Gas hydrate and free gas volumes in marine sediments: Example from the Niger Delta front

Hovland, Martin; Gallagher, Joseph W.; Clennell, Michael B.; Lekvam, Knut

doi:10.1016/s0264-8172(97)00012-3

Cited by 115 publications

(71 citation statements)

References 34 publications

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“…Pore water flow can be focused by layers of high permeability in sediments (Hovland et al, 1997;Aoki et al, 2000;Flemings et al, 2002). Lateral flow steered by sediment permeability predicts expulsion of fluid near the base of the continental slope off New Jersey, consistent with the observed patterns of porewater seeps, and leading to nucleation of landslides from the base of the slope, consistent with the observation of submarine canyons on continental margins (Dugan and Flemings, 2000).…”

Section: Aqueous Flowsupporting

confidence: 73%

Methane hydrate stability and anthropogenic climate change

2007

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Abstract. Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO 2 .Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release as much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

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Section: Aqueous Flowsupporting

confidence: 73%

Methane hydrate stability and anthropogenic climate change

2007

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“…The study area is the continental slope off Nigeria where a large number and variety of surveys have been carried out in recent years as a result of oil and gas industry interest. The continental slope off Nigeria is one of the areas where the occurrence near the seafloor of instability and deformation features have been detected previously by several authors (Damuth, 1994;Cohen and McClay, 1996;Hovland et al, 1997;Brooks et al, 2000;Graue, 2000;Deptuck et al, 2003 among others). This type of shallow feature is of special interest to industrial development because it could become a major risk to any future oil development.…”

Section: Introductionmentioning

confidence: 74%

Potential role of compressional structures in generating submarine slope failures in the Niger Delta

et al. 2007

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International audienceThe 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 lobes with positive relief. Monitoring of excess pore pressure for 12 months indicates the presence of negative hydraulic gradients, which is either an indication of a local present-day mechanical activity of subsurface faults or related to the regional extension of the Niger Delta and the possible creation of a regional depression in the hydraulic regime. In order to identify the triggering mechanism of the observed landslide, a three-dimensional slope stability model (SAMU-3D) based on the upper bound theorem of plasticity was used. Calculation results have shown that the gravity loading generated by the sediment weight alone is not sufficient to explain the observed submarine slide. Cylindrical cavity expansion theory was used to locally simulate the compressional structure movements and to evaluate the strength generated within the upper sediment layers. Slope stability assessment carried out by considering this additional structural strength has shown that regional compressional gravity driven deformation can explain the observed submarine failures

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“…The upper bound of the gray area corresponds to values of α = 0.77 (zero hydrate at the BSR) and υ = 0.45; the lower bound corresponds to low end values of α = 0.67 (25% bulk hydrate) and υ = 0.41. Point locations: 1, Barents Sea (Andreassen et al, 1990); 2, the norwegian margin (Mienert et al, 2000); 3, Bering Sea basin (Scholl and Hart, 1993); 4, 5, Blake Ridge (Holbrook et al, 1996); 6, Beaufort Sea (Andreassen et al, 1995); 7-9, basin in Makran accretionary prism that has experienced rapid sedimentation (Sain et al, 2000;Grevemeyer et al, 2000); 10, offshore Cascadia (Hyndman et al, 2001); 11, offshore Chile (Bangs et al, 1993;Miller, et al, 1996), niger delta (Hovland et al, 1997); 13, 15, offshore Colombia (Minshull et al, 1994); 14, Gulf of Oman anticline (Minshull and White, 1989); 16, offshore Peru (Pecher et al, 1996); 17, South Shetland islands (Tinivella et al, 1998); 18, 19, Oman accretionary toe (White, 1979). Top inset, model of the hydrate stability zone and critically thick FGZ below for a bottom water temperature of 0°C.…”

Section: Geological Hazardsmentioning

confidence: 99%

Geological Hazards

Rajput¹

2016

Geological Controls for Gas Hydrate Formations and Unconventionals

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Gas hydrate and free gas volumes in marine sediments: Example from the Niger Delta front

Cited by 115 publications

References 34 publications

Methane hydrate stability and anthropogenic climate change

Methane hydrate stability and anthropogenic climate change

Potential role of compressional structures in generating submarine slope failures in the Niger Delta

Geological Hazards

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