Three‐Dimensional Free Gas Flow Focuses Basin‐Wide Microbial Methane to Concentrated Methane Hydrate Reservoirs in Geological System

You, Kehua; Summa, Lori L.; Flemings, P. B.; Santra, Manasij; Fang, Yi

doi:10.1029/2021jb022793

Cited by 9 publications

(4 citation statements)

References 81 publications

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“…Advecting hot fluids are certainly a key factor causing the formation of the flat-lying gas to hydrate transitional system, however, the occurrence of the coarse-grained sand layer is also very important for the development of this system. Our heat transfer model indicates high gas flux present here but the horizontal sand layer with low capillary entry pressure (You et al, 2021) would reduce the gas column height and pressure by lateral porous flow. Otherwise, vertical gas-driven tensile fracturing would occur at this shallow depth and most of gas would seep out of the seafloor (Daigle et al, 2020).…”

Section: Geological Implicationsmentioning

confidence: 81%

A Flat‐Lying Transitional Free Gas to Gas Hydrate System in a Sand Layer in the Qiongdongnan Basin of the South China Sea

Kuang,

Cook,

Ren

et al. 2023

Geophysical Research Letters

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Most marine gas hydrate systems follow a vertical pattern with hydrate overlying free gas. Here we document the discovery of a gas to hydrate system in a horizontal sand layer in the Qiongdongnan Basin of the South China Sea. Eight wells were drilled by the Guangzhou Marine Geological Survey in 2021–2022 to investigate the occurrence and mechanisms responsible for the formation of the system. We describe a free gas‐bearing sand reservoir at the center of the system sustained by advecting hot fluids and gas; away from the advecting zone, the cooler, surrounding sand reservoir is filled with hydrate. Observations at this site show that advective heat has a large control on hydrate formation in sands and may be a key mechanism which allows gas migration within the hydrate stability zone and the formation of high‐saturation hydrate in sand layers.

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Section: Geological Implicationsmentioning

confidence: 81%

A Flat‐Lying Transitional Free Gas to Gas Hydrate System in a Sand Layer in the Qiongdongnan Basin of the South China Sea

Kuang,

Cook,

Ren

et al. 2023

Geophysical Research Letters

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“…The formation of concentrated methane hydrate deposit requires a large amount of methane. In deeper‐water marine sediments, three‐dimensional free gas flow is inferenced to focus the basin‐wide microbial methane into the concentrated methane hydrate reservoirs (You et al., 2019, 2021). In the terrestrial permafrost, nearly all methane hydrate deposits discovered nowadays are below the base of the permafrost (Collett et al., 2011).…”

Section: Discussionmentioning

confidence: 99%

“…The thickness of the yedoma layer used (50 m) is at the high end of the field measurements (Strauss et al., 2021), which may overestimate the seabed methane emission rate. The underlying mineral soil has a constant total organic carbon content of 1 wt.%, a typical value for the world's near seafloor sediment in the deeper water (Davie & Buffett, 2001; You et al., 2021). The reactivities of organic carbon are set to 4 orders of magnitude lower in the mineral soil than in the yedoma soil.…”

Section: Simulating Carbon Stability In the Thawing Subsea Permafrostmentioning

confidence: 99%

Biodegradation of Ancient Organic Carbon Fuels Seabed Methane Emission at the Arctic Continental Shelves

You

2024

Global Biogeochemical Cycles

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This study explores the carbon stability in the Arctic permafrost following the sea‐level transgression since the Last Glacial Maximum (LGM). The Arctic permafrost stores a significant amount of organic carbon sequestered as frozen particulate organic carbon, solid methane hydrate and free methane gas. Post‐LGM sea‐level transgression resulted in ocean water, which is up to 20°C warmer compared to the average annual air mass, inundating, and thawing the permafrost. This study develops a one‐dimensional multiphase flow, multicomponent transport numerical model and apply it to investigate the coupled thermal, hydraulic, microbial, and chemical processes occurring in the thawing subsea permafrost. Results show that microbial methane is produced and vented to the seawater immediately upon the flooding of the Arctic continental shelves. This microbial methane is generated by the biodegradation of the previously frozen organic carbon. The maximum seabed methane flux is predicted in the shallow water where the sediment has been warmed up, but the remaining amount of organic carbon is still high. It is less likely to cause seabed methane emission by methane hydrate dissociation. Such a situation only happens when there is a very shallow (∼200 m depth) intra‐permafrost methane hydrate, the occurrence of which is limited. This study provides insights into the limits of methane release from the ongoing flooding of the Arctic permafrost, which is critical to understand the role of the Arctic permafrost in the carbon cycle, ocean chemistry and climate change.

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“…Conventionally, gas hydrate recycling has been largely studied in 1D geological settings and the underlying sediments are assumed to be either homogeneous (Schmidt et al., 2022) or with vertically stacked topography (You et al., 2019, 2021) that is representative of the different granular materials, debris, and organic matter that was deposited over different geological times in the past. However, complex fault systems, fluid escape structures, and anomalous sediment layers have been observed in the seismic profiles cross‐cutting the buried layers within the GHSZ worldwide (Crutchley et al., 2021; Paganoni et al., 2018; Portnov et al., 2019; Waage et al., 2019).…”

Section: Introductionmentioning

confidence: 99%

Numerical Modeling of Gas Hydrate Recycling in Complex Media: Implications for Gas Migration Through Strongly Anisotropic Layers

2022

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Methane hydrates are one of the most complex natural geosystems whose formation and dynamics is characterized by a wide range of strongly coupled and competing multi-physics processes such as gas migration through an evolving GHSZ, rapidly changing pressure-temperature-salinity fields, gas-water-hydrate (i.e., fluid-fluid-solid) phase transitions, locally appearing and disappearing phases, and evolving sediment properties (like permeability, capillary pressure, effective flow pathways, reaction surface area, etc.). Methane hydrates form an organic carbon repository in the earth, and have a significant contribution to the global carbon cycle. Besides, methane is an important greenhouse gas with drastic implications for climate (

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Three‐Dimensional Free Gas Flow Focuses Basin‐Wide Microbial Methane to Concentrated Methane Hydrate Reservoirs in Geological System

Cited by 9 publications

References 81 publications

A Flat‐Lying Transitional Free Gas to Gas Hydrate System in a Sand Layer in the Qiongdongnan Basin of the South China Sea

A Flat‐Lying Transitional Free Gas to Gas Hydrate System in a Sand Layer in the Qiongdongnan Basin of the South China Sea

Biodegradation of Ancient Organic Carbon Fuels Seabed Methane Emission at the Arctic Continental Shelves

Numerical Modeling of Gas Hydrate Recycling in Complex Media: Implications for Gas Migration Through Strongly Anisotropic Layers

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