Seismic wave attenuation in methane hydrate‐bearing sediments: Vertical seismic profiling data from the Nankai Trough exploratory well, offshore Tokai, central Japan

Matsushima, Jun

doi:10.1029/2005jb004031

Cited by 86 publications

(46 citation statements)

References 37 publications

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“…Given the two methodological approaches for estimating Q, their inherent limitations and the constraints of the 3D seismic, as earlier reported by Quan and Harris (1997) and Matsushima (2006), we also found that the centroid frequency shift method gave more stable Q estimates. The contribution of reflectivity sequences in the calculated amplitude spectrum and scattering effects limited the vertical resolution of Q estimates.…”

Section: Sa46 Interpretation / February 2016supporting

confidence: 81%

“…For example, studies on well-log data Goldberg, 2002, 2005;Matsushima, 2005), vertical seismic profile (VSP) data Bellefleur et al, 2007), and on crosshole seismic data (Pratt et al, 2003;Bauer et al, 2005) indicated an increase in attenuation. Other studies, mainly on surface seismic data (Matsushima, 2006;Rossi et al, 2007;Dewangan et al, 2014) indicated a decrease in attenuation. The increase (Guerin and Goldberg, 2002;Gei and Carcione, 2003;Chand and Minshull, 2004;Lee and Collett, 2006) and decrease (Sain and Singh, 2011;Dewangan et al, 2014) in attenuation have been explained by using different rockphysics models depending on the assumed microstructure of the hydrate and also sediment-hydrate mixtures.…”

Section: Introductionmentioning

confidence: 94%

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Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

et al. 2016

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We have estimated the seismic attenuation in gas hydrate and free-gas-bearing sediments from high-resolution P-cable 3D seismic data from the Vestnesa Ridge on the Arctic continental margin of Svalbard. P-cable data have a broad bandwidth (20-300 Hz), which is extremely advantageous in estimating seismic attenuation in a medium. The seismic quality factor (Q), the inverse of seismic attenuation, is estimated from the seismic data set using the centroid frequency shift and spectral ratio (SR) methods. The centroid frequency shift method establishes a relationship between the change in the centroid frequency of an amplitude spectrum and the Q value of a medium. The SR method estimates the Q value of a medium by studying the differential decay of different frequencies. The broad bandwidth and short offset characteristics of the P-cable data set are useful to continuously map the Q for different layers throughout the 3D seismic volume. The centroid frequency shift method is found to be relatively more stable than the SR method. Q values estimated using these two methods are in concordance with each other. The Q data document attenuation anomalies in the layers in the gas hydrate stability zone above the bottom-simulating reflection (BSR) and in the free gas zone below. Changes in the attenuation anomalies correlate with small-scale fault systems in the Vestnesa Ridge suggesting a strong structural control on the distribution of free gas and gas hydrates in the region. We argued that high and spatially limited Q anomalies in the layer above the BSR indicate the presence of gas hydrates in marine sediments in this setting. Hence, our workflow to analyze Q using high-resolution P-cable 3D seismic data with a large bandwidth could be a potential technique to detect and directly map the distribution of gas hydrates in marine sediments.

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Section: Sa46 Interpretation / February 2016supporting

confidence: 81%

Section: Introductionmentioning

confidence: 94%

Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

et al. 2016

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“…It is consistent, however, with the positive correlation between increased hydrate content and higher Qp obtained at 'seismic' frequencies (30-110 Hz) from VSPs offshore Tokai, Japan (Matsushima, 2006). Consequently, it could be suggested that the attenuation mechanism of squirt-flow within the hydrate matrix proposed by or the combination of frictional and squirt-flow mechanisms proposed by Guerin and Goldberg (2005), both based on data from sonic logs, might not be expected to produce significant attenuation at lower, seismic frequencies This would be consistent with the attenuation model of Pride et al (2004), which predicts that squirt flow is only important at ultrasonic frequencies and that effects of mesoscale features, larger than pores but smaller than the seismic wavelength, govern attenuation at seismic frequencies.…”

Section: Inversion For Qp and Qs And The Effect Of Hydrate On Attenuasupporting

confidence: 81%

Estimation of gas hydrate concentration from multi-component seismic data at sites on the continental margins of NW Svalbard and the Storegga region of Norway

Westbrook

Chand

Rossi

et al. 2008

Marine and Petroleum Geology

119

135

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High-resolution seismic experiments, employing arrays of closely spaced, four-component ocean-bottom seismic recorders, were conducted at a site off western Svalbard and a site on the northern margin of the Storegga slide, off Norway to investigate how well seismic data can be used to determine the concentration of methane hydrate beneath the seabed. Data from P-waves and from S-waves generated by P-S conversion on reflection were inverted for P-and S-wave velocity (Vp and Vs), using 3D travel-time tomography, 2D ray-tracing inversion and 1D waveform inversion. At the NW Svalbard site, positive Vp anomalies above a sea-bottomsimulating reflector (BSR) indicate the presence of gas hydrate. A zone containing free gas up to 150-m thick, lying immediately beneath the BSR, is indicated by a large reduction in Vp without significant reduction in Vs. At the Storegga site, the lateral and vertical variation in Vp and Vs and the variation in amplitude and polarity of reflectors indicate a heterogeneous distribution of hydrate that is related to a stratigraphically mediated distribution of free gas beneath the BSR. Derivation of hydrate content from Vp and Vs was evaluated, using different models for how hydrate affects the seismic properties of the sediment host and different approaches for estimating the background velocity of the sediment host. The error in the average Vp of an interval of 20-m thickness is about 2.5%, at 95% confidence, and yields a resolution of hydrate concentration of about 3%, if hydrate forms a connected framework, or about 7%, if it is both pore-filling and framework-forming. At NW Svalbard, in a zone about 90-m thick above the BSR, a Biot-theory-based method predicts hydrate concentrations of up to 11% of pore space, and an effective-medium-based method predicts concentrations of up to 6%, if hydrate forms a connected framework, or 12%, if hydrate is both pore-filling and frameworkforming. At Storegga, hydrate concentrations of up to 10% or 20% were predicted, depending on the hydrate model, in a zone about 120-m thick above a BSR. With seismic techniques alone, we can only estimate with any confidence the average hydrate content of broad intervals containing more than one layer, not only because of the uncertainty in the layer-by-layer variation in lithology, but also because of the negative correlation in the errors of estimation of velocity between adjacent layers. In this investigation, an interval of about 20-m thickness (equivalent to between 2 and 5 layers in the model used for waveform inversion) was the smallest within which one could sensibly estimate the hydrate content. If lithological layering much thinner than 20-m thickness controls hydrate content, then hydrate concentrations within layers could significantly exceed or fall below the average values derived from seismic data.

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“…2(A)] and 83% of the P-wave velocity in the 43% saturation case. In contrast, the S-wave speed in hydrate-bearing sediment is expected to be less than $60% of the P-wave speed (Lee, 2002;Matsushima, 2006;Yun et al, 2005), even if the hydrate is cementing the sediment grains (Priest et al, 2005). Therefore, the large-amplitude arrival immediately following the P-wave is too fast to be an S-wave.…”

Section: B Sample Preparationmentioning

confidence: 98%

Anomalous waveforms observed in laboratory-formed gas hydrate-bearing and ice-bearing sediments

Lee

Waite

2011

The Journal of the Acoustical Society of America

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Acoustic transmission measurements of compressional, P, and shear, S, wave velocities rely on correctly identifying the P-and S-body wave arrivals in the measured waveform. In cylindrical samples for which the sample is much longer than the acoustic wavelength, these body waves can be obscured by high-amplitude waveform features arriving just after the relatively small-amplitude Pbody wave. In this study, a normal mode approach is used to analyze this type of waveform, observed in sediment containing gas hydrate or ice. This analysis extends an existing normal-mode waveform propagation theory by including the effects of the confining medium surrounding the sample, and provides guidelines for estimating S-wave velocities from waveforms containing multiple large-amplitude arrivals.

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Seismic wave attenuation in methane hydrate‐bearing sediments: Vertical seismic profiling data from the Nankai Trough exploratory well, offshore Tokai, central Japan

Cited by 86 publications

References 37 publications

Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data

Estimation of gas hydrate concentration from multi-component seismic data at sites on the continental margins of NW Svalbard and the Storegga region of Norway

Anomalous waveforms observed in laboratory-formed gas hydrate-bearing and ice-bearing sediments

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