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  • 2020-2024  (2)
  • 2005-2009  (2)
  • 2023  (1)
  • 2021  (1)
  • 2005  (2)
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  • 2020-2024  (2)
  • 2005-2009  (2)
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  • 1
    Online Resource
    Online Resource
    Methane sources, distributions, and fluxes from cold vent sites at Hydrate Ridge, Cascadia Margin (2005)
    Associated volumes
    Details Availability
    In: Global biogeochemical cycles, Hoboken, NJ : Wiley, 1987, 19(2005), 1944-9224
    In: volume:19
    In: year:2005
    In: extent:21
    Type of Medium: Online Resource
    Pages: 21 , graph. Darst
    ISSN: 1944-9224
    DOI: 10.1029/2004GB002266
    Language: English
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  • 2
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    Methane sources, distributions, and fluxes from cold vent sites at Hydrate Ridge, Cascadia Margin (2005)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 19 . GB2016.
    Details
    Publication Date: 2018-03-16
    Description: To constrain the fluxes of methane (CH4) in the water column above the accretionary wedge along the Cascadia continental margin, we measured methane and its stable carbon isotope signature (δ13C-CH4). The studies focused on Hydrate Ridge (HR), where venting occurs in the presence of gas-hydrate-bearing sediments. The vent CH4 has a light δ13C-CH4 biogenic signature (−63 to −66‰ PDB) and forms thin zones of elevated methane concentrations several tens of meters above the ocean floor in the overlying water column. These concentrations, ranging up to 4400 nmol L−1, vary by 3 orders of magnitude over periods of only a few hours. The poleward undercurrent of the California Current system rapidly dilutes the vent methane and distributes it widely within the gas hydrate stability zone (GHSZ). Above 480 m water depth, the methane budget is dominated by isotopically heavier CH4 from the shelf and upper slope, where mixtures of various local biogenic and thermogenic methane sources were detected (−56 to −28‰ PDB). The distribution of dissolved methane in the working area can be represented by mixtures of methane from the two primary source regions with an isotopically heavy background component (−25 to −6‰ PDB). Methane oxidation rates of 0.09 to 4.1% per day are small in comparison to the timescales of advection. This highly variable physical regime precludes a simple characterization and tracing of “downcurrent” plumes. However, methane inventories and current measurements suggest a methane flux of approximately 3 × 104 mol h−1 for the working area (1230 km2), and this is dominated by the shallower sources. We estimate that the combined vent sites on HR produce 0.6 × 104 mol h−1, and this is primarily released in the gas phase rather than dissolved within fluid seeps. There is no evidence that significant amounts of this methane are released to the atmosphere locally.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2004GB002266
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Production Method under Surveillance: Laboratory Pilot-Scale Simulation of CH 4 –CO 2 Exchange in a Natural Gas Hydrate Reservoir (2021)
    ACS (American Chemical Society)
    Details
    Publication Date: 2024-02-07
    Description: The "guest exchange"of methane (CH4) by carbon dioxide (CO2) in naturally occurring gas hydrates is seen as a possibility to concurrently produce CH4 and sequester CO2. Presently, process evaluation is based on CH4-CO2 exchange yields of small-or medium-scale laboratory experiments, mostly neglecting mass and heat transfer processes. This work investigates process efficiencies in two large-scale experiments (210 L sample volume) using fully water-saturated, natural reservoir conditions and a gas hydrate saturation of 50%. After injecting 50 kg of heated CO2 discontinuously (E1) and continuously (E2) and a subsequent soaking period, the reservoir was depressurized discontinuously. It was monitored using electrical resistivity, temperature and pressure sensors, and fluid flow and gas composition measurements. Phase and component inventories were analyzed based on mass and volume balances. The total CH4 production during CO2 injection was only 5% of the initial CH4 inventory. Prior to CO2 breakthrough, the produced CH4 roughly equaled dissolved CH4 in the produced pore water, which balanced the volume of the injected CO2. After CO2 breakthrough, CH4 ratios in the released CO2 quickly dropped to 2.0-0.5 vol %. The total CO2 retention was the highest just before the CO2 breakthrough and higher in E1 where discontinuous injection improved the distribution of injected CO2 and subsequent mixed hydrate formation. The processes were improved by the succession of CO2 injection by controlled degassing at stability limits below that of the pure CH4 hydrate, particularly in experiment E2. Here, a more heterogeneous distribution of liquid CO2 and larger availability of free water led to smaller initial degassing of liquid CO2. This allowed for quick re-formation of mixed gas hydrates and CH4 ratios of 50% in the produced gases. The experiments demonstrate the importance of fluid migration patterns, heat transport, sample inhomogeneity, and secondary gas hydrate formation in water-saturated sediments.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Physical oceanographic profiles of 43 CTD casts during MARIA S. MERIAN cruise MSM98 in 20201 in the North Sea (2023)
    PANGAEA
    Details
    Publication Date: 2024-06-25
    Description: During the RV Maria S. Merian cruise 98, which took place between 08.01.2021 to 23.01.2021 bathymetry data based on multibeam echosounder (MBES) was recorded. The main objective of the cruise was focused on the hydrocarbon fluid emissions in the German North Sea and focused on the 'Entenschnabel'- area. In total, 43 CTDs were deployed, mainly to sample the methane content in the water column and to observe the stratigraphy of the water column. Oceanographic data as well as water samples have been collected at every CTD station. At the borehole locations of B11-2 and B18-1 but also at the DOK1-X Thor-1 and D1 well 4 CTDS per site have been deployed.Detailed information about the temperature, conductivity and oxygen of the water column have been carried out with a Seabird CTD/Rosette SBE911 with SBE-32 water sampler, equipped with 24 OTE bottles (10L).
    Keywords: -; borehole logging; Boreholes; Bottle number; Center for Marine Environmental Sciences; Counts; CTD/Rosette; CTD-RO; Density, mass density; Density, sigma-theta (0); DEPTH, water; Elevation of event; Entenschnabel; Event label; Fluorescence; Fluorometer, WET Labs ECO AFL/FL; GeoB24404-1; GeoB24404-2; GeoB24404-3; GeoB24404-4; GeoB24406-1; GeoB24407-1; GeoB24408-1; GeoB24414-1; GeoB24415-1; GeoB24416-1; GeoB24417-1; GeoB24418-1; GeoB24419-1; GeoB24420-1; GeoB24421-1; GeoB24422-1; GeoB24423-1; GeoB24424-1; GeoB24425-1; GeoB24426-1; GeoB24427-1; GeoB24428-1; GeoB24429-1; GeoB24445-1; GeoB24445-2; GeoB24445-3; GeoB24445-4; GeoB24450-1; GeoB24450-2; GeoB24450-3; GeoB24450-4; GeoB24451-1; GeoB24451-2; GeoB24452-1; GeoB24452-2; GeoB24455-1; GeoB24455-2; GeoB24455-3; GeoB24455-4; GeoB24456-1; GeoB24456-2; GeoB24456-3; GeoB24456-4; GPF 20‐3 092; hydrocarbons; Latitude of event; Longitude of event; Maria S. Merian; MARUM; MSM98; MSM98_14-1; MSM98_15-1; MSM98_16-1; MSM98_17-1; MSM98_18-1; MSM98_19-1; MSM98_20-1; MSM98_21-1; MSM98_22-1; MSM98_23-1; MSM98_24-1; MSM98_25-1; MSM98_26-1; MSM98_27-1; MSM98_28-1; MSM98_29-1; MSM98_4-1; MSM98_4-2; MSM98_4-3; MSM98_4-4; MSM98_45-1; MSM98_45-2; MSM98_45-3; MSM98_45-4; MSM98_50-1; MSM98_50-2; MSM98_50-3; MSM98_50-4; MSM98_51-1; MSM98_51-2; MSM98_52-1; MSM98_52-2; MSM98_55-1; MSM98_55-2; MSM98_55-3; MSM98_55-4; MSM98_56-1; MSM98_56-2; MSM98_56-3; MSM98_56-4; MSM98_6-1; MSM98_7-1; MSM98_8-1; North Sea; Optional event label; Oxygen; Oxygen saturation; Oxygen sensor, SBE 43; Pressure, water; Pressure sensor, Digiquartz; Radiation, photosynthetically active; Salinity; Sound velocity in water; Temperature, water; Temperature, water, potential; Turbidity (Nephelometric turbidity unit); Turbidity Meter, WET Labs ECO NTU
    Type: Dataset
    Format: text/tab-separated-values, 6524548 data points
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    DATA PANGAEA
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