Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 053
On Hydrate Equilibria in Porous Media
Østergaard, K. K., Llamedo, M. B., Burgass, R. W., and Tohidi, B.
AGU 2000 Fall Meeting, San Francisco, USA, 15-19 December (2000).
It is well known that gas hydrate equilibria in capillary media differ from bulk conditions. Deep marine sediments can be viewed as such capillary media. However, marine sediments are very complex systems with broad pore size distribution and various surface effects. The huge amounts of hydrates in deep sea sediments represent a potential source of energy as well as a safety hazard to drilling operations. Furthermore, they influence ocean margin stability and global climate changes. Before hydrate formation and decomposition in complex marine sediment systems can be successfully described it is necessary to understand the basic interactions between the fluids/hydrates and the porous medium. Such information can be obtained by performing experiments in controlled laboratory environments using well defined porous media and fluids. The available hydrate equilibrium data in tight porous media are sparse and inconsistent. Recently, we have presented an improved test procedure and subsequent measurements obtained from porous glass beads. In this paper we present further experimental results on gas hydrate equilibria of methane and carbon dioxide in porous glass with 251 Å, 128 Å, and 82 Å pore sizes in systems saturated as well as under-saturated with respect to water. Some of the experimental data can be predicted applying an existing conceptual thermodynamic model whereas others cannot be described using existing models. After discussion of phase distribution and wettability we propose a new conceptual model for hydrate equilibria in porous media which enables successful prediction of the experimental data.