天然气水合物未水合水与冻土未冻水的异同性的实验研究

In formation process of natural gas hydrate in porous medium, not all pore water is converted into hydrate. Some of the pore water does not change into hydrate and still exists in liquid form in porous sediment to maintain a three-phase equilibrium state jointly with hydrate and hydrocarbon gases which is called nonclathrated water. In most experimental studies of porous media hydrate, the conversion rate of water converted into hydrate is overestimated and this portion of porous water in liquid form is ignored which leads to a far overestimated of hydrate reserve in nature. Thus, it is a great theoretical significance to conduct experimental comparison study between unfrozen water in frozen soil and nonclathrated water in natural gas hydrate based on the reference of unfrozen water in frozen soil in order to have a thoroughly understanding of the variation characteristics of nonclathrated water in natural gas hydrate. This research project studies nonclathrated water in natural gas hydrate and unfrozen water in frozen soil in which it employs a low field intensity NMR spectrometer to uncover the similarities and differences between them. This study could help to reveal the formation mechanism and the distribution pattern of porous media hydrate as well as to refine the formation dynamics theory of hydrate. To simulate and analyze the nonclathrated water on the basis of the theory of unfrozen water to reveal the properties and distribution pattern of nonclathrated water. This study provides new theoretical support for prospecting, storage & transport management and the reserve estimation of natural gas hydrate in the nature.

多孔介质天然气水合物形成过程中，并不是所有的孔隙水都转变成水合物，其中有一部分水并没有形成水合物，仍然以液态形式在多孔沉积物中与水合物、烃类气体保持三相平衡状态，称之为未水合水。在大部分多孔介质水合物的实验研究中，都过高的估计了水合物中水分的转化率而忽略了以液相存在的这部分孔隙水，从而造成了水合物储量的评估远高于实际储量。因此以冻土中的未冻水为参照指导，开展未冻水与未水合水之间对比性的实验研究，深入认识了解天然气水合物未水合水的变化特征具有非常重要的理论意义。本项目以天然气水合物未水合水和冻土未冻水为研究对象，采用低场核磁共振仪进行分析测试两者之间异同性的研究方法，为多孔介质水合物的形成机理特性及分布规律提供数据依据，完善水合物形成动力学理论；通过未冻水的存在形态来模拟分析未水合水的存在形态，揭示未水合水的特性及分布特征；为自然界天然气水合物的勘测、储运和储量估算提供新的理论。