Gas hydrate versus geological features: The South Shetland case study

Loreto, Maria Filomena; Tinivella, Umberta

doi:10.1016/j.marpetgeo.2012.04.005

Cited by 19 publications

(16 citation statements)

References 43 publications

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“…In fact, along this profile, sectors are characterised by high/low velocity above/below the BSR in correspondence to deformation areas and faults (see RC2901-731 seismic profile in Figures 2 and 3). Our result is in agreement with several authors who reported slight folding structures as structural traps for fluid storing associated to gas hydrate occurrences [7,[56][57][58].…”

Section: Discussionsupporting

confidence: 94%

High Gas Hydrate and Free Gas Concentrations: An Explanation for Seeps Offshore South Mocha Island

et al. 2018

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Recent studies have reported cold seeps offshore of Mocha Island. Gas hydrate occurrences along the Chilean margin could explain seeps presence. Gas-phase (gas hydrate and free gas) and geothermal gradients were estimated analysing two seismic sections. Close to Mocha Island (up to 20 km) were detected high (up to 1900 m/s) and low (1260 m/s) velocities associated with high gas hydrate (up to 20% of total volume) and free gas (up to 1.1% of total volume) concentrations, respectively. A variable and high geothermal gradient (65-110 • C/km) was obtained. These results are related to high supply of deep fluids canalised by faults and fractures. Faraway from Mocha Island (>60 km), free gas concentrations decrease to 0.3% of total volume and low geothermal gradient (from 35 to 60 • C/km) are associated with low fluids supply. Finally, we propose gas hydrate dissociation processes as the main supply source for seeps in the vicinity of Mocha Island. These processes can be caused by: (a) active faults and seismic activity; and (b) warm fluid expulsion from deeper zones altering hydrate stability conditions. In both cases, gas hydrate dissociation could generate slope instability and landslides, as occurred in the past in this region and reported in the literature.Energies 2018, 11, 3062 2 of 13 close to 3000 km (from 33 • S until 56 • S). In the second case, some authors have modelled possible scenarios for gas hydrate dissociation in shallow water (from 150 to 600 m water depth) considering the increasing temperature due to the global warming and the consequent potential methane release into the atmosphere. They concluded that the gas hydrate dissociation processes are induced just by a slight increment of temperature [25][26][27][28][29][30][31]. In this context, gas hydrate estimates contribute to evaluate submarine geohazards, global warming contribution related to gas hydrate dissociation and the potential methane reservoir. Moreover, estimates of methane stored in marine sediments as gas hydrate and free gas phases can be used to model more realistic scenarios associated with gas hydrates dissociation and its effects as a greenhouse gas.Relationships between gas hydrates and cold seeps have been documented in active and passive margins [5,[31][32][33][34][35][36], in which chemosynthetic communities, authigenic carbonate nodules, enrichment stable isotopes in pore water, and faults and fractures, connected with BSR and detected in seismic profiles, can be related to gas hydrate presence.The present study adds new information regarding gas-phase concentrations of the southern Chilean margin by using seismic and theoretical velocity models (Figure 1). Mocha Island is characterised by active seismicity and constitutes an emerged block uplifted during the Quaternary in the Arauco peninsula [37,38]. Further, Mocha Island is known for intertidal and subtidal gas seepage system [39,40] and deeper seeps at 1400 water depth [41], whose presence probably is related to gas hydrates dissociation. In this context, gas-phase est...

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Section: Discussionsupporting

confidence: 94%

High Gas Hydrate and Free Gas Concentrations: An Explanation for Seeps Offshore South Mocha Island

et al. 2018

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“…2 and 3). Our result is in agreement with several authors that have reported anticlinal structures as structural traps for fluid storing associated to gas hydrate occurrences [12,[36][37][38].…”

Section: Discussionsupporting

confidence: 94%

High Gas Hydrate and Free Gas Concentrations: An Explanation for Seeps Offshore South Mocha Island

Vargas-Cordero

Tinivella

Villar-Muñoz

et al. 2018

Preprint

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Recent studies have reported shallow and deep seep areas offshore Mocha island. Gas hydrate occurrences along the Chilean margin could explain seeps presence. Gas phases (gas hydrate and free gas) and geothermal gradients were estimated analysing two seismic sections. Close to Mocha island (up to 20 km) were detected high (up to 1900 m/s) and low (1260 m/s) velocities associated with high gas hydrate (up to 20 % of total volume) and free gas (up to 1.1% of total volume) concentrations respectively. These values are in agreement with a variable and high geothermal gradient (65 to 110 °C/km) related to high supply deep fluids canalised by faults and fractures. Faraway from Mocha island (more than 60 km), free gas concentrations decrease to 0.3 % of total volume and low geothermal gradient (from 35 to 60 °C/km) are associated with low fluids supply. Finally, we propose gas hydrate dissociation processes as the main supply source for seeps in the vicinity of Mocha island. These processes can be triggered by ancient sliding reported in literature.

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“…Moreover, the seismic data provide information about the geometry of the main geological structures, allowing for possible explanations of the presence/absence of gas hydrate [18,19]. In the last few years, the integration of geophysical (mainly seismic and electromagnetic data), geochemical, and heat-flow data have allowed for detecting and characterizing gas hydrate and free gas volumes and their distribution in the sediments, i.e., [20][21][22][23]. Thus, reviews of extensive geophysical surveys and direct measurements combined with geological interpretation and theoretical modelling will increase our understanding of the occurrence, distribution, and concentration of gas hydrate and the underlying free gas beneath the ocean bottom and in the permafrost regions, i.e., [24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Gas Hydrate: Environmental and Climate Impacts

et al. 2019

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This Special Issue reports research spanning from the analysis of indirect data, modelling, laboratory and geological data confirming the intrinsic multidisciplinarity of the gas hydrate studies. The study areas are (1) Arctic, (2) Brazil, (3) Chile and (4) the Mediterranean region. The results furnished an important tessera of the knowledge about the relationship of a gas hydrate system with other complex natural phenomena such as climate change, slope stability and earthquakes, and human activities.

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Gas hydrate versus geological features: The South Shetland case study

Cited by 19 publications

References 43 publications

High Gas Hydrate and Free Gas Concentrations: An Explanation for Seeps Offshore South Mocha Island

High Gas Hydrate and Free Gas Concentrations: An Explanation for Seeps Offshore South Mocha Island

High Gas Hydrate and Free Gas Concentrations: An Explanation for Seeps Offshore South Mocha Island

Gas Hydrate: Environmental and Climate Impacts

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