Geophysical evidence for gas hydrates in the deep water of the South Caspian Basin, Azerbaijan

Diaconescu, Camelia; Kieckhefer, R. M.; Knapp, J. H.

doi:10.1016/s0264-8172(00)00061-1

Cited by 62 publications

(46 citation statements)

References 23 publications

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“…In low heat flow sedimentary basins such as the South Caspian Basin, where the geothermal gradients are as low as 13°C/km [Tagiyev et al, 1997], such geometries will be critical in assessing the extent of shallow gas hydrate systems. However, the well-defined BSRs observed in the South Caspian Basin [Diaconescu et al, 2001] do not reach the shallow depths that would correspond to our modeled hydrate bulge.…”

Section: Discussioncontrasting

confidence: 58%

“…That said, extremely high sedimentation rates with the greatest effect on geothermal gradients might be considered more likely in high-energy, sand-dominated systems [cf. Diaconescu et al, 2001]. Contrasting this, however, is the requirement for organic sediments (greater in clays) that are necessary to source methane for hydrate accumulations in the HSZ.…”

Section: Discussionmentioning

confidence: 99%

“…High sedimentation rates also may lead to high rates of vertical fluid flux, thereby supporting the presence of gas hydrates. Well-defined BSRs in the South Caspian Basin support this [Diaconescu et al, 2001]. geothermal gradients, bottom water conditions, and slope geometries [Senger, 2006;Senger et al, 2006].…”

Section: Introductionmentioning

confidence: 86%

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Defining the updip extent of the gas hydrate stability zone on continental margins with low geothermal gradients

Gorman¹,

Senger²

2010

J. Geophys. Res.

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[1] The distribution of gas hydrate on a continental slope is often characterized as a wedge that pinches out on the seafloor. This part of the hydrate stability zone is particularly relevant for studies of the dynamics of hydrate accumulations, such as processes related to slope stability or hydrate dissociation leading to methane release into the overlying ocean. For regions with very low geothermal gradients, we have produced a series of thermobaric models of the shallow hydrate stability zone that contain an unexpected geometrical distribution of hydrated sediments. In these models, the shallowest part of the stability field thickens and bulges landward. Such a feature is more likely to happen in regions where low geothermal gradients are further lowered by high sedimentation rates. Also, the effect is greater beneath colder oceans. Although a hydrate stability zone bulge would be difficult to image with conventional seismic methods, there are numerous locations around the world where such a system could develop.Citation: Gorman, A. R., and K. Senger (2010), Defining the updip extent of the gas hydrate stability zone on continental margins with low geothermal gradients,

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Section: Discussioncontrasting

confidence: 58%

Section: Discussionmentioning

confidence: 99%

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Defining the updip extent of the gas hydrate stability zone on continental margins with low geothermal gradients

Gorman¹,

Senger²

2010

J. Geophys. Res.

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“…During intensive expropation in South Caspian gas hydrates were discovered offshore Azerbaijan both on the top of mud volcanoes [Ginsburg & Soloviev, 1994] and in fairly undisturbed sedimentary section by clear seismic BSR [Diaconescu et al, 2001]. Zones A on heat flow map adopted from Glumov [2004] on Figure 1 correlate with "allowed existence" areas caluculated from parameters in Diaconesu [2001].…”

Section: Figure 2 (Right)mentioning

confidence: 99%

Sediment waves: geohazard or geofeature?

Putans¹

2012

Hydro12 - Taking Care of the Sea

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“…In particular, using high quality seismic information, Diaconescu et al (2001) obtain a depth range this way for hydrates in the deep waters of the South Caspian basin. They obtain a basal estimate for the hydrates of around 500m below the sediment surface, which is the same zone range as obtained by other methods of estimation (Lerche and Bagirov, 1999).…”

Section: A Theoretical Considerationsmentioning

confidence: 99%

Hydrate Composition from Seismic Data: An Inverse Procedure

Lerche

Noeth

2002

Energy Exploration & Exploitation

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Hydrate existence conditions and the associated thermal gradients are examined using equations of state for mixes of gases. Three examples are developed to illustrate the resolution possible in determining the composition of a hydrate and the required range of thermal gradient using seismic information concerning the depth and thickness of a hydrate-bearing body. The examples use shallow (70m), medium (250m) and deep (600m) water as archetypical conditions. In general, it is shown that one cannot determine a unique composition for the hydrate due to incomplete knowledge of parameters in the hydrate existence equations of state, including the lack of knowledge concerning salinity and sedimentary lithological effects on parameters in the equations of state, and also due to such parameters being massively influenced by the types and mixing fractions of gases that compose the hydrate. What is shown is that it is possible to determine the cumulative probability that a hydrate has greater than a given fraction of methane and at the same time determine the probability that the associated thermal gradient lies within geologically required constraints. In association with this determination, one can also identify the relative contributions of each uncertain parameter to the resolution of the methane fraction and the thermal gradient, including geological parameters (such as sediment density) and "kinetic" parameters in the hydrate equation of state. In this way one can determine where to place effort in any further attempt to narrow down the uncertainty in the methane fraction for a given hydrate, and one can also identify when it is necessary to do so. These aspects are developed in the paper. There is also the point that, for deep water hydrates, the attempt to use the top of the hydrate body as the shallowest depth for hydrate existence can fail and recourse to a more appropriate strategy, but one that is not so statistically sharp, is required. This aspect, too, is developed in the paper. The main point to make is that the quantitative procedure developed here allows one to use seismic data directly to assess a hydrate body, to determine what can be deduced concerning hydrate composition, the sort of uncertainty one has to contend with, and also to determine the worth of proceeding further with more information collection to help resolve better the uncertainties.

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Geophysical evidence for gas hydrates in the deep water of the South Caspian Basin, Azerbaijan

Cited by 62 publications

References 23 publications

Defining the updip extent of the gas hydrate stability zone on continental margins with low geothermal gradients

Defining the updip extent of the gas hydrate stability zone on continental margins with low geothermal gradients

Sediment waves: geohazard or geofeature?

Hydrate Composition from Seismic Data: An Inverse Procedure

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