Modeling Pure Methane Hydrate Dissociation Using a Numerical Simulator from a Novel Combination of X-ray Computed Tomography and Macroscopic Data

Abstract

The numerical simulator TOUGH+HYDRATE (T+H) was used to predict the transient pure methane hydrate (no sediment) dissociation data. X-ray computed tomography (CT) was used to visualize the methane hydrate formation and dissociation processes. A methane hydrate sample was formed from granular ice in a cylindrical vessel, and slow depressurization combined with thermal stimulation was applied to dissociate the hydrate sample. CT images showed that the water produced from the hydrate dissociation accumulated at the bottom of the vessel and increased the hydrate dissociation rate there.CT images were obtained during hydrate dissociation to confirm the radial dissociation of the hydrate sample. This radial dissociation process has implications for dissociation of hydrates in pipelines, suggesting lower dissociation times than for longitudinal dissociation. These observations were also confirmed by the numerical simulator predictions, which were in good agreement with the measured thermal data during hydrate dissociation. System pressure and sample temperature measured at the sample center followed the CH 4 hydrate L w +H+V equilibrium line during hydrate dissociation. The predicted cumulative methane gas production was within 5% of the measured data. Thus, this study validated our simulation approach and assumptions, which include stationary pure methane hydrateskeleton, equilibrium hydrate-dissociation and heat-and mass-transfer in predicting hydrate dissociation in the absence of sediments. It should be noted that the application of T+H for the pure methane hydrate system (no sediment) is outside the general applicability limits of T+H. This approach is generally not recommended into the regime explored here (no sediment), but it can be considered only after fully evaluating the conditions and being fully aware of the physics and limitations.

Methane Hydrate in Confined Spaces: An Alternative Storage System

“…This method, for instance, has shown that the hydrate formation starts from dissolved CH 4 rather than from the gas interface. X‐ray computed tomography was also used to visualize the decomposition of methane hydrate, its reformations, and the development of flow pathways during dissociation . In general, the spatial resolution of MRI is not high enough to visualize nanopores.…”

Depressurization‐Induced Fines Migration in Sediments Containing Methane Hydrate: X‐Ray Computed Tomography Imaging Experiments

“…Therefore, this study explored the fines migration induced by depressurization of HBS using X‐ray computed tomography (X‐ray CT) imaging. X‐ray CT imaging is frequently deployed to observe the inner processes in HBS under high‐pressure conditions, including hydrate formation, dissociation, and gas production, (e.g.Abegg et al, ; Freifeld et al, ; Gupta et al, ; Kneafsey et al, ; Sell et al, ; Seol & Kneafsey, ; Ta et al, ). We prepared three different sediment samples composed of host sands with fine particles at controlled fractions.…”

Application of X‐Ray Computed Tomography Technology in Gas Hydrate

“…The gas hydrate formation progress [111][112][113] The gas hydrate decomposition progress [111,113,114] Analyzing the longitudinal displacement and sediments particle size…”