Following our previous communications on the impact of the amount of water phase on the time required at each temperature‐step 1 and the limitations of visual techniques in determining hydrate dissociation points, 2 a series of tests were conducted in this laboratory to investigate the impact of measuring techniques, mixing efficiency, heating method and heating rate on the accuracy of hydrate dissociation point measurements. The results showed that nonvisual techniques combined with stepwise heating and satisfactory mixing could save a significant amount of time while providing accurate hydrate dissociation data.

We present experimental structure-I clathrate hydrate (methane, carbon dioxide, and methane-carbon dioxide) equilibrium and ice-melting data for mesoporous silica glass. In both cases, high capillary pressures result in depressed solid decomposition temperatures (clathrate dissociation and ice melting), as a function of pore diameter. Clathrate dissociation data show a significant improvement over existing literature data, which is attributed to the improved experimental techniques and interpretative methods used. Through application of a melting (or clathrate dissociation) modified Gibbs-Thomson relationship to experimental data, we determine similar values of 32 ( 2, 32 ( 3, and 30 ( 3 mJ/m 2 for ice-water, methane clathrate-water, and carbon dioxide clathrate-water interfacial tensions, respectively. The data are important for the accurate thermodynamic modeling of clathrate systems, particularly with respect to subsea sedimentary environments, and should prove useful in the simulation of potential methane hydrate exploitation and carbon dioxide sequestration schemes.

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The characteristics of clathrate hydrate equilibria in mesoporous media are discussed in terms of a conceptual model, with the aim of resolving current inconsistencies concerning experimental and interpretative methods employed in studies of such systems. This conceptual model is used as the basis for an analysis of experimental results from our own work and that of others. From this review, we conclude the following: (1) the GibbsThomson (or Kelvin) relationship used to model clathrate inhibition in porous media must be modified correctly to reflect the hysteresis between growth and dissociation; (2) step heating provides more-reliable data than continuous heating techniques; (3) if equilibrium dissociation data cover the complete pore size distribution, then, contrary to what has previously been proposed by some researchers, inhibition can be interpreted in terms of the mean pore diameter; and (4) the enthalpy of clathrate dissociation is not a strong function of pore size (crystal size), as has been suggested in other studies.

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