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

Singhroha, Sunny, Bünz, Stefan, Plaza-Faverola, Andreia and Chand, Shyam (2016) Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data. Interpretation, 4 (1). SA39-SA54. DOI 10.1190/INT-2015-0023.1.

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Abstract

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.

Document Type: Article
Keywords: Gas hydrates, free gas, sediments, P-cable 3D seismic data, Vestnesa Ridge, Svalbard
Refereed: Yes
Open Access Journal?: No
Publisher: Society of Exploration Geophysicists
Projects: Enrichment
Date Deposited: 06 Jun 2016 12:11
Last Modified: 01 Feb 2019 15:06
URI: https://oceanrep.geomar.de/id/eprint/33012

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