Capillary controls on methane hydrate distribution and fracturing in advective systems

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doi: 10.1029/2010GC003392
Author(s): Daigle, Hugh; Dugan, Brandon
Author Affiliation(s): Primary:
William March Rice University, Department of Earth Science, Houston, TX, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 12(1). Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 95 refs.; illus., incl. sketch map
Summary: We simulate 1-D, steady, advective flow through a layered porous medium to investigate how capillary controls on solubility including the Gibbs-Thomson effect in fine-grained sediments affect methane hydrate distribution in marine sediments. We compute the increase in pore fluid pressure that results from hydrate occluding the pore space and allow fractures to form if the pore fluid pressure exceeds a fracture criterion. We apply this model to Hydrate Ridge and northern Cascadia, two field sites where hydrates have been observed preferentially filling cm-scale, coarse-grained layers. We find that at Hydrate Ridge, hydrate forms in the coarse-grained layers reaching saturation of 90%, creating fractures through intervening fine-grained layers after 2000 years. At northern Cascadia, hydrate forms preferentially in the coarse-grained layers but 2 × 105 years are required to develop the observed hydrate saturations (∼20%-60%), suggesting that hydrate formation rates may be enhanced by an additional source of methane such as in situ methanogenesis. We develop expressions to determine the combinations of sediment physical properties and methane supply rates that will result in hydrate-filled coarse-grained layers separated by hydrate-filled fine-grained layers, the conditions necessary to fracture the fine-grained layers, and the conditions that will lead to complete inhibition of hydrate formation as pore space is constricted. This work illustrates how sediment physical properties control hydrate distribution at the pore scale and how hydrate distribution affects fracturing behavior in marine sediments.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Advection; Aliphatic hydrocarbons; Alkanes; Capillarity; Cascadia Basin; East Pacific; Expedition 311; Fine-grained materials; Fracturing; Gas hydrates; Gibbs-Thomson effect; Hydrate Ridge; Hydrocarbons; IODP Site U1325; Integrated Ocean Drilling Program; Leg 204; Marine sediments; Methane; North Pacific; Northeast Pacific; ODP Site 1250; Ocean Drilling Program; Ocean floors; One-dimensional models; Organic compounds; Pacific Ocean; Permeability; Physical properties; Porosity; Sediments
Coordinates: N440000 N490000 W1230000 W1280000
Record ID: 2012013433
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