Electrical properties of polycrystalline methane hydrate

Electromagnetic (EM) remote‐sensing techniques are demonstrated to be sensitive to gas hydrate concentration and distribution and complement other resource assessment techniques, particularly seismic methods. To fully utilize EM results requires knowledge of the electrical properties of individual p...

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Bibliographic Details
Published in:Geophysical research letters 2011-05, Vol.38 (9), p.np-n/a
Main Authors: Du Frane, Wyatt L., Stern, Laura A., Weitemeyer, Karen A., Constable, Steven, Pinkston, John C., Roberts, Jeffery J.
Format: Article
Language:English
Subjects:
Assessments
Complement
Earth sciences
Earth, ocean, space
Electric properties
electrical conductivity
Electrical properties
electromagnetic methods
Exact sciences and technology
gas hydrate
Gas hydrates
Geophysics
Greenhouse gases
Hydrates
ice
impedance spectroscopy
Magnetism
Marine geology
Materials science
methane
Oceanography
Physical properties
Pressure cells
Rocks
Scanning electron microscopy
Synthesis
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Summary:Electromagnetic (EM) remote‐sensing techniques are demonstrated to be sensitive to gas hydrate concentration and distribution and complement other resource assessment techniques, particularly seismic methods. To fully utilize EM results requires knowledge of the electrical properties of individual phases and mixing relations, yet little is known about the electrical properties of gas hydrates. We developed a pressure cell to synthesize gas hydrate while simultaneously measuring in situ frequency‐dependent electrical conductivity (σ). Synthesis of methane (CH4) hydrate was verified by thermal monitoring and by post run cryogenic scanning electron microscope imaging. Impedance spectra (20 Hz to 2 MHz) were collected before and after synthesis of polycrystalline CH4 hydrate from polycrystalline ice and used to calculate σ. We determined the σ of CH4 hydrate to be 5 × 10−5 S/m at 0°C with activation energy (Ea) of 30.6 kJ/mol (−15 to 15°C). After dissociation back into ice, σ measurements of samples increased by a factor of ∼4 and Ea increased by ∼50%, similar to the starting ice samples. Key Points We developed a pressure cell to synthesize and measure sigma of gas hydrate We determined the sigma of CH4 hydrate to be 5 × 10−5 S/m at 0° C Sigma measurements are a factor of ∼4 and Ea is ∼50% lower for CH4 hydrate than ice
ISSN:0094-8276
1944-8007
DOI:10.1029/2011GL047243