沉积物孔隙空间天然气水合物微观分布观测

在高分辨率工业型X射线层析扫描仪上（X-CT，X-Ray Computerized Tomography），研制了适用于沉积物中水合物微观赋存状态研究的CT原位探测装置，可通过模拟天然气水合物生成/分解过程，直接观测水合物在沉积孔隙中的微观分布特征.对粒径为0.425~0.85 mm沉积物中水合物形成过程进行了CT观测研究，结果表明，沉积孔隙中水合物呈混合分布模式，但在水合物不同形成阶段，以某种分布模式为主导：在水合物形成初期，仅有极少量水合物悬浮在流体中，水合物主要以接触或胶结模式为主；在水合物形成中期（如饱和度为24.6%、35.0%时），水合物倾向于在孔隙流体中以悬浮状形态生成；在水合物形成后期（如饱和度为51.4%之后），悬浮状的水合物慢慢生长聚拢在一起，水合物又重新胶结沉积物颗粒.

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 0.425~0.85 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.