Hydrate Formation In Porous Media Research Articles

A Method To Predict Equilibrium Conditions of Gas Hydrate Formation in Porous Media

A predictive model has been developed to determine the incipient hydrate formation conditions in porous media. The only additional information that is needed to determine the incipient hydrate formation conditions is the pore radius, surface energy per unit area, and wetting angle. It was found that the model performed well in predicting the experimental data of Handa and Stupin (J. Phys. Chem. 1992, 96, 8599).

Methane Hydrate Formation in Porous Media

It is known that methane hydrate formation has mainly been studied by stirring in homogeneous systems such as autoclave systems. To simulate methane hydrate formation in porous media new heterogeneous experimental models were designed, and by their use, the hydrate formation without stirring in porous media such as glassbeads and Berea sandstone cores was observed.In the electrical resistivity observation at constant temperatures at which methane pressure had increased, sharp peaks were monitored. The starting point of the rise in electrical resistivity was assigned to the starting point of hydrate formation, and a hydrate formation-pressure curve was obtained. In the observation of temperature and pressure in a closed system, a rapid drop in pressure and a rapid rise in temperature due to the methane hydrate formation were observed after a certain induction period. The starting points of the observations are on the curve obtained from the electrical resistivity measurements. The methane consumption rate, that is, the methane hydrate formation rate was higher at lower temperatures and at higher levels of super-cooling. These relationships are the same as those of the studies made by autoclave experiments. The methane hydrate in porous media, without stirring, was formed inhomogeneously. Reformation began in the whole media at the same time, after a short induction period because of the memory effects.

Formation and accumulation of gas hydrate in porous media

Vast quantities of clathrate hydrate are found in the Arctic and in marine sediments along continental margins. The clathrate structure traps enormous volumes of methane gas, which is both a possible source of global climate change and a potential energy resource. The growth rate and spatial distribution of gas hydrate in the shallow sediments are influenced by a variety of interacting physical processes. In order to quantify these processes, we develop mathematical models for hydrate formation in porous media. An analytical model is derived for the idealized problem of hydrate growth in a porous half‐space which is cooled on its boundary. Our calculations predict the growth rate of a hydrate layer for a given rate of cooling and show that the volume of hydrate is strongly dependent on the two‐phase equilibrium between hydrate and seawater. For a representative phase diagram we find that the volume of hydrate in the layer is less than 1% of the pore volume. Larger volumes of hydrate observed in some locations demand a sustained supply of gas and a long accumulation time. Numerical calculations are used to investigate situations that are more representative of conditions in marine sediments. A simple theoretical expression is derived for the rate of hydrate accumulation due to advection of methane gas from depth. Using typical estimates of fluid velocities in accretionary environments, we obtain an accumulation rate of 1% of the pore volume in 105 years. The predicted vertical distribution of hydrate is consistent with geophysical inferences from observed hydrate occurrences along the Cascadia margin. Similar distributions can arise from the combined effects of in situ methane production and warming due to ongoing sedimentation. Predicted differences between these two formation models may be detectable in geophysical and geochemical measurements.