水合物沉积物介电特性测量实验

介电常数法是探测冻土区水合物的一项有效技术。通过物理模拟实验，研究冻土区砂岩水合物沉积物的介电特性与水合物饱和度、骨架粒度等因素的关系，对水合物的勘探和开发具有重要意义。在实验室以不同粒度石英砂为骨架制备甲烷水合物和四氢呋喃（THF）水合物沉积物样品，并使用探地雷达测量其介电常数。结果显示：不同石英砂粒度条件下，两种甲烷水合物沉积物的介电常数均随饱和度增大而减小；相同饱和度条件下，围岩粒度小的甲烷水合物沉积物介电常数高，推断是孔隙内未反应的水引起的；在相同石英砂粒度条件下，THF水合物沉积物与甲烷水合物沉积物的介电常数随饱和度变化趋势相同，均表现为介电常数随饱和度增大而减小；在相同饱和度和石英砂粒度条件下，甲烷水合物沉积物介电常数整体大于THF水合物沉积物，推断是甲烷水合物沉积物孔隙中气相因素及未反应的水等综合因素所致。

An experimental study on dielectric properties of hydrate sediments in radar wave propagation

As an effective way to detect hydrate in permafrost regions,the dielectric constant can be used to investigate the relations between dielectric constant characteristics of sandstone hydrate sediments and the hydrate saturation as well as the surrounding rock granularity with physical simulation tests,which is of great significance for the hydrate exploration and development.Soil samples of methane hydrate and tetrahydrofuran (THF) hydrate with different granularities of quartz sand framework are obtained through sample preparation in laboratory and their dielectric constants are analyzed.The following phenomena are observed:A.Under different granularities of quartz sands,the dielectric constants of two kinds of methane hydrate sediments decrease with the increase of saturation; B.Under the condition of same saturation,the dielectric constant of methane hydrate sediments with small granularity of surrounding rock is larger,which is inferred to be caused by the unreacted water in the pores; C.Under the same granularity of quartz sands,the changing trend of dielectric constant with the saturation in THF hydrate sediments is the same as that in methane hydrate sediments i.e.,both dielectric constant decreases with the increase of saturation; D.Under the condition of the same saturation,the dielectric constant of hydrate sediments is overall larger than that of THF hydrate,which is inferred to be caused by the combination of gas-phase factors in the pores of methane hydrate sediments and the presence of unreacted water.