Exploring methane-hydrate formation and dissociation in geologic materials through laboratory experiments: Kinetic behavior and morphology

• A novel apparatus for studying hydrate formation in geologic matrices is presented.
• Kinetics of methane-hydrate formation in sand was investigated.
• Influence of methane injection rate was studied.
• Repeated experiments at constant methane injection flow rate showed different formation patterns.
• Morphology of hydrates in sand–clay mixtures changes with the proportion of clay.

To gain in-depth understanding of natural gas hydrate behavior it is necessary to identify key parameters that affect their formation, distribution and destabilization within sediments. Hydrate formation kinetics in porous media is amongst the aspects which deserve important considerations as it may provide useful information on the formation history and the formation mechanisms of natural gas hydrate accumulations. Yet, it is at its early stage.In this paper, experiments on methane hydrate formation and dissociation in porous media are reported and discussed. The first part of this work is devoted to the investigation of the kinetics of methane hydrate formation within silica sand using a custom-design apparatus. The latter is suitable for investigating small hydrate-bearing cores. The influence of the methane injection flow-rate is examined, and then a straightforward method is proposed to quantify the amount of hydrate-bound gas. In the second part, three mixtures of clays and sand are used as geologic matrix to study the influence of clay content on the hydrate morphology for a predetermined amount of injected water. Visual observations showed that the morphology shifts from disseminated through massive to moussy hydrates with increasing proportion of clays.