Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 072
Application of High Pressure Glass Micromodels to Gas Hydrates Studies
Tohidi, B., Anderson, R., Clennell, B., Yang, J., Bashir, A. and Burgass, R.
4th International Conference on Gas Hydrates, Yokohama, Japan, 19-23 May (2002).
Glass micromodels provide a unique opportunity for the observation of phase behaviour in reservoir fluid systems. This technique has been used to study hydrates in porous media. Such observations can contribute significantly to our understanding of the mechanism of gas hydrate formation and their distribution within sediments. Here we present details of a glass micromodel set-up for the visual observation of gas hydrate formation and dissociation in porous media. Several series of tests have been conducted with C1, CO2, a mixture of C1/CO2 and a natural gas to investigate the effect of fluid composition, presence or absence of free gas and the presence of nucleation sites on gas hydrate formation in porous media, as well as the effect of salt on the mechanism of gas hydrate formation. The results show that gas hydrates could be formed at the gas water interface or from dissolved gas within the water phase, whereas the amount of hydrates formed in the water phase is a function of gas solubility. It is demonstrated that the formation of hydrates reduces gas saturation in the adjacent water phase, resulting in a concentration gradient and gas diffusion from the surrounding water. Gas diffusion plays an important role in gas hydrate growth, in particular at low degrees of subcooling, where some gas bubbles are dissolved in the water phase and transported to the hydrate forming regions. The presence of salts, and their transportation from the hydrate forming region, can have a significant effect on gas hydrate growth. The gas hydrates formed initially under subcooled conditions underwent annealing.

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