scholarly journals Pore-water in marine sediments associated to gas hydrate dissociation offshore Lebu, Chile

2018 ◽  
Author(s):  
Carolina Cárcamo ◽  
Iván Vargas-Cordero ◽  
Francisco Fernandoy ◽  
Umberta Tinivella ◽  
Diego López-Acevedo ◽  
...  
Keyword(s):  
Pore Water ◽  
Gas Hydrate ◽  
Core Sample ◽  
Theoretical Modelling ◽  
Water Isotopes ◽  
Fluid Migration ◽  
Stable Water Isotopes ◽  
Hydrate Dissociation ◽  
Bathymetric Data ◽  
The Core

Abstract. Gas hydrate occurrences along the Chilean margin has been documented, but the processes associated to fluid escapes originated by gas hydrate dissociation yet are unknown. Here, we report morphologies growing related to fluid migration in the continental shelf offshore western Lebu (37 °S) by analysing mainly geochemical features. In this study oxygen and deuterium stable water isotopes in pore water were measured. Knowledge was completed by analysing bathymetric data, biological and sedimentological data. From bathymetric interpretation a positive relief at 127 m below sea level was recognised; it is oriented N55 °E and characterised by five peaks. Moreover, enrichment values for δ18O (from 0.0 to 1.8 ‰) and δD (from 0.0 to 5.6 ‰) were obtained. These are typical values related to hydrate melting during coring and post-sampling. The evident orientation of positive relief could be associated with faults and fractures reported by others authors, in which these structures constitute pathways for fluid migration from deep to shallow zones. Finally, benthic foraminifera observed in the core sample can be associated to seep areas. On the basis of theoretical modelling, we conclude that the positive relief correspond to mud growing processes related to gas hydrates dissociation and represent a key area to investigate fluid migration processes.

scholarly journals Gas hydrate versus seabed morphology offshore Lebu (Chilean margin)

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Iván Vargas-Cordero ◽  
Umberta Tinivella ◽  
Lucía Villar-Muñoz ◽  
Joaquim P. Bento ◽  
Carolina Cárcamo ◽  
...  
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Seismic Data ◽  
Cold Seep ◽  
Water Isotopes ◽  
Fluid Migration ◽  
Stable Water Isotopes ◽  
Surrounding Area ◽  
Suitable Area ◽  
Chilean Margin

AbstractGas-hydrate occurrences along the Chilean margin have been widely documented, but the processes associated with fluid escapes caused by the dissociation of gas hydrates are still unknown. We report a seabed morphology growth related to fluid migration offshore Lebu associated with mud cones by analysing oxygen and deuterium stable water isotopes in pore water, bathymetric, biological and sedimentological data. A relief was observed at − 127 m water depth with five peaks. Enrichment values of δ18O (0.0–1.8‰) and δD (0.0–5.6‰) evidenced past hydrate melting. The orientation of the relief could be associated with faults and fractures, which constitute pathways for fluid migration. The benthic foraminifera observed can be associated with cold seep areas. We model that the mud cones correspond to mud growing processes related to past gas-hydrate dissociation. The integration of (i) the seismic data analysis performed in the surrounding area, (ii) the orientation of our studied relief, (iii) the infaunal foraminifera observed, (iv) the grain size and (v) the total organic matter and isotope values revealed that this area was formerly characterised by the presence of gas hydrates. Hence, this part of the Chilean margin represents a suitable area for investigating fluid-migration processes.

Rock magnetic signature as a result of gas hydrate dissociation off southwestern Taiwan

2020 ◽  
Author(s):  
Yin-Sheng Huang ◽  
Chorng-Shern Horng ◽  
Chih-Chieh Su ◽  
Shu-Kun Hsu ◽  
Jing-Yi Lin
Keyword(s):  
Magnetic Susceptibility ◽  
Gas Hydrate ◽  
Magnetic Mineral ◽  
Magnetic Minerals ◽  
Hydrate Dissociation ◽  
Core Sediments ◽  
The Core ◽  
Potential Reservoir ◽  
Core Depth ◽  
Southwestern Taiwan

<p>Marginal areas off southwestern Taiwan have been widely considered a high potential reservoir of gas hydrates based on several geophysical, geological, and geochemical investigations since the past decades. First gas hydrate sample has been collected on 21 June 2018 during the cruise MD214 at the core site MD18-3542 on the South Yung-An East Ridge. In the study, we focus on magnetic properties of this MD core. The most attractive feature in the magnetic susceptibility is an abrupt drop recorded at about 4 meters core depth. To clarify and identify the dominant magnetic mineral in the core, hysteresis loop parameters were first measured and then presented on the Day Plot, and further the X-ray diffraction analysis was applied to the selected core samples. Based on the magnetic results, the clear drop in the magnetic susceptibility is related to the change of dominant magnetic minerals in core sediments. Before about 4 meters core depth, the dominant magnetic mineral remains detrital magnetite. Below the depth, however, core sediments should have been infected by methane released by gas hydrate dissociation. Authigenic greigite and pyrite have become dominant, and therefore low magnetic susceptibility appears below 4 meters core depth.</p>

Business Model of Natural Gas Hydrate Sample Management Based on Workflow and its Realization

2013 ◽  
Vol 278-280 ◽  
pp. 2123-2127
Author(s):  
Bin Feng ◽  
Wen Huan Zhan ◽  
Jie Sun
Keyword(s):  
Natural Gas ◽  
Business Model ◽  
Gas Hydrate ◽  
Core Sample ◽  
Management Model ◽  
Analytic Model ◽  
Natural Gas Hydrate ◽  
The Core ◽  
Sample Management ◽  
Hydrate Sample

By introducing workflow methods to the research on natural gas hydrate core sample management, we have built the management model and designed the core object analytic model. With the help of models above, the underlying information of core sample exposes to the researchers visually and simply. Based on models and WEBGIS, a natural gas hydrate sample management system has been established and successfully applied by Guangzhou Marine Geological Survey.

scholarly journals Phosphorous Supply to a Eutrophic Artificial Lake: Sedimentary versus Groundwater Sources

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 563
Author(s):  
Wiebe Förster ◽  
Jan C. Scholten ◽  
Michael Schubert ◽  
Kay Knoeller ◽  
Nikolaus Classen ◽  
...  
Keyword(s):  
Water Quality ◽  
Stable Isotope ◽  
Pore Water ◽  
Lake Water ◽  
Sediment Cores ◽  
Eutrophic Lake ◽  
Stable Water Isotopes ◽  
Artificial Lake ◽  
Sediment Pore Water ◽  
Mass Balance Models

The eutrophic Lake Eichbaumsee, a ~1 km long and 280 m wide (maximum water depth 16 m) dredging lake southeast of Hamburg (Germany), has been treated for water quality improvements using various techniques (i.e., aeration plants, removal of dissolved phosphorous by aluminum phosphorous precipitation, and by Bentophos® (Phoslock Environmental Technologies, Sydney, Australia), adsorption) during the past ~15 years. Despite these treatments, no long-term improvement of the water quality has been observed and the lake water phosphorous content has continued to increase by e.g., ~670 kg phosphorous between autumn 2014 and autumn 2019. As no creeks or rivers drain into the lake and hydrological groundwater models do not suggest any major groundwater discharge into the lake, sources of phosphorous (and other nutrients) are unknown. We investigated the phosphorous fluxes from sediment pore water and from groundwater in the water body of the lake. Sediment pore water was extracted from sediment cores recovered by divers in August 2018 and February 2019. Diffusive phosphorous fluxes from pore water were calculated based on phosphorus gradients. Stable water isotopes (δ2H, δ18O) were measured in the lake water, in interstitial waters in the banks surrounding the lake, in the Elbe River, and in three groundwater wells close to the lake. Stable isotope (δ2H, δ18O) water mass balance models were used to compute water inflow/outflow to/from the lake. Our results revealed pore-water borne phosphorous fluxes between 0.2 mg/m2/d and 1.9 mg/m2/d. Assuming that the measured phosphorous fluxes are temporarily and spatially representative for the whole lake, about 11 kg/a to 110 kg/a of phosphorous is released from sediments. This amount is lower than the observed lake water phosphorous increase of ~344 kg between April 2018 and November 2018. Water stable isotope (δ2H, δ18O) compositions indicate a water exchange between an aquifer and the lake water. Based on stable isotope mass balances we estimated an inflow of phosphorous from the aquifer to the lake of between ~150 kg/a and ~390 kg/a. This result suggests that groundwater-borne phosphorous is a significant phosphorous source for the Eichbaumsee and highlights the importance of groundwater for lake water phosphorous balances.

Review of natural gas hydrate dissociation effects on seabed stability

2021 ◽  
Author(s):  
Min Zhang ◽  
Ming Niu ◽  
Shiwei Shen ◽  
Shulin Dai ◽  
Yan Xu
Keyword(s):  
Natural Gas ◽  
Gas Hydrate ◽  
Natural Gas Hydrate ◽  
Hydrate Dissociation

Improving the Accuracy of Gas Hydrate Dissociation Point Measurements

2006 ◽  
Vol 912 (1) ◽  
pp. 924-931 ◽  
Author(s):  
B. TOHIDI ◽  
R. W. BURGASS ◽  
A. DANESH ◽  
K. K. ØSTERGAARD ◽  
A. C. TODD
Keyword(s):  
Gas Hydrate ◽  
Hydrate Dissociation

scholarly journals A Lagrangian perspective on stable water isotopes during the West African Monsoon

2021 ◽  
Author(s):  
Christopher Johannes Diekmann ◽  
Matthias Schneider ◽  
Peter Knippertz ◽  
Andries Jan de Vries ◽  
Stephan Pfahl ◽  
...  
Keyword(s):  
West African Monsoon ◽  
West African ◽  
Water Isotopes ◽  
Stable Water Isotopes ◽  
The West ◽  
African Monsoon
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