Characteristics of Clathrate Hydrate Equilibria in Mesopores and Interpretation of Experimental Data

Abstract

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.

Formation and Dissociation of Methane Hydrates from Seawater in Consolidated Sand: Mimicking Methane Hydrate Dynamics beneath the Seafloor

“…The hydrate dissociation in pores smaller than 300 Å differed from the dissociation of bulk hydrates. A similar shift in hydrate stability for pore radii between 0.9 Å and 251 Å was observed by Seshadri et al [4], Anderson et al [5][6][7] and Ostergaard et al [8]. Anderson et al [7] found the equilibrium conditions to be a strong function of pore diameter for methane, carbon dioxide, and methane-carbon dioxide hydrates.…”

Preliminary study on measurement technology for hydrate phase equilibrium

“…Each equilibrium dissociation point obtained by this method corresponds to the condition on the univariant phase boundary for an appropriate pore size [43]. For this issue, CH4 hydrate dissociation path in silica sand sample saturated by pure water (no SDS) was studied and the results are shown in Fig.…”

“…Anderson et al [43] and Mohammad-Taheria et al [44] considered that the step heating technique provided a more-reliable method for isochoric determination of hydrate equilibrium conditions, when compared to the continuous-heating technique. Beltran et al [45] clarified the common mistake existing in literatures.…”

Characteristics of Methane Hydrate Formation in Artificial and Natural Media

“…As the surrounding environment significantly influences natural gas hydrate formation, understanding the thermodynamic mechanism underlying the formation of natural gas hydrates in porous media is instrumental to research on gas hydrate storage [5]. Handa and Stupin [5] pioneered the effort to characterize pore size effects on hydrate equilibrium conditions in porous media, opening the way for many other researchers to refine and expand their work, not only on experiments [6][7][8][9][10][11][12][13][14][15][16], but also from theoretical points of view [17][18][19][20][21][22].…”