|
|
|
| Registros recuperados: 64 | |
|
|
| 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 |
| |
|
|
| Marsset, Bruno; Menut, Eric; Ker, Stephan; Thomas, Yannick; Regnault, Jean-pierre; Leon, Pierre; Martinossi, Henri; Artzner, Laurent; Chenot, Damien; Dentrecolas, Stephane; Spychalski, B.; Mellier, G.; Sultan, Nabil. |
| High Resolution (220–1050 Hz) seismic acquisition performed in deep water using deep-towed systems provides unrivalled lateral resolution when compared to conventional surface seismic. The lateral resolution of these acquisitions is controlled by the width of the first Fresnel zone, taking advantage of their positions close to the sea bottom. No current existing deep towed equipment can benefit from seismic imaging processing techniques to improve this resolution as a consequence of positioning inaccuracies. The technological developments of a digital deep-towed multichannel streamer are presented with a particular attention to positioning: each hydrophone incorporates a pitch, roll and heading sensor in order to monitor the constant deformation of the... |
| Tipo: Text |
Palavras-chave: Deep-towed seismics; Multichannel streamer; Seismic imaging. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00206/31745/35690.pdf |
| |
|
|
| Riboulot, Vincent; Sultan, Nabil; Imbert, P.; Ker, Stephan. |
| A review of recent literature shows that two geomorphologically different types of pockmarks, contribute to gas seepage at the seafloor. Type-1 pockmarks are defined as seafloor craters associated to fluid seepage and are the most classical type referred to as “pockmarks” in the literature. In contrast, Type-2 pockmarks reveal a complex seafloor morphology that may result from the formation/decomposition of gas hydrates in underlying sedimentary layers. Interpretation of very-high-resolution seismic data, sedimentological analyses and geotechnical measurements acquired from the Eastern Niger Submarine Delta reveal that Type-2 pockmarks are associated to the presence at depth of a conical body of massive gas hydrates. Based on acquired data, theoretical... |
| Tipo: Text |
Palavras-chave: Pockmarks; Gas hydrates; VHR seismic data; Piezocone; Numerical modelling; Niger Delta. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00301/41215/40643.pdf |
| |
|
|
| Sibuet, Jean-claude; Rangin, C; Le Pichon, X; Singh, S; Cattaneo, Antonio; Graindorge, D; Klingelhoefer, Frauke; Lin, Jing-yi; Malod, Jacques-andre; Maury, Tanguy; Schneider, J; Sultan, Nabil; Umber, Marie; Yamaguchi, H. |
| Trench-parallel thrust faults verging both landward and seaward were mapped in the portion of wedge located between northern Sumatra and the Indian-Indonesian boundary. The spatial aftershocks distribution of the 26th December 2004 earthquake shows that the post-seismic motion is partitioned along two thrust faults, the Lower and Median Thrust Faults, the latter being right-laterally offset by a N-S lower plate fracture zone located along the 93.6 degrees N meridian. Between February 2005 and August 2005, the upper plate aftershock activity shifted from southeast of this fracture zone to northwest of it, suggesting that the lower plate left-lateral motion along the fracture zone may have induced a shift of the upper plate post-seismic activity along the... |
| Tipo: Text |
Palavras-chave: Active thrust faults; Co seismic rupture; Aftershocks; 2004 Sumatra Andaman earthquake. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-3508.pdf |
| |
|
|
| Taleb, Farah; Garziglia, Sebastien; Sultan, Nabil. |
| The hydro‐mechanical properties of gas hydrate‐bearing sediment are key in assessing offshore geo‐hazards and the resource potential of gas hydrates. For sandy materials, such properties were proved highly dependent on hydrate content (Sh) as well as on their distribution and morphology. Owing to difficulties in testing gas hydrate‐bearing clayey sediments, the impact of hydrates on the behaviour of such materials remains poorly understood. Hence, to provide insight into the characterisation of clayey sediments containing hydrate, this study relies on a unique database of in‐situ acoustic, piezocone and pore‐pressure dissipation measurements collected in a high gas flux system offshore Nigeria. Compressional wave velocity measurements were used as means of... |
| Tipo: Text |
|
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00466/57746/59974.pdf |
| |
|
|
| Bayon, Germain; Pierre, C; Etoubleau, Joel; Voisset, Michel; Cauquil, E; Marsset, Tania; Sultan, Nabil; Le Drezen, Eliane; Fouquet, Yves. |
| We report on a reconnaissance analysis of the geochemical composition of authigenic carbonates and sediment samples collected from various seepage sites on the Niger deep-sea fan. Our aim has been to investigate whether evidence for the presence of authigenic carbonates and gas hydrates within sediments is discernible from solid-phase sediment geochemistry. We show that sedimentary Sr/Ca and Mg/Ca ratios can be used to infer the presence of authigenic aragonite (Sr-rich) and Mg-rich carbonate phases (high-Mg calcite, dolomite) in cold seep settings. Using Sr/Ca and Mg/Ca ratios, the proportion (wt.%) of authigenic carbonates in Niger Fan sediments can be calculated from a mixing model between sediment fractions of terrigenous material, biogenic calcite,... |
| Tipo: Text |
Palavras-chave: Niger Delta; Gas hydrates; Cold seeps; Mg/Ca; Sr/Ca; Authigenic carbonates. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2696.pdf |
| |
|
|
| Sultan, Nabil; Voisset, Michel; Marsset, Bruno; Marsset, Tania; Cauquil, E; Colliat, J. |
| The study area, offshore Nigeria, is located in one of the compressional zones within the Niger Delta, which is characterized by imbricate thrust structures. Although the low mean slope angle (around 2°), bathymetry data from the study area have shown the existence of several submarine landslides which coincide with known subsurface faulted compressive features. In this paper, we have focused on a submarine slide occurring in water depths ranging between 1690 and 1750 m. Headwall scars, internal architecture and associated deposits have been characterized using a combination of 3D seismic data, near-bottom echosounder seismic profiles, Kullenberg cores and in-situ geotechnical measurements. The slide shows horseshoe shaped headwall scars and depositional... |
| Tipo: Text |
Palavras-chave: Slope stability; Piezometer; Penetrometer; Niger Delta; Modelling; Compressional structures. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2408.pdf |
| |
|
| |
|
|
| Sultan, Nabil; Garziglia, Sebastien. |
| Multi-phase fluid conditions encountered in geotechnical and geo-environmental problems have led to the development of models that account for the influence of gas solubility and compressibility on the behaviour of soils of various grain sizes. Yet, no consideration has been given to damages related to the nucleation and growth of gas bubbles in fine-grained soils. The purpose of this paper is to present a Cam Clay based constitutive model extended to incorporate such detrimental effects on gassy soils. This is achieved by deriving an analytical expression relating the preconsolidation pressure to a damage parameter dependent on the gas content. That expression is coupled to a deviatoric yield surface accounting for inherent and stress-induced anisotropy.... |
| Tipo: Text |
Palavras-chave: Compressibility; Constitutive relations; Offshore engineering; Shear strength. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00245/35621/34133.pdf |
| |
|
|
| 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 |
| |
|
|
| Taleb, Farah; Garziglia, Sebastien; Sultan, Nabil. |
| Increasing needs for energy resources have moved deep offshore developments and research efforts towards regions where high pressure and low temperature conditions allow gas and water to form Gas Hydrates (GH). However, owing to difficulties in sampling and preserving GH under in-situ stability conditions, GH-bearing sediments remain particularly challenging to characterise using conventional laboratory methods. This paper presents the experience gained in the use acoustic and piezocone soundings in characterising gas-hydrate bearing clayey sediments offshore Nigeria. Acoustic measurements of compressional wave velocity are shown to be an expedient means of both detecting and quantifying GH in sediments. Piezocone data and their location in normalised soil... |
| Tipo: Text |
|
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00466/57748/60000.pdf |
| |
|
| |
|
|
| Payo-payo, Marta; Silva Jacinto, Ricardo; Lastras, G.; Rabineau, Marina; Puig, P.; Martin, J.; Canals, M.; Sultan, Nabil. |
| Bottom trawling leads to recurrent sediment resuspension events over fishing grounds. Recent studies have shown how bottom trawling can drive seascape reshaping at large spatial scales and enhance sediment transport in submarine canyons, which subsequently impacts deep-sea ecosystems. Present knowledge on the transfer and accumulation of sediment flows triggered by bottom trawling is based on localized and infrequent measurements whilst a more complete picture of the process is needed. The present work focuses on the modeling of sediment transport and accumulation resulting from trawling activities in La Fonera submarine canyon, northwestern Mediterranean Sea, thus contributing to an improved assessment of trawling impacts. Based on mooring data within a... |
| Tipo: Text |
Palavras-chave: Bottom trawling; Inverse model; Modeling; Sediment transport; Submarine canyon; Turbidity currents. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00374/48549/48862.pdf |
| |
|
|
| Garziglia, Sebastien; Sultan, Nabil; Cattaneo, Antonio; Ker, Stephan; Marsset, Bruno; Riboulot, Vincent; Voisset, Michel; Adamy, J.; Unterseh,. |
| In a site investigation of the eastern part of the offshore Niger delta, cone penetration tests (CPTU) showed significant drops in tip resistance, associated with decreases in sleeve friction and induced excess pore pressures at the interface between superficial sediments and the underlying deposits of a mass-transport complex (MTC) called NG1. Such signature characteristics of weakened zones are clearly expressed at three sites where the drop in tip resistance reaches more than 40% over 2-3 m-thick intervals. Correlations between CPTU profiles and both 3D and ultrahigh-resolution 2D seismic data suggest that the weakened zones surround syndepositional the within the frontal part of NG1. Hence, weakening appears associated with the remobilization of thrust... |
| Tipo: Text |
Palavras-chave: Cone penetration tests; Shear zone; 3D seismic data; Ultrahigh-resolution 2D seismic; Mass-transport complex; Slope stability. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00105/21662/19695.pdf |
| |
|
|
| Sultan, Nabil. |
| While it is well accepted that gas hydrate dissociation at the base of the Gas Hydrate Stability Zone (GHSZ) can generate high excess pore pressure and leads to sediment deformation, the consequence in terms of pore pressure of the dissolution of the gas hydrate at the top of the Gas Hydrate Occurrence Zone (GHOZ) remains neglected. The purpose of this comment on Xu and Germanovich [2006] article is to demonstrate that gas hydrate dissolution in the GHSZ may generate excess pore pressure and to point out the risk related to hydrate dissolution at the top of the GHOZ. |
| Tipo: Text |
Palavras-chave: Pore pressure; Hydrate; Dissolution; Dissociation. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2318.pdf |
| |
|
|
| 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 |
| |
|
|
| Sultan, Nabil; Cattaneo, Antonio; Urgeles, R; Lee, H; Locat, J; Trincardi, F; Berne, Serge; Canals, M; Lafuerza, S. |
| This study is among the first to examine the genesis of the seafloor and subsurface undulations on the Adriatic continental shelf by integrating stratigraphic information and in situ and laboratory geotechnical measurements. Interpretation of sediment behavior is based on a 32-m-long borehole crossing ( 1) a possible shear plane and ( 2) a silty clay layer at about 20 m below seafloor (mbsf) on which sediment undulations are rooted and could be interpreted as a potential weak layer succession. Our main results in terms of triggering mechanism for the observed undulations show that under an earthquake, liquefaction and/or failure of the silty-clay sediments ( weak layer) leading to deformation of the upper more cohesive sediments is possible only when such... |
| Tipo: Text |
Palavras-chave: Sediment deformation; Shear strength; Earthquake; Adriatic shelf. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4105.pdf |
| |
|
|
| 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 |
| |
|
|
| Sultan, Nabil; Garziglia, Sebastien; Colliat, Jean-louis. |
| Published laboratory geotechnical data by Masui and co-authors showed that increase in gas hydrates content tend to increase the peak shear strength and stimulate strain softening of the host sediment. Therefore, development of shear strains may lead to an important degradation of the shear strength (strain softening). In the present work, the strain softening of gas hydrate-bearing sediments was implemented in a 3D slope stability model (SAMU-3D). This was done by adding to the classical limit analysis method a shear strain field compatibility equivalent to the velocity field compatibility. Examples of slope failures related to strain softening behavior documented in the literature were used to test the model formulation. The developed model was then used... |
| Tipo: Text |
|
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00035/14625/11903.pdf |
| |
|
|
| 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 |
| |
| Registros recuperados: 64 | |
|
|
|
