Kinetic Behavior of CH-Hydrate Formation in a Sandy Medium Induced by a Multi-Stage Cooling Process

Methane hydrates (MHs) have been considered as the future clean energy resource because of the vast resource volume and the capability to store methane effectively. To synthesize MH-bearing samples in laboratory for analysis of the thermophysical/geomechanical properties and the formation/dissociation behavior is important because of the scarcity of obtaining naturally-occurring MH cores. With the aim to achieve maximum uniformity in the MH-bearing samples, we designed experiment involving a three- stage cooling process to induce MH formation in the sandy medium under an excess-water condition. The experimental measured P and T were used to estimate the phase saturations of all phases (aqueous, gas and hydrate) over time based on a pore-volume balance method. In the absence of direct visualization capability, we further analyzed the experimental results through numerical simulation to derive the spatial distributions of all phases in the sample. Heterogeneity was identified because of the heat inflow from the surrounding resulting from the imperfect insulation of the reactor. We reached the conclusion that creating homogeneous MH-bearing samples in laboratory is extremely challenging and may not be possible. Our results offer explanations for MH formation at preferential locations and shed light on alternative innovative designs of experimental apparatus or cooling processes (with increased number of cooling steps and longer duration) to create uniform MH-bearing core samples.