Seismic attribute identification through waveform analysis of gas hydrates in the Pegasus Basin, offsore New Zealand

Clairmont, Roberto; Bedle, Heather

doi:10.1190/segam2019-3216753.1

Cited by 2 publications

(1 citation statement)

References 3 publications

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“…This study utilizes two seismic surveys, the PEG09 and APB13 surveys-both conducted within the Pegasus Basin, for a comparative analysis of the efficiency of the applied methods. The former has been used in many studies compared to the latter, which makes it an ideal survey candidate for exploring a new method [10,21,23,39,41]. The APB13 survey is used to validate the transferability of the geophysical attenuation method to ensure it provides consistent results across both surveys.…”

Section: Seismic Datamentioning

confidence: 99%

Seismic Attribute Analyses and Attenuation Applications for Detecting Gas Hydrate Presence

et al. 2021

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Identifying gas hydrates in the oceanic subsurface using seismic reflection data supported by the presence of a bottom simulating reflector (BSR) is not an easy task, given the wide range of geophysical methods that have been applied to do so. Though the presence of the BSR is attributed to the attenuation response, as seismic waves transition from hydrate-filled sediment within the gas hydrate stability zone (GHSZ) to free gas-bearing sediment below, few studies have applied a direct attenuation measurement. To improve the detection of gas hydrates and associated features, including the BSR and free gas accumulation beneath the gas hydrates, we apply a recently developed method known as Sparse-Spike Decomposition (SSD) that directly measures attenuation from estimating the quality factor (Q) parameter. In addition to performing attribute analyses using frequency attributes and a spectral decomposition method to improve BSR imaging, using a comprehensive analysis of the three methods, we make several key observations. These include the following: (1) low-frequency shadow zones seem to correlate with large values of attenuation; (2) there is a strong relationship between the amplitude strength of the BSR and the increase of the attenuation response; (3) the resulting interpretation of migration pathways of the free gas using the direct attenuation measurement method; and (4) for the data analyzed, the gas hydrates themselves do not give rise to either impedance or attenuation anomalies that fully differentiate them from nearby non-hydrate zones. From this last observation, we find that, although the SSD method may not directly detect in situ gas hydrates, the same gas hydrates often form an effective seal trapping and deeper free gas accumulation, which can exhibit a large attenuation response, allowing us to infer the likely presence of the overlying hydrates themselves.

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Section: Seismic Datamentioning

confidence: 99%

Seismic Attribute Analyses and Attenuation Applications for Detecting Gas Hydrate Presence

et al. 2021

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Revisit seismic attenuation attributes: Influences of the spectral balancing operation on seismic attenuation analysis

Liu

Lou

et al. 2021

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Seismic attenuation analysis is important for seismic processing and quantitative interpretation. Nevertheless, the classic quality factor estimation methods make certain assumptions that may be invalid for a given geologic target and seismic volume. For this reason, seismic attenuation attribute analysis, which reduces some of the theoretical assumptions, can serve as a practical alternative in apparent attenuation characterization. Unfortunately, most of the published literature defines seismic attenuation attributes based on a specific source wavelet assumption, such as the Ricker wavelet, rather than wavelets that exhibit a relatively flat spectrum produced by modern data processing workflows. One of the most common processing steps is to spectrally balance the data either explicitly in the frequency domain, or implicitly through wavelet shaping deconvolution. If the post-stack seismic data have gone through the spectral balancing/whitening to improve the seismic resolution, the wavelet would exhibit a flat spectrum instead of a Ricker or Gaussian shape. We address the influence of the spectral balancing on seismic attenuation analysis. Our mathematical analysis shows that attenuation attributes are still effective for the post-stack seismic data after certain types of spectral balancing. More importantly, this analysis explains why seismic attenuation attributes work for real seismic applications with common seismic processing procedures. Synthetic and field data examples validate our conclusions.

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Seismic attribute identification through waveform analysis of gas hydrates in the Pegasus Basin, offsore New Zealand

Cited by 2 publications

References 3 publications

Seismic Attribute Analyses and Attenuation Applications for Detecting Gas Hydrate Presence

Seismic Attribute Analyses and Attenuation Applications for Detecting Gas Hydrate Presence

Revisit seismic attenuation attributes: Influences of the spectral balancing operation on seismic attenuation analysis

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