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| De Prunele, Alexis; Ruffine, Livio; Riboulot, Vincent; Peters, Carl A.; Croguennec, Claire; Guyader, Vivien; Pape, Thomas; Bollinger, Claire; Bayon, Germain; Caprais, Jean-claude; Germain, Yoan; Donval, Jean-pierre; Marsset, Tania; Bohrmann, Gerhard; Geli, Louis; Rabiu, Abdulkarim; Lescanne, Marc; Cauquil, Eric; Sultan, Nabil. |
| The Niger Delta is one of the largest hydrocarbon basin offshore Africa and it is well known for the presence of active pockmarks on the seabed. During the Guineco-MeBo cruise in 2011, long cores were taken from a pockmark cluster in order to investigate the state of its current activity. Gas hydrates, oil and pore-water were sampled for geochemical studies. The resulting dataset combined with seismic data reveal that shallow hydrocarbon migration in the upper sedimentary section was focused exclusively within the pockmarks. There is a clear tendency for gas migration within the hydrate-bearing pockmarks, and oil migration within the carbonate-rich one. This trend is interpreted as a consequence of hydrate dissolution followed by carbonate precipitation... |
| Tipo: Text |
Palavras-chave: Anaerobic oxidation of methane; Cluster of pockmarks; Fluid flow; Gas hydrates; Pore-water profiles; Transient state. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00365/47647/47676.pdf |
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| Sultan, Nabil; Marsset, Bruno; Ker, Stephan; Marsset, Tania; Voisset, Michel; Vernant, Antoine-mathieu; Bayon, Germain; Cauquil, Eric; Adamy, J.; Colliat, J. L.; Drapeau, D.. |
| Based on acquired geophysical, geological and geotechnical data and modeling, we suggest hydrate dissolution to cause sediment collapse and pockmark formation in the Niger delta. Very high-resolution bathymetry data acquired from the Niger delta reveal the morphology of pockmarks with different shapes and sizes going from a small ring depression surrounding an irregular floor to more typical pockmarks with uniform depression. Geophysical data, in situ piezocone measurements, piezometer measurements and sediment cores demonstrate the presence of a common internal architecture of the studied pockmarks: inner sediments rich in gas hydrates surrounded by overpressured sediments. The temperature, pressure and salinity conditions of the studied area have allowed... |
| Tipo: Text |
Palavras-chave: Methane gas hydrate; Sea floor; Marine sediments; Pore pressure; Porous media; Continental margin; Clathrate hydrate; Fluid flow; Stability; Slope. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00012/12300/9092.pdf |
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| Bayon, Germain; Henderson, Gideon M.; Etoubleau, Joel; Caprais, Jean-claude; Ruffine, Livio; Marsset, Tania; Dennielou, Bernard; Cauquil, Eric; Voisset, Michel; Sultan, Nabil. |
| The application of uranium-thorium dating methods to authigenic carbonates provides unique constraints on the temporal evolution of methane seeps at ocean margins. In this study, we report U-Th isotope measurements for carbonate breccias collected from within a hydrate-bearing pockmark located at the Niger Delta margin. These concretions were extracted from a carbonate-rich layer in the upper two meters of a sediment core (N2-KS-44; ~ 1200 m water depth), well above the present-day sulphate-methane transition zone (about 3 m depth) and the presence of gas hydrates in the sediment. The stratigraphy of core N2-KS-44 was established by tuning its downcore Al/Ti profile to a well-dated nearby reference core, and carbonate 230Th/U ages were calculated using... |
| Tipo: Text |
Palavras-chave: Gas hydrates; Pockmarks; U-series; Authigenic carbonates; Niger delta. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00286/39708/41518.pdf |
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