiparameter viscoelastic shallow-seismic full-waveform inversion: reconstruction tests and first field-data application

2020 ◽  
Vol 222 (1) ◽  
pp. 560-571
Author(s):  
Lingli Gao ◽  
Yudi Pan ◽  
Thomas Bohlen
Keyword(s):  
Wave Velocity ◽  
Wave Attenuation ◽  
Waveform Inversion ◽  
P Wave ◽  
S Wave ◽  
Velocity Models ◽  
Full Waveform ◽  
Shallow Seismic ◽  
P Wave Velocity ◽  
Data Application

SUMMARY 2-D full-waveform inversion (FWI) of shallow-seismic wavefields has recently become a novel way to reconstruct S-wave velocity models of the shallow subsurface with high vertical and lateral resolution. In most applications, seismic wave attenuation is ignored or considered as a passive modelling parameter only. In this study, we explore the feasibility and performance of multiparameter viscoelastic 2-D FWI in which seismic velocities and attenuation of P and S waves, respectively, and mass density are inverted simultaneously. Synthetic reconstruction experiments reveal that multiple crosstalks between all viscoelastic material parameters may occur. The reconstruction of S-wave velocity is always robust and of high quality. The parameters P-wave velocity and density exhibit weaker sensitivity and can be reconstructed more reliably by multiparameter viscoelastic FWI. Anomalies in S-wave attenuation can be recovered but with limited resolution. In a field-data application, a small-scale refilled trench is nicely delineated as a low P- and S-wave velocity anomaly. The reconstruction of P-wave velocity is improved by the simultaneous inversion of attenuation. The reconstructed S-wave attenuation reveals higher attenuation in the shallow weathering zone and weaker attenuation below. The variations in the reconstructed P- and S-wave velocity models are consistent with the reflectivity observed in a ground penetrating radar (GPR) profile.

Frequency-dependent P-wave anisotropy due to scattering in rocks with aligned fractures

Geophysics ◽  
2020 ◽  
Vol 85 (2) ◽  
pp. MR97-MR105 ◽  
Author(s):  
Junxin Guo ◽  
Boris Gurevich ◽  
Da Shuai
Keyword(s):  
Wave Velocity ◽  
Wave Scattering ◽  
Wave Attenuation ◽  
P Wave ◽  
Frequency Dependent ◽  
Velocity Anisotropy ◽  
P Wave Velocity ◽  
Anisotropy Parameters ◽  
Scattering Anisotropy ◽  
Attenuation Anisotropy

Frequency-dependent P-wave anisotropy due to scattering often occurs in fractured formations, whereas the corresponding theoretical study is lacking. Hence, based on a newly developed P-wave scattering model, we have studied the frequency-dependent P-wave scattering anisotropy in rocks with aligned fractures. To describe P-wave scattering anisotropy, we develop the corresponding anisotropy parameters similar to those for elastic anisotropy. Our results indicate that the P-wave velocity anisotropy parameters [Formula: see text] and [Formula: see text] do not change with frequency monotonically, which is different from that caused by wave-induced fluid flow. Fluid saturation in fractures can greatly decrease the P-wave velocity anisotropy, whose effects depend on the ratio of the fluid bulk modulus to the fracture aspect ratio. The P-wave exhibits elliptical anisotropy for the dry fracture case at low frequencies, but anelliptical anisotropy for the case with fluid-filled fractures. The P-wave attenuation anisotropy parameters [Formula: see text] and [Formula: see text] vanish in the low- and high-frequency limits but reach their maxima at the characteristic frequency when the P-wavelength is close to the fracture length. The influence of fluid on the P-wave attenuation anisotropy is similar to that on the velocity anisotropy. To further analyze frequency-dependent P-wave scattering anisotropy, theoretical predictions are compared with experimental results, which indicate reasonable agreement between them.

Effects of Exciting Frequency and Grain Size in Ultrasonic NDE of Concrete

1999 ◽  
Author(s):  
J. W. Ju ◽  
L. Weng ◽  
Y. Liu
Keyword(s):  
Grain Size ◽  
Frequency Shift ◽  
Wave Velocity ◽  
Wave Attenuation ◽  
Ultrasonic Waves ◽  
P Wave ◽  
Peak Amplitude ◽  
P Wave Velocity ◽  
Exciting Frequency ◽  
Ultrasonic Nde

Abstract This investigation focuses on experimental study of the effects of the exciting frequency and the grain (aggregate) size upon the ultrasonic P-wave velocity and the wave attenuation characteristics such as the peak-to-peak amplitude and dominant frequency-shift when performing the ultrasonic nondestructive evaluation of concrete. Furthermore, this presentation studies the extent of wave attenuation as influenced by different grain (aggregate) sizes with or without the well-distributed embedded micro-damage under different exciting frequencies. The damage index or damage assessment of concrete is certainly linked to the reduction in the ultrasonic P-wave velocity, the reduction in the peak-to-peak amplitude response, and the increase in frequency-shift through a damaged concrete specimen. In this study, we cast concrete cylinders with five different aggregate sizes in our laboratory, including some mortar samples without coarse aggregates. In addition, small styrofoam particles are mixed into the control samples in all batches to simulate microvoids in damaged concrete. The exciting frequency ranges from a low frequency at 50 kHz to a demium frequency at 300 to 400 kHz to demonstrate the frequency effect upon the ultrasonic NDE of concrete for each batch. The grain size also affects the concrete microstructure and influences the propagation and attenuation of ultrasonic waves through undamaged and damaged concrete specimens.

scholarly journals Wave Properties of Gas-Hydrate Bearing Sediments Based on Poroelasticity

2021 ◽  
Vol 9 ◽  
Author(s):  
Wei Wang ◽  
Jing Ba ◽  
José M. Carcione ◽  
Xu Liu ◽  
Lin Zhang
Keyword(s):  
Wave Velocity ◽  
Pore Space ◽  
Laboratory Data ◽  
Double Porosity ◽  
P Wave ◽  
Sonic Log ◽  
P Wave Velocity ◽  
Hydrate Bearing Sediments ◽  
Wave Induced ◽  
Dispersion And Attenuation

Natural gas hydrates have the properties of ice with a microporous structure and its concentration in sediments highly affects the wave velocity and attenuation. Previous studies have performed investigations based on the measurements of laboratory data, sonic-log data, and field data, whereas the variation trend of wave dissipation with increasing hydrate concentration at different frequencies is still unclear. We consider two different models to study this problem, both based on the Biot-Rayleigh double-porosity theory. In the first model, hydrate is part of the pore infill, unbonded from the grains, and brine saturates the remaining pore space. In the second model, hydrate forms a second skeleton and cements the grains. We obtain the P-wave velocity dispersion and attenuation as a function of the inclusion radius, porosity, and hydrate content. The analysis shows that the predictions of both models agree with the experimental data. At sonic log frequencies, the second model predicts much more attenuation, due to wave-induced local fluid flow (mesoscopic loss), and the behavior is such that below a given hydrate concentration the dissipation increases and then decreases beyond that concentration.

High-frequency seismic response during permeability reduction due to biopolymer clogging in unconsolidated porous media

Geophysics ◽  
2013 ◽  
Vol 78 (6) ◽  
pp. EN117-EN127 ◽  
Author(s):  
Tae-Hyuk Kwon ◽  
Jonathan B. Ajo-Franklin
Keyword(s):  
Porous Media ◽  
Seismic Response ◽  
Wave Velocity ◽  
Wave Attenuation ◽  
P Wave ◽  
Ultrasonic Frequency ◽  
Permeability Reduction ◽  
Frequency Range ◽  
P Wave Velocity

The accumulation of biopolymers in porous media, produced by stimulating either indigenous bacteria or artificially introduced microbes, readily blocks pore throats and can effectively reduce bulk permeability. Such a microbial clogging treatment can be used for selective plugging of permeable zones in reservoirs and is considered a potentially promising approach to enhance sweep efficiency for microbial enhanced oil recovery (MEOR). Monitoring in situ microbial growth, biopolymer formation, and permeability reduction in the reservoir is critical for successful application of this MEOR approach. We examined the feasibility of using seismic signatures (P-wave velocity and attenuation) for monitoring the in situ accumulation of insoluble biopolymers in unconsolidated sediments. Column experiments, which involved stimulating the sucrose metabolism of Leuconostoc mesenteroides and production of the biopolymer dextran, were performed while monitoring changes in permeability and seismic response using the ultrasonic pulse transmission method. We observed that L. mesenteroides produced a viscous biopolymer in sucrose-rich media. Accumulated dextran, occupying 4%–6% pore volume after [Formula: see text] days of growth, reduced permeability more than one order of magnitude. A negligible change in P-wave velocity was observed, indicating no or minimal change in compressive stiffness of the unconsolidated sediment during biopolymer formation. The amplitude of the P-wave signals decreased [Formula: see text] after [Formula: see text] days of biopolymer production; spectral ratio analysis in the 0.4–0.8-MHz band showed an approximate 30%–50% increase in P-wave attenuation ([Formula: see text]) due to biopolymer production. A flow-induced loss mechanism related to the combined grain/biopolymer structure appeared to be the most plausible mechanism for causing the observed increase in P-wave attenuation in the ultrasonic frequency range. Because permeability reduction is also closely linked to biopolymer volume, P-wave attenuation in the ultrasonic frequency range appears to be an effective indicator for monitoring in situ biopolymer accumulation and permeability reduction and could provide a useful proxy for regions with altered transport properties.

scholarly journals Geophysical and analytical determination of overstressed zones in exploited coal seam: a case study

2021 ◽  
Author(s):  
Dariusz Chlebowski ◽  
Zbigniew Burtan
Keyword(s):  
Coal Seam ◽  
Wave Velocity ◽  
Seismic Tomography ◽  
Analytical Modeling ◽  
Coal Mines ◽  
Vertical Stress ◽  
P Wave ◽  
Rockburst Hazard ◽  
State Of Stress ◽  
P Wave Velocity

AbstractA variety of geophysical methods and analytical modeling are applied to determine the rockburst hazard in Polish coal mines. In particularly unfavorable local conditions, seismic profiling, active/passive seismic tomography, as well as analytical state of stress calculating methods are recommended. They are helpful in verifying the reliability of rockburst hazard forecasts. In the article, the combined analysis of the state of stress determined by active seismic tomography and analytical modeling was conducted taking into account the relationship between the location of stress concentration zones and the level of rockburst hazard. A longwall panel in the coal seam 501 at a depth of ca.700 m in one of the hard coal mines operating in the Upper Silesian Coal Basin was a subject of the analysis. The seismic tomography was applied for the reconstruction of P-wave velocity fields. The analytical modeling was used to calculate the vertical stress states basing on classical solutions offered by rock mechanics. The variability of the P-wave velocity field and location of seismic anomaly in the coal seam in relation to the calculated vertical stress field arising in the mined coal seam served to assess of rockburst hazard. The applied methods partially proved their adequacy in practical applications, providing valuable information on the design and performance of mining operations.

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