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| Registros recuperados: 22 | |
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| Goswami, Bedanta K.; Weitemeyer, Karen A.; Minshull, Timothy A.; Sinha, Martin C.; Westbrook, Graham; Chabert, Anne; Henstock, Timothy J.; Ker, Stephan. |
| We acquired coincident marine controlled-source electromagnetic (CSEM), high-resolution seismic reflection and ocean-bottom seismometer (OBS) data over an active pockmark in the crest of the southern part of the Vestnesa Ridge, to estimate fluid composition within an underlying fluid-migration chimney. Synthetic model studies suggest resistivity obtained from CSEM data can resolve gas or hydrate saturation greater than 5% within the chimney. Acoustic chimneys imaged by seismic reflection data beneath the pockmark and on the ridge flanks, were found to be associated with high-resistivity anomalies (+2-4 m). High-velocity anomalies (+0.3 km/s), within the gas hydrate stability zone (GHSZ) and low-velocity anomalies (-0.2 km/s) underlying the GHSZ, were also... |
| Tipo: Text |
Palavras-chave: Gas hydrate; Svalbard; CSEM; Saturation; Pockmark; Vestnesa. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00283/39458/37928.pdf |
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| Pierre, Catherine; Fouquet, Yves. |
| Submersible investigations with the ROV Victor 6000 of some pockmark structures on the seafloor of the Congo deep-sea fan have shown that they are active venting sites of methane-rich fluids, associated with abundant fauna and carbonate crusts. Moreover, methane hydrates have been observed both outcropping and deep in the sediments in the centre of the "Regab" giant pockmark. Authigenic carbonates, mostly calcite sometimes mixed with aragonite, are cementing the sedimentary matrix components and fauna; diatoms are abundant but only as moulds, indicating that biogenic silica dissolution occurred in situ synchronous with carbonate precipitation. The occurrence of diagenetic barite and pyrite in some carbonate crusts demonstrates that they can be formed... |
| Tipo: Text |
Palavras-chave: Oxygen isotopes; Carbon isotopes; Congo deep sea fan; Gas hydrate; Methane seep; Authigenic carbonate. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2608.pdf |
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| De Prunele, Alexis. |
| The present work describes the dynamics of two pockmark areas, off West Africa. The intention is to propose two different approaches to study the relationships between fluid migration and pockmarks. The first investigated area corresponds to a pockmark cluster called Preowei, located off Nigeria. Geochemical analyses and modeling were combined with seismic data to detail the hydrocarbon migration pattern at this area, with implication on both the pockmark formation and the evolution of their morphology. The proposed interpretation seeks to identify the conceptual bases of pockmark evolution over time at this area. It is argued that the cluster has been active for at least 2700 years, and it is still at the stage of hydrate formation for some pockmarks and... |
| Tipo: Text |
Palavras-chave: Hydrate de gaz; Marge africaine; Hydrates; Gas hydrate; Pockmark; African margin; Hydrate. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00498/60936/64329.pdf |
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| Graves, Carolyn A.; James, Rachael H.; Sapart, Celia Julia; Stott, Andrew W.; Wright, Ian C.; Berndt, Christian; Westbrook, Graham; Connelly, Douglas P.. |
| Offshore western Svalbard plumes of gas bubbles rise from the seafloor at the landward limit of the gas hydrate stability zone (LLGHSZ; ∼400 m water depth). It is hypothesized that this methane may, in part, come from dissociation of gas hydrate in the underlying sediments in response to recent warming of ocean bottom waters. To evaluate the potential role of gas hydrate in the supply of methane to the shallow subsurface sediments, and the role of anaerobic oxidation in regulating methane fluxes across the sediment-seawater interface, we have characterised the chemical and isotopic compositions of the gases and sediment pore waters. The molecular and isotopic signatures of gas in the bubble plumes (C1/C2+ = 1 × 104; δ13C-CH4 = -55 to -51 ‰; δD-CH4 = -187... |
| Tipo: Text |
Palavras-chave: Methane; Seafloor sediments; Gas hydrate; Offshore Svalbard; Seabed fluxes; Anaerobic oxidation. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00358/46914/46819.pdf |
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| Wei, Jiangong; Pape, Thomas; Sultan, Nabil; Colliat, Jean-louis; Himmler, Tobias; Ruffine, Livio; De Prunele, Alexis; Dennielou, Bernard; Garziglia, Sebastien; Marsset, Tania; Peters, Carl A.; Rabiu, Abdulkarim; Bohrmann, Gerhard. |
| A joint research expedition between the French IFREMER and the German MARUM was conducted in 2011 using the R/V Pourquoi pas? to study gas hydrate distributions in a pockmark field (1141 – 1199 meters below sea surface) at the continental margin of Nigeria. The sea floor drill rig MeBo of MARUM was used to recover sediments as deep as 56.74 meters below seafloor. The presence of gas hydrates in specific core sections was deduced from temperature anomalies recorded during continuous records of infrared thermal scanning and anomalies in pore water chloride concentrations. In situ sediment temperature measurements showed elevated geothermal gradients of up to 258 °C/km in the center of the so-called pockmark A which is up to 4.6 times higher than that in the... |
| Tipo: Text |
Palavras-chave: Gas hydrate; Pockmark; Chloride profile; Infrared thermal imaging; Fluid flow; Nigerian continental margin; MeBo drill rig. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00213/32382/30846.pdf |
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| Waite, W. F.; Santamarina, J. C.; Cortes, D. D.; Dugan, B.; Espinoza, D. N.; Germaine, J.; Jang, J.; Jung, J. W.; Kneafsey, T. J.; Shin, H.; Soga, K.; Winters, W. J.; Yun, T-s.. |
| Methane gas hydrates, crystalline inclusion compounds formed from methane and water, are found in marine continental margin and permafrost sediments worldwide. This article reviews the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate-bearing sediments. Formation phenomena include pore-scale habit, solubility, spatial variability, and host sediment aggregate properties. Physical properties include thermal properties, permeability, electrical conductivity and permittivity, small-strain elastic P and S wave velocities, shear strength, and volume changes resulting from hydrate dissociation. The magnitudes and interdependencies of these properties are critically important for predicting and quantifying... |
| Tipo: Text |
Palavras-chave: Physical properties; Hydrate-bearing sediment; Gas hydrate. |
| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00219/33030/31519.pdf |
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| Pape, Thomas; Ruffine, Livio; Hong, Wei‐li; Sultan, Nabil; Riboulot, Vincent; Peters, Carl A.; Kölling, Martin; Zabel, Matthias; Garziglia, Sebastien; Bohrmann, Gerhard. |
| The evolution of submarine pockmarks is often related to the ascent of fluid from the subsurface. For pockmarks located within the gas hydrate stability zone, methane oversaturation can result in the formation of gas hydrates in the sediment. A ca. 600 m‐wide sea floor depression in deep‐waters offshore Nigeria, Pockmark A, was investigated for distributions and quantities of shallow gas hydrates, origins of hydrocarbons and time elapsed since the last major fluid ascent event. For the first time, pressure coring of shallow sediments and drilling of more than 50‐m‐long cores with the sea floor drill rig MARUM‐MeBo70 were conducted in this pockmark. Unusually high hydrate saturations of up to 51% of pore volume in the uppermost 2.5 meters of sediment in the... |
| Tipo: Text |
Palavras-chave: Pockmark; Gas hydrate; Methane; MeBo; Pressure coring; Pore water modeling. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75491/76344.pdf |
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| Ker, Stephan; Thomas, Yannick; Riboulot, Vincent; Sultan, Nabil; Bernard, Céline; Scalabrin, Carla; Ion, G; Marsset, Bruno. |
| A comprehensive characterization of the gas hydrate system offshore the western Black Sea was performed through an integrated analysis of geophysical data. We detected the Bottom Simulating Reflector (BSR), which marks, in this area, the base of gas hydrate stability. The observed BSR depth does not fit the theoretical steady-state base of gas hydrate stability zone (BGHSZ). We show that the disparity between the BSR and predicted BGHSZ is the result of a transient state of the hydrate system due to the ongoing re-equilibrium since the Last Glacial Maximum. When gas hydrates are brought outside the stability zone due to changes in temperature and sea level, their dissociation generates an increase in interstitial pore pressure. This process is favorable to... |
| Tipo: Text |
Palavras-chave: Gas hydrate; BSR; Excess pore pressure; Black Sea. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00474/58531/61081.pdf |
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| Lu, Zhengquan; Sultan, Nabil. |
| A series of empirical expressions for predicting gas hydrate stability, its volume fraction out of pore space and gas hydrate mass-density were established in different systems in consideration of gas composition (CH4, C2H6, H2S) and salinity (NaCl, seawater), and pore size at temperature between 273.15 and 300 K, based on our gas hydrate thermodynamic model (Sultan et al., 2004b, c). Six of the developed expressions for predicting gas hydrate stability were validated against the available published experimental data and they were also compared with other models. At temperature 273.15 to 290.15 K, the ARDPs (Average Relative Deviation of Pressures between the prediction and the experimental data) have shown that these empirical expressions are in agreement... |
| Tipo: Text |
Palavras-chave: Empirical expressions; Mass density; Fraction out of pore space; Stability law; Gas hydrate. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4958.pdf |
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| Bourry, Christophe; Chazallon, Bertrand; Charlou, Jean-luc; Donval, Jean-pierre; Ruffine, Livio; Henry, Pierre; Geli, Louis; Cagatay, M. Namik; Inan, Sedat; Moreau, Myriam. |
| Gas hydrates and gas bubbles were collected during the MARNAUT cruise (May-June 2007) in the Sea of Marmara along the North Anatolian Fault system, Turkey. Gas hydrates were sampled in the western part of the Sea of Marmara (on the Western High), and three gas-bubble samples were recovered on the Western High, the Central High (center part of the Sea of Marmara) and in the Cinarcik Basin (eastern part of the Sea of Marmara). Methane is the major component of hydrates (66.1%), but heavier gases such as C-2, C-3, and i-C-4 are also present in relatively high concentration. The methane contained within gas hydrate is clearly thermogenic as evidenced by a low C-1/C-2 + C-3 ratio of 3.3, and carbon and hydrogen isotopic data (delta C-13(CH4) of -44.1 parts per... |
| Tipo: Text |
Palavras-chave: Isotopes; Thermogenic gas; Gas bubbles; Gas hydrate; Sea of Marmara. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6844.pdf |
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| Villar-muñoz, Lucía; Vargas-cordero, Iván; Bento, Joaquim; Tinivella, Umberta; Fernandoy, Francisco; Giustiniani, Michela; Behrmann, Jan; Calderón-díaz, Sergio. |
| Large amounts of gas hydrate are present in marine sediments offshore Taitao Peninsula, near the Chile Triple Junction. Here, marine sediments on the forearc contain carbon that is converted to methane in a regime of very high heat flow and intense rock deformation above the downgoing oceanic spreading ridge separating the Nazca and Antarctic plates. This regime enables vigorous fluid migration. Here, we present an analysis of the spatial distribution, concentration, estimate of gas-phases (gas hydrate and free gas) and geothermal gradients in the accretionary prism, and forearc sediments offshore Taitao (45.5°–47° S). Velocity analysis of Seismic Profile RC2901-751 indicates gas hydrate concentration values <10% of the total rock volume and extremely... |
| Tipo: Text |
Palavras-chave: BSR; Gas hydrate; Methane; Seepage; Active margin; Chile Triple Junction. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00475/58678/61173.pdf |
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| Chuang, Pei-chuan; Dale, Andrew W.; Wallmann, Klaus; Haeckel, Matthias; Yang, Tsanyao Frank; Chen, Nai-chen; Chen, Hsiao-chi; Chen, Hsuan-wen; Lin, Saulwood; Sun, Chih-hsien; You, Chen-feng; Horng, Chorng-shern; Wang, Yunshuen; Chung, San-hsiung. |
| Geochemical data (CH4, SO42-, I-, Cl-, particulate organic carbon (POC), C-13-CH4, and C-13-CO2) are presented from the upper 30 m of marine sediment on a tectonic submarine accretionary wedge offshore southwest Taiwan. The sampling stations covered three ridges (Tai-Nan, Yung-An, and Good Weather), each characterized by bottom simulating reflectors, acoustic turbidity, and different types of faulting and anticlines. Sulfate and iodide concentrations varied little from seawater-like values in the upper 1-3 m of sediment at all stations; a feature that is consistent with irrigation of seawater by gas bubbles rising through the soft surface sediments. Below this depth, sulfate was rapidly consumed within 5-10 m by anaerobic oxidation of methane (AOM) at the... |
| Tipo: Text |
Palavras-chave: Gas hydrate; Methane flux; Bubble irrigation; Anaerobic oxidation of methane; POC degradation; Accretionary wedge; Taiwan. |
| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37514/35843.pdf |
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| Omoregie, E; Mastalerz, V; De Lange, G; Straub, K; Kappler, A; Roy, H; Stadnitskaia, A; Foucher, Jean-paul; Boetius, A. |
| In this study we determined the composition and biogeochemistry of novel, brightly colored, white and orange microbial mats at the surface of a brine seep at the outer rim of the Chefren mud volcano. These mats were interspersed with one another, but their underlying sediment biogeochemistries differed considerably. Microscopy revealed that the white mats were granules composed of elemental S filaments, similar to those produced by the sulfide-oxidizing epsilonproteobacterium "Candidatus Arcobacter sulfidicus." Fluorescence in situ hybridization indicated that microorganisms targeted by a "Ca. Arcobacter sulfidicus"-specific oligonucleotide probe constituted up to 24% of the total the cells within these mats. Several 16S rRNA gene sequences from organisms... |
| Tipo: Text |
Palavras-chave: Gulf of mexico; Sulfate reducing bacteria; Egyptian continental margin; Northeast pacific ocean; Ribosomal rna sequences; In situ hybridization; Anaerobic oxidation; Marine sediments; Gas hydrate; Oxiding bacteria. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6201.pdf |
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| Winters, W. J.; Wilcox-cline, R. W.; Long, P.; Dewri, S. K.; Kumar, P.; Stern, L.; Kerr, L.. |
| The sediment characteristics of hydrate-bearing reservoirs profoundly affect the formation, distribution, and morphology of gas hydrate. The presence and type of gas, porewater chemistry, fluid migration, and subbottom temperature may govern the hydrate formation process, but it is the host sediment that commonly dictates final hydrate habit, and whether hydrate may be economically developed. In this paper, the physical properties of hydrate-bearing regions offshore eastern India (Krishna-Godavari and Mahanadi Basins) and the Andaman Islands, determined from Expedition NGHP-01 cores, are compared to each other, well logs, and published results of other hydrate reservoirs. Properties from the hydrate-free Kerala-Konkan basin off the west coast of India are... |
| Tipo: Text |
Palavras-chave: Physical properties; Gas hydrate; Porosity; Atterberg limits; Consolidation; Permeability; Shear strength; Scanning electron microscopy. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00289/40036/38799.pdf |
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| Lu, Zhen Quan; Sultan, Nabil; Jin, Chun Shuang; Rao, Zhu; Luo, Xu Rong; Wu, Bi Hao; Zhu, You Hai. |
| Based on field investigated gas geochemistry and predecessors' data such as the permafrost ground temperature, thermal gradients within/below the frozen layer, the modeling on gas hydrate formation conditions is conducted in the Qinghai Tibet plateau permafrost. The modeled results show that the permafrost characteristics generally meet gas hydrate formation conditions in the study area. Gas composition, temperature-related permafrost parameters (e. g. permafrost thickness or its ground temperature and thermal gradients within / below the frozen layer) are the most important factors affecting gas hydrate occurrences, whose variance may cause the heterogeneity of gas hydrate occurrences in the study area. The most probable gas hydrate is the kind of hybrid... |
| Tipo: Text |
Palavras-chave: Qinghai Tibet plateau; Modeling; Formation conditions; Gas hydrate; Permafrost. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6230.pdf |
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| Hillman, Jess I. T.; Klaucke, Ingo; Bialas, Joerg; Feldman, Howard; Drexler, Tina; Awwiller, David; Atgin, Orhan; Cifci, Gunay; Badhani, Shray. |
| A large geophysical dataset, including bathymetry, and 2D and 3D P-cable seismic data, revealed evidence of numerous gas flares near the S2 Canyon in the Danube Fan, northwestern Black Sea. This dataset allows us to investigate potential relationships between gas migration pathways, gas vents observed at the seafloor and submarine slope failures. Vertical gas migration structures as revealed in the seismics appear to be concentrated near submarine slope failure structures. Where these seismically defined features extend upwards to the seafloor, they correlate with the location of gas flares. However, not all these structures reach the seafloor, in some cases because they are capped by overlying sediments. A strong correlation is inferred between gas... |
| Tipo: Text |
Palavras-chave: Gas migration; Chimneys; Gas hydrate; Danube Fan; Slope failure; Black Sea. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00439/55013/57803.pdf |
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| Registros recuperados: 22 | |
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