World Atlas of Submarine Gas Hydrates in Continental Margins

2022 ◽  
Keyword(s):  
Gas Hydrates ◽  
Continental Margins

Natural Gas Hydrates – A Review of the Resources Offshore Nigeria and around the Globe

2011 ◽  
Vol 4 ◽  
pp. 27-33
Author(s):  
U.P. Igboanusi ◽  
J.U. Okere
Keyword(s):  
Climate Change ◽  
Natural Gas ◽  
Geographical Distribution ◽  
Gas Hydrates ◽  
Co2 Sequestration ◽  
Large Scale ◽  
Continental Margins ◽  
Natural Gas Hydrates ◽  
Pure Methane ◽  
Permafrost Regions

Natural gas hydrates are ice-like materials which exist in permafrost regions and in the continental margins of oceans. They constitute a huge unconventional reservoir of natural gas around the globe including offshore Nigeria. The paper is a review of this important global resource with particular focus on the Nigerian deposits. The reasons for the interest on hydrates are discussed including the potential for the recovery of large quantities of methane, the climate change and ocean floor instability that may result from their dissociation. They may also be exploited for large-scale CO2 sequestration. The geographical distribution of hydrates deposits on earth, the thermodynamics of why they occur in those particular places and source of the methane gas that is eventually enchlathrated into hydrates are discussed. The natural gas in the Nigerian hydrate is essentially biogenic in origin and is almost pure methane (more than 99% methane). The hydrates exist in finely disseminated or massive aggregate forms within clay-rich sediment.

scholarly journals Estimation of the global inventory of methane hydrates in marine sediments using transfer functions

2013 ◽  
Vol 10 (2) ◽  
pp. 959-975 ◽  
Author(s):  
E. Piñero ◽  
M. Marquardt ◽  
C. Hensen ◽  
M. Haeckel ◽  
K. Wallmann
Keyword(s):  
Transfer Function ◽  
Marine Sediments ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Large Scale ◽  
Transfer Functions ◽  
Methane Hydrates ◽  
Continental Margins ◽  
Transport Reaction ◽  
Methane Generation

Abstract. The accumulation of gas hydrates in marine sediments is essentially controlled by the accumulation of particulate organic carbon (POC) which is microbially converted into methane, the thickness of the gas hydrate stability zone (GHSZ) where methane can be trapped, the sedimentation rate (SR) that controls the time that POC and the generated methane stays within the GHSZ, and the delivery of methane from deep-seated sediments by ascending pore fluids and gas into the GHSZ. Recently, Wallmann et al. (2012) presented transfer functions to predict the gas hydrate inventory in diffusion-controlled geological systems based on SR, POC and GHSZ thickness for two different scenarios: normal and full compacting sediments. We apply these functions to global data sets of bathymetry, heat flow, seafloor temperature, POC input and SR, estimating a global mass of carbon stored in marine methane hydrates from 3 to 455 Gt of carbon (GtC) depending on the sedimentation and compaction conditions. The global sediment volume of the GHSZ in continental margins is estimated to be 60–67 × 1015 m3, with a total of 7 × 1015 m3 of pore volume (available for GH accumulation). However, seepage of methane-rich fluids is known to have a pronounced effect on gas hydrate accumulation. Therefore, we carried out a set of systematic model runs with the transport-reaction code in order to derive an extended transfer function explicitly considering upward fluid advection. Using averaged fluid velocities for active margins, which were derived from mass balance considerations, this extended transfer function predicts the enhanced gas hydrate accumulation along the continental margins worldwide. Different scenarios were investigated resulting in a global mass of sub-seafloor gas hydrates of ~ 550 GtC. Overall, our systematic approach allows to clearly and quantitatively distinguish between the effect of biogenic methane generation from POC and fluid advection on the accumulation of gas hydrate, and hence, provides a simple prognostic tool for the estimation of large-scale and global gas hydrate inventories in marine sediments.

Mathematical model of a non-stationary process of accumulation of gas hydrates, confined to deep-water mud volcanoes

2021 ◽  
Author(s):  
Alexey L. Sobisevich ◽  
Elena I. Suetnova ◽  
Ruslan A. Zhostkov
Keyword(s):  
Mathematical Model ◽  
Gas Hydrates ◽  
Stationary Process ◽  
Sedimentary Basins ◽  
Physical Parameters ◽  
Continental Margins ◽  
Mud Volcanoes ◽  
Environment Temperature ◽  
Hydrate Saturation ◽  
Sea Mud

<p>Large amounts of methane hydrate locked up within marine sediments are associated to mud volcanoes. We have investigated by means of mathematical modeling the unsteady process of accumulation of gas hydrates associated with the processes of mud volcanism. A mathematical model has been developed. The system of equations of the model describes the interrelated processes of filtration of gas-saturated fluid, thermal regime and pressure, and accumulation of gas hydrates in the seabed in the zone of thermobaric stability of gas hydrates. The numerical simulation of the accumulation of gas hydrates in the seabed in the deep structures of underwater mud volcanoes has been carried out using the realistic physical parameters values. The influence of the depth of the feeding reservoir and the pressure in it on the evolution of gas hydrate accumulations associated with deep-sea mud volcanoes is quantitatively analyzed. Modeling quantitatively showed that the hydrate saturation in the zones of underwater mud volcanoes is variable and its evolution depends on the geophysical properties of the bottom environment (temperature gradient, porosity, permeability, physical properties of sediments) and the depth of the mud reservoir and pressure in it. The volume of accumulated gas hydrates depends on the duration of the non-stationary process of accumulation between eruptions of a mud volcano. The rate of hydrate accumulation is tens and hundreds times the rate of hydrate accumulation in sedimentary basins of passive continental margins.</p>

scholarly journals Evidences for Paleo-Gas Hydrate Occurrence: What We Can Infer for the Miocene of the Northern Apennines (Italy)

Geosciences ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 134 ◽  
Author(s):  
Claudio Argentino ◽  
Stefano Conti ◽  
Chiara Fioroni ◽  
Daniela Fontana
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Northern Apennines ◽  
Stability Field ◽  
Continental Margins ◽  
Shallow Gas ◽  
Hydrate Decomposition ◽  
Oxygen Isotopic ◽  
The Stability ◽  
Seep Carbonate

The occurrence of seep-carbonates associated with shallow gas hydrates is increasingly documented in modern continental margins but in fossil sediments the recognition of gas hydrates is still challenging for the lack of unequivocal proxies. Here, we combined multiple field and geochemical indicators for paleo-gas hydrate occurrence based on present-day analogues to investigate fossil seeps located in the northern Apennines. We recognized clathrite-like structures such as thin-layered, spongy and vuggy textures and microbreccias. Non-gravitational cementation fabrics and pinch-out terminations in cavities within the seep-carbonate deposits are ascribed to irregularly oriented dissociation of gas hydrates. Additional evidences for paleo-gas hydrates are provided by the large dimensions of seep-carbonate masses and by the association with sedimentary instability in the host sediments. We report heavy oxygen isotopic values in the examined seep-carbonates up to +6‰ that are indicative of a contribution of isotopically heavier fluids released by gas hydrate decomposition. The calculation of the stability field of methane hydrates for the northern Apennine wedge-foredeep system during the Miocene indicated the potential occurrence of shallow gas hydrates in the upper few tens of meters of sedimentary column.

scholarly journals Assessment of Marine Gas Hydrates and Associated Free Gas Distribution Offshore Uruguay

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Juan Tomasini ◽  
Héctor de Santa Ana ◽  
Bruno Conti ◽  
Santiago Ferro ◽  
Pablo Gristo ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Hydrates ◽  
Probabilistic Approach ◽  
Mean Value ◽  
Continental Margins ◽  
Gas Distribution ◽  
Free Gas ◽  
Natural Gas Hydrates ◽  
Bottom Simulating Reflectors ◽  
Thermobaric Conditions

Natural gas hydrates are crystalline solids formed by natural gas (mainly methane) and water that are stable under thermobaric conditions of high pressure and low temperature. Methane hydrate is found in polar areas of permafrost and in offshore basins of continental margins. These accumulations may represent an enormous source of methane. Based on global estimations of methane concentration in natural gas hydrates, the methane content may be several times greater than those of technically recoverable, conventional natural gas resources. In the continental margin of Uruguay, seismic evidence for the occurrence of gas hydrate is based on the presence of (bottom simulating reflectors) BSRs in 2D seismic reflection sections. Here we present results regarding gas hydrates and associated free gas distribution assessment offshore Uruguay, based on BSR mapping and applying a probabilistic approach. A mean value of 25,890 km2 for the area of occurrence shows a great potential for this nonconventional resource, encouraging further research.

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