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GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, VOL. 8, Q06003, doi:10.1029/2006GC001531, 2007

Observations related to tetrahydrofuran and methane hydrates for laboratory studies of hydrate-bearing sediments

J. Y. Lee

School of Civil and Environmental Engineering, Georgia Institute of Technology, 790 Atlantic Drive NW, Atlanta, Georgia 30332-0355, USA


T. S. Yun

School of Civil and Environmental Engineering, Georgia Institute of Technology, 790 Atlantic Drive NW, Atlanta, Georgia 30332-0355, USA


J. C. Santamarina

School of Civil and Environmental Engineering, Georgia Institute of Technology, 790 Atlantic Drive NW, Atlanta, Georgia 30332-0355, USA


C. Ruppel

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332, USA


Abstract

The interaction among water molecules, guest gas molecules, salts, and mineral particles determines the nucleation and growth behavior of gas hydrates in natural sediments. Hydrate of tetrahydrofuran (THF) has long been used for laboratory studies of gas hydrate-bearing sediments to provide close control on hydrate concentrations and to overcome the long formation history of methane hydrate from aqueous phase methane in sediments. Yet differences in the polarizability of THF (polar molecule) compared to methane (nonpolar molecule) raise questions about the suitability of THF as a proxy for methane in the study of hydrate-bearing sediments. From existing data and simple macroscale experiments, we show that despite its polar nature, THF's large molecular size results in low permittivity, prevents it from dissolving precipitated salts, and hinders the solvation of ions on dry mineral surfaces. In addition, the interfacial tension between water and THF hydrate is similar to that between water and methane hydrate. The processes that researchers choose for forming hydrate in sediments in laboratory settings (e.g., from gas, liquid, or ice) and the pore-scale distribution of the hydrate that is produced by each of these processes likely have a more pronounced effect on the measured macroscale properties of hydrate-bearing sediments than do differences between THF and methane hydrates themselves.

Received 16 November 2006; accepted 27 February 2007; published 6 June 2007.

Keywords: clathrate; methane; tetrahydrofuran; sediment; clay; salt.

Index Terms: 3004 Marine Geology and Geophysics: Gas and hydrate systems; 5460 Planetary Sciences: Solid Surface Planets: Physical properties of materials; 1012 Geochemistry: Reactions and phase equilibria (3612, 8412).

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 459305 bytes)

Citation: Lee, J. Y., T. S. Yun, J. C. Santamarina, and C. Ruppel (2007), Observations related to tetrahydrofuran and methane hydrates for laboratory studies of hydrate-bearing sediments, Geochem. Geophys. Geosyst., 8, Q06003, doi:10.1029/2006GC001531.