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| Registros recuperados: 15 | |
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| Sultan, Nabil; Cochonat, Pierre; Foucher, Jean-paul; Mienert, J. |
| We present a theoretical study of the thermodynamic chemical equilibrium of gas hydrate in soil by taking into account the influence of temperature, pressure, pore water chemistry, and the mean pore size distribution. The model uses a new formulation based on the enthalpy form of the law of conservation of energy. The developed model shows that due to a temperature and pressure increase, hydrates may dissociate at the top of the hydrate occurrence zone to ensure a chemical equilibrium with the surrounding bulk water. This original result confirms what has been already shown through experiments. The second part of the paper presents an application of the model through a back-analysis of the giant Storegga Slide on the Norwegian margin. Two of the most... |
| Tipo: Text |
Palavras-chave: Storegga; Slope failure; GLE; Finite difference; Methane hydrate. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-699.pdf |
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| Sultan, Nabil; Cochonat, Pierre; Canals, M; Cattaneo, Antonio; Dennielou, Bernard; Haflidason, H; Laberg, J; Long, D; Mienert, J; Trincardi, F; Urgeles, R; Vorren, T; Wilson, C. |
| The Costa target areas exhibit the variability of slope instabilities needed to improve our understanding of sediment physical and mechanical properties in areas prone to sliding. That is why in this project, we have analysed the different slope failures events from different parts of the Costa target areas, which reflect diverse triggering mechanisms. The aim of the first part of this study was to identify the geotechnical response of the sediment to different external mechanisms (earthquake, rapid sedimentation and gas hydrate melting). We have focused on the relation between external mechanisms and the consequence change in the in-situ stress state and the physical, mechanical, and elastic properties of the sediment. In the second part of the paper, the... |
| Tipo: Text |
Palavras-chave: Slope instability; Sensitivity; Sedimentation; Hydrate; Earthquake. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-700.pdf |
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| Sultan, Nabil; Savoye, Bruno; Jouet, Gwenael; Leynaud, Didier; Cochonat, Pierre; Henry, P.; Stegmann, Sylvia; Kopf, Achim. |
| The Var prodelta progrades across a straight, narrow shelf (less than 2 km wide) with a very steep continental slope reaching locally more than 30 degrees. Historically, the Var delta front is sadly famous for the 1979 catastrophic submarine landslide that resulted in several casualties and infrastructural damage. Geotechnical and geophysical investigations carried out in late 2007 to the east of the 1979 landslide scar provide evidence for the possible occurrence of a new important sedimentary collapse and submarine landslide. Geophysical data acquired in the area show the presence of several seafloor morphological steps rooted to shallow subsurface seismic reflections. Moreover, in situ piezocone measurements demonstrate the presence of several shear... |
| Tipo: Text |
Palavras-chave: CPTu; Gassy soil; Piezocone; Shear zone; Submarine landslides. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00004/11481/8096.pdf |
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| Mulder, Th.; Tisot, J.-p.; Cochonat, Pierre; Bourillet, Jean-francois. |
| The Baie des Anges shows some particularities. Consequently, it is a model site for the offshore instabilities study. The application of the infinite slope analysis including the seismicity, allows to prove the potential instability of the area. Two kinds of slides are possibles : firstly, local readjustments of the slope, involving the top-continental plate underconsolidated sediments ; secondly, huge ridge-side instabilities. Their volume allows the transformation of the slides into some turbidity currents. |
| Tipo: Text |
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| Ano: 1993 |
URL: https://archimer.ifremer.fr/doc/00479/59103/61741.pdf |
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| Ondreas, Helene; Olu, Karine; Fouquet, Yves; Charlou, Jean-luc; Gay, Aurelien; Dennielou, Bernard; Donval, Jean-pierre; Fifis, Alexis; Nadalig, Thierry; Cochonat, Pierre; Cauquil, E; Bourillet, Jean-francois; Le Moigne, Morgan; Sibuet, Myriam. |
| A giant, 800-m wide pockmark, called Regab, was discovered along the Equatorial African margin at 3160-m water depth and was explored by remote operated vehicle (ROV) as part of the Zaiango (1998-2000) and Biozaire (2001-2003) projects carried out conjointly by TOTAL and a number of French research institutes. A microbathymetric map obtained using the ROV sensors shows that the pockmark actually consists of a cluster of smaller pockmarks aligned N70 along a 15-m deep depression. Methane was recorded all over the pockmark, the highest values along the axis of the depression where massive carbonate crusts and dense seep communities were also found. Several faunal species belong to the Vesicomyidae and Mytilidae bivalve families, as well as to Siboglinidae... |
| Tipo: Text |
Palavras-chave: Gabon; Microbathymetric map; ROV; Exploration; Pockmark; Equatorial African margin. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-1239.pdf |
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| Gay, Aurelien; Lopez, M; Ondreas, Helene; Charlou, Jean-luc; Sermondadaz, G; Cochonat, Pierre. |
| The origin of the cold fluid venting from a Giant Pockmark within the Lower Congo Basin has been elucidated based upon results of precise mapping, submersible dives, gravity coring and isotopic analyses realized under a TOTAL-IFREMER cooperative project (ZAIANGO and BIOZAIRE projects). During four dives of the IFREMER ROV-Victor 6000, the bottom was filmed, hard and soft samples were lifted from the sediment, and water samples were collected with a CTD-rosette system. The detailed dip map shows that the 800 in wide Giant Pockmark is a composite feature due to the coalescence of multiple 100 in wide depressions that displays a broad range of biological, mineralogical and chemical features on the seafloor, leading to a seafloor anomaly recorded on the... |
| Tipo: Text |
Palavras-chave: BIOZAIRE; ZAIANGO; Palaeochannel; Hydrates; Chemosynthesis; Seafloor facies; Fluid migration; Pockmark. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1114.pdf |
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| Sultan, Nabil; Cochonat, Pierre; Bourillet, Jean-francois; Cayocca, Florence. |
| This article presents a methodology developed to evaluate the instability of submarine slopes that extend over a large area. Special attention was paid to (1) the complex geometry (bathymetry) and the expanse of the slope, (2) the heterogeneity of the sediment, and (3) the distribution of the pore pressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfies equilibrium conditions, was used for evaluating the stability of the marine slope. The submarine slope failure, which occurred on 16 October 1979 during the construction of the new Nice airport, was studied in order to test the developed model. Geotechnical parameters were taken from experimental tests carried... |
| Tipo: Text |
Palavras-chave: Shear strength; Slope stability; Safety factor; Marine sediment; Finite element; Finite difference; Failure. |
| Ano: 2001 |
URL: http://archimer.ifremer.fr/doc/2001/publication-698.pdf |
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| Gay, A; Lopez, M; Cochonat, Pierre; Levache, D; Sermondadaz, G; Seranne, M. |
| Using high quality 3D seismic data within the Lower Congo Basin (LCB), we have identified pockmarks that are aligned above the sinuous belt of a buried turbiditic palaeo-channel, 1000 m beneath the seafloor. Geochemical analyses on cores (GC traces), taken in the centre of four of these pockmarks along this channel, show no clear evidence for migrated oil. But, some features of the GC traces, including elevated baselines (UCM > 34 mu g/g) and a broad molecular weight range of n-alkanes with little odd-even preference, may be interpreted as indicating the presence of thermogenic hydrocarbons in the cores. Seismic profiles show that these pockmarks developed above two-main features representative of pore fluid escape during early compaction: (1) closely... |
| Tipo: Text |
Palavras-chave: Pipes; Seismic chimneys; Polygonal faults; Fluid migration; Turbiditic channels; Pockmarks. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1673.pdf |
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| Gay, Aurelien; Lopez, M; Cochonat, Pierre; Sermondadaz, G. |
| A new polygonal fault system has been identified in the Lower Congo Basin. This highly faulted interval (HFI), 700+/-50 m thick, is characterized by small extensional faults displaying a polygonal pattern in plan view. This kind of fracturing is attributed to volumetric contraction of sediments during early stages of compaction at shallow burial depth. 3-D seismic data permitted the visualization of the progressive deformation of furrows during burial, leading to real fractures, visible on seismic sections at about 78 m below seafloor. We propose a new geometrical model for volumetrical contraction of mud-dominated sediments. Compaction starts at the water-sediment interface by horizontal contraction, creating furrows perpendicular to the present day... |
| Tipo: Text |
Palavras-chave: Water sediment interface; Seafloor; Sedimentary basin; Geometrical model; Furrow; Fault system. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-1115.pdf |
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| Augris, Claude; Cochonat, Pierre; Guillaume, Jean. |
| Un programme pilote d’aménagement physique des fonds par récifs artificiels est mené sur le plateau continental de la région Languedoc Roussillon. Cinq sites d’immersion ont été choisis le long du littoral entre Saint-Cyprien et le Cap d’Agde. Avant toute implantation, il est apparu nécessaire de connaître les caractéristiques mécaniques des sols de ces périmètres afin d’évaluer leur aptitude à supporter des récifs artificiels en béton. Pour ces objectifs, une campagne de carottage a été réalisée aux abords de Port-la-Nouvelle. Le présent rapport expose l’étude géotechnique effectuée sur les carottes obtenues. |
| Tipo: Text |
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| Ano: 1984 |
URL: http://archimer.ifremer.fr/doc/00110/22153/19799.pdf |
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| Gay, Aurelien; Lopez, M; Cochonat, Pierre; Seranne, M; Levache, D; Sermondadaz, G. |
| Based on high-resolution 3D seismic data sets, we document the subsurface reservoir architecture and organization of a portion of the Oligocene-Miocene stratigraphy within the Congo Basin, offshore southwestern Africa. Within the 3D seismic volume, we have identified four levels of turbiditic palaeochannels, which are separated by low-amplitude continuous reflectors interpreted as hemipelagic sediments. Geochemical analyses on sediment samples taken within overlying seafloor pockmarks reveal the presence of thermogenic gases and oils, suggesting that deep-seated fluids have migrated through both the channel deposits and the impermeable layers between them, forming a conduit to the surface. Deep thermogenic fluids produced within Cretaceous source rocks are... |
| Tipo: Text |
Palavras-chave: Polygonal faults; BSR; Fluid chimneys; Pipes; Hydrates; Turbiditic palaeochannels; Pockmarks; Fluid migration. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1111.pdf |
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| Vanoudheusden, Emilie; Sultan, Nabil; Cochonat, Pierre. |
| The COSTA target areas exhibit different slope failure events, which reflect different triggering mechanisms including gas hydrates dissociation. Gas hydrates stability law depends on temperature, pore pressure, gas chemistry, and pore water salinity. Any change in the equilibrium parameters may convert the hydrate to gas plus water, causing significant weakening of the sediment, and generating a rise of pore pressure. A significant consequence of the hydrate melting is the gas production, which alters significantly the behaviour and mechanical properties of the marine sediments and could be very hazardous when the sediment is unloaded in undrained conditions. The behaviour of the unsaturated marine sediment has to be accurately identified in order to... |
| Tipo: Text |
Palavras-chave: Shear strength; Andrained behaviour; Triaxial tests; Capillary pressure; Unsaturated sediment. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-701.pdf |
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| Registros recuperados: 15 | |
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