FLUID FLOW THROUGH HETEROGENEOUS METHANE HYDRATE-BEARING SAND: OBSERVATIONS USING X-RAY CT SCANNING Seol, Yongkoo; Kneafsey, Timothy J.
The effects of porous medium heterogeneity on methane hydrate formation, water flow through the heterogeneous hydrate-bearing sand, and hydrate dissociation were observed in an experiment using a heterogeneous sand column with prescribed heterogeneities. X-ray computed tomography (CT) was used to monitor saturation changes in water, gas, and hydrate during hydrate formation, water flow, and hydrate dissociation. The sand column was packed in several segments having vertical and horizontal layers with two distinct grain-size sands. The CT images showed that as hydrate formed, the water and hydrate saturations were dynamically redistributed by variations in capillary strength of the medium (the tendency for a material to imbibe water), which changed with the presence and saturation of hydrate. Water preferentially flowed through fine sand near higher hydrate-saturation regions where the capillary strength was elevated relative to the lower hydrate saturation regions. Hydrate dissociation initiated by depressurization varied with different grain sizes and hydrate saturations.
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