Seismic and heat flow constraints from the gas hydrate system in the Krishna–Godavari Basin, India

Shankar, Uma; Riedel, Michael

doi:10.1016/j.margeo.2010.06.006

Cited by 30 publications

(22 citation statements)

References 41 publications

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“…Smectite bearing Godavari Clay Formation constitutes the Holocene-Pleistocene deposit of the K-G basin (Rao, 2001). 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).…”

Section: Geological Settingmentioning

confidence: 99%

“…Bright spots, acoustic blanking/turbidity and drop in P-wave velocity below BSR testify the presence of free gas (Dewangan et al, 2010;Shankar and Riedel, 2010).…”

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

“…Shale tectonics (diapirism) induced deep fault system has been amply demonstrated from the K-G Basin (Mazumdar et al, 2009b;Dewangan et al, 2010;Shankar and Riedel, 2010;Riedel et al, 2010;Choudhury et al,2011). Shale tectonic is driven by the downward movement of thick sediment mass over a deeply buried over pressured shale strata (Damuth, 1994;Wu and Bally, 2000).…”

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

“…Migration through the deep fault systems possibly played an important role in advection of the fluids (Shankar and Riedel, 2010;Dewangan et al, 2011;Jaiswal et al, 2012). Fluids advecting from greater depths are likely to be much warmer than the shallow sediments in the GHSZ (Max et al, 2006).…”

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

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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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Section: Geological Settingmentioning

confidence: 99%

“…Bright spots, acoustic blanking/turbidity and drop in P-wave velocity below BSR testify the presence of free gas (Dewangan et al, 2010;Shankar and Riedel, 2010).…”

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

Section: Gas Hydrate Destabilzation: Tectonics and Perturbed P-t Condmentioning

confidence: 99%

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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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“…The dominant lithology in the sediments sampled during NGHP-01 is clay, with silt as a minor lithology and some authigenic carbonate-rich zones (Collett et al 2008). Stratigraphic environments across the margin include a wide range of passive margin depositional settings, including delta, shelf-slope apron, deep-sea channels and channellevee, and deep-water fan deposits (Shankar and Riedel, 2010). In particular, the very rapid sediment flux has lead to a topography on the mid-slope characterized by arcuate ridges known at "toe thrusts" that are formed as sediment flows downslope (Shankar and Riedel, 2010).…”

Section: Krishna-godavari Basin -Geologic Settingmentioning

confidence: 99%

Heat Flow and Gas Hydrates on the Continental Margin of India: Building on Results from NGHP Expedition 01

Tréhu¹,

Kannberg²

2011

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The Indian National Gas Hydrate Program (NGHP) Expedition 01 presented the unique opportunity to constrain regional heat flow derived from seismic observations by using drilling data in three regions on the continental margin of India. The seismic bottom simulating reflection (BSR) is a well-documented feature in hydrate bearing sediments, and can serve as a proxy for apparent heat flow if data are available to estimate acoustic velocity and density in water and sediments, thermal conductivity, and seafloor temperature. Direct observations of temperature at depth and physical properties of the sediment obtained from drilling can be used to calibrate the seismic observations, decreasing the uncertainty of the seismically-derived estimates. Anomalies in apparent heat flow can result from a variety of sources, including sedimentation, erosion, topographic refraction and fluid flow. We constructed apparent heat flow maps for portions of the Krishna-Godavari (K-G) basin, the Mahanadi basin, and the Andaman basin and modeled anomalies using 1-D conductive thermal models.Apparent heat flow values in the Krishna-Godavari (K-G) basin and Mahanadi basin are generally 0.035 to 0.055 watts per square meter (W/m 2 ). The borehole data show an increase in apparent heat flow as water depth increases from 900 to 1500 m. In the SW part of the seismic grid, 1D modeling of the effect of sedimentation on heat flow shows that ~50% of the observed increase in apparent heat flow with increasing water depth can be attributed to trapping of sediments behind a "toe-thrust" ridge that is forming along the seaward edge of a thick, rapidly accumulating deltaic sediment pile. The remainder of the anomaly can be explained either by a decrease in thermal conductivity of the sediments filling the slope basin or by lateral advection of heat through fluid flow along stratigraphic horizons within the basin and through flexural faults in the crest of the anticline. Such flow probably plays a role in bringing methane into the ridge formed by the toe-thrust. Because of the small anomaly due to this process and the uncertainty in thermal conductivity, we did not model this process explicitly. In the NE part of the K-G basin seismic grid, a number of local heat flow lows and highs are observed, which can be attributed to topographic refraction and to local fluid flow along faults, respectively. No regional anomaly can be resolved. Because of lack of continuity between the K-G basin sites within the seismic grid and those ~70 km to the NE in water depths of 1200 to 1500 m, we do not speculate on the reason for higher heat flow at these depths. The Mahanadi basin results, while limited in geographic extent, are similar to those for the K-G basin.The Andaman basin exhibits much lower apparent heat flow values, ranging from 0.015 to 0.025 W/m 2 . Heat flow here also appears to increase with increasing water depth. The very low heat flow here is among the lowest heat flow observed anywhere and gives rise to a very thick hydrate stability zone in the...

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Controls on evolution of gas‐hydrate system in the Krishna‐Godavari basin, offshore India

Badesab

Dewangan

Usapkar

et al. 2017

Geochem Geophys Geosyst

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In this study, we integrate environmental magnetic, sedimentological, and geochemical records of sediment core of Hole NGHP-01-10D overlying methane hydrate deposits to decipher the controls on the evolution of fracture-filled gas-hydrate system in the Krishna-Godavari (K-G) basin. Four distinct sedimentary units have been identified, based on the sediment magnetic signatures. An anomalous zone of enhanced magnetic susceptibility (Unit III: 51.9-160.4 mbsf) coinciding with the gas hydrate bearing intervals is due to the presence of magnetite-rich detrital minerals brought-in by the river systems as a result of higher sedimentation events in K-G basin and has no influence over hydrate formation. A strong to moderate correlation between magnetite concentration and chromium reducible sulfur (CRS) content indicates significant influence of sulfidization on the magnetic record and could be further exploited as a proxy to decipher paleo-H 2 S seepage events. Analysis of high-resolution seismic, bathymetry, and subbottom profiler data reveals the existence of a regional fault system in K-G basin. The opening and closing dynamics of the faults facilitated the migration and trapping of required gas concentrations resulting in accumulation of gas hydrates at the studied site. The seismic data provides support to the rock-magnetic interpretations. The observed variations in magnetic and geochemical properties have resulted from the episodic flow of methane and sulfide-enriched fluids through the fracture-filled network formed as a result of shale-tectonism. Our study demonstrated the potential of using an enviro-magnetic approach in combination with other proxies to constrain the evolution of gas-hydrate system in marine environments. Key Points:Magnetic signatures of detrital and diagenetic processes associated with evolution of gas-hydrate system. Changes in magnetic and geochemical properties controlled by underlying gas-hydrates. Magnetic proxy to decipher paleo-H2S seepage events in marine sediments.

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Seismic and heat flow constraints from the gas hydrate system in the Krishna–Godavari Basin, India

Cited by 30 publications

References 41 publications

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

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

Heat Flow and Gas Hydrates on the Continental Margin of India: Building on Results from NGHP Expedition 01

Controls on evolution of gas‐hydrate system in the Krishna‐Godavari basin, offshore India

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