Methane Hydrate and Free Gas on the Blake Ridge from Vertical Seismic Profiling

Seismic velocities measured in three drill holes through a gas hydrate deposit on the Blake Ridge, offshore South Carolina, indicate that substantial free gas exists to at least 250 meters beneath the bottom-simulating reflection (BSR). Both methane hydrate and free gas exist even where a clear BSR...

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Bibliographic Details
Published in:Science
Main Authors: Holbrook, W. Steven, Hoskins, Hartley, Wood, Warren T., Stephen, Ralph A., Lizarralde, Daniel
Format: Article in Journal/Newspaper
Language:English
Published: American Association for the Advancement of Science (AAAS) 1996
Subjects:
Methane hydrate
Online Access:http://dx.doi.org/10.1126/science.273.5283.1840
https://www.science.org/doi/pdf/10.1126/science.273.5283.1840
Description
Summary:Seismic velocities measured in three drill holes through a gas hydrate deposit on the Blake Ridge, offshore South Carolina, indicate that substantial free gas exists to at least 250 meters beneath the bottom-simulating reflection (BSR). Both methane hydrate and free gas exist even where a clear BSR is absent. The low reflectance, or blanking, above the BSR is caused by lithologic homogeneity of the sediments rather than by hydrate cementation. The average methane hydrate saturation above the BSR is relatively low (5 to 7 percent of porosity), which suggests that earlier global estimates of methane in hydrates may be too high by as much as a factor of 3.

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