Fracture networks and hydrate distribution at Hydrate Ridge, Oregon

Weinberger, J. L.; Brown, Kevin M.

doi:10.1016/j.epsl.2006.03.012

Cited by 80 publications

(98 citation statements)

References 41 publications

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“…Our observations also provide critical experimental evidence to explain the means by which gas may transit through the gas hydrate stability zone through new or reactivated pathways within fine grained-sediments [Gorman et al, 2002;Hornbach et al, 2004;Weinberger and Brown, 2006;Daigle and Dugan, 2010].…”

Section: Discussionmentioning

confidence: 97%

“…[4] These gas invasion phenomena have important implications for understanding hydrates in natural systems (either ocean sediments or permafrost regions) [Hornbach et al, 2004;Weinberger and Brown, 2006;Uchida et al, 2009;Daigle and Dugan, 2010]. They suggest that, in fine sediments, hydrate will likely form as planar, graindisplacing veins, whereas, in coarse sediments, the buoyant methane gas will likely invade the pore space more uniformly and with minimal grain displacement, in a process akin to invasion percolation, causing hydrate in a pore-filling morphology.…”

Section: Introductionmentioning

confidence: 99%

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X-ray computed-tomography imaging of gas migration in water-saturated sediments: From capillary invasion to conduit opening

Choi

Seol

Boswell

et al. 2011

Geophys. Res. Lett.

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The strong coupling between multiphase flow and sediment mechanics determines the spatial distribution and migration dynamics of gas percolating through liquid‐filled soft granular media. Here, we investigate, by means of controlled experiments and computed tomography (CT) imaging, the preferential mode of gas migration in three‐dimensional samples of water‐saturated silica‐sand and silica‐silt sediments. Our experimental system allowed us to independently control radial and axial confining stresses and pore pressure while performing continuous x‐ray CT scanning. The CT image analysis of the three‐dimensional gas migration provides the first experimental confirmation that capillary invasion preferentially occurs in coarse‐grained sediments whereas grain displacement and conduit openings are dominant in fine‐grained sediments. Our findings allow us to rationalize prior field observations and pore‐scale modeling results, and provide critical experimental evidence to explain the means by which conduits for the transit of methane gas may be established through the gas hydrate stability zone in oceanic sediments, and cause large episodic releases of carbon into the deep ocean.

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Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

X-ray computed-tomography imaging of gas migration in water-saturated sediments: From capillary invasion to conduit opening

Choi

Seol

Boswell

et al. 2011

Geophys. Res. Lett.

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“…Seep-dominant SMT environments have higher sulfate and methane concentrations that occur coincident with a higher abundance of cells involved with AOM. We have not measured methane or sulfate flux in the fractures where we collected the biofilms; however, fractures in the sediment may be preferred flow paths for fluids (54). If advective flux of methane and sulfate occurs in these environments, most would probably travel through the fractures, making them the most likely location for higher biomass.…”

Section: Discussionmentioning

confidence: 99%

Macroscopic Biofilms in Fracture-Dominated Sediment That Anaerobically Oxidize Methane

Briggs

Pohlman

Torres

et al. 2011

Appl Environ Microbiol

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Methane release from seafloor sediments is moderated, in part, by the anaerobic oxidation of methane (AOM) performed by consortia of archaea and bacteria. These consortia occur as isolated cells and aggregates within the sulfate-methane transition (SMT) of diffusion and seep-dominant environments. Here we report on a new SMT setting where the AOM consortium occurs as macroscopic pink to orange biofilms within subseafloor fractures. Biofilm samples recovered from the Indian and northeast Pacific Oceans had a cellular abundance of 10 7 to 10 8 cells cm ؊3 . This cell density is 2 to 3 orders of magnitude greater than that in the surrounding sediments. Sequencing of bacterial 16S rRNA genes indicated that the bacterial component is dominated by Deltaproteobacteria, candidate division WS3, and Chloroflexi, representing 46%, 15%, and 10% of clones, respectively. In addition, major archaeal taxa found in the biofilm were related to the ANME-1 clade, Thermoplasmatales, and Desulfurococcales, representing 73%, 11%, and 10% of archaeal clones, respectively. The sequences of all major taxa were similar to sequences previously reported from cold seep environments. PhyloChip microarray analysis detected all bacterial phyla identified by the clone library plus an additional 44 phyla. However, sequencing detected more archaea than the PhyloChip within the phyla of Methanosarcinales and Desulfurococcales. The stable carbon isotope composition of the biofilm from the SMT (؊35 to ؊43‰) suggests that the production of the biofilm is associated with AOM. These biofilms are a novel, but apparently widespread, aggregation of cells represented by the ANME-1 clade that occur in methane-rich marine sediments.

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“…Bright regions (high resistivity) are indicative of gas hydrate when they also correspond to low-density zones. Th e detail shows considerable azimuthal variation in gas hydrate distribution, suggesting that the gas hydrate forms in steeply dipping faults and fractures in this interval (Janik et al, 2003;Weinberger and Brown, 2006). Cl data from Hole 1244B; Pressure core data from Holes 1244B, C and E et al, 2004b).…”

Section: Geochemical Proxiesmentioning

confidence: 99%

“…In Cascadia, where the sediments hosting gas hydrates include highly deformed accretionary complex sediments and turbidite-fi lled slope basins, lithologic variation is greater than on Blake Ridge and gas hydrate distribu-tion is strongly infl uenced by permeability variations induced by lithologic variations (Weinberger et al, 2005) and fractures controlled by the local effective stress ( Weinberger and Brown, 2006 …”

Section: Focused High-flux Gas Hydrate Depositsmentioning

confidence: 99%