A direct comparison between vibrational resonance and pulse transmission data for assessment of seismic attenuation in rock

Geophysics ◽  
1990 ◽  
Vol 55 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Dane P. Blair
Keyword(s):  
Elastic Scattering ◽  
Wave Attenuation ◽  
Seismic Attenuation ◽  
Experimental Results ◽  
P Wave ◽  
Whole Body ◽  
Frequency Range ◽  
Vibrational Resonance ◽  
Fine Grained ◽  
Pulse Transmission

For the same volume of rock, I compare the attenuation obtained by seismic pulse transmission over the frequency range 1–150 kHz with that obtained by vibrational resonance techniques over the frequency range 1–50 kHz. The initial studies were performed on a rectangular block of medium‐grained granite which was large enough to permit the installation of a seismic pulse transmission array over a 1.8 m path length, yet small enough to permit whole‐body resonance. A Q of 82, for the P wave, was derived from the vibrational resonance results, whereas a Q of 15 was derived from the pulse transmission results. In light of models proposed for the viscoelastic, geometric, and elastic scattering attenuation mechanisms, the experimental results suggest that this large discrepancy in Q values is due to elastic scattering by grain clusters (rather than individual grains) within the granite. Scattering is significant in the high‐frequency pulse transmission tests, but is considered insignificant in the lower frequency resonance tests. Furthermore, this scattering is represented approximately by a constant-Q loss mechanism, which makes it difficult to separate unambiguously elastic scattering and viscoelastic losses. Subsequent studies performed on a large block of fine‐grained norite yield a resonance Q of 89 and a pulse Q of approximately 102 and suggest a negligible scattering loss for this material. The experimental results for the norite imply that the constant-Q theory of seismic pulse attenuation provides a reasonable description of wave attenuation in a dry, fine‐grained crystalline rock over the frequency range 1–150 kHz.

HOW GAS HYDRATE SATURATION AND MORPHOLOGY CONTROL SEISMIC ATTENUATION: A CASE STUDY FROM THE SOUTH HYDRATE RIDGE

2021 ◽  
pp. 1-63
Author(s):  
Aoshuang Ji ◽  
Tieyuan Zhu ◽  
Hector Marin-Moreno ◽  
Xiong Lei
Keyword(s):  
Gas Hydrate ◽  
Wave Attenuation ◽  
Rock Physics ◽  
Seismic Profile ◽  
Seismic Attenuation ◽  
P Wave ◽  
Frequency Range ◽  
The South ◽  
Hydrate Ridge ◽  
Hydrate Saturation

Prior studies have shown an ambiguous relationship between gas hydrate saturation and seismic attenuation in different regions, but the effect of gas hydrate morphology on seismic attenuation of hydrate-bearing sediments was often overlooked. Here we combine seismic data with rock physics modeling to elucidate how gas hydrate saturation and morphology may control seismic attenuation. To extract P-wave attenuation, we process both the vertical seismic profile (VSP) data within a frequency range of 30 – 150 Hz and sonic logging data within 10 – 15 kHz from three wells in the south Hydrate Ridge, offshore of Oregon (USA), collected during Ocean Drilling Program (ODP) Leg 204 in 2000. We calculate P-wave attenuation using spectral matching and centroid frequency shift methods, and use Archie's relationship to derive gas hydrate saturation from the resistivity data above the bottom simulating reflection (BSR) at the same wells. To interpret observed seismic attenuation in terms of the effects of both gas hydrate saturation and morphology, we employ the Hydrate-Bearing Effective Sediment (HBES) rock physics model. By comparing the observed and model-predicted attenuation values, we infer that: (1) seismic attenuation appears to not be dominated by any single factor, instead, its variation is likely governed by both gas hydrate saturation and morphology; (2) the relationship between seismic attenuation and gas hydrate saturation varies with different hydrate morphologies; (3) the squirt flow, occurring at different compliances of adjacent pores driven by pressure gradients, may be responsible for the significantly large or small attenuation over a broad frequency range.

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.

P-wave attenuation measurements from laboratory resonance and sonic waveform data

Geophysics ◽  
1989 ◽  
Vol 54 (1) ◽  
pp. 76-81 ◽  
Author(s):  
D. Goldberg ◽  
B. Zinszner
Keyword(s):  
Wave Attenuation ◽  
Compressional Wave ◽  
P Wave ◽  
Laboratory Measurements ◽  
Frequency Range ◽  
Waveform Data ◽  
Sonic Log ◽  
In Situ Conditions ◽  
The Mean

We computed compressional‐wave velocity [Formula: see text] and attenuation [Formula: see text] from sonic log waveforms recorded in a cored, 30 m thick, dolostone reservoir; using cores from the same reservoir, laboratory measurements of [Formula: see text] and [Formula: see text] were also obtained. We used a resonant bar technique to measure extensional and shear‐wave velocities and attenuations in the laboratory, so that the same frequency range as used in sonic logging (5–25 kHz) was studied. Having the same frequency range avoids frequency‐dependent differences between the laboratory and in‐situ measurements. Compressional‐wave attenuations at 0 MPa confining pressure, calculated on 30 samples, gave average [Formula: see text] values of 17. Experimental and geometrical errors were estimated to be about 5 percent. Measurements at elevated effective pressures up to 30 MPa on selected dolostone samples in a homogeneous interval showed mean [Formula: see text] and [Formula: see text] to be approximately equal and consistently greater than 125. At effective stress of 20 MPa and at room temperature, the mean [Formula: see text] over the dolostone interval was 87, a minimum estimate for the approximate in‐situ conditions. We computed compressional‐wave attenuation from sonic log waveforms in the 12.5–25 kHz frequency band using the slope of the spectral ratio of waveforms recorded 0.914 m and 1.524 m from the source. Average [Formula: see text] over the interval was 13.5, and the mean error between this value and the 95 percent confidence interval of the slope was 15.9 percent. The laboratory measurements of [Formula: see text] under elevated pressure conditions were more than five times greater than the mean in‐situ values. This comparison shows that additional extrinsic losses in the log‐derived measurement of [Formula: see text], such as scattering from fine layers and vugs or mode conversion to shear energy dissipating radially from the borehole, dominate the apparent attenuation.

scholarly journals Azimuthal Attenuation Elastic Impedance Inversion for Fluid and Fracture Characterization Based on Modified Linear-Slip Theory

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-18
Author(s):  
Xinpeng Pan ◽  
Guangzhi Zhang ◽  
Yian Cui
Keyword(s):  
Porous Medium ◽  
Wave Attenuation ◽  
Real Data ◽  
Seismic Attenuation ◽  
P Wave ◽  
Inversion Method ◽  
S Wave ◽  
Fracture Characterization ◽  
Fractured Porous Medium ◽  
Elastic Impedance

The seismic attenuation should be considered while accounting for the effect of anisotropy on the seismic wave propagating through a saturated fractured porous medium. Based on the modified linear-slip theory and anisotropic Gassmann’s equation, we derive an analytical expression for a linearized PP-wave reflection coefficient and an azimuthal attenuation elastic impedance (AAEI) equation in terms of fluid/porosity term, shear modulus, density, dry normal and tangential fracture weaknesses, and compressional (P-wave) and shear (S-wave) attenuation parameters in a weak-attenuation isotropic background rock containing one single set of vertical aligned fractures. We then propose an AAEI inversion method to characterize the characteristics of fluids and fractures using two kinds of constrained regularizations in such a fractured porous medium. The proposed approach is finally confirmed by both the synthetic and real data sets acquired over a saturated fractured porous reservoir.

scholarly journals Seismic wave attenuation and dispersion resulting from wave-induced flow in porous rocks — A review

Geophysics ◽  
2010 ◽  
Vol 75 (5) ◽  
pp. 75A147-75A164 ◽  
Author(s):  
Tobias M. Müller ◽  
Boris Gurevich ◽  
Maxim Lebedev
Keyword(s):  
Fluid Flow ◽  
Velocity Dispersion ◽  
Wave Attenuation ◽  
Field Measurements ◽  
Theoretical Models ◽  
Seismic Attenuation ◽  
P Wave ◽  
Induced Flow ◽  
Wave Induced ◽  
Attenuation And Dispersion

One major cause of elastic wave attenuation in heterogeneous porous media is wave-induced flow of the pore fluid between heterogeneities of various scales. It is believed that for frequencies below [Formula: see text], the most important cause is the wave-induced flow between mesoscopic inhomogeneities, which are large compared with the typical individual pore size but small compared to the wavelength. Various laboratory experiments in some natural porous materials provide evidence for the presence of centimeter-scale mesoscopic heterogeneities. Laboratory and field measurements of seismic attenuation in fluid-saturated rocks provide indications of the role of the wave-induced flow. Signatures of wave-induced flow include the frequency and saturation dependence of P-wave attenuation and its associated velocity dispersion, frequency-dependent shear-wave splitting, and attenuation anisotropy. During the last four decades, numerous models for attenuation and velocity dispersion from wave-induced flow have been developed with varying degrees of rigor and complexity. These models can be categorized roughly into three groups ac-cording to their underlying theoretical framework. The first group of models is based on Biot’s theory of poroelasticity. The second group is based on elastodynamic theory where local fluid flow is incorporated through an additional hydrodynamic equation. Another group of models is derived using the theory of viscoelasticity. Though all models predict attenuation and velocity dispersion typical for a relaxation process, there exist differences that can be related to the type of disorder (periodic, random, space dimension) and to the way the local flow is incorporated. The differences manifest themselves in different asymptotic scaling laws for attenuation and in different expressions for characteristic frequencies. In recent years, some theoretical models of wave-induced fluid flow have been validated numerically, using finite-difference, finite-element, and reflectivity algorithms applied to Biot’s equations of poroelasticity. Application of theoretical models to real seismic data requires further studies using broadband laboratory and field measurements of attenuation and dispersion for different rocks as well as development of more robust methods for estimating dissipation attributes from field data.

P-wave seismic attenuation by slow-wave diffusion: Effects of inhomogeneous rock properties

Geophysics ◽  
2006 ◽  
Vol 71 (3) ◽  
pp. O1-O8 ◽  
Author(s):  
José M. Carcione ◽  
Stefano Picotti
Keyword(s):  
Fluid Flow ◽  
Wave Attenuation ◽  
Fluid Pressure ◽  
Seismic Attenuation ◽  
P Wave ◽  
Rock Properties ◽  
Stratified Medium ◽  
P Waves ◽  
Low Frequencies ◽  
Attenuation Mechanism

Recent research has established that the dominant P-wave attenuation mechanism in reservoir rocks at seismic frequencies is because of wave-induced fluid flow (mesoscopic loss). The P-wave induces a fluid-pressure difference at mesoscopic-scale inhomogeneities (larger than the pore size but smaller than the wavelength, typically tens of centimeters) and generates fluid flow and slow (diffusion) Biot waves (continuity of pore pressure is achieved by energy conversion to slow P-waves, which diffuse away from the interfaces). In this context, we consider a periodically stratified medium and investigate the amount of attenuation (and velocity dispersion) caused by different types of heterogeneities in the rock properties, namely, porosity, grain and frame moduli, permeability, and fluid properties. The most effective loss mechanisms result from porosity variations and partial saturation, where one of the fluids is very stiff and the other is very compliant, such as, a highly permeable sandstone at shallow depths, saturated with small amounts of gas (around 10% saturation) and water. Grain- and frame-moduli variations are the next cause of attenuation. The relaxation peak moves towards low frequencies as the (background) permeability decreases and the viscosity and thickness of the layers increase. The analysis indicates in which cases the seismic band is in the relaxed regime, and therefore, when the Gassmann equation can yield a good approximation to the wave velocity.

Effective properties of a porous medium with aligned cracks containing compressible fluid

2019 ◽  
Vol 221 (1) ◽  
pp. 60-76 ◽  
Author(s):  
Yongjia Song ◽  
Hengshan Hu ◽  
Bo Han
Keyword(s):  
Porous Medium ◽  
Wave Propagation ◽  
Elastic Scattering ◽  
Wave Velocity ◽  
Compressible Fluid ◽  
Effective Properties ◽  
P Wave ◽  
Frequency Range ◽  
P Wave Velocity ◽  
Fluid Compressibility

SUMMARY Understanding the wave propagation in fluid-saturated cracked rocks is important for detecting and characterizing cracked reservoirs and fault zones with applications in geomechanics, hydrogeology, exploration geophysics and reservoir engineering. In sedimentary rocks, microscopic-scale pores are usually filled with fluid. One logical means of modelling the essential features of such rocks is to use poroelasticity theory. But previous models of wave propagation in cracked porous medium are either restricted to low frequencies at which effects of the elastic scattering (scattering into fast-P and S waves via mode conversion at the crack faces) are negligible or to the case that the crack-filling fluid is assumed to be incompressible. To overcome these restrictions, we consider the effects of crack fluid compressibility by extending spring condition into poroelasticity and derive exact solutions of the scattering problem of an incident P wave by a circular crack containing compressible fluid in a porous medium. Based on the solutions, we develop two different effective medium models to estimate frequency-dependent effective velocity and attenuation in a fluid-saturated porous rock with a set of aligned cracks. The mixed-boundary value problem reveals that both the wave-induced fluid flow (WIFF) and elastic wave scattering can cause important velocity dispersion and attenuation. The diffusion-type WIFF dominates the velocity change and attenuation for the low frequency range, while the elastic scattering dominates them for the relatively higher frequency range. The dependences of the P-wave velocity on the crack fluid compressibility are different at different frequencies. For the WIFF-dominated frequency range and Rayleigh-scattering frequency range, the P-wave velocity decreases with the crack fluid compressibility. In contrast, for the Mie scattering frequency range, the opposite occurs (the P-wave velocity increases with the crack fluid compressibility).

Seismic attenuation: Effects of pore fluids and frictional‐sliding

Geophysics ◽  
1982 ◽  
Vol 47 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Kenneth W. Winkler ◽  
Amos Nur
Keyword(s):  
Fluid Flow ◽  
Strain Amplitude ◽  
Seismic Wave ◽  
Wave Attenuation ◽  
Velocity Ratio ◽  
Seismic Attenuation ◽  
P Wave ◽  
Amplitude Dependence ◽  
S Wave ◽  
Frictional Sliding

Seismic wave attenuation in rocks was studied experimentally, with particular attention focused on frictional sliding and fluid flow mechanisms. Sandstone bars were resonated at frequencies from 500 to 9000 Hz, and the effects of confining pressure, pore pressure, degree of saturation, strain amplitude, and frequency were studied. Observed changes in attenuation and velocity with strain amplitude are interpreted as evidence for frictional sliding at grain contacts. Since this amplitude dependence disappears at strains and confining pressures typical of seismic wave propagation in the earth, we infer that frictional sliding is not a significant source of seismic attenuation in situ. Partial water saturation significantly increases the attenuation of both compressional (P) and shear (S) waves relative to that in dry rock, resulting in greater P‐wave than S‐wave attenuation. Complete saturation maximizes S‐wave attenuation but causes a reduction in P‐wave attenuation. These effects can be interpreted in terms of wave induced pore fluid flow. The ratio of compressional to shear attenuation is found to be a more sensitive and reliable indicator of partial gas saturation than is the corresponding velocity ratio. Potential applications may exist in exploration for natural gas and geothermal steam reservoirs.

Spectral estimates of teleseismic P-wave attenuation to 15 Hz

1988 ◽  
Vol 78 (2) ◽  
pp. 726-740
Author(s):  
Marianne C. Walck
Keyword(s):  
Wave Attenuation ◽  
Decay Rates ◽  
P Wave ◽  
Frequency Range ◽  
Nuclear Explosions ◽  
Spectral Estimates ◽  
Spectral Attenuation ◽  
Double Averaging ◽  
Attenuation Models ◽  
Southern Norway

Abstract NORESS recordings of nuclear explosions in central Asia (Δ = 38°) provide new spectral attenuation estimates for frequencies from about 3 to 15 Hz. Two path spectra, representing propagation losses from the Shagan River and Degelen test sites to southern Norway, are calculated using the double-averaging technique of Bache et al. (1985, 1986). Both paths exhibit less attenuation than previously documented for explosions recorded teleseismically at the UKAEA arrays over the 1- to 8-Hz frequency range. The Shagan and Degelen spectra have somewhat different decay rates, perhaps reflecting variations in average source properties. Since the NORESS data extend to higher frequencies than previously available for attenuation measurements, we compare the NORESS spectral data to published models derived from NORSAR data (1 to 8 Hz) for the same path. The Degelen-NORSAR model is compatible with the NORESS data to about 7 Hz, but from 7 to 15 Hz, it predicts higher spectral amplitudes than are observed Using a hybrid absorption band-constant t* formulation, new models are derived which fit both the Shagan River path spectrum (t0* = 0.6 sec, τm = 0.05 sec, (t1* = 0.07 sec) and the Degelen spectrum (t0* = 0.6 sec, τm = 0.05 sec, (t1* = 0.05 sec) from 3 to 15 Hz. The NORESS data support frequency-dependent t* in the 3- to 15-Hz frequency range. The results also demonstrate that extrapolation of attenuation models obtained from longer period data to shorter periods may not predict the correct spectral levels. Actual high-frequency measurements are needed in order to characterize attenuation behavior at high frequencies.

Sign in / Sign up

Export Citation Format

Share Document