Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 115
Capillary Pressure Controlled Methane Hydrate Growth and Dissociation Hysteresis in Narrow Interconnected Pores
Anderson, R., and Tohidi, B.
The 5th International Conference on Gas Hydrates, Trondheim, Norway, June 13-16 (2005).
The potential for capillary pressure induced inhibition of gas hydrates in fine-grained seafloor sediments has recently been the subject of considerable laboratory investigation. However, although there is now a significant volume of experimental hydrate dissociation data available in the literature (for both porous glasses and real sediment samples), capillary pressure effects on the equally (if not more) important process of hydrate growth have not been explored. Here, we present the results of a detailed experimental investigation into methane hydrate growth and dissociation equilibria in synthetic mesoporous silica glasses. Results demonstrate that hydrate formation and decomposition in a network of narrow, interconnected pores, is characterised by a distinct hysteresis between opposing transitions - hydrate growth occurring at temperatures considerably lower (or pressures higher) than those of dissociation. The hysteresis is an equilibrium phenomenon (i.e. not related to supercooling), and takes the form of repeatable closed primary bounding growth/dissociation PT loops within which various secondary (scanning) growth and dissociation specific PT pathways may be followed, depending on initial conditions. Preliminary analysis of data suggests that hysteresis arises as a result of the interplay between pore size distribution, pore geometry, interconnectivity and pore blocking effects.

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