Attenuation measurements from sonic waveform logs in methane hydrate‐bearing sediments at the Nankai Trough exploratory well off Tokai, central Japan

Matsushima, Jun

doi:10.1029/2004gl021786

Cited by 36 publications

(28 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From the association of highest Qp with the zone in which, from the locally increased Vp, hydrate concentration is likely to be greatest one might expect the increase in elastic modulii caused by hydrate would also lead to an increase in Q, but this is contrary to the observations of Guerin et al (1999), Guerin and Goldberg (2002) and Matsushima (2005) that Qp is inversely dependent upon hydrate content at sonic frequencies (10-25 kHz). 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).…”

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

confidence: 73%

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

View full text Add to dashboard Cite

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.

show abstract

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

confidence: 73%

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

View full text Add to dashboard Cite

show abstract

“…It has also been shown that seismic frequency content is reduced below gas-bearing sediments and the presence of gas hydrate also reduces the frequency content and increases seismic attenuation in both marine and permafrost settings (e.g. Sain et al, 2009;Guerin and Goldberg, 2002;Bellefleur et al, 2007;Matsushima, 2005Matsushima, , 2006. Thus the instantaneous seismic frequency attribute may highlight zones that are affected by either gas hydrate or free gas by showing reduced attribute values.…”

Section: Lateral Extent Of the Fractured Systemmentioning

confidence: 99%

Seismic imaging of a fractured gas hydrate system in the Krishna–Godavari Basin offshore India

Riedel

Collett

Kumar

et al. 2010

Marine and Petroleum Geology

112

View full text Add to dashboard Cite

“…Laboratory experiments in hydrate bearing sediments indicated increase of attenuation with hydrate saturation (Priest et al, 2006;Best et al, 2013), whereas attenuation estimates from field experiments on gas hydrates indicated contradicting results. 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.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

View full text Add to dashboard Cite

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.

show abstract

Attenuation measurements from sonic waveform logs in methane hydrate‐bearing sediments at the Nankai Trough exploratory well off Tokai, central Japan

Cited by 36 publications

References 9 publications

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

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

Seismic imaging of a fractured gas hydrate system in the Krishna–Godavari Basin offshore India

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

Contact Info

Product

Resources

About