Velocity Structure of a Gas Hydrate Reflector

Singh, S. C.; Minshull, T. A.; Spence, G. D.

doi:10.1126/science.260.5105.204

Cited by 250 publications

(170 citation statements)

References 16 publications

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“…Previous studies suggest that most of the BSR amplitude is due to the velocity reduction of the underlying free gas (Singh et al, 1993;MacKay et al, 1994;Hyndman et al, 2001;Pecher et al, 2001). The presence of a free-gas zone (FGZ) is an important part of the gas hydrate system, and is particularly important if the presence of gas hydrate is to be…”

Section: Geophysical Explorationmentioning

confidence: 99%

Review of exploration and production technology of natural gas hydrate

Cui

Lü

et al. 2018

Adv. Geo-Energy Res.

108

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Abstract:Natural gas hydrate is an ice-like substance which is sometimes called "combustible ice" since it can literally be lighted on fire and burned as fuel. Natural gas hydrate is characterized by widespread distribution, large reserves and little pollution. This paper introduced the distributions of hydrate, hydrate reserves and properties of hydrate. The main exploration methods, such as geophysical exploration and geochemical exploration have been presented. In addition, the main production techniques of natural gas hydrate including depressurization, thermal stimulation and chemical injection have been summed up. Finally, the challenges and outlooks of natural gas hydrate production have been proposed.

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Section: Geophysical Explorationmentioning

confidence: 99%

Review of exploration and production technology of natural gas hydrate

Cui

Lü

et al. 2018

Adv. Geo-Energy Res.

108

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“…BSRs are generally caused by gas at the base of the gas hydrate stability zone (Singh et al 1993), a phase boundary determined by pressure and temperature conditions. BSRs in seismic data are therefore subparallel to the seafloor, often crosscutting the stratigraphic structure.…”

Section: Introductionmentioning

confidence: 99%

Seismic images of gas conduits beneath vents and gas hydrates on Ritchie Ridge, Hikurangi margin, New Zealand

Pecher¹,

Henrys

Zhu

2004

New Zealand Journal of Geology and Geophysics

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Recently acquired seismic reflection data across the southern edge of Ritchie Ridge, a prominent bathymetric high on the Hikurangi margin, display zones of high amplitudes and reflections that crosscut strata. We interpret the latter as bottom-simulating reflections which are commonly associated with gas beneath gas hydrates. An analysis of reflection strength indicates the high-amplitude zones are caused by free gas in the pore space of sediments, probably migrating upward along layers. One of the highamplitude regions is situated beneath the projected location of a known gas vent site. The seismic data appear to image the conduits that supply this vent site with gas. The seafloor in most of the study area is likely to be within the zone of gas hydrate stability, depending on bottom water temperatures and hydrate composition. Hence, gas appears to be venting through the gas hydrate stability zone, favouring locally high concentrations of gas hydrates.

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“…The seismic reflection data off K-G basin (Collett et al, 2008;Dewangan et al, 2010;Shankar and Riedel, 2010) show regional presence of gas hydrates manifested in the form of bottom simulating reflectors (BSR) observed at depth of 125 mbsf (water depth: 945m) to 220 mbsf (water depth 1146 m). BSRs represent a phase boundary, where the low-velocity, gas-charged sediments occur below the high-velocity gas hydrate bearing sediments (Singh and Minshull, 1993). Ramana et al (2007) and Dewangan et al (2010) have reported various shale tectonics induced structures like bathymetric mounds, deep seated shale diapirs and toe thrust faults from the K-G basin.…”

Section: Geological Settingmentioning

confidence: 99%

Gas hydrate destabilization and methane release events in the Krishna–Godavari Basin, Bay of Bengal

Joshi¹,

Mazumdar²,

Peketi³

et al. 2014

Marine and Petroleum Geology

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Methane release events have been linked to global warming, alteration of the carbon cycle and influence on biota. However, unequivocal evidence of paleomethane release events are limited. We report several negative carbon stable isotope excursions in planktic and benthic foraminifera in a core (MD161-8) from the Krishna-Godavari (K-G) Basin, Bay of Bengal. The most negative δ 13 C spikes are recorded during the marine isotope stages MIS-4 and at the transition of MIS-5 to 4. Occurrence of highly 13 C depleted (average δ 13 C = -48±2.4 ‰ VPDB) authigenic high magnesian calcite are also reported within this time window from the core MD161-8. In the present work an unequivocal explanation for the observed 13 C depletion in the marine planktic and benthic foraminifera is difficult to achieve solely from the optical/ electron microscopy or C-O stable isotope ratio analyses due to possible influence of diagenetic alteration. We attribute the observed episodic methane expulsion events, as inferred from the negative δ 13 C excursions and earlier reports on the occurrence chemosynthetic bivalves and Mo concentration anomaly to the destabilization of the base of gas hydrate stability zone (BGHSZ). Sea level drop and shale tectonics induced focused fluid flow are the two possible causes of hydrate destabilization discussed here. Shale tectonics were possibly responsible for creating fault systems which acted as the conduit for gas flow through the sediment column and subsequent seepage. Shale and salt tectonics in the passive continental margins being a globally observed phenomenon, its role as an important driving force for enhanced methane emission needs detailed investigation to understand the climatic perturbations through geologic time. Additional evidence of methane emission from site MD161-15 further supports the link between shale tectonics and methane emission.

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Velocity Structure of a Gas Hydrate Reflector

Cited by 250 publications

References 16 publications

Review of exploration and production technology of natural gas hydrate

Review of exploration and production technology of natural gas hydrate

Seismic images of gas conduits beneath vents and gas hydrates on Ritchie Ridge, Hikurangi margin, New Zealand

Gas hydrate destabilization and methane release events in the Krishna–Godavari Basin, Bay of Bengal

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