scholarly journals Potential Instability of Gas Hydrates along the Chilean Margin Due to Ocean Warming

Geosciences ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 234 ◽  
Author(s):  
Giulia Alessandrini ◽  
Umberta Tinivella ◽  
Michela Giustiniani ◽  
Iván de la Cruz Vargas-Cordero ◽  
Silvia Castellaro
Keyword(s):  
Climate Change ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Natural Phenomena ◽  
Intergovernmental Panel ◽  
The Relationship ◽  
Natural Laboratory ◽  
High Seismicity ◽  
Hydrate Stability ◽  
Chilean Margin

In the last few years, interest in the offshore Chilean margin has increased rapidly due to the presence of gas hydrates. We have modelled the gas hydrate stability zone off Chilean shores (from 33° S to 46° S) using a steady state approach to evaluate the effects of climate change on gas hydrate stability. Present day conditions were modelled using published literature and compared with available measurements. Then, we simulated the effects of climate change on gas hydrate stability in 50 and 100 years on the basis of Intergovernmental Panel on Climate Change and National Aeronautics and Space Administration forecasts. An increase in temperature might cause the dissociation of gas hydrate that could strongly affect gas hydrate stability. Moreover, we found that the high seismicity of this area could have a strong effect on gas hydrate stability. Clearly, the Chilean margin should be considered as a natural laboratory for understanding the relationship between gas hydrate systems and complex natural phenomena, such as climate change, slope stability and earthquakes.

scholarly journals A review of the gas hydrate distribution offshore Chilean margin

2021 ◽  
Vol 230 ◽  
pp. 01007
Author(s):  
Ivan Vargas-Cordero de la Cruz ◽  
Michela Giustiniani ◽  
Umberta Tinivella ◽  
Giulia Alessandrini
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
The Other ◽  
Hydrate Dissociation ◽  
Hydrate Reservoir ◽  
Gas Hydrate Reservoir ◽  
Submarine Slides ◽  
Seismic Lines ◽  
Natural Laboratory ◽  
Chilean Margin

In last decades, the Chilean margin has been extensively investigated to better characterize the complex geological setting through the acquisition of geophysical data and, in particular, seismic lines. The analysis of seismic lines allowed identifying the occurrence of gas hydrates and free gas in many places along the margin. Clearly, the gas hydrate reservoir could be a strategic energy reserve for Chile, but, on the other hand, the dissociated of gas hydrate due to climate change could be an issue to face. Moreover, this region is characterized by large and mega-scale earthquakes that may contribute to gas hydrate dissociation and consequent submarine slides triggering. In this context, Chilean margin should be considered a natural laboratory to study the hydrate system evolution.

scholarly journals Role of Salt Migration in Destabilization of Intra Permafrost Hydrates in the Arctic Shelf: Experimental Modeling

Geosciences ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 188 ◽  
Author(s):  
Evgeny Chuvilin ◽  
Valentina Ekimova ◽  
Boris Bukhanov ◽  
Sergey Grebenkin ◽  
Natalia Shakhova ◽  
...  
Keyword(s):  
Gas Hydrates ◽  
Methane Emission ◽  
Gas Hydrate ◽  
Negative Temperature ◽  
Arctic Shelf ◽  
The Arctic ◽  
Permafrost Degradation ◽  
Stability Zone ◽  
Local Pressure ◽  
Hydrate Stability

Destabilization of intrapermafrost gas hydrate is one possible reason for methane emission on the Arctic shelf. The formation of these intrapermafrost gas hydrates could occur almost simultaneously with the permafrost sediments due to the occurrence of a hydrate stability zone after sea regression and the subsequent deep cooling and freezing of sediments. The top of the gas hydrate stability zone could exist not only at depths of 200–250 m, but also higher due to local pressure increase in gas-saturated horizons during freezing. Formed at a shallow depth, intrapermafrost gas hydrates could later be preserved and transform into a metastable (relict) state. Under the conditions of submarine permafrost degradation, exactly relict hydrates located above the modern gas hydrate stability zone will, first of all, be involved in the decomposition process caused by negative temperature rising, permafrost thawing, and sediment salinity increasing. That’s why special experiments were conducted on the interaction of frozen sandy sediments containing relict methane hydrates with salt solutions of different concentrations at negative temperatures to assess the conditions of intrapermafrost gas hydrates dissociation. Experiments showed that the migration of salts into frozen hydrate-containing sediments activates the decomposition of pore gas hydrates and increase the methane emission. These results allowed for an understanding of the mechanism of massive methane release from bottom sediments of the East Siberian Arctic shelf.

The Double (or Multiple) BSRs Observations and their Tentative Interpretations

2013 ◽  
Vol 734-737 ◽  
pp. 467-475
Author(s):  
Yi Luo ◽  
Xin Su
Keyword(s):  
Climate Change ◽  
Marine Environment ◽  
Gas Hydrate ◽  
Seismic Reflection ◽  
Continental Margins ◽  
Tectonic Movement ◽  
Stability Zone ◽  
Bottom Simulating Reflector ◽  
Seismic Reflection Profiles ◽  
Hydrate Stability

Gas hydrate is a solid ice-like compound and is stable at low temperature and high pressure conditions found beneath permafrost and in marine sediments on continental margins offshore. In the marine environment, the bottom-simulating reflector (BSR) in seismic reflection profiles is interpreted to indicate the base of the gas hydrate stability zone (GHSZ).In many locations two or more sub-parallel BSRs have been reported. We not only compared the BSRs characteristics from reported areas but also discussed the mechanism of GHSZ shifts by climate change, sedimentation process and tectonic movement. We also considered the mix gases composition hydrate stability in certain marine environment and gave a simple model for the BSR differences on water depth.

scholarly journals A Geophysical Review of the Seabed Methane Seepage Features and Their Relationship with Gas Hydrate Systems

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-26
Author(s):  
Jinxiu Yang ◽  
Mingyue Lu ◽  
Zhiguang Yao ◽  
Min Wang ◽  
Shuangfang Lu ◽  
...  
Keyword(s):  
Climate Change ◽  
Gas Hydrate ◽  
Greenhouse Gas Emission ◽  
Spatial Relationship ◽  
Methane Flux ◽  
Fluid Migration ◽  
Stability Zone ◽  
Methane Seepage ◽  
Migration Pathways ◽  
Hydrate Stability

Seabed methane seepage has gained attention from all over the world in recent years as an important source of greenhouse gas emission, and gas hydrates are also regarded as a key factor affecting climate change or even global warming due to their shallow burial and poor stability. However, the relationship between seabed methane seepage and gas hydrate systems is not clear although they often coexist in continental margins. It is of significance to clarify their relationship and better understand the contribution of gas hydrate systems or the deeper hydrocarbon reservoirs for methane flux leaking to the seawater or even the atmosphere by natural seepages at the seabed. In this paper, a geophysical examination of the global seabed methane seepage events has been conducted, and nearby gas hydrate stability zone and relevant fluid migration pathways have been interpreted or modelled using seismic data, multibeam data, or underwater photos. Results show that seabed methane seepage sites are often manifested as methane flares, pockmarks, deep-water corals, authigenic carbonates, and gas hydrate pingoes at the seabed, most of which are closely related to vertical fluid migration structures like faults, gas chimneys, mud volcanoes, and unconformity surfaces or are located in the landward limit of gas hydrate stability zone (LLGHSZ) where hydrate dissociation may have released a great volume of methane. Based on a comprehensive analysis of these features, three major types of seabed methane seepage are classified according to their spatial relationship with the location of LLGHSZ, deeper than the LLGHSZ (A), around the LLGHSZ (B), and shallower than LLGHSZ (C). These three seabed methane seepage types can be further divided into five subtypes considering whether the gas source of seabed methane seepage is from the gas hydrate systems or not. We propose subtype B2 represents the most important seabed methane seepage type due to the high density of seepage sites and large volume of released methane from massive focused vigorous methane seepage sites around the LLGHSZ. Based on the classification result of this research, more measures should be taken for subtype B2 seabed methane seepage to predict or even prevent ocean warming or climate change.

Seismic attribute enhancement of weak and discontinuous gas hydrate bottom-simulating reflectors in the Pegasus Basin, New Zealand

2019 ◽  
Vol 7 (3) ◽  
pp. SG11-SG22 ◽  
Author(s):  
Heather Bedle
Keyword(s):  
New Zealand ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Seismic Data ◽  
Rock Physics ◽  
Stability Zone ◽  
Seismic Attribute ◽  
Rock Physics Modeling ◽  
Physics Modeling ◽  
Hydrate Stability

Gas hydrates in the oceanic subsurface are often difficult to image with reflection seismic data, particularly when the strata run parallel to the seafloor and in regions that lack the presence of a bottom-simulating reflector (BSR). To address and understand these imaging complications, rock-physics modeling and seismic attribute analysis are performed on modern 2D lines in the Pegasus Basin in New Zealand, where the BSR is not continuously imaged. Based on rock-physics and seismic analyses, several seismic attribute methods identify weak BSR reflections, with the far-angle stack data being particularly effective. Rock modeling results demonstrate that far-offset seismic data are critical in improving the imaging and interpretation of the base of the gas hydrate stability zone. The rock-physics modeling results are applied to the Pegasus 2009 2D data set that reveals a very weak seismic reflection at the base of the hydrates in the far-angle stack. This often-discontinuous reflection is significantly weaker in amplitude than typical BSRs associated with hydrates. These weak far-angle stack BSRs often do not appear clearly in full stack data, the most commonly interpreted seismic data type. Additional amplitude variation with angle (AVA) attribute analyses provide insight into identifying the presence of gas hydrates in regions lacking a strong BSR. Although dozens of seismic attributes were investigated for their ability to reveal weak reflections at the base of the gas hydrate stability zone, those that enhance class 2 AVA anomalies were most effective, particularly the seismic fluid factor attribute.

scholarly journals Arctic megaslide at presumed rest

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Wolfram H. Geissler ◽  
A. Catalina Gebhardt ◽  
Felix Gross ◽  
Jutta Wollenburg ◽  
Laura Jensen ◽  
...  
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Seismic Data ◽  
Slope Failure ◽  
Slope Instability ◽  
Stability Zone ◽  
Gas Reservoir ◽  
Methane Seepage ◽  
Failure Event ◽  
Hydrate Stability

Abstract Slope failure like in the Hinlopen/Yermak Megaslide is one of the major geohazards in a changing Arctic environment. We analysed hydroacoustic and 2D high-resolution seismic data from the apparently intact continental slope immediately north of the Hinlopen/Yermak Megaslide for signs of past and future instabilities. Our new bathymetry and seismic data show clear evidence for incipient slope instability. Minor slide deposits and an internally-deformed sedimentary layer near the base of the gas hydrate stability zone imply an incomplete failure event, most probably about 30000 years ago, contemporaneous to or shortly after the Hinlopen/Yermak Megaslide. An active gas reservoir at the base of the gas hydrate stability zone demonstrate that over-pressured fluids might have played a key role in the initiation of slope failure at the studied slope, but more importantly also for the giant HYM slope failure. To date, it is not clear, if the studied slope is fully preconditioned to fail completely in future or if it might be slowly deforming and creeping at present. We detected widespread methane seepage on the adjacent shallow shelf areas not sealed by gas hydrates.

Agriculture under Climate Change in the Northern Territories of Russia

2020 ◽  
pp. 41-46
Author(s):  
A.S. Shcherbakova ◽  
Keyword(s):  
Climate Change ◽  
Pair Correlation ◽  
Climatic Data ◽  
Ordinary People ◽  
Intergovernmental Panel ◽  
The North ◽  
Northern Territories ◽  
Relationship Of ◽  
The Impact ◽  
The Relationship

A special report published in October 2018 by the Intergovernmental Panel on Climate Change on the effects of global warming at 1.5 °C caused another resonance among the scientific community, experts, politicians and ordinary people [20]. It has been prove that northern territories are most affect by climate change. Because of this report, it becomes relevant to study the impact of climate change on agriculture in the North, which is the most climate-dependent in comparison with other sectors of the economy. The work is devoted to assessing the impact of agro-climatic indicators on productivity and gross harvest of the main agricultural crops of some regions of the Far North and equivalent areas for 1960-2018. The analysis of the relationship of pair correlation between the yield of cereals, potatoes, vegetables and selected climatic indicators relating to the growing season is carry out. Agro-climatic resources for half a century of time in the studied regions are analyzed. Each region was considered in the context of the available meteorological stations and their climatic data.

Characterization of gas accumulation at a venting gas hydrate system in Shenhu area, south china sea

2021 ◽  
pp. 1-45
Author(s):  
JInqiang Liang ◽  
Zijian Zhang ◽  
Jingan Lu ◽  
Guo Yiqun ◽  
Zhibin Sha ◽  
...  
Keyword(s):  
South China Sea ◽  
Wave Velocity ◽  
South China ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Stability Zone ◽  
Shenhu Area ◽  
Free Gas ◽  
Seismic Amplitude ◽  
Hydrate Stability

Bottom-simulating reflections (BSR) in seismic data have been widely accepted to indicate the base of methane gas hydrate stability zone (MGHSZ) and free gas was thought to exist only below it. However, real geologic systems are far more complex. Here, we presented the results of three-dimensional seismic, logging while drilling (LWD), in situ and coring measurements at a venting gas hydrate system in the Shenhu area of the South China Sea. Our studies reveal that free gas has migrated upward through the thermogenic gas hydrate stability zone (TGHSZ) into the MGHSZ and become a part of the gas hydrate system. Seismic amplitude anomalies and core results suggest the presence of free gas above the base of MHSZ at 165 mbsf and the presence of thermogenic gas hydrates below it in the well SC-W01. Analyses of P-wave velocity, S-wave velocity, density, and porosity logs reveal free gas occurs above and below the MGHSZ as well. Integrating log and core analysis with seismic interpretation suggests that the variation in seismic amplitude within chaotic zone is associated with variable gas saturations, and a large amount of methane and thermogenic gases accumulate near the complex BSRs. We propose that relative permeability likely plays a significant role in the free gas distribution and formation of gas hydrates within a venting gas hydrate system, while the effect of dissolved-gas short migration is not ignored. Our results have important implications for understanding the accumulation and distribution of gas hydrates and free gas in the venting gas hydrate system and seeps at the seafloor.

scholarly journals The politics of anticipation: the IPCC and the negative emissions technologies experience

2018 ◽  
Vol 1 ◽  
Author(s):  
Silke Beck ◽  
Martin Mahony
Keyword(s):  
Climate Change ◽  
Intergovernmental Panel ◽  
Political Landscape ◽  
The World ◽  
Negative Emissions ◽  
Science And Politics ◽  
The Relationship ◽  
Political Realities

Non-technical summaryIn the post-Paris political landscape, the relationship between science and politics is changing. We discuss what this means for the Intergovernmental Panel on Climate Change (IPCC), using recent controversies over negative emissions technologies (NETs) as a window into the fraught politics of producing policy-relevant pathways and scenarios. We suggest that pathways and scenarios have a ‘world-making’ power, potentially shaping the world in their own image and creating new political realities. Assessment bodies like the IPCC need to reflect on this power, and the implications of changing political contexts, in new ways.

scholarly journals Role of Warming in Destabilization of Intrapermafrost Gas Hydrates in the Arctic Shelf: Experimental Modeling

Geosciences ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 407 ◽  
Author(s):  
Chuvilin ◽  
Davletshina ◽  
Ekimova ◽  
Bukhanov ◽  
Shakhova ◽  
...  
Keyword(s):  
Gas Hydrates ◽  
Methane Emission ◽  
Gas Hydrate ◽  
Arctic Shelf ◽  
The Arctic ◽  
Effect Of Temperature ◽  
Permafrost Degradation ◽  
Local Pressure ◽  
Hydrate Dissociation ◽  
Hydrate Stability

Destabilization of intrapermafrost gas hydrates is one of the possible mechanisms responsible for methane emission in the Arctic shelf. Intrapermafrost gas hydrates may be coeval to permafrost: they originated during regression and subsequent cooling and freezing of sediments, which created favorable conditions for hydrate stability. Local pressure increase in freezing gas-saturated sediments maintained gas hydrate stability from depths of 200–250 meters or shallower. The gas hydrates that formed within shallow permafrost have survived till present in the metastable (relict) state. The metastable gas hydrates located above the present stability zone may dissociate in the case of permafrost degradation as it becomes warmer and more saline. The effect of temperature increase on frozen sand and silt containing metastable pore methane hydrate is studied experimentally to reconstruct the conditions for intrapermafrost gas hydrate dissociation. The experiments show that the dissociation process in hydrate-bearing frozen sediments exposed to warming begins and ends before the onset of pore ice melting. The critical temperature sufficient for gas hydrate dissociation varies from −3.0 to −0.3 °C and depends on lithology (particle size) and salinity of the host frozen sediments. Taking into account an almost gradientless temperature distribution during degradation of subsea permafrost, even minor temperature increases can be expected to trigger large-scale dissociation of intrapermafrost hydrates. The ensuing active methane emission from the Arctic shelf sediments poses risks of geohazard and negative environmental impacts.

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