Observation of gas hydrate distribution in sediment pore space

Based on the high-resolution industrial x-ray computerized tomography (X-CT), a dedicated apparatus was developed to observe in-situ pore scale distribution of gas hydrate directly during hydrate formation and subsequently dissociation in artificial cores. Methane gas hydrate was formed in 0. 425 similar to 0. 85 mm sands and CT scanning was conducted during the process to observe the hydrate distribution in sediment pore space. The result shows that at each hydrate saturation level, the distribution models of gas hydrate are complicated. The occurrence of "floating model" (i.e. hydrate floats in pore fluid), "contact model" (i.e. hydrate contact with the sediment particle), and the "cementing model" (i.e. hydrates cement the sediment particles) can be found at the same time. It also shows that at different hydrate formation stages, the dominant models are not the same: although there are some hydrates floating in the pore fluid at the first stage of hydrate formation, most hydrates connect the sediment particles. Consequently, the hydrate distribution at this moment can be described as a cementing model. At the second stage of hydrate formation (e. g., hydrate saturation at 24. 6% and 35. 0%), hydrates are mainly growing as a floating or contact model. As hydrate saturation is much higher (e. g. after hydrate saturation is more than 51. 4%), the floating hydrates coalesce with each other and the hydrates cement the sediment particles again.