scholarly journals Research on the Attenuation Characteristics of AE Signals of Marble and Granite Stone

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Haiyan Wang ◽  
Ji Ma ◽  
Feng Du ◽  
Gongda Wang ◽  
Quan Zhang ◽  
...  
Keyword(s):  
Elastic Wave ◽  
Large Scale ◽  
Wave Attenuation ◽  
Propagation Distance ◽  
Internal Force ◽  
Residual Energy ◽  
P Wave ◽  
S Wave ◽  
Attenuation Characteristics ◽  
Ae Signals

When an underground rock is deformed or fractured by an external or internal force, the energy will be released in the form of an elastic wave, which is known as the acoustic emission (AE) phenomenon. Extracting useful information from complex AE signals for the early warning of fracture characteristics and the damage monitoring of rock materials is of great significance for the prevention and control of dynamic disasters in coal mines. In this work, by taking rod-shaped rocks and plate-shaped rocks with different lithologies as the research objects, the elastic wave propagation characteristics of the rod-shaped rocks and plate-shaped rocks were studied by a self-constructed experimental platform. The results demonstrate that the elastic wave attenuation of the rod-shaped marble was the fastest, and the elastic wave attenuation characteristics of the three groups of rod-shaped granite were similar. The attenuation of the P-wave preceded that of the S-wave. With the increase in the propagation distance, the amplitude of the large-scale plate-shaped rock showed an approximate exponential attenuation characteristic. The elastic wave attenuation of the plate-shaped granite in the 0° direction was stronger than that of the plate-shaped marble, and it was weaker than that of the plate-shaped marble in the 45° and 90° directions. The energy changes in marble were more severe than those in granite. The main dominant energy of the AE signals of experimental rock was concentrated in the range of 0–176.78 kHz, and part of the residual energy was located in the high-frequency band of 282.25–352.56 kHz.

The Distance Attenuation of Acoustic Emission Signals in Turbine Runners

2011 ◽  
Vol 103 ◽  
pp. 262-267 ◽  
Author(s):  
Xiang Hong Wang ◽  
Hong Wei Hu ◽  
Yi Min Shao ◽  
Jun Qing Fu
Keyword(s):  
Acoustic Emission ◽  
Large Scale ◽  
Propagation Distance ◽  
Francis Turbine ◽  
Power Stations ◽  
Turbine Runner ◽  
Series Of Experiments ◽  
Safety Operation ◽  
Attenuation Characteristics ◽  
Ae Signals

Initiation of blade cracks in Francis turbine runners endangers the safety operation of power stations, so it is crucial to detect the cracks before emergencies happen. This article is a preliminary study of applying acoustic emission (AE) technique to detecting the large-scale turbine runners. A series of experiments had been carried out on an HLA286a-LJ-800 Francis turbine runner. The attenuation characteristics due to propagation distance were studied. From the tests, it is concluded that AE signals are detectable after propagating at a distance of 6 m. The propagation distance is the major factor of attenuation. As a result, although attenuation is incurred, it is feasible to apply AE technique to monitoring crack signals in runners. However, it depends on the understanding of background noise and extraction of right signals.

P- and S-wave attenuation logs from monopole sonic data

Geophysics ◽  
2000 ◽  
Vol 65 (3) ◽  
pp. 755-765 ◽  
Author(s):  
Xinhua Sun ◽  
Xiaoming Tang ◽  
C. H. (Arthur) Cheng ◽  
L. Neil Frazer
Keyword(s):  
Wave Attenuation ◽  
Fluid Velocity ◽  
P Wave ◽  
Reservoir Rock ◽  
Rock Properties ◽  
S Wave ◽  
Intrinsic Attenuation ◽  
Modified Method ◽  
Receiver Array ◽  
Attenuation Profiles

In this paper, a modification of an existing method for estimating relative P-wave attenuation is proposed. By generating synthetic waveforms without attenuation, the variation of geometrical spreading related to changes in formation properties with depth can be accounted for. With the modified method, reliable P- and S-wave attenuation logs can be extracted from monopole array acoustic waveform log data. Synthetic tests show that the P- and S-wave attenuation values estimated from synthetic waveforms agree well with their respective model values. In‐situ P- and S-wave attenuation profiles provide valuable information about reservoir rock properties. Field data processing results show that this method gives robust estimates of intrinsic attenuation. The attenuation profiles calculated independently from each waveform of an eight‐receiver array are consistent with one another. In fast formations where S-wave velocity exceeds the borehole fluid velocity, both P-wave attenuation ([Formula: see text]) and S-wave attenuation ([Formula: see text]) profiles can be obtained. P- and S-wave attenuation profiles and their comparisons are presented for three reservoirs. Their correlations with formation lithology, permeability, and fractures are also presented.

scholarly journals A method of geo-acoustic parameter inversion in shallow sea by the Bayesian theory and the acoustic pressure field

2019 ◽  
Vol 283 ◽  
pp. 06003
Author(s):  
Guangxue Zheng ◽  
Hanhao Zhu ◽  
Jun Zhu
Keyword(s):  
Sound Pressure ◽  
Pressure Field ◽  
Wave Attenuation ◽  
Acoustic Parameter ◽  
Bayesian Theory ◽  
P Wave ◽  
Shallow Sea ◽  
S Wave ◽  
Wave Velocities ◽  
Parameter Inversion

A method of geo-acoustic parameter inversion based on the Bayesian theory is proposed for the acquisition of acoustic parameters in shallow sea with the elastic seabed. Firstly, the theoretical prediction value of the sound pressure field is calculated by the fast field method (FFM). According to the Bayesian theory, we establish the misfit function between the measured sound pressure field and the theoretical pressure field. It is under the assumption of Gaussian data errors which are in line with the likelihood function. Finally, the posterior probability density (PPD) of parameters is given as the result of inversion. Our research is conducted in the light of Metropolis sample rules. Apart from numerical simulations, a scaled model experiment has been taken in the laboratory tank. The results of numerical simulations and tank experiments show that sound pressure field calculated by the result of inversion is consistent with the measured sound pressure field. Besides, s-wave velocities, p-wave velocities and seafloor density have fewer uncertainties and are more sensitive to complex sound pressure than s-wave attenuation and p-wave attenuation. The received signals calculated by inversion results are keeping with received signals in the experiment which verify the effectiveness of this method.

Rock-physics modeling of ultrasonic P- and S-wave attenuation in partially frozen brine and unconsolidated sand systems and comparison with laboratory measurements

Geophysics ◽  
2019 ◽  
Vol 84 (5) ◽  
pp. MR153-MR171 ◽  
Author(s):  
Linsen Zhan ◽  
Jun Matsushima
Keyword(s):  
Ultrasonic Wave ◽  
Wave Attenuation ◽  
Freezing Point ◽  
Rock Physics ◽  
Ultrasonic Waves ◽  
P Wave ◽  
Dominant Factor ◽  
S Wave ◽  
High Attenuation ◽  
Unconsolidated Sand

The nonintuitive observation of the simultaneous high velocity and high attenuation of ultrasonic waves near the freezing point of brine was previously measured in partially frozen systems. However, previous studies could not fully elucidate the attenuation variation of ultrasonic wave propagation in a partially frozen system. We have investigated the potential attenuation mechanisms responsible for previously obtained laboratory results by modeling ultrasonic wave transmission in two different partially frozen systems: partially frozen brine (two phases composed of ice and unfrozen brine) and unconsolidated sand (three phases composed of ice, unfrozen brine, and sand). We adopted two different rock-physics models: an effective medium model for partially frozen brine and a three-phase extension of the Biot model for partially frozen unconsolidated sand. For partially frozen brine, our rock-physics study indicated that squirt flow caused by unfrozen brine inclusions in porous ice could be responsible for high P-wave attenuation around the freezing point. Decreasing P-wave attenuation below the freezing point can be explained by the gradual decrease of squirt flow due to the gradual depletion of unfrozen brine. For partially frozen unconsolidated sand, our rock-physics study implied that squirt flow between ice grains is a dominant factor for P-wave attenuation around the freezing point. With decreasing temperature lower than the freezing point, the friction between ice and sand grains becomes more dominant for P-wave attenuation because the decreasing amount of unfrozen brine reduces squirt flow between ice grains, whereas the generation of ice increases the friction. The increasing friction between ice and sand grains caused by ice formation is possibly responsible for increasing the S-wave attenuation at decreasing temperatures. Then, further generation of ice with further cooling reduces the elastic contrast between ice and sand grains, hindering their relative motion; thus, reducing the P- and S-wave attenuation.

Seismic wave attenuation and modulus dispersion in sandstones

Geophysics ◽  
2016 ◽  
Vol 81 (3) ◽  
pp. D211-D231 ◽  
Author(s):  
James W. Spencer ◽  
Jacob Shine
Keyword(s):  
Wave Attenuation ◽  
High Viscosity ◽  
P Wave ◽  
S Wave ◽  
Local Flow ◽  
Shear Moduli ◽  
Low Viscosity ◽  
Confining Pressures ◽  
Wave Induced ◽  
Dispersion And Attenuation

We have conducted laboratory experiments over the 1–200 Hz band to examine the effects of viscosity and permeability on modulus dispersion and attenuation in sandstones and also to examine the effects of partial gas or oil saturation on velocities and attenuations. Our results have indicated that bulk modulus values with low-viscosity fluids are close to the values predicted using Gassmann’s first equation, but, with increasing frequency and viscosity, the bulk and shear moduli progressively deviate from the values predicted by Gassmann’s equations. The shear moduli increase up to 1 GPa (or approximately 10%) with high-viscosity fluids. The P- and S-wave attenuations ([Formula: see text] and [Formula: see text]) and modulus dispersion with different fluids are indicative of stress relaxations that to the first order are scaling with frequency times viscosity. By fitting Cole-Cole distributions to the scaled modulus and attenuation data, we have found that there are similar P-wave, shear and bulk relaxations, and attenuation peaks in each of the five sandstones studied. The modulus defects range from 11% to 15% in Berea sandstone to 16% to 26% in the other sandstones, but these would be reduced at higher confining pressures. The relaxations shift to lower frequencies as the viscosity increased, but they do not show the dependence on permeability predicted by mesoscopic wave-induced fluid flow (WIFF) theories. Results from other experiments having patchy saturation with liquid [Formula: see text] and high-modulus fluids are consistent with mesoscopic WIFF theories. We have concluded that the modulus dispersion and attenuations ([Formula: see text] and [Formula: see text]) in saturated sandstones are caused by a pore-scale, local-flow mechanism operating near grain contacts.

The effects of pore‐fluid salinity on ultrasonic wave propagation in sandstones

Geophysics ◽  
1998 ◽  
Vol 63 (3) ◽  
pp. 928-934 ◽  
Author(s):  
Simon M. Jones ◽  
Clive McCann ◽  
Timothy R. Astin ◽  
Jeremy Sothcott
Keyword(s):  
Wave Propagation ◽  
Ultrasonic Wave ◽  
Wave Attenuation ◽  
Clay Content ◽  
Seismic Wave Propagation ◽  
Ultrasonic Pulse ◽  
Pore Fluid ◽  
P Wave ◽  
S Wave ◽  
Shear Moduli

Petrophysical interpretation of increasingly refined seismic data from subsurface formations requires a more fundamental understanding of seismic wave propagation in sedimentary rocks. We consider the variation of ultrasonic wave velocity and attenuation in sandstones with pore‐fluid salinity and show that wave propagation is modified in proportion to the clay content of the rock and the salinity of the pore fluid. Using an ultrasonic pulse reflection technique (590–890 kHz), we have measured the P-wave and S-wave velocities and attenuations of 15 saturated sandstones with variable effective pressure (5–60 MPa) and pore‐fluid salinity (0.0–3.4 M). In clean sandstones, there was close agreement between experimental and Biot model values of [Formula: see text], but they diverged progressively in rocks containing more than 5% clay. However, this effect is small: [Formula: see text] changed by only 0.6% per molar change in salinity for a rock with a clay content of 29%. The variation of [Formula: see text] with brine molarity exhibited Biot behavior in some samples but not in others; there was no obvious relationship with clay content. P-wave attenuation was independent of pore‐fluid salinity, while S-wave attenuation was weakly dependent. The velocity data suggest the frame bulk and shear moduli of sandstones are altered by changes in the pore‐fluid salinity. One possible mechanism is the formation damage caused by clay swelling and migration of fines in low‐molarity electrolytes. The absence of variation between the attenuation in water‐saturated and brine‐saturated samples indicates the attenuation mechanism is relatively unaffected by changes in the frame moduli.

Converted-wave model building and imaging based on common-focus-point methodology

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. U139-U149
Author(s):  
Hongwei Liu ◽  
Mustafa Naser Al-Ali ◽  
Yi Luo
Keyword(s):  
Elastic Wave ◽  
Wave Velocity ◽  
Seismic Data ◽  
Model Building ◽  
P Wave ◽  
Rock Properties ◽  
S Wave ◽  
Converted Wave ◽  
Seismic Images ◽  
Focus Point

Seismic images can be viewed as photographs for underground rocks. These images can be generated from different reflections of elastic waves with different rock properties. Although the dominant seismic data processing is still based on the acoustic wave assumption, elastic wave processing and imaging have become increasingly popular in recent years. A major challenge in elastic wave processing is shear-wave (S-wave) velocity model building. For this reason, we have developed a sequence of procedures for estimating seismic S-wave velocities and the subsequent generation of seismic images using converted waves. We have two main essential new supporting techniques. The first technique is the decoupling of the S-wave information by generating common-focus-point gathers via application of the compressional-wave (P-wave) velocity on the converted seismic data. The second technique is to assume one common VP/ VS ratio to approximate two types of ratios, namely, the ratio of the average earth layer velocity and the ratio of the stacking velocity. The benefit is that we reduce two unknown ratios into one, so it can be easily scanned and picked in practice. The PS-wave images produced by this technology could be aligned with the PP-wave images such that both can be produced in the same coordinate system. The registration between the PP and PS images provides cross-validation of the migrated structures and a better estimation of underground rock and fluid properties. The S-wave velocity, computed from the picked optimal ratio, can be used not only for generating the PS-wave images, but also to ensure well registration between the converted-wave and P-wave images.

Theory of scattered P- and S-wave energy in a random isotropic scattering medium

1993 ◽  
Vol 83 (4) ◽  
pp. 1264-1276 ◽  
Author(s):  
Yuehua Zeng
Keyword(s):  
Elastic Wave ◽  
Wave Field ◽  
Wave Energy ◽  
Wave Scattering ◽  
Energy Equation ◽  
P Wave ◽  
Isotropic Scattering ◽  
Scattering Medium ◽  
S Wave ◽  
Elastic Wave Energy

Abstract A new theory is presented to study the scattered elastic wave energy propagation in a random isotropic scattering medium. It is based on a scattered elastic wave energy equation that extends the work of Zeng et al. (1991) on multiple scattering by considering S to P and P to S wave scattering conversions. We obtain a complete solution of the scattered elastic wave energy equation by solving the equation in the frequency/wave-number domain. Using a discrete wave-number sum technique combined with a modified repeated averaging and the FFT method, we compute numerically the complete solution. By considering that the scattering conversion from P- to S-wave energy is about (α/β)4 times greater than that from S to P waves (Aki, 1992), we found that the P-wave scattering field was converted quickly to the S-wave scattering field, leading to the conclusion that coda waves generated from both P- and S-wave sources are actually dominated by scattered S waves. We also compared our result with that obtained under the acoustic wave assumption. The acoustic wave assumption for seismic coda works quite well for the scattered S-wave field but fails for the scattered P-wave field. Our scattered elastic wave energy equation provides a theoretical foundation for studying the scattered wave field generated by a P-wave source such as an explosion. The scattered elastic wave energy equation can be easily generalized to an inhomogeneous random scattering medium by considering variable scattering and absorption coefficients and elastic wave velocities in the earth.

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