Gas hydrate/free gas migration pathways in submarine slope failures: East Indian Margin

2021 ◽  
Vol 130 (2) ◽  
Author(s):  
Jyothsna Palle ◽  
Satyavani Nittala ◽  
Kiranmai Samudrala
Keyword(s):  
Gas Hydrate ◽  
Gas Migration ◽  
Slope Failures ◽  
Free Gas ◽  
Submarine Slope ◽  
East Indian ◽  
Migration Pathways

Submarine slope failure due to gas hydrate dissociation: a preliminary quantification

2007 ◽  
Vol 44 (3) ◽  
pp. 314-325 ◽  
Author(s):  
M F Nixon ◽  
J LH Grozic
Keyword(s):  
Slope Stability ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Numerical Study ◽  
Fluid Pressure ◽  
Slope Failures ◽  
Case Histories ◽  
Hydrate Dissociation ◽  
Methane Gas ◽  
Submarine Slope

Gas hydrates are icelike compounds composed of water and methane gas in very compact form. There is substantial evidence from case histories that links gas hydrate dissociation to submarine slope failures and other geohazards. Theoretical analyses have also shown that upon dissociation gas hydrates will cause an increase in fluid pressure and a reduction in effective stress and thus result in loss of the soil strength. This paper presents a preliminary quantification of the effects of gas hydrate dissociation through development of a pore-pressure model that was incorporated into one- and two-dimensional slope stability analyses. The ensuing numerical study investigated submarine slope stability through parametric studies and application to two important case histories and found that dissociation of even small amounts of hydrate can have a significant destabilizing effect. Yet whether gas hydrate dissociation can alone cause large-scale slope failures has still to be demonstrated as there are often many destabilizing processes; however, this research highlights the importance of assessing the effects of gas hydrate dissociation on the behaviour of submarine slopes.Key words: gas hydrates, slope stability, marine, offshore, methane gas, instability.

scholarly journals Gas migration pathways and slope failures in the Danube Fan, Black Sea

2018 ◽  
Vol 92 ◽  
pp. 1069-1084 ◽  
Author(s):  
Jess I.T. Hillman ◽  
Ingo Klaucke ◽  
Joerg Bialas ◽  
Howard Feldman ◽  
Tina Drexler ◽  
...  
Keyword(s):  
Black Sea ◽  
Gas Migration ◽  
Slope Failures ◽  
Migration Pathways

scholarly journals On the potential of gassy marine soils triggering submarine slope instabilities

2020 ◽  
Vol 205 ◽  
pp. 12006
Author(s):  
Pauline Kaminski ◽  
Jürgen Grabe
Keyword(s):  
Slope Failure ◽  
Turbidity Currents ◽  
Continental Margins ◽  
Extensive Literature ◽  
Slope Failures ◽  
Free Gas ◽  
Submarine Slope ◽  
Failure Event ◽  
Liquefaction Failure ◽  
Excess Pore Pressures

The development of debris flows and turbidity currents in the course of a submarine slope failure event can cause major damage in offshore infrastructure. Additionally, the tsunamogenic potential of large slope failures at continental margins poses a direct threat to coastal communities. Therefore, the trigger mechanisms of submarine slope failures have been thoroughly investigated in the past. However, the influence of free gas in the sediment, which has been observed close to several slide events, remains unexplained. In order to evaluate the potential of gassy marine soils to precondition or trigger slope failure the mechanical behaviour of gassy soils is assessed based on an extensive literature review. It is found that gas-induced excess pore pressures can lead to liquefaction failure in sands, while cohesive, gassy soils show a less conclusive response. Hence, fine-grained soils and approaches to implement the gas impact into relevant existing constitutive soil models are assessed in greater detail. Concludingly, based on the predominant boundary conditions in failure prone regions at the continental margins, free gas occurrence can be defined as a preconditioning factor rather than as a definite trigger mechanism.

scholarly journals Seismic Attribute Analyses and Attenuation Applications for Detecting Gas Hydrate Presence

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 450
Author(s):  
Roberto Clairmont ◽  
Heather Bedle ◽  
Kurt Marfurt ◽  
Yichuan Wang
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Seismic Reflection Data ◽  
Attenuation Measurement ◽  
Free Gas ◽  
Gas Accumulation ◽  
Wide Range ◽  
Effective Seal ◽  
Migration Pathways ◽  
Attribute Analyses

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.

Characterization of elastic properties of near-surface and subsurface deepwater hydrate-bearing sediments

Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. D169-D179 ◽  
Author(s):  
Zijian Zhang ◽  
De-hua Han ◽  
Daniel R. McConnell
Keyword(s):  
Wave Velocity ◽  
Elastic Constants ◽  
Gas Hydrate ◽  
Effective Medium Theory ◽  
Pore Space ◽  
Seismic Interpretation ◽  
P Wave ◽  
Near Surface ◽  
Free Gas ◽  
Hydrate Bearing Sediments

Hydrate-bearing sands and shallow nodular hydrate are potential energy resources and geohazards, and they both need to be better understood and identified. Therefore, it is useful to develop methodologies for modeling and simulating elastic constants of these hydrate-bearing sediments. A gas-hydrate rock-physics model based on the effective medium theory was successfully applied to dry rock, water-saturated rock, and hydrate-bearing rock. The model was used to investigate the seismic interpretation capability of hydrate-bearing sediments in the Gulf of Mexico by computing elastic constants, also known as seismic attributes, in terms of seismic interpretation, including the normal incident reflectivity (NI), Poisson’s ratio (PR), P-wave velocity ([Formula: see text]), S-wave velocity ([Formula: see text]), and density. The study of the model was concerned with the formation of gas hydrate, and, therefore, hydrate-bearing sediments were divided into hydrate-bearing sands, hydrate-bearing sands with free gas in the pore space, and shallow nodular hydrate. Although relations of hydrate saturation versus [Formula: see text] and [Formula: see text] are different between structures I and II gas hydrates, highly concentrated hydrate-bearing sands may be interpreted on poststack seismic amplitude sections because of the high NI present. The computations of elastic constant implied that hydrate-bearing sands with free gas could be detected with the crossplot of NI and PR from prestack amplitude analysis, and density may be a good hydrate indicator for shallow nodular hydrate, if it can be accurately estimated by seismic methods.

Estimation of gas-hydrate concentration and free-gas saturation at the Norwegian-Svalbard continental margin

2005 ◽  
Vol 53 (6) ◽  
pp. 803-810 ◽  
Author(s):  
José M. Carcione ◽  
Davide Gei ◽  
Giuliana Rossi ◽  
Gianni Madrussani
Keyword(s):  
Continental Margin ◽  
Gas Hydrate ◽  
Free Gas ◽  
Gas Saturation
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