Methane migration within the submarine gas-hydrate stability zone under deep-water conditions

Ginsburg, G. D.; Soloviev, V. A.

doi:10.1016/s0025-3227(96)00078-3

Cited by 88 publications

(56 citation statements)

References 12 publications

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“…In mud volcanoes or other areas of focused gas flow, the sediment around the gas pathways may become dried out and lined with hydrates. This "frozen" barrier allows the passage of more gas through the conduit without it combining with water to form clathrates [Ginsburg and Soloviev, 1997].…”

Section: Hydrate Growth In a Partially Closed System And Sediment Watmentioning

confidence: 99%

“…In this water depletion scenario the hydrate does not inhabit the original pore space of the sediment, and the residual pore space is diminished by overconsolidation, so that calculations of the amount of hydrate within a particular depth interval may be underestimates. [Ginsburg and Soloviev, 1997] would suggest that the physical properties, and so the seismic response, of sediments adjacent to hydrate concentrations are modified by water depletion. Such overconsolidated sediments will have increased velocity and the reflectivity of interval boundaries will be affected.…”

Section: Implications For Estimates Of Gas Hydrate Volumesmentioning

confidence: 99%

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Formation of natural gas hydrates in marine sediments: 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

Clennell¹,

Hovland²,

Booth³

et al. 1999

J. Geophys. Res.

596

511

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Abstract. The stability of submarine gas hydrates is largely dictated by pressure and temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of deep marine sediments may also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our conceptual model presumes that gas hydrate behaves in a way analogous to ice in a freezing soil. Hydrate growth is inhibited within finegrained sediments by a combination of reduced pore water activity in the vicinity of hydrophilic mineral surfaces, and the excess internal energy of small crystals confined in pores. The excess energy can be thought of as a "capillary pressure" in the hydrate crystal, related to the pore size distribution and the state of stress in the sediment framework. The base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature (nearer to the seabed) than would be calculated from bulk thermodynamic equilibrium. Capillary effects or a build up of salt in the system can expand the phase boundary between hydrate and free gas into a divariant field extending over a finite depth range dictated by total methane content and pore-size distribution. Hysteresis between the temperatures of crystallization and dissociation of the clathrate is also predicted. Growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, and lenses in muds; cements in sands) can largely be explained by capillary effects, but kinetics of nucleation and growth are also important. The formation of concentrated gas hydrates in a partially closed system with respect to material transport, or where gas can flush through the system, may lead to water depletion in the host sediment. This "freezedrying" may be detectable through physical changes to the sediment (low water content and overconsolidation) and/or chemical anomalies in the pore waters and metastable presence of free gas within the normal zone of hydrate stability.

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Section: Hydrate Growth In a Partially Closed System And Sediment Watmentioning

confidence: 99%

Section: Implications For Estimates Of Gas Hydrate Volumesmentioning

confidence: 99%

Formation of natural gas hydrates in marine sediments: 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

Clennell¹,

Hovland²,

Booth³

et al. 1999

J. Geophys. Res.

596

511

View full text Add to dashboard Cite

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“…As a consequence of overpressure, a fraction of volatiles can escape from deeply buried gas reservoirs. These volatiles are transported towards the seafloor by diffusive upward migration along concentration gradients or by fluid advection through conduits and can be incorporated into gas hydrates, provided that the percolated sediments are located within the gas hydrate stability zone (GHSZ) and given that methane concentrations in the pore space exceed in situ solubilities (Ginsburg and Soloviev, 1997).…”

Section: Introductionmentioning

confidence: 99%

Molecular and isotopic partitioning of low-molecular-weight hydrocarbons during migration and gas hydrate precipitation in deposits of a high-flux seepage site

et al. 2010

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Detailed knowledge of the extent of post-genetic modifications affecting shallow submarine hydrocarbons fueled from the deep subsurface is fundamental for evaluating source and reservoir properties. We investigated gases from a submarine high-flux seepage site in the anoxic Eastern Black Sea in order to elucidate molecular and isotopic alterations of low-molecular-weight hydrocarbons (LMWHC) associated with upward migration through the sediment and precipitation of shallow gas hydrates. For this, nearsurface sediment pressure cores and free gas venting from the seafloor were collected using autoclave technology at the Batumi seep area at 845 m water depth within the gas hydrate stability zone. Vent gas, gas from pressure core degassing, and from hydrate dissociation were strongly dominated by methane (> 99.85 mol.% of ∑[C 1 -C 4 , CO 2 ]). Molecular ratios of LMWHC (C 1 /[C 2 + C 3 ] > 1000) and stable isotopic compositions of methane (δ 13 C = − 53.5‰ V-PDB; D/H around − 175‰ SMOW) indicated predominant microbial methane formation. C 1 /C 2+ ratios and stable isotopic compositions of LMWHC distinguished three gas types prevailing in the seepage area. Vent gas discharged into bottom waters was depleted in methane by > 0.03 mol.% (∑[C 1 -C 4 , CO 2 ]) relative to the other gas types and the virtual lack of 14 C-CH 4 indicated a negligible input of methane from degradation of fresh organic matter. Of all gas types analyzed, vent gas was least affected by molecular fractionation, thus, its origin from the deep subsurface rather than from decomposing hydrates in near-surface sediments is likely. As a result of the anaerobic oxidation of methane, LMWHC in pressure cores in top sediments included smaller methane fractions [0.03 mol.% ∑(C 1 -C 4 , CO 2 )] than gas released from pressure cores of more deeply buried sediments, where the fraction of methane was maximal due to its preferential incorporation in hydrate lattices. No indications for stable carbon isotopic fractionations of methane during hydrate crystallization from vent gas were found. Enrichments of 14 C-CH 4 (1.4 pMC) in short cores relative to lower abundances (max. 0.6 pMC) in gas from long cores and gas hydrates substantiates recent methanogenesis utilizing modern organic matter deposited in top sediments of this high-flux hydrocarbon seep area.

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“…Em focos de migração, como em zonas de fraturas e falhas, o gás pode percolar através dos sedimentos até o fundo marinho, criando exudações ou vulcões de lama. Nestas localidades são encontrados veios e nódulos de clatrato em abundância (Ginsburg & Soloviev, 1997). As exudações sustentam comunidades biossintéticas, incluindo pelo menos uma espécie de artrópode que consome hidratos de gás (Fisher et al, 2000).…”

Section: Formação E Distribuição De Hidratos De Gás Submarinosunclassified

“…Segunda, a quantidade de metano necessária para estabilizar hidratos está encontrada somente além da profundidade onde todos os íons de sulfato e outras espécies receptoras de elétrons além de CO 2 tem sido consumidos. Hidratos de gás encontrados próxima ao fundo marinho normalmente estão associadas à exudações de gás natural ou vulcões de lama (Ginsburg & Soloviev, 1997). Para obter sucesso na amostragem de hidratos de gás nesses locais, devem ser usadas imagens de alta resolução do fundo marinho e ROV (Remotely Operated Vehicle).…”

Section: Detecção Direta E Amostragem De Hidratos De Gás Submarinounclassified

Hidrato de gás submarino: natureza, ocorrência e perspectivas para exploração na margem continental brasileira

Clennell¹

2000

Rev. Bras. Geof.

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Hidrato de gás, ou clatrato é um sólido cristalino sendo composto de água e gases de peso molecular pequeno. Os hidratos de metano são abundantes em sedimentos submarinhos nas margens continentais. A distribuição dos clatratos pode ser mapeada através de perfilagem sísmica, perfis de poço, e amostragem geoquímica. A quantidade estimada de hidratos de gás submarino no mundo equivale aproximadamente a duas vezes o total de todos os recursos convencionais de óleo e gás. Entretanto, a exploração de hidratos de gás submarino como fonte de energia ainda não é viável em termos técnicos ou econômicos. Deslizamentos de grandes proporções podem ser desencadeados pela dissociação dos hidratos. O gás liberado durante um evento dessa natureza pode entrar na atmosfera, estimulando o efeito estufa. O talude continental do Brasil mostra em várias localidades assinaturas geofísicas da presença de hidratos de gás, e isto não é incomum, uma vez que as condições geológicas adequadas para a formação deste mineral são encontradas em outras áreas da margem continental. Apesar da existência de recurso como os hidrocarbonetos não-convencionais em águas brasileiras, esses também apresentam um risco desconhecido quanto às operações de exploração e de produção em campos de óleo e gás já em desenvolvimento em águas profundas. Palavras-chave:Hidrato de gás; Margem continental; Geoquímica orgânica; Recursos marinhos. SUBMARINE GAS HYDRATES: NATURE, OCCURRENCE & PERSPECTIVES FOR EXPLORATION IN THE BRAZILIAN CONTINENTAL MARGIN -

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Methane migration within the submarine gas-hydrate stability zone under deep-water conditions

Cited by 88 publications

References 12 publications

Formation of natural gas hydrates in marine sediments: 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

Formation of natural gas hydrates in marine sediments: 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

Molecular and isotopic partitioning of low-molecular-weight hydrocarbons during migration and gas hydrate precipitation in deposits of a high-flux seepage site

Hidrato de gás submarino: natureza, ocorrência e perspectivas para exploração na margem continental brasileira

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