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Electrical properties of carbon dioxide hydrate: Implications for monitoring CO2 in the gas hydrate stability zone

July 15, 2021

CO2 and CH4 clathrate hydrates are of keen interest for energy and carbon cycle considerations. While both typically form on Earth as cubic structure I (sI), we find that pure CO2 hydrate exhibits over an order of magnitude higher electrical conductivity (σ) than pure CH4 hydrate at geologically relevant temperatures. The conductivity was obtained from frequency-dependent impedance (Z) measurements made on polycrystalline CO2 hydrate (CO2·6.0 ± 0.2H2O by methods here) with 25% gas-filled porosity, compared with CH4 hydrate (CH4·5.9H2O) formed and measured in the same apparatus and exhibiting closely matching grain characteristics. The conductivity of CO2 hydrate is 6.5 × 10−4 S/m at 273K with an activation energy (Ea) of 46.5 kJ/mol at 260–281 K, compared with ∼5 × 10−5 S/m and 34.8 kJ/m for CH4 hydrate. Equivalent circuit modeling indicates that different pathways govern conduction in CO2 versus CH4 hydrate. Results show promise for use of electromagnetic methods in monitoring CO2 hydrate formation in certain natural settings or in CO2/CH4 exchange efforts.

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